MASSACHUSETTS INSTITUTE
OFTECHNOLOGY
NUCLEAR ENGINEERING
Investigations
of
ORNL Pressurized Thermal Shock Experiments
by
Dong W. Jerng and Robert G. Carter
Report No. MITNE-300
March 30, 1992
Investigations
of
ORNL Pressurized Thermal Shock Experiments
by
Dong W. Jerng and Robert G. Carter
Report No. MITNE-300
March 30, 1992
Foreword
This report is prepared under the contract (Contract No. : Pending ) between Yankee
Atomic Electric Company and Massachusetts Institute of Technology.
Principal investigator:
Neil. E. Todreas, Professor
Nuclear Engineering Dept., M.I.T
Research assistant:
Project Monitor:
Dong W. Jerng, Postdoctoral Associate
Nuclear Engineering Dept. M.I.T.
Robert G. Carter, Senior Engineer
Yankee Atomic Electric Company
Research period: February 12, 1992
-
March 25,1992
Table of Contents
1. Introduction .....................................................................
. . --.--
1.1 B ackground .......................................................--......
1
- - -1
1.2 A Brief Description of the PTSE Series .........................................
2
2. Dimensions and Material Properties.......................................................4
2.1 PTSE Vessel......................................................................5
2.2 PTSE Inserts......................................................................5
2.3 Yankee Rowe Reactor Vessel......................................................15
3. PTS Transients and Stress Distributions.................................................
16
3.1 PT SE series..........................................................................16
3.2 Yankee Rowe PTS Transients ...................................................
19
4. Discussion.....................................................................
47
References .......................................................................................
50
i
List of Figures
Fig.1.1 Temperature and stress distribution in the PTSE tests and the actual PTS in
nuclear reactors......................................................................
.3
Fig.2.1 Piecewise linear stress-strain relationship used for the pretest analysis of
PTSE-1 (source from Fig. 10.18 of Ref.1).......................................5
Fig.2.2 KIC data for PTSE-1. Curves represent functions in the pretest analysis.
(source from Fig.10.16 of Ref.1).................................................6
Fig.2.3 KIA data for PTSE-1. Curve represents function in the pretest analysis
(source from Fig. 10.17 of Ref.1).................................................7
Fig.2.4 True stress vs. strain from tensile test of specimen (pretest material) at
212 OF. (source from Fig.2.24 of Ref.2)........................................9
Fig.2.5 KIC data for PTSE-2 insert (pretest). (source from Fig.10.10 of Ref.2)........10
Fig.2.6 KIA data for PTSE-2 insert (pretest). (source from Fig.10.9 of Ref.2) ......... 11
Fig.2.7 True stress vs. strain from tensile test of specimen (posttest material) at
212 OF. (source from Fig.2.25 of Ref.2)........................................13
Fig.2.8 Posttest fracture toughness KjC for PTSE-2 insert compared with similar
pretest specimens. (source from Fig.2.52 of Ref.2).............................14
Fig. 3.1 Transient conditions and stress distributions in PTSE-lA.....................20
Fig. 3.2 Transient conditions and stress distributions in PTSE-1B.....................23
Fig. 3.3 Transient conditions and stress distributions in PTSE-1C.....................26
Fig. 3.4 Transient conditions and stress distributions in PTSE-2A.....................29
Fig. 3.5 Transient conditions and stress distributions in PTSE-2B.....................32
Fig. 3.6 Transient conditions and stress distributions in Yankee SBLOCA
(Case 170)...............................................................................35
Fig. 3.7 Transient conditions and stress distributions in Yankee MSLB (Case 971).....38
Fig. 3.8 Transient conditions and stress distributions in Yankee MSLB(Case 973)......41
Fig. 3.9 Transient conditions and stress distributions in Yankee MSLB(Case 974)......44
ii
List of Tables
Table 1.1 Summary of experimental observations of the PTSE ............................
