MITNE -48
SRO - 87
'3 4
ROLES OF PYROLYSIS
RADIOLYSIS IN THE
ATION OF TERPHENYLS
AEC Research and Development Report
Contract No. AT (38-1) - 334
Department of Nuclear Engineering
Massachusetts
Institute of Technology
Cambridge 39, Massachusetts
MITNF,48
SRO-47
REIATIVE ROLES OF PYROLYSIS AND RADXOLYSIS
IN THE DEGRADATION OF TERPHENYLS
By
Jean-Francois Terrien
Edward A. Mason
DEPARTMENT OF NUCLEAR ENGINEERING
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
CAMBRIDGE,
MASSACHUSETTS 02139
(M.IT. Project No. DSR 9819)
Work Performed Under Contract No. AT(38-1)-334
with the
Savannah River Operations Office
U.
S.
ATOMIC ENERGY COMMISSION
Issued;
.;rune, 1964
ABSTRACT
An evaluation of recent radiolysis and pyrolysis studies
with terphenyl coolants for nuclear reactors indicates that
the rate of pyrolysis of irradiated coolant is significantly
greater than that of unirradiated coolant ant that a consistent
correlation of the total degradation yields from a large
number of the previous experiments is realized by treating
the effects of radiolysis and pyrolysis as additive in the
following manner:
-dCi
G*(-)
=
kRqiCidT + kprjCi dt
G()
=
G*
pr
R (-i) + G*r
where G(-1) = 0.26 + 0.01 molecules of component i
degraded by radiolysis alone/(100 ev radiations
absorbed) (weight % of component i)
k
= pyrolytic constant of irradiated component i
pr*i
(hr-1 ).
Values of kprei are reported for terphenyl coolants over the
temperature range from about 4000F (2000C) to 8000F (4250C),
Comparison of the results of the loop experiments on this
basis indicates that the rate of fast neutron degradation to
gamma ray degradation per unit of energy absorbed G§(-i)/G*(-i)
(a measure of the "fast neutron effect") is not significantly
different from unity. The G values reported for electron irradiations of encapsulated samples are lower than those reported
from gamma irradiations; it is suggested that the electron
values reported are low because of incomplete mixing during
irradiation. Evaluation of the results of capsule irradiations
in reactors using the G values obtained from gamma (not electron)
irradiations and first-order kinetics, gives values of G*(-1)/
G*(-i) of between 1 and a high of 2.4.
Y
The activation energy for the radiolysis process AE ,
appears to be low (values obtained range from 0 to about 2
kcal/mole, but insufficient data are available to establish
the magnitude of AE% with confidence).
TABLE OF CONTENTS
CHAPTER
PAGE
I
INTRODUCTION
1
II
RADIOLYSIS
2.1 Radiolytic Experiments
2.2 Types of Ionizing Particles
2.3 Linear Energy Transfer Effect
4
4
2.4 Temperature Effect
2.5 Dose Rate Effect
9
9
III PYROLYSIS
3.1 Pyrolysis of Non-Irradiated Material
3.2 Pyrolysis of Irradiated Material
3.3 Relative Roles of Radiolysis and Pyrolysis
Their Temperature Dependence
IV
4
5
11
11
'12
16
3.4 Pyrolytic Reaction Constant of Irradiated
Material
18
RADIOLYTIC AND PYROLYTIC DEGRADATION RATES
4.1 Kinetics of Coolant Degradation
20
20
4.2 Kinetics of the Radiolytic and Pyrolytic
Coolant Degradation
20
4.3 First-Order Kinetics
4.3.1. Time of Radiolysis
21
Time of Pyrolysis
22
4.3.2. Time of Radiolysis / Time of Pyrolysis
4.4 G Values
23
24
4.5 Relative Contribution of G*(-i) and G* (-1)
R
pr
4.6 Relative Effects of Fast Neutrons and
Gamma Rays
25
4.7 Pyrolytic Contribution to the "Fast Neutron
Effect"
4.8 Determination of G*(-i)/G*(-i)
4.9 Applications
25
28
28
30
TABLE OF CONTENTS (Continued)
CHAPTER
V
PAGE
EXPERIMENTS DONE IN THE M.I.T. IN-PILE
LOOP FACILITY AND BY EURATOM IN GRENOBLE (FRANCE)
5.1 The M.I.T. In-Pile Loop Facility
5.1.1. Composition of the Irradiated Material
5.1.2. Irradiation of Santowax OMP
5.1.3. Irradiation of Santowax WR
5.1.4. Irradiation Procedure
5.1.5. Dosimetry
5.1.6. Calculation Procedure of G and G*
Values for Steady-State and Transient
Periods
5.2 Euratom Loops
5.2.1. Irradiation Procedure
5.2.?. Dosimetry
5.3 Results Obtained at M.I.T.- Comparison with
Euratom's G* Values
5.3.1. Determination of G*(-i)
R
5.3.2. Relative Pyrolytic and Radiolytic
Contributions in the M.I.T. Loop
and at Grenoble (France)
5.3.3. Temperature Iteration of the M.I.T.
Experimental Pyrolytic Constants
31
31
31
32
32
33
34
35
37
37
38
39
39
39
47
5.3.4. Pyrolytic Degradation of the Terphenyl
Isomers
VI
48
5.4. Conclusions
51
REVIEW OF IRRADIATIONS PERFORMED BY VARIOUS
FACILITIES
54
6.1 Irradiations Performed at Harwell, 03ngland)
6.1.1. Irradiation Procedure
6.1.2. Dosimetry
6.1.3.
54
54
56
Analytical Determinations and
Experimental Results
57
TABLE OF CONTENTS (Continued)
PAGE
CHAPTER
6.1.4. Interpretation of the Electron
Irradiations
6.1.5. Interpretation of BEPO Irradiations
6.2 Irradiations Performed by Phillips Petroleum Co.
6.3.A.E.C.L. Irradiations
6.3.1. Electron Irradiations by Mackintosh
6.3.1.1 Irradiation Procedure
6.3.1.2 Dosimetry
6.3.1.3 Analytical Determination
6.3-1.4 Experimental Results
6.3.2. Mixed In-Pile Capsule Experiments
6.3.2.1 NRX, X-Rod Facility
6.3.2.2 E-3 Facility, NEX Reactor
6.4 Atomics International Irradiations
6.4.1. Transient In-Pile Loop Irradiations
6.4.2. Organic Moderated Reactor Experiments,
OMRE
59
62
63
64
64
64
64
64
64
66
68
69
70
71
73
6.4,3. In-Pile Capsule Experiments in the
CWRR and the OGR
6.4.3.1 CWRR Facility
6.4.3.2 OGR Facility
6.4.4. Recent Experiments
6.4.5. Conclusions on A.I. Experiments
6.5 California Research Corporation Irradiations
6.5.1. Irradiation Procedure
6.5.2. Dosimetry
6.5.3. Analytical Determination and
Experimental Results
6.5.4. Interpretation of the Experimental
Results
73
73
76
78
79,
79
80
80
82
82
TABLE OF CONTENTS (Continued)
CHAPTER
PAGE
VII CONCLUSIONS
90
7.1 Loop Irradiations
7.2 Capsule Irradiations
7.3 Summary
90
93
94
APPENDICES
Al
A2
THE EFFECT OF NON-MIXING ON OBSERVED HARWELL
Ge VALUES
A.E.C.L.
A2.1
A?.2
IRRADIATION DATA
Electron Irradiations
In-Pile Irradiations
96
101
101
104
CONCENTRATION OF THE TERPHENYL ISOMERS IN
THE SANTOWAX OMP IRRADIATIONS OF CALIFORNIA
RESEARCH CORPORATION
109
ITERATION METHOD FOR DETERMINING PYROLYSIS
RATE CONSTANTS AS FUNCTION OF TEMPERATURE
114
A5
NOMENCLATURE
115
A6
REFERENCES
118
A6.1
A6.2
References for Chapter I
References for Chapter II
A6.3
A6.4
A6.5
A6.6
References
References
References
References
118
118
120
122
for Chapter VI
124
A6.7
References for Appendices
127
A3
A4
for Chapter III
for Chapter IV
for Chapter V
123
LIST OF TABLES
PAGE
2.1
3.1
4.1
5.1
5.2
5.3
5.4
5.5
5.6
5.7
G Values for Electron and In-Pile Irradiations
for Some Aromatic Compounds (_..)
Densities and Viscosities Measured at 700 0 F
for the M.I.T. Irradiations of Santowax OMP
With 33 w/o HB
16
Pyrolytic Correction to the "Fast Neutron
Effect"
29
G*(-i) Values for the 425OF and 610 0 F
Irradiations at M.I.T.
40
Preliminary Euratom's G*(-i) Values
G*(-i) Values for the 700, 750 and 7800F
Irradiations at M.I.T.
Pyrolytic and Radiolytic Contributions
in the M.I.T. In-Pile Loop Facility
Pyrolytic and Radiolytic Contributions
in BLO2 and BLO3 (Euratom)
Temperature Profile of the M.I.T.
Loop Facility
6.2
6.3
40
42
43
44
In-Pile
50
Pyrolytic and Radiolytic Contributionsin
the M.I.T. In-Pile Loop Facility for the
Terphenyl Isomers During the Santowax WR
Irradiations
6.1,
6
Initial G Values for Electron and Pile
Irradiations, Second-Order Kinetics
Harwell Initial G Values, G 0 (-coolant),
Second-Order Kinetics
Comparison of Initial G(-* HB) Values from
52
57
58
Electron and Gamma Ray Irradiations (A.E.R.E.)
at 3500C
61
LIST OF TABLES (Continued)
PAGE
6.5
G* Values for the 375 0 C Electron Irradiations
(A.E.C.L.), First-Order Kinetics
Differential G* Values at a Given Dose
66
6.6
For Electron Irradiations (AE.C.L.)
Irradiation of Santowax OM by A.E.C.L,,
NRX, X-rod Facility
G* Values of Irradiated Ortho and MetaTerphenyl, E-3 Facility, NRX Reactor,
A.E.C.L., First-Order Kinetics
G(-compound) Values for the MTR In-Pile Loop
(First-Order Kinetics)
G*(-i) Values Obtained from CWER at M.I.T,
(First-Order Kinetics)
Threshold Detectors for the OGR Irradiations
Obtained at M.I.T.,
G*(-i) Values from OG,
(First-Order Kinetics)
Irradiation of Ortho-Terphenyl, 1 Mev
Electrons (A.I.)
68
6.4
6.7
6.8
6.9
6.10
6.11
6.12
6.13
6.14
6.15
6.16
6.17
6.18
Threshold Detectors Used in Susie
Initial G* Values for the Irradiationsof
Pure Terphenyl Isomers at 6000F from the
Susie Canisters (C.R.C.)
65
70
72
75
76
77
79
81
82
G*(-i) Values for the Susie Reactor,
Neutron Rich Canister and Gamma Rich Canister,
Santowax OMP Irradiations
G*(-i) Values for the Santowax OMP Irradiations,
MTR Gamma Facility (C.R.C.)
G*(-i) Values for the Irradiations of Pure
Terphenyl Isomers (C.R.C.)
Predictions of G*(-omp) Values at 4250F
from C.R.C. Data
85
86
87
88
LIST OF TABLES (Continued)
PAGE
7.1
Loop Irradiations
91
7.2
Capsule Irradiations
92
Al.1
The Effect of Non-Mixing on Observed
G* Values
Van de Graaf Irradiations of Ortho and MetaTerphenyl at 3750C (7070F), A.E.C.L.,
Terphenyl and HB Concentrations
A2.1
A2.2
A2.3
A2.4
A2.5
A2.6
A2.7
A2.8
Van de Graaf Irradiations of Santowax OM
at 3750C, A.E.C.L., Terphenyl and HB
Concentrations
Van de Graaf Irradiations of Santowax OM
at Different Temperatures, A.E.C.L., Dose:
8.8 watt.hr/gm, Terphenyl and HB Concentrations
Irradiation of Ortho and Meta-Terphenyl,
NEX Reactor, E-3 Facility, A.E.C.L., 100-30 0 C
Terphenyl Concentration and Dose Received
Irradiation of Ortho and Meta-Terphenyl,
NRX Reactor, E-3 Facility, A.E.C.L., at 3504C,
Terphenyl Concentration and Dose Received
Irradiation of Ortho-Terphenyl, NRX Reactor,
E-3 Facility, A.E.C.L. at 42400, Terphenyl
99
101
102
103
104
105
Concentration and Dose.
Irradiation of Ortho and Meta-Terphenyl
NRX Reactor, E-3 Facility, A.E.C.L.,
Terphenyl Concentration and Dose, Dose
106
Rate: 0.100 watt/gm
Irradiation of Ortho and Meta-Terphenyl
NRX Reactor, E-3 Facility, A.E.C.L,,
Terphenyl Concentration and Dose,
107
Dose Rate: 0.300 watt/gm
108
LIST OF TABLES (Continued)
PAGE
A3.1
A3.2
A3.3
Terphenyl Concentrations During the
Neutron Rich Canister Irradiations at
425, 600 and 7500F, Susie Reactor, (C.R.C.)
Terphenyl Isomer Concentrations During
the Gamma Rich Canister Irradiations at
425 and 6000F, Susie Reactor, C.R.C.
Terphenyl Isomer Concentrations During the
MTR Gamma Grid Irradiations at 425, 600,
675 and 7504F, C.R.C.
iil
112
113
LIST OF FIGURES
PAGE
1.1
Structure of the Terphenyls and Biphenyl
2
2.1
Radiation Damage to Benzene (0Z)
8
2.2
Radiation Damage to Toluene (2)
8
2.3
Temperature Dependence of the Total
Degradation Rate Obtained in the M.I.T.
In-Pile Loop Facility
10
3.1
Pyrolysis Data for Unirradiated Terphenyls
13
3.2
Pyrolysis Data for Terphenyls
14
5.1
Pyrolysis Data of Irradiated Terphenyl
Obtained by Euratom and M.I.T.
45
5.2
Schematic of Circulation Volume of Loop
49
5.3
Pyrolysis Data of Terphenyls Obtained at M.I.T.
53
6.1
Schematic of Harwell Electron Irradiation Cell
55
6.2
Qualitative Representation of the HB
Concentration in the Irradiation Cell
60
A.E.C.L. Electron Irradiations at Different
Temperatures and at the same Dose, 8.8 watt-hr/gm
67
6.4
Decomposition Rate of OMRE Coolant
74
A1.1
Zero-Order Kinetics
98
Al.2
First-Order Kinetics
98
6.3
-1-
CHAPTER I
INTRODUCTION
Aromatic compounds such as biphenyl, ortho-terphenyl, metaterphenyl and para-terphenyl whose configurations are given in
Fig. 1.1, and mixtures of these isomers called Santowax, have
received most attention because among the organic fluids
which have desirable physical and heat transfer properties,
they have been found to be the most stable to radiation.
The relatively high stability of aromatic components under
irradiation has been explained on the basis of their high resonance
energy due mostly to the electronic configuration of the aromatic
ring (1.1, 1.2). Factors favoring their use as reactor coolants
are (;):
- a low induced activity under irradiation,
- low operating pressures at high temperatures,
- negligible corrosion of classical materials,
- good moderating properties due to the presence of
hydrogen atoms.
The principal disadvantages are:
- the degradation of the isomers under irradiation and
high temperature (600 0 F and above), which results in
a decrease in their heat transfer capabilities, and
requires coolant processing and makeup.
- poor heat transfer properties (relative to water),
- fouling of surfaces has also been observed.
0
I\
p
ORTHO-TERPHENYL
FIG. 1-1
META- TERPHENYL
STRUCTURE
OF THE
PARA-TERPHENYL
TERPHENYLS
BIPHENYL
AND BIPHENYL
-3-
As a result of their possible application for cooling nuclear
reactors, the radiolytic and pyrolytic behaviour of the polyphenyls have been studied for many years now, by various facilities
and laboratories.
The possibility for being used as coolant for large,
heavy-water moderated, natural-uranium fueled reactors, is
studied by A.E.C.L. of Canada and Euratom. The Piqua Reactor
in Ohio is an operating terphenyl cooled and moderated nuclear
reactor and the Arbus Reactor in U.S.S.R. is cooled and moderated
with an aromatic-rich gas oil (1.4).
The behaviour of terphenyls has been studied in the presence
of various types of radiation, over a wide range of temperatures
using both encapsulated samples of coolant as well as circulating loop systems. However, there has been a considerable degree
of discrepancy between the results and interpretations reported
from these studies. Questions remain regarding the relative
(and sometimes the absolute) effects of temperature, fast neutron
and gamma ray fractions, dose rates, concentration of degradation
products.
This study examines the various reported experimental
techniques and methods of data treatment, in an attempt to
determine whether,and to what degree, the apparent discrepancies
are the result of difference in technique or interpretation.
Initially, the results of recent pyrolysis and radiolysis
experiments carried out by Euratom, A.E.C.L. and at M.I.T.,
are used to examine and define the relative effects of radiolysis
and pyrolysis. Utilizing the model for the combined effects of
radiation and pyrolysis that is developed, the sets of data
obtained by Euratom and at M.I.T. are shown to be in good agreement.
An evaluation of most of the data reported from other
experiments on the radiolysis of terphenyls is then presented
along with a discussion of the experimental procedures and
results.
CHAPTER II
RADIOLYSIS
2.1. Radiolytic Experiments
The mechanisms of the radiolysis of terphenyls are not
fully understood. Different interpretations have been presented
but none of them explains entirely the data obtained.
Irradiations of pure terphenyls and mixtures of the
isomers have been performed in various laboratories such as
Harwell (England), Atomics International, California Research
Corporation, Phillips Petroleum Company, M.I.T. (U.S.A.),
Euratom and A.E.C.L. (Canada), under different experimental
conditions including various types of radiation and ionizing
properties, dose rates, temperatures.
2.2. Types of Ionizing Particles
As the energy required for damaging the terphenyls must
be greater than the dissociation bond energy, which is in the
order of some 25 ev, only the energetic particles -and in a
reactor environment, only fast neutrons and gamma rays- will
contribute to the degradation. It has been observed also that
the C-H bond has a greater probability of rupture than the
C-C one (2.1). This radiolytic process has been explained by
the following consideration: electrons and gamma rays lose
their energy by ionization. The gamma rays interact mainly by
Compton scattering and produce electrons. The fast neutrons are
scattered by the hydrogen nucleus, and the proton thus formed
causes ionization. Other particles such as protons, deuterons,
alphas, have also been used to study the effect of ionizing
density. But since the same mechanism (i.e. ionization) occurs,
it might be concluded that the damage should be proportional
to the amount of energy absorbed and should not depend on the
type of the ionizing radiation (2.2). However, in some
radiolytic processes, another effect is introduced which
characterizes the ion density along the track of an ionizing
-5-
particle. The LET, -Linear Energy Transfer- is a measure of the
rate of an ionizing radiation per unit length. In fact, it has
been observed that different degradation yields are obtained with
different types of radiation. A proton for instance, whose path
in a medium is short, would have a higher LET than an electron
and therefore could be more damaging (2.1).
Linear Energy Transfer Effect
The effects of LET have been studied for dilute aqueous
solutions and organic systems. For aqueous solutions, there is
a definitive LET effect, whereas the conclusions for organic
systems are not so sharp as shown below by some experiments
carried out by several workers.
2.3.
Aromatic compounds (toluene, ethylbenzene, i-propylbenzene,
t-butylbenzene) were radiolyzed with electrons and mixed in-pile
radiations by Sworski and Burton (2.?). The doses received are
not specified. While the yields of the gases formed do not seem
to be exactly
irradiations.
capsules were
heated by the
the same, they found similar effects in these
Their values are presented in Table 2.1. The
kept at 20-25 0 C and the irradiated materials were
radiation energy.
Similarly, Schuler and Allen (2.4) conducted irradiations
of pure cyclohexane with 20 Mev helium ions, 20 Mev deuterons
and 2 Mev electrons, and found no LET effect. They quote
G(H 2 ) = 5.25. This behaviour was also noticed by Dewhurst and
with alpha particles on the same component.
Schuler (.5)
No difference in
yield was found by Charlesby (2.6) on
polymers with X-rayselectron and mixed in-pile irradiations.
Collins and Calkins (2Z) have carried out an extensive
program of irradiation on elastomers, organic liquids and
plastics, using both pure gamma ray and mixed in-pile radiations.
Their main conclusions are that neither the type of radiation
particle nor the rate of dosage is important within a factor of
2 in accuracy, and that radiation effects on organic liquids are
-6-
Table
G Values
2.1
for Electron (e) and In-Pile (p) Irradiations
For Some Aromatic Compounds (2)
Component
G(H2)(a)
G(CH 4 )
G(C 2 Hn)
e
Re
Toluene
0.13
0.16
0.008
0.006
0.001
0.016
Ethylbenzene
0.18
0.22
0.030
0.023
0.004
0.022
i-propylbenzene
0.17
0.21
0.073
0.050
0.009
0.011
t-butylbenzene
0.11
0.16
0.070
0.045
0.009
0.018
eR
(a) G = number of molecules of gas produced per 100 ev
absorbed.
-7-
dependent only on the total energy (dosage) absorbed by the compound.
Furthermore, they quote that significant effects of temperature
have been observed in the irradiation although this appears small,
but we must remember that their temperature range was most of the
time well below 6000F. They have also noticed some evidence of an
"optimum irradiation temperature" above which other processes
may occur. The radiation damages of benzene and toluene presented
by Collins and Calkins (2.7) under various fluxes, are shown in
Fig. 2.1 and 2.2. There seems to be no significant difference in
the effects of the various type-s of radiation used. (The iodine
number quoted in these two figures represents the number of grams
of iodine which reacts with 100 gm of material.)
Zebroski and Finderman, comparing the irradiation effects
on organic liquids of high-ene-rgy electrons and gamma rays,
have obtained the same gas yield (2.8).
As for benzene, biphenyl and terphenyls, several values
were found by Harwell workers (2.14) at various temperatures
above 400 0 F, which indicated that the damage due to electron
irradiations was less than the damage of an equivalent amount
of energy deposited from mixed in-pile irradiations. They
assumed that the degradation yields (GY(-+ HB) values) for the
gamma rays in the reactor radiation were the same as the Ge (- HB)
values obtained from the electron irradiations, and hence,
concluded that fast neutrons were more damaging, per unit of
energy deposited, than electrons and gamma rays, presumably
due to a LET effect. Degradation rates obtained from reactor
irradiations at other facilities were also analyzed, assuming
that the electron values found at Harwell could be used for
gamma rays. Then, the contribution of fast neutrons was
calculated and a conclusion similar to Harwell's was reached.
A survey and an explanation of the electron values obtained
in England are given in Chapter VI, in which it is suggested
that these discrepancies between the electron and fast neutron
degradation yields may be due to the exDerimental procedures
and the unaccounted-for influence of temperature.