3
Table 2.1 Dimension and material properties of the PTSE vessel.......................4
Table 2.2 Material properties of the insert in PTSE-1...................................5
Table 2.3 Pretest material properties of the insert in PTSE-2.............................8
Table 2.4 Post-test material properties of the insert in PTSE-2...........................12
Table 2.5 Dimension and material properties of the Yankee Rowe Reactor Vessel
Plate material........................................................................15
Table 3.1 The maximum thermal stress calculated by VISAY with different
.....----..-------------values of he
17
Table 3.2 Sources of the pressure and temperature data for PTSE stress calculations... 17
Table 4.1 A comparison of RTNT between PTSE and Yankee Rowe....................48
Table 4.2 Comparisons of the maximum stresses between PTSE and Yankee Rowe
PT S .................................................................................
iii
49
1. Introduction
1.1 Background
This study investigates a series of the pressurized thermal shock experiments (PTSE)
performed by the Oak Ridge National Laboratory (ORNL) to provide a basis of
applicability of the PTSE results to the pressurized thermal shock (PTS) evaluation of the
Yankee Rowe Reactor Vessel.
The consequence of a PTS on the reactor vessel depend on factors such as material
properties, transient conditions (cooling rate of the vessel and pressure transient), stresses
(thermal, hoop, clad, and residual), and the size, location, and orientation of flaws in the
vessel wall.
Because information about flaws in the Yankee Rowe Reactor Vessel is not available
and the PTSE vessel does not have clad and residual stress data, this report examines the
PTSE series from the aspects of the material properties and stresses (thermal and hoop)
imposed on the vessel in comparison with the Yankee Rowe PTS analyses. Specifically,
this report provides :
1. Properties of material used in the PTSE: toughness, yield and tensile strength,
and the nil-ductility temperature - A comparison of these material properties
among the PTSE vessel, inserts and Yankee Rowe Reactor vessel is presented
in Section 2, and
2. Stress distributions and associated transient conditions in the PTSE: vessel
temperature and pressure transient conditions, and thermal and hoop stress*
resulting from these transient conditions - this is presented in Section 3.1, and
in Section 3.2 the transient conditions and resulting stresses for the Yankee
Rowe Reactor Vessel are presented for the comparison with the PTSE results.
In Section 4, a discussion about the interpretation of the PTSE results in conjunction with
the Yankee Rowe PTS evaluation will be made for experimental method, material
properties, and magnitude of stress.
* In this report, thermal stress refers to the stress due to temperature gradient
in the vessel wall, and hoop stress refers to the stress due to pressure. Because
only the longitudinal flaw was investigated in the PTSE (because the
logitudinal flaw is most important under PTS), both thermal and hoop stresses
refered in this report are in the circumpherential direction (i.e., hoop
direction) so that the longtudinal flaw is subject to tensile or compressive
force in the circumferential direction.
1
For the evaluation of the PTSE series, two reports from the ORNL, NUREG/CR4106 [1] and NUREG/CR-4888 [2] were used. For the evaluation of the Yankee Rowe
PTS transients, four representative cases developed by Yankee Atomic were utilized.
1.2 A Brief Description of the PTSE Series
The pressurized thermal shock experiment series in the ORNL were performed in
two steps: the PTSE-1 series during December 1984 and the PTSE-2 series during
November to December 1986.
In both series of the PTSE, the crack behavior was examined by monitoring a 1-mlong flaw implanted in an insert material welded into the exterior wall of the pressure
vessel. In the PTSE-1 series, a high toughness material was used for the investigation of
warm prestressing and the nature of crack propagation and arrest. In the PTSE-2 series, a
low toughness material was used for the investigation of the crack behavior and warm
prestressing with low tearing resistance.