-8-
GAMMA RAY
A ELECTRON
o MIXED IN- PILE
0
O
4
w
0)
z
w
z
0
EA
I
A
0
y
FIG. 2-1
w
21-
RADIATION
IOe
DAMAGE
DOSE, RADS
TO BENZENE (2.7)
o GAMMA RAY
O ELECTRON
A MIXED IN-PILE
z
w
z
0
I
107
106
10
0
0L~
0
I
0
10
FIG. 2.2
El
I
10
10
DOSE, RADS
RADIATION DAMAGE TO TOLUENE (2.7)
-9-
2.4. Temperature Effect
Fig. 2.3 shows the temperature dependence of the total
degradation rate of two mixtures of the terphenyl isomers,
Santowax WR and OMP, irradiated in the M.I.T. In-Pile Loop
Facility. The degradation rate G*(-omp) is defined by the
following relation:
G*(-omp)
where
= G(-omp)
Comp
G(-omp) = number of molecules of terphenyl
degraded per 100 ev absorbed in the
total coolant
C
= concentration of terphenyls in the
coolant.
A sharp increase in the degradation yield takes place after
6504F. The relative effects of temperature on radiolysis and
pyrolysis in causing this phenomendis are discussed in the next
chapter dealing with the pyrolysis of non-irradiated and irradiated materials, and with the temperature dependence of radiolysis and pyrolysis.
2.5.
Dose Rate Effect
In general, when the results of different experiments have
been compared, dose rate effects have not been considered, but
the initial exDeriments done at Harwell with Santowax R were
performed at 6 to 80 watt/gm for the electron irradiations and
at about 8 milliwatt/gm for the mixed in-pile irradiations (2
).
This difference affects the time of irradiation. Indeed, in
order to get the same concentration of degradation products,
a short time is needed with a high dose rate and a long one
with a low dose rate. If pyrolysis occurs during this period
(see Chapter III), the pyrolytic contribution to the total degradation will also be different -perhaps negligible at high dose
rate, and appreciable at low dose rate. Hence, the dose rate has
an indirect effect which is considered in Chapters III and IV,
c.
E
%%
0.70
0.60_
0.
E
0
0
0.50
-Q
0.40
E
0
0300.20_
400
500
600
IRRADIATION
FIG. 2.3 TEMPERATURE
RATE OBTAINED
700
CAPSULE
DEPENDANCE
IN THE
800
TEMPERATURE,
*F
OF THE TOTAL DEGRADATION
M. I.T.
IN-PILE LOOP FACILITY.
-11-
CHAPTER III
PYROLYSIS
3.1. Pyrolysis of Non-Irradiated Material
Extensive pyrolytic experiments have been conducted on
benzene, biphenyl and the terphenyls by various workers and
among them,
Wilkinson and Bates (J 1) pyrolyzed para-terphenyl
-
-
-
and Santowax R.
de Halas conducted pyrolytic studies on ortho, meta and
para-terphenyl (2).
Houllier and Puig report data on the pyrolysis of meta
and para-terphenyl (.).
Kuper has also performed pyrolytic studies on orthoterphenyl (Q4) and found a somewhat greater activation
energy than usually quoted.
A.I. workers also pyrolyZed ortho-terphenyl (2,
6
Lately, Bolt et al. (0Z) report pyrolytic constants
for meta-terphenyl and biphenyl, Whereas the values
quoted in day~ agree with their data points, those
quoted in hr~ 1 at 750 and 80 0 F seem to be off by a factor
of 10.
The results of all these studies agree within the limits of
the experimental errors. All these degradation rates were analyzed
by first
order kinetics such as:
dC
-mu". = k piC
where
t
k
C4
= time (hr)
= pyrolysis reaction constant (hrr1) of
component i
= weight fraction of component i.
(3.l)
-12-
The dependence of the reaction constant k
temperature T is given by:
k
p~i
=exp
p4iR
(--L
i with the
)
(3.2)
which is the classical Arrhenius relationship.
Fig. 3.1 shows some of the data quoted above, k
being
plotted versus 1 where T is the absolute temperature in OK.
The calculated activation energies for each isomer and for
the Santowax are, depending on the investigation, between 70
and 73 kcal/mole.
3.2. Pyrolysis of Irradiated Material
In addition to these rate constants obtained with fresh
(i.e. unirradiated) coolant, pyrolysis of irradiated material
and mixtures of fresh and irradiated coolant has been performed
respectively by Euratom (3.8) and A.E.C.L. workers (.).
The pyrolytic rate constants reported in these two communications are significantly higher than those obtained with nonirradiated
material; see Fig. 3.2 where the following data are
displayed: a) the pyrolytic reaction constant of non-irradiated
terphenyl OM.2 pyrolyzed during capsule and loop experiments,
at various temperatures (3.8),
b) the results obtained in
autoclaves with irradiated terphenyl OM.2 at one temperature
and about the same concentration of degradation products (2,),
c) data obtained at Ispra (Italy) in the Chemistry Department
of Euratom, with terphenyl OM,2 previously irradiated at
Grenoble (France), at 380 0 C, and containing approximately
35% DP (.8
l).
d) Three capsule experiments performed by
Charlesworth with Santowax OM to which 30% OMRE HB had been
added (Q.2).
Information is not available regarding the effect of the
concentration of degradation products (DP), from both pyrolysis
and radiolysis, nor on the effect, if any, of the age of the
irradiated material before pyrolysis (for the cases of post-pyrolysis
-13-
10-1
10-2
A
a.
10-3 _-
0
A
a:
0
0 o -4
3
KUPER (3-4)
010
-3,
, AI (3-5, 3-6)
O m-03, HOULLIER AND
PUlG (3-3)
* m-493 , KUPER (3_4)
-8 p - 46,
HOULLIER AND
PUIG (3-3)
Sp-4
,WILKINSON AND
-510o
3
i
FIGURE 3. I
,,
A
BATES (3-1)
0
0
Ic)
1.30
0
i.
.
.
,
.| , , , , , .
1.40
TEMPERATURE, l/T,
PYROLYSIS
f
DATA FOR UNIRRADIATED
TERPHENYLS
-
, 1
1.50
-14-
E0
I
PYROLYSIS OF NON ~RRADIATED
SANTO WAX (3.8)
3:
RESULTS
A
PYROLYSIS IN AUTOCLAVES( 3.8)
0
CHARLESWORTH
EURATOM-ISPRA ( 3.8)
DATA ( 39)
-2
10
T
cc
I.
-
C
---
A
z
0
u
w
0
c:
ED
0
I-
4&
a:
o
o
OD
u0
o
0
0
0
0
Lc)
O
lii
1.35
fL
II
II
womomommommm.lbm
1.40
1.45
TEMPERATURE,
FIG. 3.2 PYROLYSI S
II
1.50
1/T, *K x10-3
DATA FOR TERPHENYLS
II
I
I
1.55
-15-
of previously irradiated material). These two factors may have
an effect on the results obtained.
A study is now underway at M.I.T., using different DP
concentrations and a fixed temperature, to provide information
on the effect of DP.
More recently, Boyd (.__,
3.18) has radiolyzed and then
pyrolyzed two terphenyl isomers, ortho and meta, and Santowax
OM. While an increase of about four fold in the pyrolytic rate
constant of irradiated material was noted at 42400 for metaterphenyl and Santowax OM, no change was found for orthoterphenyl. This last finding seems surprising since unirradiated
ortho-terphenyl has been found to be less stable to pyrolysis
than the other terphenyl isomers and furthermore, Santowax OM
contains about 60% of ortho-terheny.
The fact remains that, if the pyrolytic constant of
irradiated coolant is 4 to 10 times greater than that of fresh
material (i.e. unirradiated), a different approach to the total
degradation rate under radiolysis at high temperature should
be undertaken. The rate of pyrolysis of unirradiated terphenyl
has, until this new data becameavailable, been used to estimate
the effect of pyrolysis in out-of-pile sections of experimental
loops and of reactor coolant systems themselves, Thus, pyrolysis
has been considered to be negligible up to temperatures on the
order of 750 OF.
For example, Sawyer and Mason (lQ),
for the 7500F Irra-
diation of Santowax OMP in the M,I.T. In-Pile Loop Facility,
have calculated the pyrolysis in the out-of-pile section for
non-irradiated terphenyl and found it to be in the order of 10%
of the total degradation rate. However, if the new pyrolysis
data for irradiated terphenyl is used, the pyrolytic contribution
becomes of the same order of magnitude as that of radiolysis,
i.e. an equivalent number of Molecules are degraded by pyrolysis
as by radiolysis.
The new data on the pyrolysis of irradiated material also
suggests that temperature control in the various sections of
loops used to study organic coolants, can be more important
than previously was considered to be the case. Generally, an
experimental loop is equipped with coolers, heaters, surge tanks
in
etc., so that the coolant is not at the same temperature
these various sections. It will be shown later that a small
variation in temperature, 50 for instance, gives an appreciable
change in the pyrolysis reaction constant and thus affects the
total degradation yields obtained with loop and capsule experiments.
Relative Role of Radiolysis and Pyrolysis,
Their Temperature Dependences
and Moffat (3.12),
The studies done by Hutchinson (L)
tend to confirm the hypothesis that most of the products formed
by the radiolysis of terphenyls are high polymer components,
3.3.
This is also verified by physical measurements, densities,
viscosities and number average molecular weights, done at M.I.T,
on irradiated samples taken at different irradiation temperatures,
and at different concentrations of degradation products. But
these measurements show also that at a fixed DP concentration,
the viscosity and density decrease as the irradiation temperatures
increase. Table 3.1 presents some measurements made at 7000F on
Santowax OMP irradiated at two different temperatures, at M.I.T.
(3.10). Measurements at other temperatures are given in the
original report (3.0).
Table 3.1
Densities and Viscosities Measured at 700 0 F
for the M.I.T. Irradiations of Santowax OMP with 33 w/o HB
Capsule
Irradiation
Density (gm/cc)
Viscosity (cp)
_ Temperture - - - - - - - - - - - - - - - - -- - - - - - 610OF
0.87
0.58
7500F
0.86
0.47
-17-
Elberg and Fritz ( 1) report recently that, besides the
variation with HB content of the coolant, they have noticed
that viscosity and vapour pressures were effected by the "history"
of the liquid, but they do not indicate in which direction these
properties vary. The history of the liquid presumably refers to
its irradiation temperature. These results suggest that, according
to the irradiation temperature, the relative composition of the
original material and the degradation products is modified.
The total degradation rate has been found to be independent
of temperature up to 600 0F after which a net increase occurs
with an activation energy greater than that related to the diffusion
of molecules, which is in the order of 2 to 5 koal/mole (3.20).
Below 600 0 F, the only significant mechanism contributing to the
degradation is radiolysis, whereas above this temperature, a new
effect characterized by a strong temperature dependence, seems
to take place.
The radiolytic process depends primarily on the ionization
of the molecules of coolant, ionization due to high energy
incoming particles -high with respect to the thermal energy
of the medium. A change in the coolant temperature will not
affect the probability of this process which creates mainly
high polymer materials. These polymeric materials and any
active species formed by radiolysis reactions, are then subject
to subsequent thermal reactions. This second effect, a pyrolytic
one, contributes to the change in the coolant composition
obtained by radiolysis, by degrading some high polymers and/or
favoring the polymerization of terphenyls and low and intermediate
boilers.
T.O. Jones et al. (3.14), considering the reactions induced
by radiation, note that it is common to consider the reactions
involving the initial "hot processes", as temperature independent,
but continue that this may not be so for subsequent thermal
reactions which involve different rate constants and for which
the temperature dependence would be expected to follow a
classical Arrhenius relationship.
-18-
In agreement with this line of thought, the total rate of
degradation under irradiation of polyphenyls has been found to
increase little, if at all, up to temperatures of about 36000
and then to increase sharply with temperatures above 4000C. A
plausible explanation of this phenomenom is that radiolysis which
is the predominant process at low temperature may have a very
small
(Possibly zero) activation energy, while pyrolysis has
a relatively high activation energy, which leads to the sharp
temperature dependence at temperatures over about 400 0 C.
For the activation energy of the pure radiolysis process,
Euratom (3.10) quotes 0.5 kcal/mole as a preliminary number.
Boyd (
has found in the irradiation of Santowax OM, between
230 and 35000 in the NEX reactor, a value of 1.6 koal/mole which
he notes, is in good agreement with results obtained by Atomics
International for the irradiation of ortho-terphenyl with a
particles, which gave an activation energy of 1,3 koal/mole.
De Halas (12l) has proposed a different explanation for
degradation under irradiation at high temperature, i.e. further
polymerization and splitting of some phenyl group of HB, characterized by changes $n the viscosity. He proposed an equation of
the following form to explain the radiolytic and pyrolytic
processes:
where
C
kg
k2
T
E
=
C -
T
(33)
= concentration of a component,
= radiolytic and pyrolytic degradation constant
for the original component,
= degradation constant of the "tar".
= 1 - C can be defined as DP,
= the dose absorbed.
Pyrolytic Reaction Constant of Irradiated Material
In view of the differences in the pyrolysis of irradiated
and unirradiated terphenyl coolants, the rate constants for
pyrolysis of an unirradiated component, k
, and for the irradiated component, kpri, will be considered separately.
3.4.
-19-
As mentioned above, both k9ps and kpr,i are temperature dependent
and an Arrhenius type relation fits the data. The values of
k pr,i obtained at M.I.T. and Grenoble (France) will be presented
in Chapter V. These experiments were done at nearly constant HB
concentrations at M.I.T. (30 to 35% HB), while the range of HB
concentrations in the Grenoble experiments seems greater (16).
In Section 3.2, it was mentioned that irradiated coolant
has been found to undergo pyrolysis at a higher rate than
unirradiated coolant, presumably due to the presence of some
type of irradiation-produced active species (i.e. more thermally
reactive with the terphenyls). In view of this, it is reasonable
to expect that the activation energy for the pyrolysis of irradiated coolant, AEpr, would be different, -probably lower- than
that for fresh terphenyl coolant, AEp.
The following notation will then be used:
k pr,i
k0pr,i ep(
pr
RT
(3,4
*
for a particular initial coolant and for a given DP concentration,
Steady-state experiments with Santowax WR are now being conducted
in the In-Pile Loop Facility at M.I.T., to determine the extent
to which kpri is dependent on the concentration of the degradation
products.
CHAPTER IV
RADIOLYTIC AND PYROLYTIC DEGRADATION RATES
4.1.
Kinetics of Coolant Degradation
In the treatment of the radiolytic degradation of organic
liquids such as terphenyls, (isomers and mixtures of the isomers),
rate equations for the disappearance of a component, or the
appearance of a new one, have been written as follows:
-
where
dC
= ki,n (C)n dT
(4.1)
i
refers to a particular component,
n = reaction order for radiolysis,
C = weight fraction of the component,
k = radiolytic reaction constant (temperature dependent)
T = specific dose delivered to the coolant,
No term representing the separate contribution of pyrolysis
has usually been included in Eq, (4.1), since the pyrolytic
contribution was estimated to be negligible beoause the rate
of pyrolysis of irradiated coolant was assumed to be the same
as that of unirradiated coolant.
4.2. Kinetics of the Radiolytic and Pyrolytic
Coolant Degradation
Where pyrolysis is important, its contribution should be
included in writing the rate equations for the disappearance
of terphenyls. The interrelationship between radiolysis and
pyrolysis is not known at this time so that the form of the
differential equation relating the degradation due to pyrolysis
and radiolysis cannot be specified with certainty. One assumption,
(perhaps the most simple) is that the degradations caused by
these two processes are independent and additive. This assumption
permits writing the differential equation in the form that for
any temperature and radiation field, the change in concentration
of a component is a linear function of the absorbed dose and
the time, aso:
-21-
- dC
where
= kR ,,n
(Cindr + k prim(C )mdt
(4.2)
kR,i,n = radiolytic constant of component i
(may be dependent on temperature and type of
radiation).
n
= reaction order for radiolysis,
kpr,1,m= pyrolytic constant of irradiated component i
(may be temperature dependent)
m
= reaction order for pyrolysis
T specific dose delivered to the coolant,
t
physical time elapsed at the temperature T,
C
= weight fraction of component i.
The validity of the assumption regarding the additivity of
radiolysis and pyrolysis made here requires verification; this
can be done, presumably, by varying the relative contribution of
the two factors by changing the dose rate and temperature. Even
granting the assumption, the values of k
and kpri for any
given reaction mechanism may be functions of temperature, coolant
composition, (including variation in both original component and
degradation product type and concentration), and type of radiatio4,
4.3. First Order Kinetics
Most of the data available on radiolysis and pyrolysis can
be correlated best using first order degradation kinetics (4.1).
Using first order kinetics, therefore for the disappearance of
a component, Eq. (4.2) becomes:
- dC
= (kRi d + k
idt) C
(4,3)
We have to consider the two following cases:
a) The pyrolysis and the radiolysis occur at a constant
temperature and during the same period of time. This means
for example, that during the shut-down period of the
reactor, the prescribed temperature is dropped to a level
where pyrolysis is negligible (such as 4000F).
b) The period of time the irradiated material is maintained
at a certain temperature is not necessarily the same as
the period of time of irradiation. This would occur if the
temperature was maintained during the shut down reactor period.
4.3.1. Timeof radiolysis_=_Time of_pyrglysis
For an irradiation time tr (hr), where the temperature is
kept constant, we can define the average dose rate r
-
d-r
trt dT dt
dtTT(0
=t dttl
r dt
t
r
-To
t 0
T
(4,4)
-
r
integrated dose
time elapsed during the irradiation
r is expressed in watt/gm when d'r is expressed in (watt)(hr)/gm.
Hence, Eq. (4.3) becomes:
dO
+
-(k
r,)
C
(4.5)
r
which, after integration, becomes:
Ci
k
= exp
CoRti
- (k
and the dimensions of kR,i and k
kR,i
=
+
)T-r
(4.6)
r
are
(watt) (hr)/(gm)
kpri = [hrT 1
As an example, we can consider the case of a steady state
irradiation
If
F = total dose rate factor in (watt)(hr)(co)/(MWH)(gm)
p = average density of the coolant in gm/cc
l = average mass of the irradiated material in gm
hence,
MWH = number of megawatt hours of reactor operation
H
= cumulative time in hr,
the dose is:
(MWH1 - MWH2 )
T
(4.7)
and the average dose rate r is:
MWH - MWH 2
H - H2
(4.8)
(
4.3.2. Time of radiolys is_# Time opyrolysis
When the time elapsed during the irradiation is different
from the time at which the high temperature was maintained, we
have to consider again Eq. (4.3) which must be treated differently.
-
dCi
Cd
Integrating this equation, where
time from 0 to (t + t ):
r
T
varies from 0 to T and the
p
-
exp (-kR,i)
pr,i(tr + t))
t
Ci
= exp
where
(4.3a)
kR,idT + kpr,idt
-(k,,
(4.9a)
+ t
+ kpri
) i
(4.9b)
tr = time of radiolysis and pyrolysis
tp = time of pyrolysis alone.
This last equation shows that the pyrolytic factor in this
latter case is greater than in the former one by an amount
(tr + tp)/tr
, proportional to the two different periods of time
considered.
4.4. G Values
In radiation chemistry, it is convenient to define two
stability terms, G(-i) and G*(-i). G(-i) is defined as the
number of molecules of component i degraded per 100 ev absorbed
in the total coolant or, in terms of the previous nptations,
-dCi
G(-i) =
x conversion factor
(4.10)
For the terphenyls (molecular weight = 230 gm), this conversion factor is
11.65 (molecules) (watt) (hr)/(100ev) (gm ct terphenyl)
sog
G (-1)
=-11.65
-~
k
G(-1) = 11.65 (k
+
c
r)
(4.11)
The second stability term, G*(-i) is defined as:
(4.12)
G*(-i) = G(-i)
Ci
G*(-i) = 11.65 (k
+
R~i
'+)
(4.13)
r
It should be noted that for first order kinetics, G*(-i) is
independent of the concentration and is proportional to the
slope of the line relating In C and the dose.
The radiolytic and pyrolytic contribution can be represented
respectively by defining:
G* (-1)
11.65 kR,i
G*(_i)
pr
11.65
r
(4.14)
and
kp(4.15)
r~
so that
G*(-i)
=
G* (-i) + G* (-i)
B
pr
(4.16)
-25-
It should be remembered that G* (-i) may be dependent on the
temperature and type of radiation, while G*
pr (-I) may be
dependent on the temperature and the concentration of degradation
products.
4.5. Relative Contribution of G* (-i) and G* (-i)
Generally it has been assumed that
G*(-i) = G* (-i)
R
and comparisons of the data obtained at different facilities,
temperatures and dose rates, have been made with this total
degradation constant.
Eq. (4.16) shows that, with this new model, G* (-I) is
actually smaller than the total G*(-i) by an amount G* (pi)
pr
which depends on two factors: the first one is the pyrolytic
constant of the irradiated material, which has been introduced
in the previous chapter; the second one is the average dose
rate delivered to the coolant,. This pyrolytic term, for very
low dose rates and consequently long irradiation periods, can
be more important than the radiolytic one.
In the following chapters, this effect is used to explain
some of the discrepancies existing between capsule and loop
experiments. Most of the electron irradiations were carried
out at high dose rates, in the order of 1 watt/gm and more,
whereas mixed in-pile irradiations of coolant in capsules and
loops are generally performed at low dose rate, in the order
of 10 to 200 milliwatt/gm. Hence a factor of 100 to 5 exists
between the time of irradiation for a given dose, and consequently at least some of the special effects attributed to
fast neutrons in the in-pile irradiations, may have been due
to pyrolysis.
4.6. Relative Effects of Fast Neutrons and Gamma Rays
It has generally been assumed that the effects of fast
neutron and gamma ray irradiations are additive (4.2). In
terms of the relative fraction of gamma rays and fast neutrons,
-26-
one can write:
G* (-i) =
where
G* (-I) + f
(4.17)
G* (-1)
Y y
N N
fN = fraction of absorbed energy due to fast neutron
interactions,
f
= 1 - fN
So that Eq. (4.16) can be rewritten as
+ f
G*(-i) = fN G*N (-i)
~ Ny
G* (-i) + G*
pr (-i) (4.16a)
Equation (4.17) can also be written in terms of G values:
GR (-i
and
where
= fN GN (-i) + fyG
G(-i) = fNGN
(4.18)
(-1)
(-i) + fyGY (-i) + G
(-i)
(4.16b)
G (-I) = CiG* (-i) = number of molecules of
component i degraded by radiolysis per 100 ev
of total energy absorbed in the totgl Qoolant.
GN(-I) = CG* (-i) is the number of molecules of
component i degraded by radiolysis per 100 ev
of fast neutron energy absorbed in the total
coolant.
G (-i) = C G* (-I) is the number of molecules of
y
component I degraded by radiolysis per 100 ev
of gamma ray energy absorbed in the total coolant.
Instead of using Eq. (4.17) and Eq. (4.16a) or Eq. (4.18)
J) have used the
and Eq. (4.16b), other investigators (.4..
following relationship:
G*(-I) was decomposed also in two terms:
G*(-i) = fN [G* (-I)
+ fy [G* (-i)
(4.19)
, have been included here to call attention
The square brackets,[
to the fact that the effect of pyrolysis was not separated from
the effects attributed to fast neutrons and gamma rays.