There are three tests labeled as PTSE-1A, PTSE-1B, and PTSE-1C in the PTSE-1
series, and two tests, PTSE-2A and PTSE-2B, in the PTSE-2 series. These test cases
differed from each other in the transient conditions applied to each case. In the PTSE
series, the cooling was applied at the outer surface of the vessel to induce the thermal
shock in contrast to the actual situation occurring in nuclear reactor PTS transients (i.e., the
cooling occurs at the inside of the vessel). Fig. 1.1 illustrates temperature and stress
distribution incurred in the PTSE compared with those due to an actual PTS in a nuclear
reactor.
The summary of experimental observations of the PTSE series are listed in Table
1.1. Through both series of PTSE, the effect of warm prestressing was recognized, i.e.,
crack was observed not to propagate while K, are decreasing even if Ki is greater than KICThus, the vessel rupture occurred only for PTSE-2B in which the pressure was controlled
to steadily increase resulting the monotonic surge of K, with time. More details of the
transient conditions for each PTSE test will be presented in Section 3.1.
2
Table 1.1 Summary of experimental observations of the PTSE
Observation
PTSE-1Aa PTSE-1Ba PTSE-1Ca PTSE-2Ab PTSE-2Bb
Initial Crack Depth
a (inch)
0.48
0.48
0.96
0.59
1.67
0.288
0.098
0.165
0.083
0.083
a/w
Final Crack Depth
0.48
0.96
1.61
1.67
Rupture
a (in)
a/w
0.083
0.165
0.278
0.288
1.0
40.8
125.3
249.4
67.1
No Crack
Time of Crack
Jump (sec) c
Propagation
72.6
172
135.9
61
253.6
119
280.1
Re1the
'itlcrckcepths
10110
of
Ref 11ITal11oRe.
In Table 103
a- From
Table
FnTbe110oRf.
.:
. of~
.
.iiilcakd
h are
r listi
i edas
11.4 mm for PTSE-1A and 1B, and 22.1 mm for PTSE-1C.
b: From Table 10.10 and 9.2 of Ref.2
c: Time measured from the initiation of transients
Time of Maximum
K1 (sec) c
Side view
I
I
0,.
Flaw
distribution
I
I
Cooling
at the outer surface
-
I
I
Cooling
a
at the inner surface
C-Thermal
stress
distribution
Hoop stress
distribution
I
-
Tensile
-%
(thermal stress
at the cooled side
and hoop stress)
Top view
compressive
T
(thermal stress
at the uncooled side)
(b) Actual PTS case
(a) PTSE case
Fig.1.1 Temperature and stress distribution in the PTSE tests and the actual PTS in
nuclear reactors
3
2. Dimensions and Material Properties
2.1 PTSE Vessel
The dimension and material property of the vessel used in the PTSE are listed in
Table 2.1. The same vessel was used for both PTSE- 1 and PTSE-2.
Table 2.1 Dimension and material properties of the PTSE vessel
Dimension and
Property
Measured Value
Outer Radius (inch)
19.31
Inner Radius (inch)
13.50
Thickness (inch)
5.81
Yield Strength
(ksi)
65.27 (26 %elongation)a
62.66 (29 %elongation)a
Tensile Strength
84.99 (26 %elongation)a
(ksi)
81.66 (29 %elongation)a
NDT (OF)
-59.8a
Remark
87.02 ksi (value used for the
pretest analysis) b
a: from Table 2.1 of Ref.1. The RTNDT is not defined for the vessel material
b: from Table 10.8 of Ref. 1
4
2.2 PTSE Inserts
Table 2.2 shows the material properties* of the insert for the PTSE- 1 series. The
stress - strain for the PTSE-1 insert is shown in Fig.2.1. The KIC and KIA data and curves
for the PTSE-1 insert are shown in Fig.2.2 and 2.3 respectively.
Table 2.2 Material properties of the insert in PTSE-1
Remark
Measured Value
Property
Yield Strength (ksi)
[92.78 - 0.046 (T-32)
+ 7.315x10-5(T-32) 2 ]a (T in OF)
87.02 (value used for the
pretest analysis) b
[116.73 - 3.543x10-4 (T-32)
Tensile Strength
+ 9.568x10-5(T-32)2 ]a (T in OF)
(ksi)
RTNIT (OF)
196.3 c
a: From Table 2.3 of Ref.1
b: From Table 10.2 of Ref.1
c: From Section 2.3.3 (page 18) of Ref.1
1000
900
800
V)
V)
U,
700
U,
D
a: 600
500
400
0
0.01
0.02
0.03
0.04
0.05
0.06
TRUE STRAIN
0.07
0.08
0.09
Fig.2.1 Piecewise linear stress-strain relationship used for the pretest analysis of PTSE-1
(source from Fig.10.18 of Ref.1)
In Ref.1 it is not mentioned whether the material properties of the insert are
of those examined before or after the tests.
*
5
400
300
200
100
0
-50
0
50
150
100
200
250
0
TEMPERATURE ( C)
Fig.2.2 KIC data for PTSE-1.* Curves represent functions in the pretest analysis. (source
from Fig.10.16 of Ref.1)
The original figure caption(Fig.10.16 of Ref.1) reads " KIc for PTSE-1
vessel". However, it is believed that the data shown in Fig 2.2 are for the
PTSE-1 insert because the pretest analysis was performed for the insert
material..
*
6
400
300
a
b
=
c
=
35.0
4.0177
0.02408
200
0
0
0
100A
00
-50
0
50
100
150
TEMPERATURE (0 C)
200
250
Fig.2.3 KIA data for PTSE-1.* Curve represents function in the pretest analysis
(source from Fig. 10.17 of Ref. 1)
original figure caption(Fig1O.16 of Ref.1) reads " KIA for PTSE-1
vessel" . However, it is believed that the data shown in Fig 2.2 arefoth
PTSE-1I insert because the pretest analysis was performed for the insert
*The
material..
7
In the PTSE-2 series the material properties of the insert were examined before and
after the experiments. Some changes of material properties were observed before and after
the experiments possibly because of plastic deformation incurred during the tests.
However, Ref.2 mentions that the change of material properties due to plastic deformation
is not so conclusive because a regional variation of material properties were observed on
the piece of metal from which the insert and specimen were cut. We introduce both results
of material examination before and after the tests. Table 2.3 are those obtained from the
examination prior to the tests. Figs. 2.4, 2.5, and 2.6 show the stress - strain relation,
KIC, and KIA curves obtained from the pretest specimen respectively.
Table 2.3 Pretest material properties of the insert in PTSE-2
Value used for
Temperature (OF)
Property
78.8
212
392
550.4
the pretest analysisd
Yield Strengtha (ksi)
38.94
32.85
28.86
29.88
36.98
Tensile Strengtha (ksi)
80.06
69.04
62.95
63.74
75.13
NDTb (OF)
RTNDnc (OF)
120.2
210.2
a: Averaged value at a given temperature. See Table 2.6 of Ref.2 for the individual data
b: From Table 2.4 of Ref.2
c: From Section 2.3.5 (page 53) of Ref.2
d: From Table 10.4 of Ref.2
8
600
500 -
400 0-
~'300--
U,
200
PTC1 SPECIMEN P1372
100
0
0
0.04
0.02
0.06
TRUE STRAIN
Fig.2.4 True stress vs. strain from tensile test of specimen (pretest material) at 212 OF.
(source from Fig.2.24 of Ref.2)
9
400
o
300 F-
E-
200
V ALID KIC
K AT CLEAVAGE
*Mi AXIMUM LOAD
PRECEDEDCLEAVAGE
£
RA TE-ADJUSTED K
* UPPER AND LOWER BOUNDS
0- ADJUSTED K
U PPER TOUGHNESS
..-L )WER TOUGHNESS
$
$
a
$
1I of
0
1
|
0
100
t|
/
01
-200
I
-100
0I
I
100
200
T(OC)
Fig.2.5 KIC data for PTSE-2 insert (pretest). (source from Fig. 10.10 of Ref.2)
10
400
I
I
----
i
I
I
TS ORIENTATION
300 f-
-
!.
o
VALID DATA
0
INVALID DATA
UPPER TOUGHNESS
LOWER TOUGHNESS
200
-
T
*
*
/
'a'
J.