The relation between
[G*(.i)
,[G(-i
, G*(-i) and G*(-i)
is obtained by subtracting Eq. (4.19) from Eq. (4,16a):
- G*(i)) + fy[G*(-i)
f
G*(-1)= G* (-1)
-
(4.20)
Hence,
[G*(-1)
N
G*(-1)
f
+}
G*(-1)
G* (-1)
1
+
{ Pr
(4.21)
The second term in the right hand side of Eq. (4.21) can be
neglected when
N
Y
or when
G*(-i)
0(
The second condition is fulfilled when the irradiation is
carried out at low temperatures or when the G* values are
determined using high dose rates, so that pyrolysis is negligible.
G*(-1)l
G*
+
1
G *(-1)
-r
From Eq. (4.15) and (4.22), we see that
(4.22)
*(-
/
(
is related not only to G*(-i)/G*(-i) but also to the fast neutron
N
Y
fraction, the temperature and the average dose rate. The third
term of Eq. (4,22) and the third and fourthterms of Eq. (4.21)
will become more important for small fast neutron fraction and
low dose rate, hence emphasizing the role of fast neutrons.
Therefore, if the pyrolysis contribution is not considered separately, as in Eq. (4.16a), the calculated values of
(-1) /
G*(-1)can be significantly greater than those of the desired
ratio G*(-i)/G*(-i) (due to the pyrolytic term G
/fN GA-i)
of Eq. (4.22)) .
-28-
Pyrolytic Contribution to the "Fast Neutron Effect"
To indicate how pyrolysis corrections may be applied to
and may affect the "fast neutron effect" values, two capsule
experiments, one performed at Harwell (43_) and one performed
at Atomics International at the OGR (4*. ) will be analyzed.
4.7.
Since no pyrolytic data of irradiated material were available
at the time of A.E.R.E. and A.I. capsule irradiations,
equations similar to Eq. (4.19) were used. The fast neutron
were actually in the
Y)
ratios which were reported (4,2, Y,
form of GN4 HB)1/[G+(-PHB)] where the brackets have been added
to indicate that no pyrolysis correction was made.
Table 4.1 presents, along with the data used, the calculations
based on Eq. (4.15) and (4.21). The conclusions which may be
reached are the following:
a.
At low dose rates, the pyrolytic contribution can be
relatively important.
b. When the pyrolysis correction is applied, the "fast
neutron effect" becomes smaller than previously found.
(i.e. from 10 to 2 for Harwell, and fromw2 toN1. for OGR),
4.8. Determination of G*(-i)/G*(-i)
Several methods can be looked at to determine the ratio
G(-1)/G*(-i). One of them has been to take the total G*(-i)
values obtained at various fast neutron fractions in different
facilities, and to solve Eq. (4.19) for [G(-i)1 and G*(-)
However, if the effects of pyrolysis and radiolysis can be treated
independently, Eq. (4.16a) should be prefered. In order to use
the data from different facilities, the relative contributions
of gamma ray and fast neutron fractions, the temperature, the
experimental conditions, the dose rate, the reactor spectrum
must be carefully analyzed and related. Sawyer and Mason (4.1)
have found large discrepancies for the ratio G*(-i)/G*(-i) at
6104F and 750 0 F, depending on what data points were used.
Therefore, in order to diminish these uncertainties and errors
specific to each facility, it is recommended that the fast neutron
-29-
Table 4.1
Pyrolytic Correction to the Fast Neutron Effect
Comment
Harwell (h)
A.
Type of irradiation
mixed Inpile
mixed In-pile
Material irradiated
Santowax R
Santowax QP
(4
Temperature
400 0C
3250C
Fast Neutron Fraction
0.54
0.64
Dose Rate (F, watt/gm)
*(-coolanta
[GN(+ HB)J
N(+'OHBtl
or f
-olat
G*N((-Cop)]n
8 x 10 -3
2
0
x 103
0
assumed 10.5
[G* (-omp)
kkpr,omp
1
~N
8 x 10'4
Groi
was assumed that
.0-7881
0*5-
rv 2.4
4.5
2.20
4 x 10,5
8.3
yT~ip
G*(-omp)
from Eq. (4.21)
GG*V (-omp)
m
It
0
0.9
rv
13
[G*(-omp)j= G*(-omp)
a. Reported assuming second order kinetics
b. Due to lack of experimental data, it was not possible to get
order kinetics
this value in terms of first
c. Calculated by Sawyer and Mason (Q), assumiig first order
kinetics and G*(-omp) = 0.26.
Y
d. Values obtained from Fig. 5.1, assuming a stability to
pyrolysis equal to that of the irradiated Santowax OMP.
)
-30-
fraction be significantly changed in a single facility and the
irradiations be repeated at varioustemperatures, The data obtained
in this manner should be more consistent, since adjustments for
the various experimental parameters, different for each facility,
will be unecessary.
Eq. (4.16a) will then be used to calculate the relative
contribution of pyrolysis, fast neutrons and gamma rays.
Another technique utilized by California Research Corporation
is to perform various sets of experiments under predominantly
fast neutron or gamma ray fluxes obtained with appropriate
sources and shieldings.
4.9. Applications
Using the methods of data interpretation proposed above,
the two following chapters provide an overall survey and analys~s
of the irradiations done to the present time on the terphenyls.
A careful survey of the literature was made in an attempt to
include all the pertinent studies in this analysis.
Chapter V will compare the studies done in the M.I.T.
In-Pile Loop Facility and at Grenoble (France), using the
methods outlined in the preceding sections. Chapter VI will
present a similar analysis of the data from capsule and loop
experiments of other laboratories.
-31,
CHAPTER V
EXPERIMENTS DONE IN THE M.I.T. IN-PILE LOOP FACILITY
(FRANCE)
BY EURATOM IN GRENOBLE
AND
5.1. The M.I.T. In-Pile Loop Facility
The description and characteristics of this research facility
) and (4.12),
have already been given in two previous reports (
The first of these reports describes the loop equipment installed
in the M.I.T. Reactorg and its various components. In the second
report, the methods which are used to interpret the data are
described. These include chemical measurements, dosimetry, heat
transfer and calculation of degradation rates,
5.1.1. Compesitiog
Santowax OMP and
of the Irradiated Material
WR, which are isomeric mixtures of terphe-
nyls having the following nominal composition, have been irradiated
in the M.I.T. In-Pile Loop Facility over the range of temperatures
from 425 F to 780 0 F.
Santowax OMP
Santowax WR
Component
Ortho-terphenyl
Meta -terphenyl
weight %
10%
60%
Para -terphenyl
30%
Ortho-terphenyl
Meta -terphenyl
Para -terphenyl
Degradation products and biphenyl
15%
75%
4%
6%
has been found that the relative stability of each
terphenyl isomer was in the following decreasing order;
para>meta> ortho, (5.2) so that from a composition point of
It
view, Santowax OMP with 90% of meta and para-terphenyl should
be slightly more stable to radiation and pyrolysis than Santowax
WR, which contains initially 79% only of meta and para-terphenyl,
However, the degradation yield of each individual terphenyl
isomer obtained in both irradiations
would be the same.
-32-
5.1.2. Irradiation of Santowax OMP
Santowax OMP has been irradiated in the M.I.T. Loop at
6100F and 7500F, during transient and steady state modes of
operations for the coolant composition. The average dose rate
delivered to the coolant in the core region of the in-pile
section was 0.53 watt/gm and, due to the fact that the in-pile
to out-of-pile mass ratio was ~,0.033, 0.017 watt/gm was delivered
to the entire coolant. The fast neutron fraction was 37% and the
gamma ray fraction 63%. A circulation flow of 2 gallons per
minute gave an average transit time around the loop of one
minute.
Terphenyl concentrations were measured by gas-solid
chromatography; high boilers concentration was determined by
distillation. During the transient phase, when the degradation
products varied from zero to 60 weight %, a first order kinetics
law fitted the data. During the steady state phase, the HB
concentration was maintained at 33 w/o by distilling samples
taken from the loop and returning the distillate with fresh
material as makeup. A more complete description of these irradiations
is given by Sawyer and Mason (..2).
5.1.3.
Irradiation ofSantowax WR
Santowax WR has also been irradiated, but with a slightly
different fast neutron fraction, 44%, due to the replacement of
the central fuel element used during the Santowax OMP irradiation
by a new one. The in-pile section of the Loop is located along
the axis of the central fuel element of the M.I.T. Reactor. The
average dose rate delivered to the entire coolant, in the
Santowax WR irradiations, was 0.021 watt/gm, Continuing the
methods of analysis and different procedures developed for the
irradiation of Santowax OMP, a duplicate of the 750 F run was
performed with a transient phase and a steady-state bottoms period.
A different cut-off temperature in the distillation of the sample
taken out of the loop during the steady state period was employed
in order to re-cycle most of the quaterphenyls. Therefore, a
different terminology was used, viz. "bottoms", since the HB
-33-
notation represents only these components whose volatility is
less than paraterphenyl.
The bottoms concentration in the coolant was about 30 w/o
and the quaterphenyl concentration was 3 w/o, so that the HB
concentration in the coolant was still 33 w/o, Good agreement
was found between the two 750 0F runs with Santowax OMP and WR
for the total degradation rates.
Then, in order to investigate the temperature effect on
the degradation rate, a 7800F irradiation at steady state and
25% bottoms took place. After this run, the loop was kept at
4250F for a three weeks transient period, during which radiolysis was the only process contributing significantly to the
degradation. Finally a steady state phase was performed at
7000F with a bottoms concentration of 30 to 35 w/o, to complete
the study of the temperature effect. The complete details of
these runs and the results of the measurements done will be
published in a future report (J.1).
5.1.4. Irradiation Procedure
For the irradiations of Santowax OMP and WR, the in-pile
capsule was maintained at the prescribed temperature t,54F,
during the operating period of the M.I.T. reactor. The reactor
whose power level is 2 MW (th.), is generally shut down every
week-end, from Friday evening to Monday morning. During these
shut-down periods, the loop temperature was lowered to 4250F,
so that the pyrolysis was negligible during these periods. When
the reactor was starting up, the temperature was raised. The
time of cooling down to 5000? of the loop is less than half an
hour, and the heating up time about one hour. Depending on the
irradiation, the steady state periods varied from 15 weeks (6100F)
to about 3 weeks (7800F).
In its present design, the M.I.T. Loop, shown schematically
in Fig. 5.2, has some temperature gradients throughout its
different sections. Wall and immersion thermocouples record
constantly the coolant temperature, in order to follow its
variation. If T is the irradiation temperature in OF, most of
the coolant is kept between T and T - 200F, so an iterated process
was set up to calculate the relative contribution to pyrolysis
in each section. This method is developed more completely in
Section 5.3.3.
5.1.5. Dosimetry
An extensive dosimetric program, involving calorimetric and
foil measurements was underteken to determine the fast neutron
and gamma ray dose rates in the in-pile section, Adiabatic
calorimeters containing various absorbers such as carbon, aluminum,
polyethylene, polystyrene, beryllium and Santowax, were lowered
in the reactor facility before and after the irradiations in the
In-Pile section for the OMP irradiations. The total dose was also
measured with the new element in place. The gamma ray and fast
neutron heating rates were found by analyzing the heating rates
in the different absorbers which presented different gamma ray
and fast neutron attenuation properties. Details of these methods
are given by Sawyer and Mason (l).
Concurrently, during calorimeter measurements and terphenyl
irradiations, foil activation measurements were performed
regularly. The foils used are listed below. their activity
was measured in order to calculate the thermal, epithermal and
fast neutron fluxes.
Flux
Thermal
Epithermal
Fast
Foils Used for Neutron Flux Measurements
Resonance or Effective
Reaction or
Threshold Energy
Detector
(eff)
Co5 9
C05 9
CU63
S3 2 (n,p) P32
N15 8 (n,p)Co5 8
Mg2 4 (n,p)Na2 4
Al '(n, a)Na 2 4
120
570
3.0
2.9
6.3
8.1
ev
ev
Mev
Mev
Mev
Mev
(M.I,T.)
Effective
Cross-Section
(barns) aeff
0.3
0.41
0.051
0.1
-35-
the activations of
A Watt fission spectrum was used to fit
the threshold detectors and an effective cross-section was
calculated for each one of them by iteration using the spectrum,
This method is more reliable than using literature values for Eeff
and aeff since arr depends primarily on the actual neutron flux.
Good agreement was found between the calorimeter and the
foil measurements (the latter are about 10% lower than the former).
An average dose rate of 0.53 t 0.02 watt/gm was calculated
in the in-pile section, 37% being delivered by fast neutrons,
for the OMP irradiations. After the replacement of the fuel
element, the average integrated dose rate for the WR irradiations
was 0.62 watt/gm, 44% of which was due to fast neutrons.
It should be noted that, while the average dose rate for
the total coolant is only about 20 mw/gm, the actual energy
delivered in the in-pile capsule is in the order of 500 (mw)/(gm),
which value is easier to measure than low dose rates.
5.1.6. Calculation Procedure of.G_and G* Values for
gt2Etd:g§tte and Transient Periods
The complete details of these procedures are given by
Sawyer and Mason in the report on the effects of reactor irraOnly the main
diation on Santowax OMP at 6100F and 7500F (g2).
formulas will be presented here. For a transient phase, an IBM
709/7090 Fortran program called MNDEG applies a least square fit
to the concentration versus specific dose relation and then
calculates G and G* values for the given data, This program was
used in the present study to analyze the data obtained at other
laboratories.
For a steady state -HB or bottoms- irradiation, a mass
balance around the loop is set up during that period. G(-i) for
a specific component i is given by
G(-i) = 11.65 (net grams of I makeup + A)(5)
F
p (MWH2 - MWH )
-36-
G*(-i)
and
where
A
F
= G(-i)
Ci L
(5.2)
is a correction factor taking into account the
difference, if anyq of the concentration of a
component between the start and the end of the
steady state.
is the average in-pile dose rate factor in
(watt)(hr)(cc)/(MWH)(gm)
is the average density of the coolant in
C
MWH2
(gm)/(cc)
is the average loop concentration of the ith
component, in w/o
- MWH1 is the difference between the number of
megawatt hours at the end and at the beginning
of the steady state.
These two formulas hold for each isomer, ortho, meta, paraterphenyl and the coolant omp. For the high boilers, HB (or
bottoms) and the low and intermediate boilers, LIB (or LIB + 00)
G and G* values can also be defined.
G (-+ HB) and G (or
G (-+
LIB)
Bottoms) and G (-+ LIB + #
)
The HB concentration is calculated by distillation and the
LIB is obtained by difference,
LIB = DP -B
And since
OMP = 100
G(-omp) = G(-> HB)
-
(HB + LIB)
+ G(-P LIB)
(5.3)
G* values which are a measure of the HB and LIB production rates
were converted into an equivalent amount of terphenyl degraded,
i.e.:
(5*4)
HB) = G(-* HB)
G*(CL
omp
-37-
and
G*(--+ LIB)
so that
G*(-omp) = G*(-+, HB) + G*(-* LIB)
G(-+ LIB)(55)
omp
(5.6)
These definitions are different from the values frequently
used in the literature where initial production rates for the
HB are defined by taking an average molecular weight of 460,
i.e., twice the molecular weight of terphenyl. In this respect,
the following relation holds (5.4) (assuming no production of
LIB):
G(-coolant) = 2G(-+ HB)
(5.7)
As shown in Eq. (5.1) and (5.2), the G* values do not
depend directly, for a steady-state period, on the circulating
mass of the loop, whereas its knowledge is necessary to calculate
the dose during transient periods. It has been estimated that
the total mass of the loop is known within ± 5% and the circulating mass, to within t 10%. This distinction has to be made,
since some places of the loop, such as valves, back of a pump,
can be filled with non-circulating coolant, the concentration
of which is estimated to be approximately equal to the average
loop composition.
5.2. Euratom Loops
No complete report is yet available on the different
techniques and irradiation procedures used by Euratom workers,
but the following information has been obtained (il).
5.2.1.
IrradiationProcedure
Terphenyl OM.2 whose composition is given below, has been
irradiated in two loops, BLO2 (total volume of 30 liters, of
which 7.8 liters are irradiated), and BLO3 (total volume of
36 liters, of which 6.4 liters are irradiated), at various
temperatures, ranging from 2000C to 450 0 C. The loops are in
the Melusine Reactor at Grenoble (France). The flow rates were
respectively 2 m3/hr and 4 m3/hr.
Composition of Terphenyl OM.2 (5d)
Ortho-terphenyl
Meta -terphenyl
Para -terphenyl
20.5%
76.0%
3.5%
The temperatures of the loop are within + 5 C of the
prescribed value and the temperature distribution around the
loop is controlled by immersion thermocouples and independent
heaters within t 20 C. Most of the G* values quoted are obtained
with transient runs since it is believed that the circulating
mass is known within 5% and accurate numbers can be calculated.
An analytical micro-distillation is perfonmed on the
irradiated samples in order to separate the HB products from
the terphenyls. The distillate is then analyzed by gas chromatography and the terphenyl concentration calculated.
5.2.2.
Dosimetry
Two different techniques are used to calculate the dose
deposited by the fast neutron and gamma ray interactions(j).
Threshold detectors (e.g. aluminum, nickel and sulphur) are
activated in various places of the irradiate4 section to determine
the fast neutron flux. Due to the position of the two loops
beside the core of the swimming pool type reactor, Melusine,
the fast neutron flux drops by about a factor of 10 across the
irradiated section. Hence, from these foil measurements the
average fast neutron dose rate absorbed in the coolant can be
estimated.
Moreover, an isothermal calorimeter containing graphite,
measures the absolute dose to the carbon, so that with the
foil measurements above, the relative contribution of gamma rays
and fast neutrons is determined. This calorimeter is also used
during irradiations to monitor the total dose received by the
coolant.
5.3.
Results Obtained at M.I.T.
Comparison with Euratom's G* Values
5.3.1. Determination_of.G_(-il
Two irradiations were conducted at M.I.T. at low temperatures,
0
425 F and 610 0 F, in order to find out the values of G* (-1).
Table 5.1 presents the G* values obtained for Santowax OMP and
Santowax WR (j5). These values show that the stabilities of each
component are the same within the experimental errors and that no
temperature effect is noticeable. As noted by Sawyer and Mason (ja2)
the steady state values are more accurate than the transient ones
and therefore,
G*(-omp) = 0.26 + 0.01, independent of temperature,
R
will be used in the following calculations. It is interesting to
note that this value of G*(-i) = 0.26 can be used also for the
individual isomers. Similarly, Euratom workers have irradiated
terphenyl OM.2 at low temperature (j.6) and their data are
presented in Table 5.2. Estimated errors or confidence levels
for these results were not reported. From these G*(-omp) values,
Houllier has calculated an activation energy of 0.54 koal/mole,
but he recommends more irradiations at 240 and 2800 in order to
know whether or not this low activation energy for radiolysis is
significant (
But even with this small temperature dependence, it is
remarkable to find the same G*(-omp) = 0.26, at 610 0 F for both
facilities, since the fast neutron fractions are respectively
17% for Melusine and 37% for M.I.T.. Therefore, from these two
loop experiments, there does not seem to be any fast neutron effect
at these low temperatures (i.e.,
the ratio G,/0* = 1).
5.3.2, Relative_PyrolyticandRadiglYtig.Cgntributions
In the M.I.T. Loop and at Grenoble .jPrance2
Most of the data obtained at M.I.T. and by Euratom are
presented in this section and have been re-analyzed, following
the approach mentioned
in Chapter IV.
Table 5.1
G*(-i) Values for the 4254F and 6l0*F Irradiations at M.I.T.
G*(-i) =G
Irradiation
Type-of
ISantowax
Capsule
Temprature
Irradiation
G*(-o.
)
G*(-m' )
G*(-p
I
G*(-omp)
Transient(a
0.31
0.05
0.26 ± 0.04
0.26 t 0.04
0.27
610
wa
OMP
Transient I
0.34 - 0.09
0.33 - 0.06
0.21 - 0.10
0.30 - 0.05
610
OMP
Transient 1
0.25 - 0.04
0.24 ± 0.04
0.26
-0.05
0.25 - 0.04
610
OMP
Steady (b)
0.26 - 0.02
0.26 - 0.02
0.28 - 0.03
0.26 - 0.02
425
0.04
State
(a) estimated maximum possible errors
(b) 95% confidence limits. Standard deviations are one half of the errors quoted.
4:0
Table 5.2
Preliminary Euratom's G*(-i) Values
200 0 C (3920F) 320 0 C (608 0 F) 3600C (6800F)
Temperature
----------------------------- ------------Average
Dose rate
44.5
45.4
40.0
Gr
0.24
0.26
0.31
G*(-omp)
Table 5.3 presents the different G* values calculated for
700, 750 and 7800F irradiations of Santowax WR and OMP, at
M.I.T.. The various irradiation conditions have been summarized
at the beginning of this chapter. The M.I.T. results for
Santowax WR will be compared with the Euratom results for
terphenyl OM.2 since the two coolant have the same composition.
Assuming a temperature independent radiolytic degradation
yield of 0.26 molecules degraded per 100 ev absorbed in the terphenyls, the pyrolytic contribution G* (-i) was calculated
from
(see Eq. (4.16))
G* (-i) = G*(-i) - 0.26
pr
(5.8)
and the pyrolytic constant of irradiated material was determined
from (see Eq. (4.15))
r G*
kpr,i
(-i)
11.65(59
r being expressed in watt/gm.
The values of the M.I.T. irradiations are listed in Table 5.4
as kpr,i since, as it is shown in Section 5.3.3, these values
are mass-average pyrolytic degradation constants characteristic of
the M.I.T. Loop. To calculate the pyrolytic constants of irradiated material, Euratom workers have used equations similar
to Eq. (4.16) and (4.15), G* (-i) equal to 0.26 at 320*C,
having an activation energy AER of 0.54 kcal/mole.
In order to compare the Euratom and M.I.T, values, the
pyrolytic constant kpr,
was recalculated at M.I.T., assuming
no temperature dependence for G*(-i), (i.e. dER = 0), and
temeraur
R
using Eq. (5.8) and (5.9). The result of these calculations
and Euratom values are presented in Table 5.5 as well as in
Fig. 5.1, which contains the following information:
- Curve I displays the first order pyrolytic constant of
non-irradiated terphenyl OM.2 obtained by Euratom
workers using autoclaves
Table 5.3
G* Values for the 700, 750 and 780 F Irradiations at M.I.T.
Irradiation
Capsule
Temperature
(OF)
G*(-i) = G(-i)/C (b)
Santowax -------- --------- ---------G*(-ot)
G*(-m# )
G*(-p# )
.(-HB)(a)(b)
-------or
*(-Bottoms)
G*(-omp) *(
ttoms
G*(,LIB)(a)(b)
or
G*(LB+4)
2
3
-------------------------- ------- -2-------- --------------------------------------
700
WR
750
750
W
780
WR
0MP
0.44 t0.0 3 0.35-0.03 0.420.04 0.37-0.0
3.80*0.05 0.53*0.03 0.39±0.03 0.55±0.0
3.79±0.07 0.52±0.03 0.45±0.03 0.53±0.0
.17t0.08 0.71±0.05 0.57±0.05 0.77±0.0
0.34-0.02
0.45±0.02
0.03-0.03
0.10±0.06
0.47*0.02
0.72±0.03
0.06*0.05
0.04±0.06
(a)A molecular weight of 230 gm was used for the calculation of G*(* HB or Bottoms)
and G* (- LIB or LIB +964).