100
J#
O,
o0,C
I-
C
wI
A'
-150
-100
-50
0
T(OC)
I
50
I
100
150
Fig.2.6 KIA data for PTSE-2 insert (pretest). (source from Fig. 10.9 of Ref.2)
11
Table 2.4 shows the material properties of the insert after the PTSE-2. The stress strain curve obtained from the post test examination is shown in Fig.2.7. Fig.2.8 shows
the KjC of the insert examined after the experiments compared with the pretest data
obtained from the specimen of the material of which the insert was made. It is observed
from Fig.2.8 that the toughness of the insert material decreases after the experiment. As
noticed from Table 2.3 and 2.4, the nil-ductility temperature (NDT) increased after the
experiments. However, the reference nil-ductility temperature (RTNT) could not be
defined for the post-test insert, because the insert did not achieve 68 J on the upper shelf (
see Section 2.3.5 (page 53) of Ref.2 for details).
Table 2.4 Post-test material properties of the insert in PTSE-2
Property
Temperature (OF)
392
77
67.70
212
63.45
60.92
Yield Strengthb (ksi)
(L onented)
53.81
55.33
-
Tensile Strengtha (ksi)
(T oriented)
90.33
83.7
78.97
Tensile Strengthb (ksi)
(L oriented)
89.78
80.13
-
NDT c (OF)
167
Yield Strengtha (ksi)
(T oriented)
a: Averaged value at a given temperature. See Table 2.7 of Ref.2 for the individual data
b: Averaged value at a given temperature. See Table 2.8 of Ref.2 for the individual data
c: From Table 2.4 of Ref.2
12
600
500 -
400 a.
Co
(I-
300
Co
200
PTSE-2 VESSEL INSERT SPECIMEN PE08
100
0
0
0.02
0.04
0.06
TRUE STRAIN
Fig.2.7 True stress vs. strain from tensile test of specimen (posttest material) at 212 OF.
(source from Fig.2.25 of Ref.2)
13
1
1.1
2% Cr-1 Mo
1TCS
TS ORIENTATION
400
I
1
POSTTEST, PTSE-2 INSERT
0
300
I
-
PRETEST, PTC1, RANGE OF VALUES
CL
MO
z0
I0
200
0
w
a:
U-2
-,1000
-100
-75
-50
-25
0
25
50
75
100
125
150
TEMPERATURE (OC)
Fig.2.8 Posttest fracture toughness Kjc for PTSE-2 insert compared with similar pretest
specimens. (source from Fig.2.52 of Ref.2)
14
2.3 Yankee Rowe Reactor Vessel
The dimension and material properties of the Yankee Rowe Reactor Vessel are listed
in Table 2.5. The values of yield and tensile strength are of the unirradiated vessel metal.
The properties of the irradiated vessel are not available.
Table 2.5 Dimension and material properties of the Yankee Rowe Reactor Vessel Plate
material
Dimension and Property
Value
Outer Radius (inch)
54.5
Inner Radius (inch)
62.375
Thickness (inch)
7.875
Yield Strength (ksi)
53 - 68 (unirradiated)
Tensile Strength (ksi)
Initial RTNDT (OF)
86 - 93 (unirradiated)
Irradiated RTNDT (0 F)
275 - 350 (estimated)
30
15
3. PTS Transients and Stress Distributions
A total of nine PTS transients were investigated: all five cases of the PTSE series and
four cases for the Yankee Rowe PTS analyses. For the stress field calculation, the VISAY
code was used. The VISAY code is a modified version of VISA-ID which was originally
developed in the Battell Pacific Northwest Laboratory [3].