95% confidence limits. Standard deviations are one half of the errors quoted.
Table 5.4
Pyrolytic and Radiolytic Contribution in the M.I.T. In-Pile Loop Facility
Irradiation
Capsule
Temperature
(oF)
Average
Dose Rate r
Santowax
(milliwatt)
gm
425
WR
700
WR
WR
750
780
WR
610
OP
750
OMP
i3
I3
Circulating
Mass of the
Loop
(gm)
G*(-omp)
kpri
(hr
24.6
21.7
20.7
20.3
5240
5300
0.27
5380
5340.
0.55
17.8
17.3
5560
5350
0.26
-
G* (-omp)
pr
G*(-omp)
0.37
0.77
0.53
40
i
0.26
0.26
0.26
0.26
V0
0.26
0.26
A/0
0.11
1.86x1O
0.29
5. 16x10 _
0.51
9.74xl&.
0.27
6
4.00xl04
-
Table 5.5
Pyrolytic and Radiolytic Contribution in BL02 and BLO3 (Euratom)
for Terphenyl ON.2
0
kpri obtained
p Euratom(a)
Temperature
Dose Rate
360
40.0
0.31
380
44.7
0.36
400
400
41.1
16.6
408
39.6
410
420
15.0
0.48
0.70
0.58
1.16
430
440
450
38.5
39r.2
39.1
G
41.6
0.78
1.06
3.1 x 10~4
6.1 x 10~4
5.75x 10~4
8.7 x 10~4
1.04 x 10-3
1.68 x 10-3
2.4 x 10-3
1.50
2.96
3.95x 10-3
8.81x 10-3
kpri obtained
at M.I.T.(b)
1.72 x 104
3.83 x 104
7.76 x 10~4
6.27 x 10~4
10.87 x 10~
1.16 x 10-3
1.85 x 103
2.64 x 10-3
4.17 x 10-3
9.06 x l0-3
(a) AER = 0.54 kcal/mole
(b) AER = 0. kcal/mole
G*( -i) = GT
a
reported by Euratom
-45-
I
-o')
o
0
0
0
0
I
I
0
a
0
(D
r.)
v
k(
N
)
o
0
0
Skp,UNIRRADIATED
ITk
TERPHENYL OM- 2(5.6)
TERPHENYL 0M-2
IRRADIATED
LOOP AND CAPSULE EXPERIMENTS
EURATOM - GRENOBLE (5.6 )tEgO.54
7
II[
kprCAPSULE
EXPERIMENTS
EURATOM - ISPRA ( 5.6)
z
-3
kprM. I.T. AND EURATOM
K
DATA AER=0
WR (M.IT.
£kpr, SANTOWAX
z
)
kpri SANTOWAX OMP (M.IT.
5
A kprj M.IT. TEMPERATURE
ITERATED. AER=0
kprEURATOM , AER =0
0.
m kprEURATOM
I0
LER=0.54
ir
-4
10
5
LL
o
o
0
0
0o
-0
0
Lol
0L
0
0
0
to)
wDN-C
I
0
0
(D
I
1.40
FIG.5.1
1.60
1.50
TEM PERATURE . I/T, *K~Ix
PYROLYSIS
1.70
DATA OF IRRADIATED TERPHENYL
OBTAINED BY EURATOM AND M.I.T.
I
I
I
I
1.84
- Curve II displays the first order pyrolytic constant of
terphenyl OM.2 irradiated in the Melusine loops, assuming
a temperature dependence of 0.54 kcal/mole for the
radiolysis, (AE = 0.54) (jM).
- Curve III displays the first order pyrolytic constant of
irradiated terphenyl OM.2 pyrolyzed in autoclaves at
Ispra (Italy) (5.).
- Curve IV represents the least square fit of both
Euratom data from 360 to 440 0 C, listed in Table 5.5,
and M.I.T. data obtained with Santowax WR listed in Table
5.4 treated assuming no temperature dependence for radiolysis (AER = 0).
The calculated pyrolytic constants quoted in Table 5.4 and
Table 5.5 are also displayed.
Before explaining the temperature iteration of the M.I.T.
data, Fig. 5.1 brings the following remarks:
a. The pyrolytic constants of irradiated coolant obtained
at M.I.T. and Grenoble (France) give a consistent set of values,
which can be represented by a relation such as
kpr
kr
exp
~
r
(5.10)
Assuming AER = 0, the M.I.T. data alone yield a value of
AEpr,omp of 32.4 kcal/mole and the Euratom and M.I.T. data
together give AEpromp = 33.6 kcal/mole; these values are not
significantly different. An activation energy AEpr : 49.2 koal/mole
was calculated by Euratom for Curve II, assuming AER = 0.54
kcal/mole for radiolysis.
It is suggested that more data should be obtained in the
Euratom and M.I.T. Loops to substantiate these preliminary
values. Since the M.I.T. and Euratom results were found to be
consistent with one another (see Fig. 5.1), when no temperature
effect on radiolysis was assumed and Eq. (5.8) and (5.9) were
employed, it would therefore be reasonable to assume that
-47-
agreement would also be obtained for another set of consistent
assumptions regarding the temperature dependence of radiolysis,
b. The magnitude of the rate of pyrolysis of irradiated
coolant at any temperature is significantly greater than for
non-irradiated material, although the activation energy appears
to be smaller.
o. Even with different fast neutron fractions (e.g. 44%
at M.I.T. and 20% at Grenoble) and dose rates (e.g. 20 mw/gm
at M.I.T. and 40 mw/gm at Grenoble), an agreement is found
between the reported values when they are treated consistently.
d. Curve III, obtained at Ispra, is higher than Curves II
and IV, but no information on the techniques used to get these
values is given and thus, they cannot be interpreted at this
time.
5,3.3. Temperature Iteration of the ,..T.
ExcperimentalPyrolyt ic Constants
Due to the magnitude of the pyrolytic constant of irradiated
material presented in Table 5.4 and calculated from Eq. (5,8)
and (5.9), it was realized that the temperature variation around
the loop would lead to significantly different pyrolytic contrjbutions for each section of the loop. Therefore the values
obtained from Eq. (5.8) and (5.9) are in fact the mass-average
kg
for different
resulting from the absolute value of k
portions of the loop. It was assumed that the pyrolysis for
each approximately isothermal section j of the loop, fits an
Arrhenius type relation as in the following equation:
k0
kpr,i
where
j
T
' pr,i
e
-Apr~i)
exp (-
(5.14)
refers to a section of the loop
the average temperature in section j
AEpr,i = the pyrolytic activation energy of irradiated
component i.
R = conversion factor,
from
The experimentally determined mass-average kpri
Table 5.4 is the result of the pyrolytic degradation ocouring in
each of the various isothermal sections of the loop. Thus the
following relationship applies:
M0
M
pr,i
where
exp (- -5.r)
M
Ci
c
(512)
total mass of coolant in section J,
V p3 (V being the volume of section J, and
p3 the density of coolant in section J.)
= concentration of component i in section J.
It was assumed that the concentration of component
i was the same throughout the loop so that the
Ci
terms cancel out in Eq, (5.12).
The measured temperature profile around the loop and the volume
of each section (i.e. the T 's and V3 's) are listed in Table
5.6 and shown in Fig. 5.2. The p3 can also be obtained from the
M.I.T. measurements (J2,
).
The object of the iteration technique was therefore to
which
and AE
produce a single set-of values of kp
pr,i
pr94
satisfies the experimental values of
kpr,i, Mj and T for
all the irradiations carried out at the different irradiation
capsule temperature. There are several methods of iterating,
the details of the one employed here are described in Appendix
A4.
5.3.4. Pyrolytign
gtheTerhenl Isomer
The same iterative process can be carried out with each
individual terphenyl isomer, Eq. (5.12) is iterated using the
calculated mass-average pyrolytic constants shown in Table
5.7, following the method outlined in Section 5.3.3. Here
again the radiolytic contribution was assumed independent of
0). Fig. 5.3 displays the iterated values
temperature (ABR,
and it should be noticed that an equal temperature correction
SECTION 2
SECTION 10
COOLERS
SECTION 9
I
I
SECTION 7
I
TEST
HEATER
14
LIQUID SAMPLER
SECTION 8
FIGURE 5.2
FOULING
PROBE
-
SCHEMATIC OF CIRCULATING VOLUME OF LOOP
Table 5.6
Temperature Profile of the M.I.T. In-Pile Loop Facility
Nominal
Section Circulating Volume
3
(cm )
1
2
407
3
489
750OF
Irradiation
70F75F78F
Temperature
Temperature
500
of
(-F
(oF)
700
693
685
750
743
736
800
4
4a(a)
(a)
-a,
5
6
7
1320'
370
444/
8
530
9
341-
10
11
246
200>
Filter No.
1 on Figure
360
680
450
708
6oo
730
360
730
450
761
615
500
707
444
758
680
788'
407
720
5,.2.
780 F
Loop Section
(o
780
772
765
761
400
761
450
787
420
570
786
0
-3
1-
was found. Along with these data, the pyrolysis constant of nonirradiated ortho and meta terphenyl cited in Chapter III, are
given for comparison. The data for para-terphenyl are scattered
because the precision of measurements was not as accurate for this
component, since its concentration was very low for the Santowax
WR irradiations, of the order of 2 to 4%.
5.4. Conclusions
Based on a preliminary report of Euratom workers and the
data acquired at M.I.T., a new interpretation of the role of
pyrolysis was proposed. Assuming a constant radiolytic degradation rate, values of the pyrolytic constant of irradiated
coolant were calculated and a good agreement was found between
the values obtained at M.I.T. and Grenoble (France). The Euratom
data suggest the possibility of a small temperature effect on
radiolysis, but the significance of this small value has not
yet been established. A comparison of the Euratom and M.I.T.
loop results, obtained with different fast neutron fractions,
does not indicate any fast neptron effect.
Table 5.'7
Pyrolytic and Radiolytic Contribution in the M.I.T. In-Pile Loop
Facility, for the Terphenyl Isomers During the Santowax WR Irradiations
Irradiation
Capsule
Temperature
Isomer
ortho-terpheny3
750
21.7
20.7
0.42
0.39
9.61 x 10~4
1.59 x 10-3
1.67 x 10 4
4.81 x 104
7.86 x 10~4
2.97 x 104
2.31 x 10~4
780
20.3
0.57
5.41 x 104
750
780
_________________
700
&
3.35 x 10
0.44
0.80
700
para-terphenyl
kpri (hr
G* (-1)
Dose Rate r
21.7
20.7
20.3
21.7
20.7
2G,3
700
750
780
meta-terphenyl
I
Average -
A_________________
1.17
0.35
0.53
0.71
.1
1
)
-53-
MATERIAL
-3
~Id
0
5 -
z
z
-
0
V5
ORTHO
META
-4
10
5
LL
0
0
In
OD
1.40
U.
0
U.L
IU.
0
0
0
0
80
0
1.50
160
TEMPERATURE,
FIG-5.3
LL.
0
0
1.70
I/ T, OK x 10- 3
PYROLYSIS DATA OF TERPHENYLS
OBTAINED AT M.I.T.
CHAPTER VI
REVIEW OF IRRADIATIONS PERFORMED
BY VARIOUS FACILITIES
6.1. Irradiations Performed at Harwell (England)
Extensive experiments have been conducted at Harwell
(England), to study the radiolytic stability of different
terphenyl isomers and Santowax R under various types of
l.3,
radiations (6l
6.6, §Z).
Electron irradiations were first carried out between
3000C and 4000C to obtain initial rates of formation of high
Mixed in-pile experiments were
boiler components: 1Ge(+3 HB)}
also performed in BEPO and total rates of formation of HB
were obtained. By assuming that gamma rays and electrons gave
the same radiolytic decomposition, the initial rate of formation
of HB due to fast neutrons, was calculated at various temperatures and found to be much greater than that of gamma rays. More
recently, irradiations in a pure gamma field were reported with
G(HB) values 50% higher than previously found with electrons
(§-.).
These studies are reviewed in the following sections and
a new interpretation of the G values obtained with electron,
gamma ray and mixed in-pile irradiations is given in order to
explain some of the discrepancies.
6.1.1. Irradiation Procedure
---------------
For the electron irradiations (6.1), a stainless steel cell
shown schematically on Fig. 6.1, having a total volume of about
13 cm3, was employed. It was installed in front of a horizontal
beam of electrons, which passed through a nickel or molybdenum
window before entering the cell. Thermocouples were located in
a thimble whose tip was just at the limit of the irradiated
volume, so that the irradiation temperature could be obtained.
(The range of 1 Mev electrons in terphenyls may vary between
INLET PIPE
THIMBLE
I
kun
VOLUME
I
FIG. 6-I
%--I INCH
SCHEMATIC OF HAR WELL ELECTRON
IRRADIATION
CELL
I
-56-
0.5 and 0.6 cm., depending on the density and therefore the
temperature and the concentration of DP). This means that only
a small portion of the total mass (generally 7,7 gm) was irradiated. The temperature recorded was maintained usually within
100C of the required control temperature (6.1).
For the BEPO reactor irradiations (_2) silica capsules
containing about 4 gm of coolant were irradiated in a vertical
hole, TE2. The temperature was kept within 540 and remained the
same for periods up to 6 weeks, even during shut-down periods
of the reactor. Irradiations of every terphenyl isomer and
Santowax R were carried out in these two facilities at three
temperatures, namely: 3000C (5720F), 35000 (6620F) and 4000C
(7520F).
6.1.2. Dosimetry
The energy absorbed by the coolant under electron irradiations, was calculated as the product of electron energy and
charge input, with modification by some correction factors
taking into account backscattering, loss of energy in the cell
window, etc., (§.2). The dose rate in these experiments varied
from 6 to 80 watt/gm (6.2) and the irradiation exposures from
0 to 100 (watt)(hr)/(gm).
For the BEPO pile dosimetry, cobalt and gold foilsbare
and Cd-covered, were irradiated and counted on a GM counter to
relate the activity of these foils and the thermal neutron
density. Measurements using adiabatic calorimeters were also
performed in order to relate the thermal neutron dose and the
energy absorption in different absorbers, including polyethylene
and graphite (6.4). With each capsule, a cobalt foil was irradiated and its activity measured using the same GM end-window
counter; the energy deposited in the coolant was thus determined
using
the previous calibrations.
The dose rate obtained in BEPO -8 milliwatt/gm- (54% of
which is due to fast neutrons) is much lower than with the
electron work, the ratio of these two varying from 10~3 to 10~.
-57-
6.1.3. Analytigal Determinations andExperimental Resultg
The results of the chemical analyses are given in the first
report of the series (6.1). No gas chromatography analysis was
performed to calculate the disappearance of starting material
but the polymer content was determined by a micro-sublimation
technique. These high-polymers can be identified as products
with a lower volatility than para-terphenyl and do not include
the low and intermediate boilers.
Initial G(+ HB) values for electron and in-pile irradiations
"obtained by inspection of the first few (experimental) points"
were reported for the appearance of polymer. Table 6.1 summarizes
these results given by Harwell (,
.6), As noted in these
reports, the results show a greater decomposition rate during
the in-pile irradiations than during the electron irradiations,
This conclusion will be analyzed in the next section.
Table 6.1
Initial G Values for Electron and Pile Irradiations (A.E,R,s.)
Second Order Kinetics (
6.6)
Component
Irradiated
------G ("-"RBH)
~~
ele
-----
oC
400C
ron
lconpl
Ortho-terphenyl
Meta-terphenyl
0.18
0.19
0.59
0.58
Para-terphenyl
Santowax R
0.18
0.19
eet
niI
0.47
0.20
0.19
0.18
0.70
0.63
0.58
0.28
0,24
0.29
0.99
0,77
0.88
0.51
0.19
0.59
0.21
0.83
The HB content was also plotted versus the dose and a
second order kinetics expression used to fit the data,
According to Harwell, the radiolytic degradation rate was
written as
d
= kx2
(6.1)
with T = dose in watt-hr/gm
x = concentration of original substance, here set equal to
(1 -
k = total reaction constant
P = weight per cent HB.
It was further assumed that the rate of H5 formation was
equal to the rate of degradation of the original substance
(i.e., terphenyl or coolant), thus neglecting the formation of
Low and Intermediate Boilers (L.I.B.). From Eq. (6.1) initial
G values for the formation of HB can be defined as
G, (-
HB) = 11.64 k
(6.2a)
and Harwell reported the results as G (-coolant) by assuming
G0(-coolant) = G
(-
HB)
(6.2b)
These initial G values, obtained assuming second order kinetics,
can be compared to the G*(-i) values defined with first order
kinetics, since they both are used to represent the initial
degradation yield of the terphenyls. However, it should be noted
that they are not equal, the initial degradation yield calculated
with second order kinetics being always greater than that calculated
with first
order kinetics,
The G (-coolant) values quoted by Harwell are presented in
Table 6.2, and will be considered in further discussions. The
values in Table 6.2 depend on all the experimental points (and
second order kinetics) while the values in Table 6.1 are based
on the slope of the curve drawn through the first few points.
Table 6.2
Harwell Initial G Values, G0 (-coolant), Second Order Kinetics
Component
Irradiated
G (-coolant) = G(-* HB)
004~o
-36W
electron
electron
pile
Ortho-terphenyl
0.21
0.68
Meta-terphenyl
0.16
0.19
0.16
0.67
0.62
0.17
0.17
0.63
Para-terphenyl
Santowax R I
Santowax R II
0.70
electron
0.19
On the basis of the above G (-coolant) values and the reasonable
assumption that electron and gamma ray degradation yields were
equal, the increase in the G (-coolant) values from electron to
mixed in-pile irradiations was attributed to the effect of the
fast neutrons in BEPO.
However, the following interpretations also seem to explain
some of the discrepancies found between the mixed'in-pile and
electron G (-coolant) values.
6.1.4.
Interpretation of the Electron Irradiations
In general, prediction of a given total amount of polymer
(or degradation of a given amount of coolant isomer) in a sample
by:
a. irradiation of the entire sample,
b. irradiation of a portion of the sample in the absence
of complete mixing,
do not produce the same radiation yields (see Appendix Al).
A schematic of the Harwell electron irradiation capsule is
shown in Fig. 6.1. It should be noted that the volume being
irradiated is a small portion of the total volume gf material
in the capsule. Further, because of the geometry, it is possible
that complete, continuous mixing did not occur. Since the cell
mixing was provided, the
is rigidly mounted and no artificial
mixing of the different species in the capsule during irradiation
would therefore depend on diffusion processes which would not
be expected to provide a uniform concentration of each component
in the irradiated and unirradiated volumes.
Fig. 6.2 represents possible profiles of the DP concentration
in the irradiation cell, after two irradiation times, ti and t2'
when t2 > tl' It seems reasonable to assume a higher concentration
of degradation products in the irradiated volume, since all the
energy is deposited in this small portion of the cell. Even if
the colour of the liquid appeared uniform throughout the cell
after irradiation, as mentioned by Harwell, (6.1), this test
does not insure an irradiation equivalent to that of a wellmixed experiment.
a
z
0
II-
z
w
0
z
I
0
C.)
I
0
0
FIG.
DISTANCE FROM THE WINDOW
6-2
L
QUALITATIVE REPRESENTATION
OF THE HB CONCENTRATION IN THE
IRRADIATION CELL,
Lack of mixing between the irradiated and unirradiated zone would
allow the concentration of terphenyls in the reaction (i.e.
irradiated) zone to decrease more rapidly (and the concentration
of HB product to rise more rapidly) than if mixing were effective. For reactions following higher than zero order kinetics,
the rate of reaction is dependent on the concentration of
reactants in the actual reaction zone. For first or higher
order kinetics, the local decrease in terphenyl concentration,
due to poor mixing, would therefore cause a decrease in the
total rate of radiolytic degradation of terphenyl in the
capsule. Consequently the amount of HB in the entire capsule
(i.e. the average HB concentration in the capsule) would be
lower than if all the coolant in the capsule had been uniformly
irradiated. See Appendix Al for further detailed discussion of
the effect of possible poor mixing during the electron irradiation.
Hence, a non-mixing effect might explain the relatively low
degradation yield obtained with electrons and therefore suggests
that the[G (* HB) values used in calculating the ratio of
(+- HB)1 may have been too low (since [G (-- B)]=
N(- HB) /(G
[G(- HB) . Furthermore, recent data obtained at Harwell (_6)
with gamma ray irradiations indicate higher G (-*HB) values
than those previously usedas shown in Table 6.3.
Table 6.3
Comparison of Initial G (-*- HB) Values From
Electron and Gamma Ray Irradiations (A.E.R.E.) at 350 0 C
[Type of Irradiation
G (-o-HB)
4Date-
Electrons
0.18
1959
Gamma Rays
0.28
1963
As noted by Harwell, this difference between the two
G(. HB) values may be due to the different irradiation times:
few hours for the electron irradiations and more than four
months for the gamma ray irradiations.
-62-
In attempting to estimate the contribution of pyrolysis to
the lengthy gamma irradiation experiments, using Fig. 5.1, the
fact that the HB concentration in the sample rose to only about
8% over the entire experiment must be considered. The average
pyrolysis rate constant over the entire experiment could not be
expected to be as high as those shown in Curve IV, where the HB
concentration was about 30%. If at 3504C, the pyrolysis rate
constant for the gamma irradiations is estimated to be a factor of ten
higher than that of unirradiated terphenyls, the pyrolysis correction in the reported G values of Table 6,3 is less than 0.01
(an average dose rate of I milliwatt/gm was assumed for this
calculation) so that
[G Y
HB)
= G-P( HB)
0.28
Thus, differences in pyrolysis between the electron
and gamma
ray irradiations does not appear to explain the differences in
the G values reported in Table 6.3. However, it should be noted
that in the gamma ray irradiations, the degradation rate is the
same throughout the sample (the mean free path of the gamma rays
being greater than the dimensions of the irradiated capsule)
unlike the electron irradiations, so that the gamma ray irradiations would not be subject to the possibility of a poor-mixing
error.
6.1.5. Interptation of BEPO Irradiations
Following the method outlined in
Chapter IV and using
the data presented in Chapter V, the pyrolytic contribution to
the total degradation rate in the BEPO irradiations can be calculated. This contribution, as shown in Section 4.7 for the calculation
performed with the data reported for the irradiation of Santowax
R at 400 0 C, can be more important than that obtained by radiolysis
alone. The same analysis is done hereunder for the 350 4C irradiation
of Santowax R in BEPO where relatively high HB concentrations were
obtained, so that it is possible to use the results presented in
Chapter V. Before irradiation, there was already in the sample
about 10% of products "which were not markedly less volatile than
-63-
paraterphenyl" (6.6) but were not terphenyls.
a value of 1.5 x 10~ 4 hr 1 , is obtained for
the pyrolytic degradation rate of irradiated material, at 3500C,
is
so that the pyrolytic contribution G*
From Fig. 5.,1
pr~omp
G*promp = 0.22
(
= 8 x 10~3 watt/gm)
G*(-omp) = 0.26 + 0.22 = 0.48
and
-which value is valid when the time of pyrolysis and radiolysis
are the same (see Section 4.3).
If pyrolysis occurs also during the shut-down period of the
reactor as mentioned by Harwell (
the pyrolysis contribution
is more important and, assuming a shut-down period every week-end
(i.e. one-third of the time) 9
G*
2
pr~ompp = .
and
x 0.22 =O .33
G*(-omp) = 0.26 + 0.33 = 0.59
which value is comparable to the initial G (-coolant) = 0.63
value quoted and calculated assuming second order kinetics (6.6).
Thus, if the contribution of pyrolysis of irradiated
material over the long time of the BEPO pile experiments is
subtracted from the total degradation observed, the radiolysis
degradation yields, G*(-omp) calculated for the BEPO experiments
are seen to be in general agreement with the Euratom and M.I.T.
values.
6.2. Irradiations Performed by Phillips Petroleum Co.
The Phillips Petroleum Company has also performed irradiations
of encapsulated samples of each terphenyl isomer and Santowax OMP
with 6 Mev electrons (6.8, 6.1). The capsules to be irradiated
were located in a rotating cell so that complete mixing could be
obtained during the irradiations. Unfortunately, the dose delivere4
to each sample was not measured and the Phillips Petroleum group
reports that they calculated an "approximate dosage" (6.8) from
the data obtained at Harwell with 1 Mev electrons (ki2, 6.6).
They "estimated" (§.2) the dose delivered to their irradiated
sample from the HB concentration versus irradiation dose curves
of Santowax R and para-terphenyl given by Harwell. Therefore
the results reported by Phillips Petroleum are not independent
of the Harwell results and agreement is to be expected, considering the data reduction procedures.
6.3.
A.E.C.L.
Irradiations
Electron irradiations of ortho, meta-terphenyl and Santowax
OM have been reported by MaCkintosh (6.11). Boyd (61
6.14)
has also performed irradiations on the same materials in two
facilities in the NRX reactor0 These experiments will be reviewed
in the following sections, although it should be understood that
some of the results reported by Boyd are very recent and may not
be in their final form.
6.3.1. Electron Irradiations by _Mcintosh_(6.ll
6.3.11. Irradiation Procedure
The technique used is similar to Harwell's. About 6 mis,
which occupied one third of the stainless steel cell, were
irradiated and the irradiation temperature was kept within
50 C of the prescribed one.
6.3.1.2. Dosimetry
The total dose deposited in the coolant was measured by the
input charge of 1 Mev electron delivering a beam current of 50pA.
The dose rate in the volume of terphenyl actually stopping the
electrons was about 73 watt/gm (6.11, 6.26),
6.3.1.3. Analytical Determination
Gases, HB and original components were determined by various
methods. A micro-sublimation technique similar to Harwell's was
used to determined the HB content of the irradiated sample. A
precision of ± 10% is quoted for these determinations (6.12).
The composition of the original components and biphenyl were
obtained by gas chromatography.
6.3.1.4. Experimental Results
In one set of experiments, the degradation versus irradiation dose was obtained for ortho
and meta-terphenyl at
-65-
375 0C and Santowax OM at 375 and 450 0 C, by irradiating individual
encapsulated samples of each material to different doses.
Appendix A2 presents the data used to calculate the degradation
rates, using first order kinetics. The data were originally
evaluated by A.E.C.L. assuming second order kinetics. No attempt
was made to calculate the G*(-i) values for Santowax OM at 4500c
since the omp concentrations were not given for this temperature;
the total concentrations of biphenyl and terphenyl were reported
together for that irradiation.
Table 6.4 presents the G* values obtained at M.I.T. from
the A.E.C.L.
data.
Table 6.4
G*(-i) Values for the 3750C Electron Irradiations (A.E.C.L.)
First Order Kinetics
Component
Ortho-terphenyl
Meta-terphenyl
Santowax OM
G*(-i) (a)
0.20
G (-coolant)
0.11(b)
0.15 * 0.05
0.22
0 .0 8 c)
0.25
(a) The initial concentrations at zero dose
were taken into account
(b) 95% confidence limits based on scatter data
only.
(c) For Santowax OM, the values up to 46% HB
were used.
As mentioned earlier for Harwell experiments, it is highly
possible that these G* values are lower than the true values,
since the total mass of coolant was not irradiated and a complete
mixing during irradiation may not have been realized (see Section
6.1.4 and Appendix Al).
A.E.C.L. also investigated the effect of temperature by
irradiating several samples of Santowax OM, all at a dose of
8.8 (watt)(hr)/(gm) but at different temperatures between 350
and 450*C (6.26). The percentage of omp and biphenyl is given
-66-
at each temperature and is also presented in Appendix A2.
Table 6.5 and Fig. 6.3 present the differential G* values
calculated for these data using first order kinetics and
defined as
ln CC0
G*(- (omp + biphenyl) ) = 11.65
(6.3)
8.8
Table 6.5
Differential G* Values at a Given Dose for Electron Irradiations
A.E.C.L.
Temperature ( 0C)
G*(-(omp +f))
350
375
390
396
405
412
420
435
450
0.29 0.32 0.36 0.35 0.35 0.34 0.41 0.49 0.56
This set of data is interesting since it can give an idea
of the activation energy of the radiolytic process only, because
the time of irradiation was so short that the pyrolysis effect,
estimated using Fig. 5.1, was negligible even at the high temperatures. Nevertheless, it should be remembered that the above G*
values should be corrected for the non-mixing effect and they
include not only the terphenyls but also biphenyl. However, since
ratios of these quantities will be used to calculate the activation energy of the radiolysis process, the different correction
factors may tend to cancel.
Assuming an Arrhenius type relation for the degradation
yield G*(-i),an activation energy for radiolysis, AE., of about
2 kcal/mole is obtained from Fig. 6.3 for the temperature range
350 0 C to 412 0C, while in the range 420 0 C to 450 0C, a value of about
10 kcal/mole is obtained for AER* Whether this change in the value
of AER is significant is not known; the change is not predicted
on the basis of the pyrolysis data shown in Fig. 5.1.
6.3.2. Mixed In-Pile CapsuleExperiments
In this section, Boyd's experiments (1,
6.14), in which
the analyses of the omp content of the irradiated samples have
0.
E
o)
0.70
0.60
+
0
0.50
A
0.
'A
0.
EL~
A
A
A
A
0.31
A
o
L.J
Q2(L-
*
u
0
0
0
0
0
to
V.
I
I
1.40
FIG. 6-3
I
I
L
1.60
1.55
1.50
1.45
TEMPERATURE , I /T , OK-1
A. E.C. L. ELECTRON IRRADIATIONS AT DIFFERENT
TEMPERATURES AND AT THE SAME DOSE
,
8.8 WATT - HR/GM
I
-68-
been given, are reviewed. Actually, most of the G values quoted
by A.E.C.L. are calculated assuming second order kinetics, But
when a set of data points was given at a specific temperature or
dose rate, G*(-i) values have been recalculated using first order
kinetics, so that comparisons with the results of other irradi4tions mentioned in this report, could be done. Sawyer and Mason
have shown that, in general, first order kinetics provides
(6_.)
at least as good a fit as second order to the degradation results
reported by a number of investigators.
NRX, X-Rod Facility (6_131)
Encapsultated Santowax OM has been irradiated in this
facility at a dose rate of 330 t 33 mw/gm, of which 30% was
due to fast neutron interactions (6.13). Table 6.6 presents
the final concentrations of the irradiated samples.
6.3.2.1.
Table 6.6
Irradiation of Santowax OM by A.E.C.L.
NRX, X-Rod Facility (6.1)
Sample
X 24
X 28
X 13
X 25
x 16
X 14
X 12
X 27
Temperature Composition
230
280
280-325
305
325
330
365-380
370
78.2
82.6
52.6
74.0
78.3
49.6
60.8
73.3
dose
dose
Owatt-.hr/gr
11.25
7.82
31.40
11.32
8.60
31.20
14.80
8.22
Using all of the data for the irradiations carried out
between 230 and 33000, a G*(-i) value, calculated using first
order kinetics, was found to be
G*(-omp) = 0.26
0.02
At 370 C, a value of G*(-omp) = 0.40 1 0.02 was calculated for
the two data points X 12 and X 27. This last value yields to a
pyrolytic constant of irradiated material kpr,omp of 3,6 x 10~ 3 hrwhich is higher than those quoted in Chapter V. However, the
value of 0.26 between 230 and 3300C is consistent with the loop
experiments.
6,3.2.2. E-3 Facility, N1X Reactor (6.14)
Ortho and meta-terphenyl were irradiated at two different
dose rates (100 and 300 mw/gm) and at various temperatures
between 10000 and 450 0 C. When there were sufficient data, least
square analyses of the data were performed, These data are listed
in Appendix A2, and have been arranged the following way:
- All the samples from 100 0C to 300 q were lumped together,
since pyrolysis is insignificant in this range of
temperature. It has also been observed that ortho and
meta-terphenyl have the same radiolytic stability in
this temperature range. These data were then analyzed
by first order kinetics.
- The irradiated samples of ortho-terphenyl between 3500C
and 3750C were grouped together ond analyzed by first
order kinetics,
- The irradiations of ortho-terphenyl at 42400 were reduced
separately.
- For the other samples listed, only differential G values
were calculated, as
C
lnwG*(-i) = 11.65
These last G* values could be subject to change since they
are based but on one or two experimental points at very low dose
rates (e.g. 1 to 3 watt-hr/gm). A small error in the measured composition of the irradiated sample or the measured dose could
produce a large error in the calculated value of G
-70-
Table 6.7
G* Values of Irradiated Ortho and Meta-terphenyl
E-3 Facility - NRX Reactor -
(A.E.C.L.)
(First-Order Kinetics)
Component
--
Temperature
Dose Rate
G*(-i)
(0-------------w---)----
0.1 and 0.3 0.35 + 0.03a
100-300
Ortho and meta
0.54 + 0.06
0.1
300-357
Ortho
0.52 + 0.02
0.1
353
Meta
Ortho
424
0.1
1.59 + 0.11
L--------------------j---------------------(a) 95% confidence limits on scatter of data only.
The energy deposition in the facility is equally divided
between fast neutron and gamma ray interactions, i.e. fN = 0.50
(6.27). Between 100 and 300 0 C, radiolysis is the only significant
degradation mechanism and the G*(-i) value of 0.35 is higher
than the value found with loop experiments which was 0.26.
At approximately the same dose rate, and with a fast neutron
fraction of 30%, the G*(-omp) value obtained in the X-rod
Facility was 0.26, which agrees with the results of the Euratom
and M.I.T. loops and on that basis suggests G (-i)/G*(-i) = 1.
However, if the results of the X-rod and E-3 facilities are
= 0.58,
compared according to Eq. (4.17), values of G*(-omp)
N
G*(-omp) = 0.12 and GN(-omp)/G*(-omp) -' 5 result.
6.4. Atomics International Irradiations
Atomics International has conducted several mixed in-pile
and electron irradiation studies on terphenyl materials: the
five considered to be the most significant will be discussed
in this section.
The irradiations to be analyzed are the MTR In-Pile Loop
studies (6.15), the OMRE (6.20), the two most recent capsule
experiments conducted in the Curtiss-Wright Research Reactor
(CWRR) (6.18), the experiments in the Oak Ridge Graphite Reactor
(OGR) (6.19), and recent data on ortho-terphenyl with 1 Mev
-71-
electrons (6.25).
The first two irradiations at the MTR and in the OMRE were
specifically intended to show the behaviour and utility of terphenyl
coolant whereas the capsule experiments were conducted to investigate the existence of a "fast neutron effect".
6.4.1. Transient In-Pile Loop Irradiations
Biphenyl, two isomeric terphenyl mixtures -Santowax OM
(65% ortho, 32% meta, 3% para) and Santowax R (10% ortho, 61%
meta and 24% para)- and a mixture of isopropyl biphenyl were
irradiated in an in-pile loop in the Material Testing Reactor
(MTR) by Bley (6 15). Since this discussion is concerned with
a comparison of results obtained with terphenyl coolants, only
the results pertaining to Santowax OM and R irradiations will
be considered here.
The bulk temperature was maintained around 620 to 6504F.
The dosimetry was performed with steel isothermal calorimeters
to obtain the gamma heating rate, and with nickel foils to
obtain the fast neutron heating rate. The average dose rate in
the in-pile section was 0.33 watt/gm, of which 12% was due to
fast neutron interactions. The errors estimated by Bley (6,15)
were respectively t 15% in the total dose rate and t 50% in
the fast neutron fraction.
The concentrations of each terphenyl isomer were determined
by gas chromatography developed by Keen (6.16) and the rate of
disappearance of each component was found proportional to its
concentration, as predicted by a first-order kinetics law (61),
This correlation was used to obtain the following radiation
yields G (-compound) which are equal to G*(-i) as defined in
Chapter IV,
-72-
Table 6.8
G(-compound) Values for the MTR In-Pile Loop
(First-Order Kinetics)
Component
G*(-I) = G(-1)/Ci
Ortho
0.40
Meta
Para
0.27 t 0,02
0.32 t 0.02
0 .0 2 a
(a) These errors presumably do not inplude
the errors quoted for the dosimetry
Using a composition equivalent to Santowax WR (15% ortho,
75% meta, 5% para), a value of G*(-omp) = 0.27 was calculated
for comparison with the data given in Chapter V.
Due to the fact that the ratio of the in-pile to out-pile
volume was between 0.16 to 0.21 ( .1), the average dose rate
delivered to the total coolant was:
(0.33 x 0.16) to (0.33 x 0.21) or 53 to 66 mw/gm
Using Eq. (4,16) and a value of 6 x 10-5 for kproop
obtained from Fig. 5.1, from Curve IV at 6200, the
radiolytic contribution can be calculated;
kpr,omp
G*(-omp) = G*(-omp) + 11.65
r
and with r
= 60 mw/gm,
G*(-omp) = 0.27 = GR(-omp) + 0.01
G*(-omp) = 0.26
This value of the radiolytic degradation yield is in good agreement
with the data reported by Euratom and M.I.T. so that this last
finding tends to show that in-pile loop experiments are consistent.
-73-
6.4.2. Organi2_Moderated Reactor Experiment_OMRE
Gercke and Trilling (6.20) report the degradation rates
obtained at OMRE during the first set of experiments. The
average dose rate delivered to the coolant in the core region
The
was 1.2 watt/gm of which 28% were due to fast neutrons,
0
reported values of these irradiations at 600 F are in terms of
G(polymer) and G(-coolant) at different HB concentrations, which
are shown in Fig. 6.3.
The extrapolation of the data to 0% HB gives a G (-coolant)
of 0.27. Also at 33% HB a G(-+ HB) = 0.14 ± 0,03 js quoted and.
at the same HB concentration, the 610 0 F irradiatiop of Santowax
which indicates
OMP at M.I.T., gives G(+ HB) = 0.15 ± 0.01 (
good agreement.
In the M.I.T. irradiations, the DP concentration (at 33 w/o
HB) was 40 w/o. If this value is taken for both the OMBE and
M.I.T. results, G*(e-:HB) = 0.23 and 0.25 are calculated for
the two loops. These values indicate good agreement of the
OMRE results with the Euratom, M.I.T. and MTR results for
G*(-omp) = 0.26 t 0.01 (since G*(-.*HB) = G*(-omp) - G*(P-LIB)).
This is true even though the experiments were done at different
fast neutron fractions.At a temperature of 610 0 F and for the
average dose rate of about 50 milliwatt/gm for the entire coolant
in the OMRE, the pyrolysis correction G*
pr (-omp) to G*(-omp) or
G*(*
HB)
is negligible.
6.4.3.
In-PileCapsuleExperiments
in the CWRR and the OGR
Capsule experiments were then conducted in two reactor
facilities, the Curtiss-Wright Research Reactor (6.18), 1 MW
swimming pool-type reactor, and the Oak Ridge National Laboratory
Graphite Reactor (6j1), 3.4 MW, air-cooled graphite pile, fueled
with natural uranium, in order to ascertain the influence of fast
neutrons.
6.4.3.1. CWRR Facility
In this facility, a mixture of ortho, meta and para-terphenyl (composition 1, 5, 2.8) was irradiated at temperatures
0.32
El
o
A
0.28
600*F
667*F
450 TO 675*F
00
0.24
0
j
0.20 _
I
0.16
0.12
0.08 _
I
0
FIG. 6.4
10
I
I
20
30
HB CONCENTRATION,
I
40
W/O
DECOMPOSITION RATE OF OMRE COOLANT (6.20)
-75-
between 600 and 6500F. The dosimetry was based on two different
measurements: the gamma dose rate was taken from the values
reported by Curtiss-Wright personnel, and the fast neutron dose
rate was determined using aluminum foil, The activity of this
foil was related to the fast neutron flux and the total energy
absorbed in terphenyls could then be calculated using the two
previous determinations.
A total dose rate of 400 mw/gm, of which 65% were due to
fast neutrons, was reported with an error of + 50% (6.18).
The irradiated samples were analyzed by gas chromatography and
a Go(-coolant) based on a second order fit was found to be
0.51 at 0% DP concentration. Sawyer and Mason (6 ) using the
given data of CWRR have calculated the following G*(-i) values
assuming first order kinetics. At 6400F and with a dose rate in
the order of 400 mw/gm, the pyrolysis contribution is negligible.
Table 6.2
G*(-i) Values Obtained from CWRR at M.I.T.
(First Order Kinetics)
Component
Ortho-terphenyl
Meta-terphenyl
Para-terphenyl
Total terphenyl
G*(..i)
=G(-i)/Ci
0,51
0.41
0.37
0.39
0 ,0 7 a
0.07
0.08
0.07
(a) 95% confidence limits based on scatter in
data only,
Since the G*(-i) values also depend on the dose absorbed
by the coolant, the errors on the G*(-1r) values quoted in Table
6.9 would be higher if the errors in dosimetry were included.
Using the reported error of + 50% for the dosimetry, a value of
G*(-omp) = 0.39 + 0.19 is obtained. This value does bracket the
value of 0.26, obtained from the loop experiments.
-76-
6.4.3.2. OGR Facility
Santowax OMP was then irradiated in the OGR Facility,
because the CWRR had been shut down. The dosimetry and experimental techniques used during these irradiations were more
refined and extensive than previously.
The temperature of the capsules (620 0F) was kept constant
with heaters, providing a flat temperature profile (19).
The fast neutron and gamma ray contributions were obtained with
threshold detectors and adiabatic calorimeters, The four threshold
detectors that were used, are listed below.
Table 6.10
Threshold Detectors for the 0GB Irradiations
Threshold
U238
Ni5 8
Mg2 4
Al27
(n,f) Bal40
(n,p) C05 8
(n,p) Na2 4
(nc)Na2 4
E = 1.5 Mev
E = 4.5 Mev
6.3 Mev
E
E = 8.3 Mev
Effective
0.54
0.0837
0.024
0.048
A Cranberg type fission spectrum was used to approximate
the fast neutron flux and calorimetric measurements with carbon
were performed to obtain the total dose, Hence, the respective
contribution in the terphenyls, of gamma and fast neutron could
be found (6.18).
A total dose rate of 3 milliwatt/gm (of which 63% was due
to fast neutrons) is reported. The compositions of the terphenyl
isomers and the high boilers were respectively obtained by gas
chromatography and distillation. Degradation rates were then
calculated assuming second order kinetics. Sawyer and Mason,
using the given data (6 l9) have calculated the following first
order degradation yield (6.5).
-77-
Table 6.11
G*(-i) Values from OGR, for 6200?, Calculated at M.I.T.
(First Order Kinetics)
Component
G*(-i)=
Ortho-terphenyl
Meta-terphenyl
Para-terphenyl
Total terphenyl
0.51
(i/
0.13a
0.46 + 0.07
0.46 t 0.09
0.47
0.05
(a) 95% confidence limits based on scatter in
data only.
Note that although the OGR and CWBR irradiations had essentially
the same fast neutron fraction (fN = 0.63 and 0.65 respectively),
the G*(- coolant) values at about 6200F do not agree within the
errors limitis (unless the + 50% error in dosimetry is considered
and use of such a large possible error reduces the significance
of the results to an almost meaningless value).
At 6200F and an average dose rate of 3 milliwatt/gm, the
pyrolysis contribution can be significant. The (final) DP concentrations reached in the OGR irradiations ranged generally from
15 to 30 w/o, which approach the DP concentrations in the irradiations used to define the pyrolysis constants given on Curve IV
of Fig. 5.1. Thus, if the pyrolytic constant of irradiated material
obtained by M.I.T. and Euratom in Curve IV of Fig. 5.1 is assumed
to be valid for the OGR irradiations, at 6200,
kpr,omp = 4 x 10-5 hr-1
then,
G*
so that
(-amp) = 11.6
pr
x 4 x 10-
~3 x 10
G*(-omp) = G*(-omp)
= 0.15
=01
- G*(-mp) = 0.47 - 0.15 = 0.32
This pyrolysis corrected value is considerably closer to the
value of 0.26 obtained with the loop experiments than the total
(i.e. uncorrected) value, G*(-omp) of 0.47.
Zack has averaged the total G(-coolant) values obtained
in the OGR and CWRR and used values of [GY (-coolant ) from an
unpublished report to calculate [GN(-coolant) / G(-coolantg
The experimental basis for the [G (-coolant)] values is not stated
but the value of fGy (-coolant) used at 0% DP was 0.186 and
0.075 at 30% DP; since these values agree very closely with a
tabulation of the A.E.R.E. electron irradiation results,,
(-coolant
(6.20) the Gy values used by Zack are probably
based on the A.B.R.E. electron results (see Section 6.1.4 for
discussion of these results which are believed to be too low,
due to poor mixing). The averaged total G(-coolant) values
range from 0.56 at 0% DP to about 0.27 at 30% DP. From these
values, Zack reports GN(-coolant
4. 2 at 0% DP and 5 at 30% DP.
/GY (-coolant
of about
the pyrolysis corrected value of G*.(-coolant) -see abovei s used, the average G*(-coolant) at 0% DP drops from 0.56 to
If
R
(0.32 t 0.05) + (0.39
t 0.0)
0.35
t 0,05
If a value of G* (-coolant) = 0.26 + 0,01, based on the MTR
Y
gamma irradiations (see Section 6.5.4) and the loop experiments,
is employed in Eq. (4.17), G*(-coolant) is found to be 0.40 ± 0.10,
giving G*(-coolant)/G*(-coolant) = 1.5 t 0.4 at 0% DP and 620 0p.
6.4.4. R2cent_Experiments
More recently, capsule irradiations of ortho-terphenyl have
been carried out with 1 Mev electrons at very high temperatures
(from 7504F to 900 0 F) (6,|5). Benzene was used as a dosimeter and
an average dose rate of 800 milliwatt/gm is reported for these
irradiations. No details are yet available on the experimental
apparatus,
G*(-i)
values were calculated at M.I.T. assuming first
order
-79-
kinetics. These values are presented in Table 6,12.