3.1 PTSE series
The VISAY code requires three types of thermal hydraulic transient data to calculate
the stress and analyze the PTS on a vessel. They are the coolant temperature, pressure, and
heat transfer coefficient (he) on the surface of a vessel. However, Refs 1 and 2 do not
contain the coolant temperature history nor the heat transfer coefficient values measured
from the actual tests. In order to have the code calculate temperature and stress field,
therefore, we trick the VISAY code by putting the surface temperature data as the coolant
temperature and assuming a constant value of the he. The assumed value of the he is 104
BTU/hr ft 2 which is a value reasonably enough to neglect the temperature difference
between the coolant and surface of the vessel. Thus, the vessel surface temperature
calculated in the VISAY code can be equivalent to the actual surface temperature. This
assumption of using the surface temperature as coolant temperature with the he of 104
BTU/hr ft2 was checked through the sensitivity analysis of the maximum stress on the
variation of the hc. Table 3.1 shows the change of thermal stress due to the variation of the
assumed value of he- The thermal stress with the he of 106 BTU/hr ft2 is slightly higher
than with the he of 104 because the cooling rate at the surface is faster for higher he
resulting larger temperature gradient within the vessel wall. However, the change of
thermal stress is noticed to be less than 3 % although the value of he changed 100 times.
Therefore, it is concluded that the method of modeling the PTSE for the VISAY code is
acceptable.
16
Table 3.1 The maximum thermal stress calculated by VISAY with different values of he
Case
Time (min)
I
PTSE-2A
PTSE-2B
_
_
Max. thermal stress
I
with hc= 104
0.87
1.30
1.73
2.16
0.7
1.4
2.1
6.99
Note: the unit of he is BTU/hr ft2 .
Max. thermal stress
with hc=10 6
106.2 (ksi)
111.4
111.6
109.9
108.8 (ksi)
113.4
113.1
111.1
87.7
98.2
97.9
72.9
90.0
99.8
99.1
73.2
Table 3.2 lists the sources of the pressure and vessel surface temperature data used
for the stress calculation using VISAY code.
Table 3.2 Sources of the pressure and temperature data for PTSE stress calculations
Case
Vessel Surface Temperature
Pressure
PTSE-1A
PTSE-1B
Appendix A of Ref.1
Appendix A of Ref.1
Appendix A and Fig.8.7 of Ref.1
Appendix A. 1 of Ref.2
Appendix A.2 of Ref.2
Fig.10.21 of Ref.1
Fig. 10.34 of Ref.1
Fig.8.8 of Ref.1
Table 10.11 of Ref.2
Table 10.11 of Ref.2
PTSE-1C
PTSE-2A
PTSE-2B
The PTS transient conditions and resulting stress fields calculated by VISAY are
shown in Figs 3.1a through 3.5e. Figs.3.la to 3.le are for PTSE-1A, Figs.3.2a to 3.2e
are for PTSE-1B, Figs.3.3a to 3.3e are for PTSE-lC, Figs.3.4a to 3.4e are for PTSE-2A,
and Figs.3.5a to 3.5e are for PTSE-2B. The plotted data shown in Fig.3.1a through 3.5e
are pressure and vessel surface temperature transients, temperature distributions within the
vessel wall, thermal, hoop, and total stresses for each case.
17
In the PTSE series, cooling occurred at the outer wall of the vessel. The origin of the
abscissa in the figures for the stress fields and temperature profiles in the vessel wall is the
outer wall of the vessel as marked in the figures.
For the stress calculations of the PTSE series, we assumed zero residual stress.
Since the vessel used for the PTSE does not have clad and zero residual stress was
assumed, the total stress is simply the sum of the thermal and hoop stresses.
18
3.2 Yankee Rowe PTS Transients
Four cases were analyzed for the PTS transients of the Yankee Rowe Reactor Vessel:
one case for the small break loss of coolant accident labeled as SBLOCA (Case 170) and
three cases for the main steam line break labeled as MSLB (Case 971), MSLB (Case 973),
and MSLB (Case 974) respectively. The transient input data for VISAY (coolant
temperature, pressure, heat transfer coefficient) were provided from the thermal hydraulic
analyses of these four cases developed by Yankee Atomic.