Table 6.12
Irradiation of Ortho-Terphenyl - 1 Mev Electrons
Temperature (OF)
(A I.)
G*(-o# )
752
802
0.49 + 0.10
1.18 t 0.12
850
2.49 + 2.51
898
3.36 t 0.76
(a) 95% confidence limits based on
scatter in data only
Hence, at 7504F, a G*
e value of 0.49 is obtained, which is
larger than those quoted by Harwell (6).
The experimental equipment and procedures are not described
with the data (6.1). Hence the extent of any non-mixing effect
(see Section 6.1.4) cannot be estimated. Other data on pyrolysis
of irradiated coolant at the high temperatures listed in Table
6.12 are not available so that a comparison of pyrolysis effects
is not possible.
6.4.5. Conclusions on A.I. Experiments
The G* values for the two loop experiments (MTR and OMRE)
are in good agreement with the values obtained by Euratom and
at M.I.T. for temperatures around 6000F. The fast neutron fraction
for these four facilities varied from 12% to 44% and the pyrolytic
contribution was very small. The total degradation rate was found
to be 0.26 + 0.01.
For the capsule experiments, the role of non-acopunted
pyrolysis seems to give a better explanation for the values
obtained at CWRR and OGR than that of a fast neutron effect.
6.5. California Research Corporation Irradiations
In order to ascertain the absolute effect of fast neutrons
and gamma rays, irradiations in a nearly pure fast neutron flux
-80-
(Susie Neutron Rich Canister) and a nearly pure gamma field
(Susie Gamma Rich Canister and MTR Gamma Grid) were performed
by the California Research Corporation (C.R.C.) (6.219 6.22).
The total degradation rates obtained in these two different
facilities were reported to be G*(-1) and G*(-1) respectively.
N
Y
6.5.1. Irradiation Procedure
Irradiations were conducted in the Susie Reactor and in
the MTR Gamma Facility at various temperatures: 4250F. 6000F,
6750F and 750 F, but all the data were not evaluated by C.R.C.
because of the curtailment of the organic coolant program sponsored by the USAEC. Consequently, all the data reported for the
irradiations of Santowax OMP were reduced at M.I.T. to give G*(-i)
for each isomer and the sum of the three isomers; this produced
some values not reported by C.R.C. and a check on the COR.C.
calculations for the values reported.
Generally, ten gram samples were irradiated in stainless
steel capsules and a good temperature control was obtained in
the MTR Facility (6.22). In the Susie experiments, the temperature control was such that the temperature of any capsule was
generally maintained to within + 250F of its average temperature
(sometimes excursions of about 500F occurred); furthermore capsule to
capsule temperature sometimes would be as much as 250F (6.22).
Since pyrolysis of irradiated terphenyls now appears to be more
rapid than that of unirradiated terphenyls, the temperature of
each irradiated capsule requires close control in order to
obtain consistent results, especially at temperatures over
about 6000F for irradiations conducted at low dose rates.
6.5.2. Dosimetry
An extensive program (6.21), using both isothermal calorimeter and fast neutron detectors, was set up to measure the
dose received by each capsule. Isothermal calorimeters including
various absorbers, such as polystyrene, carbon, magnesium, aluminum
and terphenyl for the Neutron Rich Facility, and beryllium,
carbon, magnesium and aluminum for the Gamma Rich one, were used
to measure the overall dose rate in the two facilities. Those
measured total dose rates were analyzed to determine the gamma
and fast neutron contributions. To do this, an estimate of the
neutron flux was required (6.21),and two different approaches
were used:
l.In the first one9 perturbations of the absorbers and
reflectors on the known Susie flux were calculated, in
order to find the new flux.
2.The second approach was experimental: the fast flux was
determined using neutron threshold foils listed in Table 6.13,
Table 6.1
Threshold Detectors Used in Susie
Reaction
Pu 2 3 9 (nf)
F.P.
N2 3 7 (n,f) F.P.
U 2 3 8 (nf)F.P.
S32 (np)P3 2
Al 2 7 (nc) Na24
Et (Mev)
at (10-24)
0.01
0.6
1.7
1.6
1.5
3.0
8.1
0.55
0.30
0.11
The thermal and epithermal fluxes were also measured with
three foils, namely Au197, C05 9 and Mn5 5 , and it was found that
they gave an insignificant contribution to the total dose (6.21).
A Cranberg type spectrum was then used to relate the activities
of the threshold measurements and a good agreement was found
between these calculations and the theoretical ones, using the
known Susie flux (6.21). The neutron energy distribution in the
Susie Neutron Rich Canister was quite different from a fission
spectrum joined to a 1/E epithermal component, presumably due
to the presence of the absorbers which were located between
the Susie core and the canister in order to increase the fast
neutron fraction. The effect of variation in fast neuitron spectrum
on coolant degradation has not been studied, The calculated dose
rate in the Susie canisters was 10 to 15 milliwatt/gm. In the MTR
-82-
Gamma Grid, ionization chambers, which were found more reliable
than calorimeters, were utilized to measure the total dose delivered
to the irradiated samples (6
). Use of calorimeters for dose
rate measurements at such low dose rates as 10 to 15 milliwatt/gm
is, in general, not very precise.
6.5.3.
Analytical Determination andExperimnental Results
Gas chromatography was chosen to find the disappearance of
each isomer in the irradiated material. The experimental data
seemed to fit first order kinetics best, over the entire range
of dose, within the experimental errors. First order rate constants
were calculated at each temperature, for the neutron rich and
gamma rich facilities.
C.R.C.
Initial G*(-i) values were calculated by
only at 6000F for each isomer and are listed in Table
6.14.
Table 6.14
Initial G* Values for Irradiation of Pure Terphenyl Isomers
at 6004F, From the Susie Canisters (C.R.C)
Material
Ortho-terphenyl
Meta-terphenyl
Para-terphenyl
[G*n(-i)1
a
[G*(i1
0.79
0.34
0.69
0.59
0.27
0.27
(a) Susie Neutron Rich Canister Irradiations
(b) Gamma Rich Canister Irradiations
These
G*(-i) values obtained under fast neutron and gamma
fluxes were reported as G* (-i) and LG(, i.e. degradation
rates due entirely to one or the other type of radiation. C.R.C.
therefore concluded that a fast neutron effect of about 2.4
existed at 6000F (6.22). This conclusion is discussed in the
following section.
6.5.4. Interpret ation
of the Experimental Results
Since all the analyses of the irradiated samples were reported
(6.22) for each irradiation in terms of the relative disappearance
-83-
of each terphenyl isomer (i.e.
, C being the weight fraction
of component i) the degradation Ates of Santowax OMP and of each
terphenyl isomer in these irradiations were calculated at M.I.T.
using first order kinetics and the calculated concentrations, C
(details of these calculations are given in Appendix A3). As
can be seen from Table 6.15 and 6.16 for these cases where C,R.Q.
had also evaluated G*(-I) values, a good agreement is generally
found between the degradation yields calculated by M.I.T. and
by C.R.C. Table 6.17 presents the G*(-i) values calculated at
M.I.T. from the first order rate constants given by C.R.C. (6.22)
for the irradiations of pure terphenyl isomers,
Note that the G*(-1) values presented by C.R.C., which are
listed in Table 6.14, are those obtained with the irradiations
in the two Susie Canisters of pure terphenyl isomers and not
Santowax OMP (see Table 6.17). Whereas a good agreement is found
between degradation yields obtained in the MTR Gamma Grid and
the Susie Gamma Rich Canister irradiations at 6000F for the pure
terphenyl isomers (see Table 6.17), the values obtained from the
irradiations of Santowax OMP at 425 0? and 6000P in these two
facilities do not agree as well (compare Tables 6,15 and 6.16).
Differences also exist between the G*(-i) values obtained from
the Santowax OMP irradiations, for each terphenyl isomer, and
from the irradiations of the pure isomers (compare Tables 6.15
6.16, 6.17).
The G* (-omp) values of 0.25 obtained at 4250F and 6000F
Y
in the MTR Gamma Grid irradiations agree closely with the total
G*(-omp) values found at these temperatures in the various loop
irradiations (and thus with the G* (-omp) values since pyrolysis
was negligible at those temperatures). Thus, a ratio G(-omp)
1 is indicated.
G*.. -omp
Y
To estimate the pyrolysis contribution in the MTR gamma
irradiations, the results shown in Fig. 5.1 were used. At 7500F
the value of kpr for the one Santowax OMP irradiation reported
(see Fig. 5.1) was about 20% lower than the corresponding value
of Santowax WR. This difference may be due to the greater
-84-
concentration of para-terphenyl in the Santowax OMP. In the
following discussion it is assumed that this factor can be applied
to Curve IV (Santowax WR and terphenyl OM.2) over the temperature
range 6750F to 7500 F, to obtain kpr for Santowax OMP.
For the 7 50 CF irradiations in the MTR Gamma Grid, the G*
values obtained is based on an irradiated sample whose final
concentration in terphenyls is around 50 weight percent so that
the pyrolysis information presented in Fig. 5.1 may be applicable.
of 8 x 10~4 hr~ is found at
From Fig. 5.1 a value of k
7500F, and from Eq. (4.16) (using the average dose rate of
18 milliwatt/gm obtained from the calculated dose rate and the
reported irradiation time (6.22))
G* (i)
pr
and
11.65 x 8 x 10~4
18 x 10-3
=
0.52
G*(-omp) = 0.75 - 0.52 = 0.23 + 0.05
within the estimated error limits, this value G*(-omp) agrees
with those obtained at 425 and 6000 F. At 675 F the final degradation product concentration in the MTR irradiations of Santowax
OMP reached was only about 22% so that the information in Fig.
5.1 for irradiated coolant may not be directly applicable.
Using the [G*(-i)] = 0.63 and
G*(-i)
=
0.25 values ob-
425 0 F
(presented in Tables 6.15 and 6.16)
tained by C.R.C. at
and Eq. (4.16), it is possible to calculate the G*(-i) values
which should be obtained at that temperature by Euratom (Grenoble,
France), A.E.C.L. and M.I.T. (6.5). No pyrolysis term is required
at this temperature. These values are presented in Table 6.18
where the calculated G*(-i) values are all higher than those
observed experimentally.
A similar analysis has been performed by C.R.C. (6.22),
where the 600 0 F data and a value of [Gg(-i) /[Gc(-i)] of 2.3 were
used. The calculated values (except for those from BEPO), were
all higher by 10 to 50% than the reported values. The temperature
Table 6.15
G*(-i) Values for the Susie Reactor
Neutron Rich Canister and Gamma Rich Canister . Santowax OMP Irradiations
I-
Temperature Facility Calculated by
(F)
425
G* (- 00,
Neutron
750
G* (-mO3
G* (-Pn
M.I.T.
0.70 t.lla
0.57
± 0.11 0.84
C.R.C.b
0.67
0. 58
0.99
Gamma
Rich
Neutron
Rich
M.I.T.
0.12
0.25
0.18 1 0.70
M.I.T.
0.08
Gamma
Rich
M.I.T.
Neutron
Rich
M.I.T.
0.74
0073
0.28
0.30
1.70
Rich
600
G*(-i) = G (-1)/Ci
C.B.C.
C.R.C.
,C.R.Cl.
0.14
0.33
G*(-omp)
0.42
0.63
0.10
0.28
0.88
0.18
0.04
0.66 t 0.55
0.60
0.08
0.66
0.05
0.70
0.21 1 0.50
0.24
1.41 t 0.14
0.59
0.08
0m06
1.41
I
0.11
0.20
0.09
0.08
1.45
0.16
1.62 . . . . .1a§-- -- -
(a) 95% confidence limits based on scatter in data only.
(b) obtained from the First Order Rate Constants For Disappearance of Polyphenyls
quoted by C.R.C. (6.22), k; G*(-i) == 11.65 k.
Table 6.16
G*(-i) Values for the Santowax OMP Irradistions,
M.T.R. Gamma Facility (Q.R.C.)
-
-
-
)
G
- --- - -----G*(-pA)
G*-i
Temperature
(OF)
- ----G*(-o
-
--)
-------
- - -G*(-m)
-
-------
425 (M.I.T.)*
0 .3 5 a
0.25
(C.R.C.)
600 (M.I.T.)
(C.R.C.)
0.23
0.47
0.16
675 (M.I.T.)
0.58
(C.R.C.)
750 (M.I.T.)
(C.R.C.)
-
--G*(-omp)
,.-"-*-
-
---
0.25
0.25
0.20
0.28
0,25
0.29
0.46
0.38
0.47
0.57
1 .3 0 ±0.10b 0.71i0.04
0.98
0.57±O.03
0.75*0.05
(a) values based on two data points
(b) average value of the two data points
(c) ( ) refers to laboratory making calculations
-
Table 6.17
G*(-i) Values for the Irradiations of Pure Terphenyl Isomers (C.R.C.)a
Temperature
(.F.) ...
425
600
Facility
750
Meta
G*(-M 3)
Para
G* (-pn )---
Susie Neutron
Rich
MTR
Gamma
Grid
0.75
0.66
0.60
0.18
0.17
0.13
Susie Neutron
Rich
Susie Gamma
Rich
0.79
0.69
0.59
MTR
675
Compound: Ortho
G* (-oo3)
Gamma
Grid
Gamma
MTR
Grid
Susie Neutron
Rich
MTR
Gamma
Grid
I
00
0.34
0.27
0.27
0.35
0.26
0.31
0.72
0.41
0.37
1.98
1.38
0.91
0.89
0.67
0.63
(a) These values were obtained by multiplying the first order rate
constants reported by C.R.C. (6.22), by 11.65. The confidence limits
or errors were not quoted.
Table 6.18
Predictions of G*(-omp) Values At 425*F
From C. R. C.o Data
TG*
Facility
fN
Euratom
M.I.T.
0,18
0.37
A.E.C.L.
0.50
"pop)
calculated from
C.R.C. data
0.3?
0.39
0.45
G(op
G*(~omp)
observed
0.24
0.26
0.33
-89-
variations in the Susie Neutron Rich Canister and high value of
that was used for these calculations could
G*(-i /G*(-i)
easily account for this discrepancy between calculated and
measured G*(-i) values. If the temperature variations during
the irradiation periods were available, it would be possible
to calculate the pyrolytic degradation rate using pyrolytic
rate constants of irradiated materials . Using Eq. (4.16) radiolytic degradation rates could be calculated after correction for
pyrolysis as it has been shown in this section for the MTR
irradiation at 7500F. Hence values of G*(-I) instead of[G*(-i3
and G*(-i) instead of G*(-i) would be found and the "fast
neutron effect" defined as G*(-i) / G*(-i) could be recalculated,
(This ratio would presumably be lower than actually found),
In summary, the C.R.C.
values of G*(-i) obtained with the
MTR Gamma Grid agree closely with the G*(-i) values obtained in
the various terphenyl loop irradiations. However the G*(-i
values reported by C.R.C. from the Susie irradiations are considerably higher than the G*(-i) values obtained with the loops.
The (G*(-i3 values from the Susie irradiations scatter considerably
but are lower than the [G*(-i)Jvalues. The significance of the
higher[G*(-i) values from the Susie irradiations is not known.
The dose rates in the Susie experiments were quite low and
measurements of the dose rates with high precision would be much
more difficult than in the loop experiments where the dose rates
in the irradiation zone were of the order of 10 to 40 times greater.
The temperature control was also sufficiently unstable to have
caused some of the differences.
-90-
CHAPTER VII
CONCLUSIONS
Using the methods discussed in Chapter IV comparisons of
all the irradiations considered in Chapters V and VI are summarized in Tables 7.1 and 7.2. Table 7.1 presents a comparison
of Atomics International, Euratom and M.I.T. loop results.
Table 7.2 presents a comparison of the results from capsule
irradiations carried out by A.E.C.L. of Canada, Atomics International, California Research Corporation and A.E.R.E.
Harwell (England).
7.1.
at
Loop Irradiations
The following observations can be made from the results of
the in-pile loop irradiation experiments:
a) Considering all the results, there is no significant
change in the total rate of terphenyl degradation with temperature
up to about 6100F but the rate increases rapidly above 700 OF
b) When the contribution of pyrolysis of irradiated terphenyl
is taken into account, good agreement is found between G*(-i)
values from the Euratom, M.I.T. and MTR loops and from the OMRE.
At low temperature (below 6000F) all the loop results obtained
at different fast neutron fractions agree, hence suggesting
equal degradation yields for gamma ray and fast neutron irradiation.
c) Degradation by pyrolysis becomes a significant factor
in the total degradation at a temperature above about 7000 F
(3700 C) and the major factor at temperatures above about 750 OF
(400 0 C). The magnitude of the relative contribution of pyrolysis
and radiolysis depends on the dose rate, temperature and ratio
of in-pile to out-of-pile volume.
The low-temperature loop irradiations reported by
Euratom suggests an activation energy for radiolysis, AER, Of
about 0.5 kcal/mole, but the confidence limits of this low
d)
value are not known. The M.I,T. results indicate AER = 0*
Additional low temperature irradiations are required to establish
the magnitude of AER.
Table 7.1
Loop Irradiations
w
Facility
MTB
OMBE
EURATOM
BLO2
BLO3
M.I.T.
Santowax B
Santowax OMP
TerphenylOM.2
TerphenylOM.2
Santowax OMP
Santowax WR
remperature
(OF)
620-30
600
390
610
770
806
680
770
6100
750
425
700
750
780
0
0
0
Material
Irradiated
Average
Dose rate
fN
G* (-omp)
0.060
0.12
0.28
0.27
0.26
0.044
0.17
0.17
0.17
0.17
0.15
0.15
0.24
0.26
0.045
0.039
0.038
0.021
0.015
0.017
0.017
0.024
0.022
0.020
0.020
0.37
0.37
0.44
0.44
0.44
0044
0.58
1.06
0.29
1.16
0.26
0.53
0.27
0.37
0.55
0.77
G
a
0.01
0
0
0
0.34
0.78
0.02
0.93
0
0.27
0
0.10
0.29
0.51
G*(-omp)b
0.26
0.26
0.24
0.26
0.24
0.28
0.27
0.23
0.26
0.26
0.27
0.27
0.26
0.26
(a) Values obtained using Eq. (4.15) and Curve IV from Fig. 5.1, assuming AE, =0
(b) Values obtained using Eq. (4.16)
(c) Irradiation capsule temperature (see Chapter V)
Table
7.2
Capsule Irradiations
__________________________
Facility
-------
I
-t
Material
Irradiated
I---------------
Dose Rate
Temperature
(OF)
.--
-6
- -
G*(-i) IG (-HB)
watt/gm
------
----
--
--
--
-
I
-
(*HB)
I
A
--
--
~~
(-I)q
0 G* (-1)
U
G (-i)
(+j31HBI)
-- -
-----
I
2
3
4
5
6
Electrons
Santowax
OM
707
7.3
0
0.22
NRX Reactor
ortho
and meta
Santowax
up to 570
0.100
and 0.300
0.50
0.35
1.7
up to 570
0.330
0.30
0.26
1
750
0.800
0
0.49
Santowax
OMP
620
0.003
0.64
0.47
Santowax
OMP
Santowax
OMP
600
0.011
0
0.25
600
0.015
0.95
0.66
Santowax R
para
Santowax R
750
660
750
~1v
vo.001
0.008
0
0
0.54
1
7
8
10
9
A.E.C.L.
E-3
X-rod
OM
0.18
A.I.
Electrons
OGR
ortho
4.3
2.2
C.R.C.
NTR
Gamma Grid
Susie
2.4
A.E.R.E.
Electrons
Gamma Rays
BEPO
&
J
0.19
0.28
1.30
A
L
10.5
~J2
assumed
10.5
1 __________
.1
-93-
7.2. Capsule Irradiations
In Table 7.2, capsule irradiations are listed according to
the following format:
- Column 6 presents the total degradation yield values, G*(-1),
calculated from experimental data, where available, assuming
first-order kinetics.
- Column 7 presents the initial G(r- HB) values quoted by some
investigators instead of G*(-i) values.
- Column 8 presents the "fast neutron effect" based on the
electron degradation yield values without any correction for
pyrolysis, [G,(- HB)J, as reported in the original reports
for second-order kinetics.
- As a comparison, Column 9 presents the calculated "fast
neutron effect" not corrected for pyrolysis, based on firstorder kinetics.
- Column 10 presents the "fast neutron effect" which has been
corrected for pyrolysis, as G*(-i)/G*(-i), for all the capsule
experiments considered for the G*(-i) values from Column 6
assuming G*(-i) = 0.26 (which agrees with the results of the
loop experiments and the results of the MTR gamma and Harwell
gamma irradiations).
The following observations are made:
a) The gamma degradation yields G*(-i) obtained using
gamma irradiation facilities agree closely with the values of
G*(-I) obtained from a comparison of the results of in-pile
Y
loop experiments.
b) The electron degradation yields, G (- HB), reported
from the electron irradiations of A.E.R.E. and A.E.C.L. are
lower than those reported by A.I. and also lower than the yields
obtained with gamma irradiation by A.E.,R.E. and C.RC,, These
discrepancies are discussed in Appendix Al, on the basis of
incomplete mixing of the samples during irradiation. On this
, quoted in
H
basis, therefore, the ratios [GN (e(+
Column 8 are therefore considered to be too high,
c) If the results of the capsule irradiations are all
analyzed by first-order kinetics to obtain G*(-i) values, and
these values are corrected for pyrolysis (see Eq. (4.16)), and
a value of G*((-i) = 0.26 is employed consistently, the magnitude
Y
of "fast neutron effect" is lowered significantly from values
previously reported for capsule irradiations. In no case is the
pyrolysis corrected ratio, G*(-i)/G*(-i), greater than 2.5,
and in one case where one determination gives a value of 1,7,
there is additional data from the same source which gives a
ratio of unity. The discrepancies between capsule experiments
have been reduced considerably by the analytical methods employed
in this investigation. Much of the remaining differences between
the results from the various capsule irradiations and between the
results from capsule and loop irradiations may be due to differences in the experimental techniques such as:
1. Variations in the experimental conditions (e.g.
temperature control and mixing effects).
2. Different analytical methods used to determnQ the
coolant composition of the irradiated samples. For instance,
both micro-sublimation, distillation and gas chromatography
have been used in the different irradiations.
3. The dosimetry including the determination of the various
fluxes and neutron spectrum in each facility.
7.3. Summary
In summary, an analysis of all the data considered in
Tables 7.1 and 7.2 indicates that the assumption of the additivity
of radiolysis and pyrolysis of irradiated terphenyl gives a better
correlation between all the investigations considered up to the
present time than does the assumption of an LST or "fast neutron
effect". Comparison of the results of loop irradiations indicates
= 1.0, while comparison
a fast neutron effect ratio, G*(-i)/G*(-i)
N
y
of irradiations of encapsulated samples indicates a ratio,
G*(-i)/G*(-i) of between 1 and a high of about 2.
N
y
The rate of pyrolysis of irradiated terphenyls (containing
about 30% HB) at any temperature in the range 400OF to 800 0 F
-95-
has been found to be significantly higher than that of unirradiated terphenyl, The activation energy for pyrolysis of irradiated terphenyl containing about 30% HB, AEpr has been found
to be less than that of unirradiated terphenyl (around 40 kcal/mole
for irradiated terphenyl, opposed to 70 kcal/mole for unirradiated
terphenyl coolant).
The activation energy of radtolysis, 4ER, appears to be
very low (in the range of zero to 2 kcal/mole).
-96-
APPENDIX Al
The Effect of Non-Mixing on
Observed Harwell Ge Values
To explain the apparent discrepancy between earlier G (-*-HB)
values (Al.1, A.2)., and more recent values of GY('-HB) (Al),
a study of the experimental equipment and techniques employed
in the Harwell experiments was made. A schematic of the Harwell
electron irradiation capsule is shown in Fig. 6.1. Note that the
volume being irradiated is a small portion of the total volume
of material in the capsule. Further, because of the geometry, it
is possible that complete, continuous mixing did not occur.
The integrated amount of degradation products formed in
the irradiation volume, is proportional to the amount of terphenyl
present at any time in all cases, except for zero order kinetics.
Hence, if the volume irradiated is subsequently diluted with
non-irradiated, or partially irradiated material, the total
amount of degradation observed for the dose specified would be
lower than if the entire volume had
irradiation (oruriformly irradiated).
the fact that the reaction order is
the concentration of material being
volume, is decreasing and therefore
been uniformly mixing during
This is a direct result of
greater than zero, and that
degraded in the irradiated
the absolute degradation
rate is decreasing more rapidly than it would if complete,
continuous mixing existed.
The effects of lack of mixing during irradiation can be
illustrated for zero and first order kinetics, by comparing
the results obtained in two assumed experiments:
1. The entire sample to be irradiated is divided into
equal parts which are not mixed together during irradiation. One part receives all the radiation and the
other none. Following irradiation, the two halves are
mixed to give the final average concentration. Thus, the
irradiated part is subjected to a specific dose twice
that of the average for the entire sample.
-97-
2.
The entire sample is
irradiated to a specific dose
equal to that of the average of case 1.
The dose rates for cases 1 and 2 are the same.
For zero-order kinetics (see Fig. A1.1) the degradation
yield -d d'r is a constant, so that similar results are obtained
either by
1. irradiating half the sample to a dose of 2T (from point
A to point B in Fig. Al.1) and then diluting the irradiated coolant with the unirradiated portion of the
sample (from point B to C),
2. irradiating the whole sample to a given dose T (point C).
Note that the slope,
, is the same for 1 and 2.
For first-order kinetics (see Fig, Al.2) different degradation yields are obtained if the two different irradiations
described are carried out since the following relationship
now holds
dC
~ Cdr
- d ln C
dT
k
G*
k1.65
Hence, in this particular example,
1. Point E is obtained when half the sample is irradiated
to twice the average dose (represented by B) and then
diluted with the unirradiated portion.
2. For a given dose T, point C is obtained when the whole
mass is irradiated uniformly (or the entire sample is
completely mixed during irradiation).
Note that the slope of the line A to R for Case 1, used to
calculate the degradation yield, is less than the slope of the
line A to C for Case 2. Thus, G*(-i) values obtained under conditions of no-mixing between irradiated and unirradiated portions
are lower than G*(-i) values obtained with complete mixing or
uniform irradiation.
Although the cases shown here are for the complete absence
of mixing, qualitatively the G*(-i) values obtained with various
-98-
A
0.9
0.8
C
0.7
_
I-
-N
z
0.6
z
0.5
-
.B
-N
0.4
-N
0
-N
0.3
0.2
0.1
FIG. Al-I
T
ZERO ORDER KINETICS
1.0
0.9
0.8
z
0
0.7
0.6
!-
0.5
0.4
Q3
FIG.
Al-2
FIRST ORDER
KINETICS
2T
DOSE
-99-
degrees of poor mixing would also be lower than with complete
mixing. Furthermore, second-order reactions are even more sensitive to lack of complete mixing than are first-order reactions.
Assuming first-order kinetics, it is possible to write a
set of equations describing the two different irradiations and
to calculate the ratio of the two G*(-i) values obtained with
incomplete and complete mixing. These calculations whose results
are presented in Table Alcl have been carried out for three
different observed coolant concentrations (concentration
represented on C in Fig. A1.2) and a ratio of 1/2 between the
irradiated and unirradiated volume. Furthermore it was assumed
that the coolant concentration in the unirradiated volume was not
100% but was slightly contaminated with degradation products
(i.e., C0
98%).
Table Al-1
The Effect of Non-Mixing on Observed G* Values
Case 1
Case 2
E
0.82
0-75
0,60
0
o.98
0.98
0.98
B
0.66
0.52
0.22
0.80
0,71
0.47
091
0.85
0,66
C
Mixing
Case 3
For the A.E.R.E. and A.E . C . L. electron irradiations where
the range of electrons was smaller than the geometrical dimensions
of the irradiation cell, the irradiated volume was only a small
fraction of the total one. From Fig. 6.1, assuming a total mass
of terphenyl of 7.7 gm, a density of one and an electron range
of 1%, 0.6 cm., the ratio between the irradiated and unirradiated
volume in Harwell electron irradiations is approximately 1/8.
-100-
Details and description of the A.E.C.L.
irradiation cell were
not given with the reported values but it is estimated from
"the energy deposition rate in the volume of terphenyl actually
stopping electrons", 73
watt/gm (Al.4) and the average dose rate
7.3 watt/gm (A1.5) that a ratio of about 1/10 exists between the
irradiated and unirradiated volumes. These ratios should not be
used to calculate the effect of non-mixing since there was
undoubtedly some mixing between the irradiated and unirradiated
zones. However, considering the absence of mechanical agitation,
the design of the capsule, the high dose rates and short times
of irradiation, one should not assume complete mixing. This
suggests that the G (-i) values reported by AE.R.E. and A.E.C.L.
may be lower than GY(-i) values due to the "poor mixing effect.
APPENDIX A2
A.E.C.L. Irradiation
Data
A2.1 Electron Irradiations
The data presented in Table A2.1 through A2.3 were analyzed
assuming first order kinetics and the different G* values
obtained are listed accordingly. The errors quoted for all the
G* values are based on 95% confidence limits on scatter of data
only.
The disappearance of the initial component for the electron
is
irradiationsof ortho and meta-terphenyl at 3750C (A2)
listed in Table A2.1. The omp concentrations of the irradiated
samples of Santowax OM at 375 0 C (A2.2) are listed in Table A2.2.
Table A2.1
Van de Graaf Irradiations of Ortho and Meta-terphenyl
at 3750C (707 0 P) - (A.E.C0.L)
Terphenyl and HO Concentrations
dose
Component
cornpositi on (1/o)1initial component
HB(/)
100
80.8
61.6
51.2
40.8
0
8.8
17.25
25.0
38.9
25.4
100
80.7
77.0
64.7
0
9.8
18.7
27.3
50.8
50.6
39.6
0
Ortho
8.8
17.6
25.4
50.8
20Q* 0.11
iL(:11_!
0
8.8
Meta
17.6
G*(-I)
= 0.15
t 0.05
-102-
Table A2.2
Van de Graaf Irradiations of Santowax OM at 375 0 C
(A.E.C.L.)
Terphenyl and HB Concentrations
Dose----------- CornpositionA!I2...
HB (w/o)
Total amp (w/o)
Sample Number
0
58 + 62
61 + 66
48 + 49 + 69
60
54
63
56
67
64
57 + 59
65
71
70
0
4.4
6.6
8.89
13.2
17.6
26.4
35.2
44.0
52.8
64.2
88.0
96.8
105.8
------------------------
98.2
81.7
81.5
74.7
71.1
55.9
62.4
46.7
42.9
46.8
6.25
6.95
14.40
15.2
27.3
23.2
34.7
37.1
41.0
36.0
33.7
49.75
50.3
27.2
24.2
58.6
64.8
An initial G* value of 0.22 + 0.08 was calculated for the
first seven sets of irradiated samples assuming first order
kinetics.
-103-
Table A2.3 presents the final concentrations obtained at
various temperatures by irradiating Santowax OM at a given dose
(A2.2). The G*(-i) values quoted were calculated using Eq. (A2.1).
In
G*-)=11.65
where
C
(A2,1)
-r
C = the final concentration
C = the initial concentration
T = the dose received in (watt))(hr)/(gm)
Table A2.3
Van de Graaf Irradiations of Santowax OM
at Different Temperatures (A.E.C.L.)
Dose: 8.8 (watt)(hr)/(gm)
Terphenyl and HB Concentrations
Teinpegture-
Composition
Wo.
G*
(.~
350
375
390
396
80.4
78.9
10.9
11-2
0.29
0.32
75.6
76.6
14.5
405
77.1
14.4
0.36
0.35
0.35
412
420
77.5
73.2
18.7
435
69.1
Z2.9
450
65.8
28.4
0.34
0q41
0.49
0.56
-104-
A2.2 In-Pile Irradiations
The irradiations performed in the E-3 Facility of the NRX
Reactor (A2.4) are listed in the following tables and G* values
were calculated using first order kinetics.
Whenever possible, G* values were obtained by a first order
least square fit of the data available. Otherwise, differential
G* values were calculated using Eq. (A2.1).
Table A2.4
Irradiation of Ortho and Meta-terphenyl
NRX Reactor, E-3 Facility (A.E.C.L.)
100 - 300 0 C
Terphenyl Concentration and Dose Received
Temperature
(0C)
Sample
Number
Terphenyl
Dose
Concentration (watt) (hr)/(gm)
G* (-i)
differential
Ortho-terphenyl
I
E 12
E 32
E 34
E 30
E 62
I
102- 9
136- 8
146-52
170- 2
176 -7
173
253 -9
303
59.51
86.38
63.26
91.46
6.12
15.0
4.55
13.9
0.36
0.40
0.38
0.39
0.48
97.1
2.19
0.42
84.43
4.75
0.42
84.28
4.12
0.49
187- 8
318-23
85.47
4.30
0.44
83.37
3.92
0.54
E 33
E 35
E 31
136- 8
146-52
170- 2
63.04
85.74
67.24
15.1
4.44
13.62
0.35
0.41
0.34
E 105
203- 4
83.66
5.81
0.36
---------- --------------------------- -----------
E 64
E 11
E 10
E 77
E 84
Meta-te rphenyl
I
82.91
Dose rate
100 mw/gm
1
II Dose rate ~'300 mw/gm
G*(-i) = 0.35 * 0.03 obtained by a least square calculation of
the given data as.suming first order kinetics
-105-
Table A2.i7
Irradiation of Ortho and Meta-terphenyl
NRX Reactor, E-3 Facility (A.E.C.L,)
at 350 0 C
Terphenyl Concentration and Dose Received
Sample
Number
[
Terphenyl
Temperature Concentration
(oc)
- (w/o) -- -
Dose
(watt) (hr)/(gn)
Ortho-terphenyl
E
E
E
E
E
E
23
38
40
7
9
36
E 66
4.40
350
353
353
350-7
354-6
354
79.7
354
94.7
0.57
52.84
12.88
78.06
3.52
4.82
4.44
11.68
74.56
76.96
54.72
Meta-terphenyl
E 37
354
62.5
10,95
E 68
353
82.8
4.11
Dose rate 0.100 watt/gm
G*(-i) = 0.54 + 0.06 obtained by a least square calculation of the above given data, assuming first
order kinetics.
-106-
Table A2.6
Irradiation of Ortho-Terphenyl
NEX Reactor, E-3 Facility (A.E,C.L.)
at 4240C
Terphenyl Concentration and Dose
Sample
Number
G*(-i)
Dose
Temperature Terphenyl
(00)
Concentration (watt)(hr)/gm differential
-------------------------E 13
E 56
E 58
424
424
424
65.23
80.18
45.68
2.52
0.95
5.05
1.98
2.73
1.81
2.12
2.16
67.61
424
~~L-------- --------------------Dose rate 0.100 watt/gm
G*(-i) = 1,59 t 0.11 obtained by a least square calculation
of the given data, assuming first order kinetics.
E 60
-107-
Table A2.7
Sample
Number
Irradiation of Ortho and Meta-terphenyl
NRX Reactor - E-3 Facility (A.E.C.L.)
Terphenyl Concentration and Dose
0.100 watt/gm
Dose Rate
Dose
G* (-i)
Temperature Terphenyl
Concentration (watt) (hr)/gm differential
(OC)
Ortho-terphenyl
E
E
E
E
E
E
8
74
14
21
22
28
397-400
401
416-417
444
449
447-449
69.01
88.14
65.86
68.84
69.13
66.06
Meta-terphenyl
E 29
Dose rate
Dose rate
44
7-
44
9
81.75
0.100 watt/gm
0.100 watt/gm
3.94
1.10
0.55
3.12
2.19
1.24
1.01
2.68
1-K
1.56
2.88
3.50
4.75
2.25
-108-
Table A2.8
Irradiation of Ortho and Meta-terphenyl
Sample
Number
NRX Reactor, E-3 Facility (A.E.C.L.)
Terphenyl Concentration and Dose
Dose Rate 0.300 watt/gm
Terphenyl
Dose
Temperature Concentration
(-1)
(watt) (hr)/gm dif G*
(OC)
f
erential
(w/o)
Ortho-terphenyl
E 82
390-403
404-408
E 85
E 83
416-423
E 78
E 79
E 76
427-430
439-441
447-452
83.77
81.76
78.16
1.36
1.53
1,46
1 *48
1.62
73.83
1.67
2.11
70.64
1.26
3.21
66.49
1.31
3.62
88.56
3.25
o.44
86.08
80.00
2.17
1.89
1.91
1.32
1.51
0.80
1.95
Meta-terphenyl
E
E
E
E
E
E
100
106
103
99
102
104
356
411-41 5
438
422-43 :1
450
444
----
Dose Rate
83.56
81.78
83.72
I----.
0.300 watt/gm
1.37
1.11
1.79
-109-
APPENDIX
A3
CONCENTRATION OF THE TERPHENYL ISOMERS
IN THE SANTOWAX OMP IRRADIATIONS
OF CALIFORNIA RESEARCH CORPORATION
Since the concentration of each terphenyl isomer in the
Santowax OMP irradiations performed by California Research
Corporation were given as
Ci
C0
,I
where
at a given dose
= composition of component i
C
composition of component i
C o = initial
and since not all the dose rates were reduced in (watt)(hr)/(gm),
the absolute concentration of each terpbenyl isomer and of omp
in each irradiated capsule, and the dose received in each case,
), as shown below.
were calculated from the given raw data (A
Susie Experiments
DTOTAL = IAMY RH + AN
In
}
D = total dose in (watt)(hr)/(gm)
P = number of megawatt-hours
AMy = 0.53396 (neutron canister and gamma canister)
AMqn = 4.4737 (neutron canister)
RH and InH
given (A3.l)
The initial composition of each terphenyl isomer in
Santowax OMP was (A,):
Composition (w/o)
Component
14.08
Ortho-terphenyl
71.24
Meta -terphenyl
14.41
Para -terphenyl
-110-
MTR Experiments
x 0.52974
l10~
D
DY = 83.8 x R x 3,600 X 0.50307
D
R
Y
= total dose in (watt)(h4/(gm)
is given and expressed in roentgens (ll)
The initial composition or each terphenyl isomer in
Santowax
OMP was (
Component
Ortho-terphenyl
Meta -terphenyl
Para -terphenyl
Composition (w/o)
14.2%
60.4%
25.2%
Since AM,Y for the Gamma Canister was not quoted, it was
assumed, based on the fact that 4 absorbers were found to have
the same coefficient in both canisters, that the value listed
for the Neutron Canister could also be used for the Gamma
Canister.
Table A3.1, A3.2, and A3.3 give respectively the concentrations
obtained with the neutron rich canister, the gamma rich canister,
and the gamma grid irradiations. The data from the irradiations
at26t#t-hr/gm were not used for the calculation of the G* values
(MTR, Gamma Grid), at 425 and 7500F. This was done so that a
comparison with the two other irradiations at 600OF and 675 0 F
could be made (the dose for these irradiations was about
9 (watt)(hr)/(gm).
-111-
Table A3. .
Terphenyl ConcentrationsDuring the Neutron Rich Canister
Irradiations at 425, 600 and 750 F, Susie Reactor (C.R.C)
Sample
Number
I Dose
Composition of Irradiated Samples (w
watt.hr/gn
-para totalterp--nyl
ortho
j-meta
F
425fF
S
S
S
S
S
76
74
77
78
75
10.40
10.07
10.18
9.04
8.98
86.40
82.30
80.67
73-11
71.11
2.30
3.66
3.66
87.30
89.24
86.84
1.88
77.46
3.66
3.66
46.33
41.79
13.20
13.34
13.51
17.76
12.27
11.68
12.06
10.73
10.91
9.15
7.33
7.55
38.88
8.55
39.59
11.37
10.47
8.84
12.64
11.66
11.29
10.47
9.56
63.36
12.53
12.30
12.96
10.41
11.08.
10.72%
9.82
8.75
62.15
8.78
7.89
60.57
59-19
53.59
52.57
5.26
6.39
600OF"
S 218
S 502
S 217
S 219
S 457
S 503
S 459
S 504
S 463
S 462
S 460
S 461
63.59
60.37
55.29
57.10
56.73
52.59
48.40
80.45
79.13
74.47
67.88
66.02
2.20
2.27
4.58
5.15
6.39
7.58
9.26
10.02
8.38
58.83
54-76
55.58
58.11
11.96
82.02
1.83
55.63
11.05
2.20
46.72
41-50
9.51
36.99
33.86
7.74
77-15
65.06
57.68
50.85
6.71
46.42
10.39
750 0 F
S 296.
S 295
S 298
S 297
S 300
S 299
7.73
6.13
5.85
8.44
3.61
4.54
5.09
6.43
-112-
Table A).2
Terphenyl Isomer ConcentrationsDuring the Gamma Rich Canister
Irradiations at 425 and 6000F, Susie Reactor (C.R.C)
-------Con-:osition
of ----------Irradiated Samples
---- (WIO
----------
Sample
Number-
ortho
-- - -
4250F
S 145
-
--
- - ---
-
90.90
90.04
5.66
6.35
87.59
53.25
12.60
12.48
12.31
10.85
58.71
13.39
9.66
55,85
53.94
12.65
12.16
82.95
78.17
4.95
6.35
11.13
11.93
12.81
14.49
13.32
13.06
65.30
64.38
12.28
S 379
12.25
S 380
12.09
62.80
60.60
381
382
383
384
9.71
S 146
total terphenyl
para
meta
Dose
watt.-hr
12.59
600OF
S
S
S
S
10.56
a
85.17
75.27
76.66
-
-113-
Table A2.3
Terphenyl Isomer ConcentrationsDuring the MTR Gamma Grid
Irradiations at 425, 600, 675 and 750 F. (q.R.C.)
-sition
orIrradatedQpS-y 01
Dose
meta
para
total terphenyl
watt. hr/
-ortho
Sample
-Number-
-- ---1 - - -- - - -
-- -
---
4250?
G 55
G 56
20.43
20.98
49.411
G 103
G 104
10.17
10.21
52.42
53.24
20.65
20.54
83.18
8.24
83.99
8.27
6754F
G 115
9.60
49.01
18.44]
??14
7.91
4.99
5.86
1.66
1.55
32.27
15.70
36,71
16,53
16.74
52.96
59.31
9.20
8.66
26.08
26.20
G 13
G 14
50.041
42.51
42.30
19.22
19.66
81.19
81.75
70.42
70.92
9.33
9.36
10.79
10.46
8.40
8.76
26.21
26.16
6000F
750OF
G 80
G 79
G 15
G 16
a
8.00
7.02
15.78
~
a
26.20
24,95
-114-
APPENDIX A4
ITERATION METHOD FOR DETERMINING PYROLYSIS
RATE CONSTANTS AS FUNCTION OF TEMPERATURE
from the M.I.T,
and AE
To obtain the values of kr,i
Loop irradiations the following procedure was employed (Refer
to Section 5.3.3).
labelled
and AE
1. An initial estimate of k 0
pr,i
pr.1
)1, respectively, were obtained using Eq.
(kpr,ioi and (AE,
and the capsule
(5.11) and the experimental values of k
irradiation temperatureTcap'
2. Using the values of (k
i)
and (AEp
)
and the
known values of M and Ti, in Eq. (5.12) a calculated value
is obtained for each irradiation experiment.
(kpri)
3. The value of (k pr,i19 (k ri)l and (AE pri) were
substituted into Eq. (5.11) to obtain an average "effective"
temperature (T1 0 0 p)1 for each irradiation experiment.
then
were
)2 and (AEprt
4. Second estimate of (kpr, i2
eete
,2)
obtained by repeating Step 1, using Eq. (5.11) and the known
experimental values of kpr,i and the value of (T1 0 0 p), obtained
from Step 3.
5. Steps 2 and 3 were repeated to obtain (T oop) 2 '
)
loop n
6. The process was repeated until (T
)
loop n+l1
(T
For the M.I.T. loop data the process converged rapidly so
) were
and (T
)2
that the second and third estimates (T
equal.
-115-
APPENDIX
A5
NOMENCLATURE
C,C
C
=
concentration of component i in a mixture, wt% or weight
fraction. Subscript i refers most frequently to ortho,
meta, para or total terphenyl.
1,3 = concentration of component i in section or sample j.
= total dose absorbed (watt)(hr)/(gm).
= degradation products. That fraction of the irradiated
coolant which is not terphenyls.
= electron
e
Eeff = effective threshold energy of a threshold detector, Mev.
radiolysis activation energy, kcal/mole.
AE R=
D
DP
AE
a=pyrolysis activation energy for unirradiated terphenyl i,
kcal/mole.
AEpr,i= pyrolysis activation energy for irradiated terphenyl i,
kcal/mole.
= total in-pile dose rate factor, (watt)(hr)(cm3)/(MWH)(gm).
F
= fraction of absorbed dose due to fast neutron interactions,
fN
= fraction of absorbed dose due to gamma ray interactions.
fy
G(-i) = total decomposition yield of component i in the coolant,
expressed as molecules of component i degraded per 100 ev
absorbed in the total coolant, where i refers to ortho,
meta, para or total terphenyl.
GR(-i) = radiolytic decomposition yield of component i in the
coolant, expressed as molecules of component i degraded
by radiolysis per 100 ev absorbed in the total coolant.
= pyrolytic decomposition yield of component i in the
G pr (-i)
coolant, expressed as molecules of component i degraded
by pyrolysis per 100 ev absorbed in the total coolant.
G(-*HB) = total (radiolytic and pyrolytic) production yield of
HB in the coolant, expressed as equivalent molecules of
omp degraded to form HB per 100 ev absorbed in the total
coolant.
-116G(-+" LIB) = total (radiolytic and pyrolytic) production yield of
LIB in the coolant, expressed as equivalent molecules of
omp degraded to form LIB per 100 ev absorbed in the total
coolant.
G*(-i) = G(-i)/Ci
G*(-1)
GR(-)/C
G*
(-i) = G (-i)/Ci
G*(+ HB) =G(+ HB)/C komp
G*(+*LIB) = G(- LIB)/Comp
= radiolytic decomposition yield of component i in the
GN(
coolant for fast neutron interactions.