Figs. 3.6a to 3.9f show the transient conditions and resulting stress fields for these
four cases: Figs.3.6a to 3.6f for SBLOCA (Case 170), Figs. 3.7a to 3.7f for MSLB (Case
971), Figs. 3.8a to 3.8f for MSLB (Case 971), and Figs. 3.9a to 3.9f for MSLB (Case
971). The plotted data shown in Fig.3.6a to 3.9f are pressure and vessel surface
temperature transients, heat transfer coefficient on the surface of the vessel, temperature
distributions within the vessel wall, thermal, hoop, and total stresses for each case.
Since cooling occurs at the inside of the reactor vessel, the origin of the the abscissa
in the figures for the stress fields and temperature profiles in the vessel wall is the inner
wall of the vessel as marked in the figures.
The total stress shown in Figs. 3.6f, 3.7f, 3.8f and 3.9f is the sum of thermal, hoop,
residual,and clad stress. The maximum residual stress give as an input is 8 ksi. The clad
of the Yankee Rowe Reactor Vessel is 0.25 inch thick (3 %of the vessel wall thickness).
The maximum clad stress was calculated to be 23 to 27 ksi for the investigated transients.
As noticed in the total stress figures, the stress level drops at the depth of 3 % (the interface
between the clad and vessel) due to the clad. Thus, the maximum total stress within the
vessel wall which occurs at the surface of the vessel wall (i.e., the interface between the
clad and the vessel wall) was calculated to be 69.4 ksi for MSLB (Case 971).
19
PTSE-1A: Imposed Conditions
600
6
500
5
W
400
4
a:
300
3
200
2W
0
-
W
W
a:
W
H-
100
1
0
0
1
0
2
4
3
5
7
6
Time (min)
(a) Transient conditions
PTSE-1 A
600
500
0
WL
a:
400
W
300
CC
HL
200
100
0 1
20
0
A
Outer wall
60
40
80
Depth(%)
100
Inner wall
(b) Temperature distribution within the vessel wall
Fig. 3.1 Transient conditions and stress distributions in PTSE-1A
20
PTSE-1 A
120
0.7
-
Time (min)
90CD
--
1.4
-2.8
-o-
- 4.9
- -+ -- 7.0
J2
Cc
60303
-
~
~
30-
-60
p
~
I
I
0
a
S
100
80
60
40
20
-'
Depth (%)
Outer wall
Inner wall
(c) Thermal stress distribution
0.7 1PTSE-1A
- a-
14-
-- A--3.5
-o-4.9
12Co
Co)
wU
CC
8
Co)
6-
17
CL
0
0
'r
- 2.8
Time (min)
-a
-
-
-0
--
EF-
420
1
0
1
Outer wall
,0
*
1 9
1
20
,0
-e
-r--19.
0,
60
40
80
Depth (%)
(d) Hoop stress distribution
Fig.3.1 continued from the previous page
21
100
Inner wall
PTSE-1A
150
100
CO)
50
CO,
0
0
-50
wl
Oue wall
20
60
40
80
Depth (%)
(e) Total stress distribution
Fig.3.1 continued from the previous page
22
100
Inner wall
PTSE-1 B: Imposed Conditions
600
12
500
10
0
Wj 400
8
I-
M 300
6
-W
0j 200
WL
4
W
a:
1 00
2
0
0
1
0
2
4
3
5
7
6
Time (min)
(a) Transient conditions
PTSE-1 B
600
0
W
-
500
400
300
W
(H
200
100
0
'
0
20
Outer wall
60
40
80
Depth(%)
100
Inner wall
(b) Temperature distribution within the vessel wall
Fig. 3.2 Transient conditions and stress distributions in PTSE- 1B
23
PTSE-1 B
120
90
Co
60
U)
30
.J
0
w
I
-30
-
60
'
0
100
80
60
40
20
Depth (%)
Outer wall
Inner wall
(c) Thermal stress distribution
PTSE-1 B
40
C/)
w
a0
0
Z:
-
35
-
30
-o-
25
E-
0.7
-2.1
- 2.8
-3.5
Time (mi)
-- +--5.6
x-
7.0 1----
20
15
10
*
-------
4
-
5
-_
0
Outer wall
I_ _
20
-
._
--
.