G Y(-i) = radiolytic decomposition yield of component i in the
coolant for gamma ray interactions.
G (-i) = radiolytic decomposition yield of component i in the
total coolant for electron interactions.
decomposition yield of component i in the coolant for
fast neutron interactions, not corrected for pyrolysis.
decomposition yield of component i in the coolant for
[G (-i I=
gamma ray interactions, not corrected for pyrolysis,
[G e(-1 = decomposition yield of component i in the coolant for
EGN(-1)1
=
electron interactions, not corrected for pyrolysis.
=[G( -i)]/C
; [G*(-i)
G* (-i) = G (-1)/C
G*(-1)
=
Ge (-i)/C 1
; [G* (-i)]
=Ge(-1/Ci
= time of reactor operations, hr.
= high boilers. Those fractions of irradiated coolant having
higher boiling points than that of para-terphenyl.
kR,i,n= radiolytic reaction constant for component i in the
coolant, n th order, gm/(watt)(hr).
pyrolytic reaction constant for irradiated component i
k
i=
H
HB
pr,i,m
th
-
order, hr 1 .
in the coolant, m
ki9 = first order pyrolytic constant for unirradiated component
i in the coolant, hr'
order pyrolytic constant for irradiated component i
k
4= first
1
hr
.
LIB = low and intermediate boilers. Those fractions of the irradiated coolant having boiling points equal to or less than
those of the terphenyls (w/o DP., w/o HB= w/o LIB).
-117-
M
MWH
m
= mass of coolant, grams.
= period of reactor operation, megawatt-hours.
= reaction order
R
= reaction order.
= ortho, meta and para-terphenyl.
= average dose rate, watt/gm.
= universal gas constant, kcal/(gram mole)(OK).
T
t
w/o
Ca
=
=
=
=
0
= beta radiation.
n
omp
r
temperature, 0 K, 0F.
time.
weight percent
alpha particle.
= gamma radiation.
= correction factor for G values calulations in steadystate HB periods, grams.
= summation sign.
aeff = effective threshold neutron cross-section, barns.
= specific dose absorbed by irradiated ecoolat,
T
y
A
[
(watt)(hr)/(gm coolant).
= pyrolysis effect not separated from radiolysis effect,
-118-
APPENDIX A6
REFERENCES
A6.1 References for Chapter I
(1.1)
H. Etherington, editor, Nuclear Engineering Handbeek,
Chapter 10, McGraw-Hill Book Co., Inc., New York, 1958.
(1.2)
R.O. Bolt and J.G. Carroll, editors, Radiation Effects
on Organic Materials, Chapters 3 and 4, Academic Press,
New York, 19631
(1i~)
C.D, Sawyer and E.A. Mason, "The Effects of Reactor
Irradiation on Santowax OMP at 610F and 7500," MITNE-39
(IDO-ll,107), Department of Nuclear Engineering, M.I.T.,
Cambridge, Mass., September, 1963.
(1.4)
"Atomic Energy in the Soviet Union," Trip Report of the
V,$. Atomic Energy Delegation, May, 1963.
A6.2 References for Chapter II
(2.1)
R.O. Bolt and J.O. Carroll, editors, Radiation Effects
on Organic Materials, p.8 5, Academic Press, New York,
1963.
(2.2)
R.H.J. Gercke and C.A. Trilling, "A Survey of the
Decomposition Rates of Organic Reactor Coolants,"
NAA-SR-3835, Atomics International, Canoga Park, Calif,,
June, 1959.
(jr))
T.H. Sworski and M, Burton, "A Study of the Effect of
Impingent Particles in Radiolysis of Some Aromatics
Compounds," Journal of the American Chemical Society,
M,
(2.4)
p. 3790,
August, 1951.
R.H. Schuler and A.O. Allen, "Radiation Chemical Studies
with Cyclotron Beams," Journal of the American Chemical
Society, Z2, p.507, 1955,.
-119-
(.)
H.A. Dewhurst and R.H. Schuler, "A Comparison of the
Decomposition of Hexane and Cyclohexane by Different
Types of Radiation," Journal of the American Chemical
Society, 81, p. 3210, 1959.
(2.6)
A. Charlesby, "Effect of Radiation on Behaviour and
Properties of Polymers," The Effects of Radiation on
Materials, J.J. Harwood and Co. (editors), p. 268, Reinhold
Publishing Corp., New York, 1958.
(2.7)
C.G. Collins and V.P. Calkins, "Radiation Damage to
Elastomers, Organic Liquids, Plastics," Report APEX 261,
General Electric Company, Atomic Products Division,
Aircraft Nuclear Propulsion Department, September, 1955.
(2.8)
E.L. Zebroski and E.M. Kinderman, "A Comparison of High-Energy
Electron anad Gamma Irradiations Effects on Organic Liquids,
Report WADC-TR-57-141, Stanford Res. Inst., February, 1957.
(2.9)
W.G. Burns, C.R.V. Reed, J.A. Winter, "The Radiation
and Thermal Stability of Some Potential Organic ModeratorCoolants, Part VIII: Pile and Elsotron Irradiation of
Various Polyphenyl Mixtures and Work with Additives,"
AERE-R 4072, Atomic Energy Research Establishment, Harwell,
England, November, 1963.
(2.10) W.M. Hutchinson et al., "Relationship Between Yields of
Dimers of a Polyphenyl and its Partial Reaction Rates,"
IDO-16706, Phillips Petroleum Co., Idaho Falls, Idaho,
August, 1963.
(2.11) A.J. Moffat, "The Electron Radiolysis of Benzene-MTerphenyl and Perdenterobenzene-M-Terphenyl Mixtures,"
IDO-16876, Phillips Petroleum Co., Idaho Falls, Idaho,
May, 1963.
(2.12) T.H. Bates, W.G. Burns et al., "The Radiation and
Thermal Stability of Some Potential Organic Moderator
Coolants, Part I: Electron Irradiation of Para-Terphenyl
and Santowax R," AERE C/R 2121, Atomic Energy Research
Establishment, Harwell, England, May, 1957.
-120-
(2.13) W.G. Burns et al.,
"The Effects of Fast Electrons and Fast
Neutrons on Polyphenyls at High Temperature," Proceedings
of the Second United Nations International Conference on
the Peaceful Uses of Atomic Energy, Vol 22,
pp.266-275, United Nations, Geneva, 1958.
P/51,
(2.14) T.H. Bates et al., "The Radiation and Thermal Stability
of Some Potential Organic Moderator Coolants, Part II:
Pile Irradiation of Para-Terphenyl and Santowax R,"
AERE C/R 2185, Atomic Energy Research Establishment,
Harwell, England, July, 1959.
A6.3 References for Chapter III
(Q1l) R.W. Wilkinson and T.H. Bates, "The Radiation and
Thermal Stability of Some Potential Organic Moderator
Coolants, Part III: Thermal Stability of Para-Terphenyl
and Santowax R," AERE-M 412, Atomic Energy Research
Establishment, Harwell, England, August, 1959.
(3.2)
D.R. de Halas, "Kinetics of the Decomposition of
Organic Reactor Coolants," HW-56769, Hanford, 1958.
()33)
A. Houllier and J.R. Puig, "Stabilits Thermique et
Radiolytique des Triphenyles," Energie Nuclgaire, 4,
No. 5, pp. 343-351, October, 1962.
(3.4)
D.G. Kuper, "Organic Coolant Degradation Studies,"
IDO-16853, Phillips Petroleum Co., Idaho Falls, Idaho,
March, 1963.
(3.5)
Annual Technical Progress Report, A.E.C., Unclassified
Programs, Fiscal Year 1962, Section III-G, NAA-SR-7400,
Atomics International, Canoga Park, Calif., August, 1961.
(3.6)
Quarterly Technical Progress Report, A.E.C. Unclassified
Programs, October-December 1962, Section III-B, NAA-SR-8080,
Atomics International, Canoga Park, Calif., February, 1963.
(3.7)
R.O. Bolt et al., "Relative Effects of Fast Neutrons and
Gamma Rays on the Radiolysis of Polyphenyls," California
Research A.E.C. Report No. 23, California Research Corporation, Richmond, Calif., June, 1963.
-1?4-
(QL8)
Personal Communication from J.P. Jourdan, Progil, to
E.A. Mason, M.I.T., December 20, 1963, Information
understood to be contained in internal document.
A. Houllier, "March d'Irradiation Euratom," CEA-Progil,
No. 117.63.4, ORGF, Lyon, 12 Novembre 1963,
(M)
Persona 1 Communication from R.F.S., Robertson, AE.C.L.
to E.A. Mason, M.I.T., January 3, 1964.
(3.10) C.D. Sawyer and E.A. Mason "The Effect of Reactor
Irradiation on Santowax OMP at 610OF and 750 OF, MITNE-39
(IDO-1,107), Department of Nuclear Engineering, M.I.T.,
Cambridge, Mass,, December, 1963.
(3._l) W.M. Hutchinson et al., "Relationship Between Yields
of Dimers of a Polyphenyl and its Partial Reaction
Rates," IDO-16706, Phillips Petroleum Co., Idaho Falls,
Idaho, August, 1961.
(32)
A.J. Moffat, "The Electron Radiolysis of Benzene-MTerphenyl and Perdenterobenzene-M-Terphenyl Mixtures,"
IDO-16876, Phillips Petroleum Co., Idaho Falls,
Idaho, May, 1963.
(33)
S.
Elberg (C.E.A.) and Fritz (Euratom), "Physical Properties
of Organic Nuclear Reactor Coolants," EUR.400e., Suratom,
Brussels, 1963,
(31.4) T.O. Jones et al., "The Sffects of Phase on Reactions
Induced by Radiation in Organic Systems," J. Phys. Chem.,
62, January, 1958.
(2)
D.R. de Halas, "Radiolysis and Pyrolytic Decomposition
of Organic Reactor Coolants," Proceedings of the Second
United Nations International Conference on the Peaceful
Uses of Atomic Energy, .L, P/611, United Nations, Geneva,
1958.
(3_6.) Persona l Communication from G.C. Nullens, Euratom to
E.A. Mason, M.I.T,, May, L964.
-122-
(212)Person al Communication from A.W. Boyd, A.E.C.L., to
E.A. Mason, M.I.T., May, 1964.
(3.18) "Report on Organic Liquid-Cooled Reactor Development,"
Excerpts from A.E.C.L. Progress Reports, October 1-December
31, 1963, PR-CM-36, Atomic Energy of Canada Limited, Ontario,
Canada.
(3.12) "Report on Organic Liquid-Cooled Reactor Development,"
Excerpts from A.E.C.L. Progress Reports, July 1September 30, 1961, PR-CM-27, Atomic Energy of Canada
Limited, Ontario, Canada.
(3.20) R.O. Bolt and J.O. Carroll, editors, Radiation Effects
on Organic Materials, p.85, Academic Press, New York,
1963.
A6.4 References for Chapter IV
(4,1)
C.D. Sawyer and E.A. Mason, "The Effects of Reactor
Irradiation on Santowax OMP at 610 0 F and 7500F,"
MITNE-39 (IDO-ll,107), Department of Nuclear Engineering,
M.I.T.,
(4.2)
Cambridge,
Mass.,
September,
1963.
T.H. Bates, W.G. Burns et al., "The Radiation and Thermal
Stability of Some Potential Organic Moderator Coolants,
Part V: Pile and Electron Irradiation of Biphenyl, Orthoterphenyl, Metaterphenyl, and Pile Irradiation of Santowax
R to High HBR Content,* AERE-R-5143, Atomic Energy
Research Establishment, Harwell, England, March, 1962.
(4.3)
T.H. Bates, W.G. Burns et al., "The Radiation and Thermal
Stability of Some Potential Organic Moderator Coolants,
Part II: Pile Irradiation of Paraterphenyl and Santowax R,"
AERE C/R 2185, Atomic Energy Research Establishment,
Harwell, England, March, 1962.
(4,41)
R.H.J. Gercke and C.A. Trilling, "A Survey of the
Decomposition Rates of Organic Reactor Coolants," NAA-SR3835, Atomics International, Canoga Park, Calif., June,
1959.
-123-
(4_)
J.F. Zack Jr. et al., "In-Pile Capsule Experiments to
Determine the Effect of Fast Neutrons on the Radiolytic
Decomposition Rate of Terphenyls," NAA-SR-7395,
Atomics International, Canoga Park, Calif., June, 1959.
A6.5 References for Chapter V
(5jl)
D.T. Morgan and E.A. Mason, "The Irradiation of Santowax
OMP in the M.I.T. In-Pile Loop," Parts I and II,
MITNE-21 (IDO-ll,104) and MITNE-22 (IDO-l1,105), Department
of Nuclear Engineering, M.I.T., Cambridge, Mass., May,
1962.
(5o2)
C.D. Sawyer and E.A. Mason, "The Effects of Reactor
Irradiation on Santowax OMP at 6100F and 7500F,"
MITNE-39 (IDO-l1,107), Department of Nuclear Engineering
M.I.T., Cambridge, Mass., September, 1963.
(5.3)
E.A. Mason and W.N. Bley, "In-Pile Loop Studies of
Organic Coolant Materials," Annual Report, MITNE-45/SRO 86,
to be published.
(L.4)
A.W. Boyd, "The Radiolysis and Pyrolysis of Organic
Coolants," Journal of Nuclear Materials, ., No. 1,
pp. 1-17, North Holland Publishing Co., Amsterdam (Netherlands)
1963.
(._$)
S. Elberg (CEA) and Fritz (Euratom), "Physical Properties
of Organic Nuclear Reactor Coolants," EUR.400e., Euratom,
Brussels (Belgium), 1963.
(56)
Personal Communication from J.P. Jourdan, Progil to
E.A. Mason, M.I.T., December 20, 1963, Information
understood to be contained in internal document,
A. Houllier, "March4 d'Irradiation Euratom," CEA-Progil,
No. 117.63.4, ORGF, Lyon (France), 12 Novembre, 1963.
(5.7)
Personal Communication from G.C. Nullens, Euratom, to
E.A. Mason, M.I.T., May, 1964.
(5s8)
Y. Droulers, "Influence du Spectre des Neutrons sur
l'Energie de Radiolyse dans les LiquidesOrganiques,"
Neutron Dosimetry, Proceedings of a Symposium, Harwell
10-14 December 19629 1, International Atomic Energy
Agency, Vienna (Austria),
1963.
A6.6 References for Chapter VI
(6.1)
T.H. Bates, W.G. Burns et al., "The Radiation and
Thermal Stability of Some Potential Moderator Coolants,
Part I: Electron Irradiation of Para-Terphenyl and
Santowax R," AERE C/R 2121, Atomic Energy Research
Establishment, Harwell, England, May, 1957.
(6.2)
W.G. Burns, et al., "The Effect of Fast Electrons and
Fast Neutrons on Polyphenyls at High Temperature,"
Proceedings of the Second United Nations International
Conference on the Peaceful Uses of Atomic Energy,
Vol 2 , P/51 9 pp. 266-275, United Nations, Geneva, 195&
(6_l)
T.H. Bates, W.G. Burns et al., "The Radiation and
Thermal Stability of Some Potential Organic Moderator
Coolants, Part II: Pile Irradiation of Para-terphenyl
and Santowax R," AERE C/R 2185, Atomic Energy Research
Establishment, Harwell, England, July, 1959.
(6.4)
A.R. Anderson and R.J. Waite, "The Calorimetric Measurement
of Energy Absorbed from Reactor Radiation in BEPO,"
AERE C/R 2253, Atomic Energy Research Establishment,
Harwell, England, March, 1960.
(
C.D. Sawyer and E.A. Mason, "The Effects of Reactor
Irradiation on Santowax OMP at 610 0 F and 750OF,"
MITNE-39 (IDO-ll,107), Department of Nuclear Engineering,
M.I.T., Cambridge, Mass., September, 1963.
(6.6)
T.H. Bates, W.G. Burns et al., "The Radiation and Thermal
Stability of Some Potential Organic Moderator Coolants,
Part V: Pile and Electron Irradiation of Biphenyl, Orthoterphenyl, Meta-terphenyl and Pile Irradiation of Santowax R
to High HBR Content," AERE-3743, Atomic Energy Research
Establishment, Harwell, England, March, 1962.
-125-
(6j7)
W.G. Burns et al., "The Radiation and Thermal Stability
of Some Potential Organic Moderator Coolants, Part VIII:
Pile and Electron Irradiation of Various Polyphenyl
Mixtures and Work with Additives," AERE-R 4072, Atomic
Energy Research Establishment, Harwell, England,
November, 1963.
(6.8)
Organic Coolant Reactor Program, Quarterly Report,
July 1-September 30, 1961, IDO-16734, Phillips Petroleum
Co., Idaho Falls, Idaho, December, 1961.
(6_)
Organic Coolant Reactor Program, Quarterly Report,
October 1-December 31, 1961, Phillips Petroleum Co.,
Idaho Falls, Idaho.
(6.10) Personal
Communication to E.A. Mason, M.I.T., Excerpts
from A.E.C.L.
Progress Reports, April 1-June 30, 1962,
PR-CM-30 (Section 7), Atomic Energy of Canada Limited,
Chalk River, Ontario.
(6.11) W.D. Mackintosh, "The Electron Irradiation of the
Potential Organic Coolant for Power Reactors, Santowax OM,"
paper presented at the Third Conference on Nuclear Reactor
Chemistry, Gatlinburg, Tenn., October, 1962.
(6.12) Personal Communication from W.D. Mackintosh, A.E.C.L.
to E.A. Mason, M.I.T., March, 1963.
(.1)
Personal Communication to E.A. Mason, M.I.T., Excerpts
frop A.E.C.L. Progress Reports, April 1-June 30, 1961,
PR-CM-26 (Section 7), Atomic Energy of Canada Limited,
Chalk River, Ontario.
(6.14) Personal Communication from A.W. Boyd, A.E.C.L., to
E.A. Mason, M.I.T., May, 1964.
(6.15) W.N. Bley, "An In-Pile Loop Study of the Performance of
Polyphenyl Reactor Coolants," NAA-SR-3835, Atomics
International, Canoga Park, Calif., June, 1959.
(6.16) R.T. Keen et al., "Methods for Analysis of Polyphenyl
Reactor Coolants," NAA-SR-4356, Atomics International,
Canoga Park, Calif., January, 1961.
-126-
(6.17) R.T. Keen et al., "Radiolysis Products of Polyphenyl
Coolants; Part I, In-Pile Loop Irradiations," NAA-SR-4355,
Atomics International, Canoga Park, Calif., March, 1962.
(6.18) S. Berg et al., "Irradiations of Santowax OMP at the
Curtiss-Wright Research Reactor," NAA-SR-TDR 5892,
Atomics International, Canoga Park, Calif., January, 1961.
(6.19) J.F. Zack et al., "In-Pile Capsule Experiments to
Determine the Effect of Fast Neutrons on the Radiolytic
Decomposition Rate of Terphenyls," NAA-SR-7395, Atomics
International, Canoga Park, Calif., May, 1963.
(6.20) R.M.J. Gercke and C.A. Trilling, "A Survey of the Decomposition Rates of Organic Reactor Coolants," NAA-SR-3835,
Atomics International, Canoga Park, Calif., June, 1959.
(6.21) R.O. Bolt et al., "Dosimetry of Reactor Radiation from
the Shield Test Pool Facility," California Research-AEC
Report No. 22, California Research Corp., Richmond,
Calif., June, 1963.
(6.22) R.O. Bolt et al., "Relative Effects of Fast Neutrons and
Gamma Rays on the Radiolysis of Polyphenyls," California
Research-AEC Report No. 23, California Research Corp.,
Richmond, Calif., June, 1963.
(6.23) Personal Communication from R.O. Bolt, California
Research Corp., to E.A. Mason, M.I.T., January, 1964.
(6.24) Person al Communication from M.A. Sweeney, California
Research Corp., to E.A.
Mason, M.I.T., April, 1964.
(6.25) "Effect of High Temperature on Radiolytic and Pyrolytic
Damage of Polyphenyls," Excerpts from NAA-SR-8888,
Annual Technical Progress Report, AEC Unclassified Program
FY 63,
Atomics International,
Canoga Park,
Calif.
(6.26) Person al Communication to E.A. Mason, M.I.T., "Radiolytic
and Pyrolytic Studies at Chalk River," R.P.S. Robertson
A.E.C.L., June, 1961, Chalk River, Ontario,
-127-
A6.7 References for Appendices
(Al.1) T.H. Bates, W.G. Burns et al., "The Radiation and Thermal
Stability of Some Potential Organic Moderator Coolants,
Part II: Pile Irradiation of Para-terphenyl and Santowax B,"
AERE C/R 2185, Atomic Energy Research Establishment,
Harwell, England, March, 1960.
(Al.2) T.H. Bates, W.G. Burns et al., "The Radiation and Thermal
Stability of Some Potential Organic Moderator Coolants,
Part V: Pile and Electron Irradiation of Biphenyl,
Ortho-terphenylg Meta-terphenyl and Pile Irradiation of
Santowax R to High HBR Content," AERE-3743, Atomic Energy
Research Establishment, Harwell, England, March, 1962.
(A1.3)
"The Radiation and Thermal Stability
of Some Potential Organic Moderator Coolants, Part VIII:
Pile and Electron Irradiation of Various Polyphenyl
Mixtures and Work with Additives," AERE-R 4072, Atomic
W.G. Burns et al.,
Energy Research Establishment, Harwell, England, November,
1963.
(Al.4) Personetl Communication to E.A. Mason, M.I.T., "Radiolytic
and Pyrolytic Studies at Chalk River, R.F.S. Robertson,
A.E.C.L., Chalk River, Ontario.
(Alj)
W.D. Mackintosh, "The Electron Irradiation of the Potential
Organic Coolant for Power Reactors, Santowax OM," paper
presented at the Third Conferenne on Nuclear Reactor
Chemistry, Gatlinburg, Tenn., October, 1962.
(A2.1) Personal Communication to E.A. Mason, M.I.T., Excerpts
from A.E.C.L. Progress Reports, July 1-September 30,
1962, PR-CM-31 (Section 7), Atomic Energy of Canada
Limited,
(A2.2)
Chalk River, Ontario.
W.D. Mackintosh, "The Electron Irradiation of the Potential
Organic Coolant for Power Reactors, Santowax OM," paper
presented at the Third Conference on Nuclear Reactor
Chemistry, Gatlinburg, Tenn., October, 1962.
-128-
(A2.3) Personal Communication to E.A. Mason, M.I.T., Excerpts
from A.E.C.L. Progress Reports, April 1-June 30, 1962,
PR-CM-30, (Section 7), Atomic Energy of Canada Limited,
Chalk River, Ontario.
(A2.4) Personal Communication from A.W. Boyd, A.E.C.L., to
E.A. Mason, M.I.T., May, 1964.
(A3.l) R.O. Bolt et al., "Relative Effects of Fast Neutrons
and Gamma Rays on the Radiolysis of Polyphenyls,"
California Research-AEC Report No. 23, California
Research Corp.,
Richmond, Calif., June, 1963.
(A3.2) Personal Communication from M.A. Sweeney, California
Research Corp., to E.A. Mason, M.I.T., April, 1964.