-+-
60
40
--
---
80
Depth (%)
(d) Hoop stress distribution
Fig.3.2 continued from the previous page
24
100
Inner wall
PTSE-1 B
150
-
Time (min)
100C/)
C/)
---- 2.8
-4.9
-- +-- 7.0
-- o-
4.
1--
50-
1-
0-
9
0.7
a- -1.4
...............
50
I
0
Outer wall
20
-~
I
I
i
60
40
-
~
80
Depth (%)
(e) Total stress distribution
Fig.3.2 continued from the previous page
25
100
Inner wall
PTSE-1C: Imposed Conditions
600
16
500
14
400
12
%-0300
10
W 200
8 W
0
W
C,)
HU
100
6
4
0
5
4
3
2
1
0
Time (min)
(a) Transient conditions
PTSE-1C
600
500
0
II'
-
400
Hj 300
a:
CW
M
HU
200
100
0 '
0
20
A
Outer wall
60
40
80
Depth(%/)
100
Inner wall
(b) Temperature distribution within the vessel wall
Fig. 3.3 Transient conditions and stress distributions in PTSE-1C
26
PTSE-1 C
120
0.43
-
Time (min)
90C/)
C/)
-
-
-0.85
- -a--
1.70
-2.55
-- +--3.40
-x- 4.25
6030-
a:
0-
I- - -30-
I I
-60
I
I
.
I
20
0
I --
40
- -
80
60
Depth (%)
Outer wall
100
Inner wall
(c) Thermal stress distribution
0.43
-1.27
-- -- 2.13
-- o- - 2.97
-+-3.83
-+- 4.25
- -
-
4035C/)
30-
Cl)
25-
cc
20-
w
HC/)
CL
0
0
r
PTSE-1 C
2-
rime (min)
---- -
-9----
0-
151050
Outer wall
-
'
20
I'
I'
40
'
60
I'
80
Depth (%)
(d) Hoop stress distribution
Fig.3.3 continued from the previous page
27
100
Inner wall
PTSE-1 C
150
&
100C',
0.43
-
ITime (min)
4%
&
3- - 1.27
-
---
-2.55
---
- 3.40
5-
C/)
50 -
0
- --I
5
a
.
0.
0
Oue wall
20
60
40
--
*-
I
80
Depth (%)
(e) Total stress distribution
Fig.3.3 continued from the previous page
28
-
100
Inner wall
PTSE-2A: Imposed Conditions
600
12
500
10
U- 400
8
a: 300
D
!T(
6
F-
a:-
200
4W
1 00
2
0
a:
0
0
1
2
3
4
5
Time (min)
(a) Transient conditions
PTSE-2A
600 -i:-___0 -0
-
500
0
L.
a:
Hr
a:
WU
CL
W
Hj
/
400-
/
II
200-
'.7
e
.7
/
E-- -1.0
or
100-,
0
0.0
0.5
0
p
300-
Time (min)
'7
-o-
-2.0
---
-3.0
-+- - 4.3
i
0
20
A
Outer wall
I
I
40
60
1"M
80
-
Depth(%)
100
Inner wall
(b) Temperature distribution within the vessel wall
Fig. 3.4 Transient conditions and stress distributions in PTSE-2A
29
PTSE-2A
1 20
0.43
- -
90-
Cn
C,
lTime (min)
-
6-
-1.30
-- A- -2.16
60-
-o-
30-
-3.03
- +-
4.33
.J
0I
-30-
60
-'~
I
20
0
..
I_
I
~
40
~
-
I
i
60
100
80
Depth (%)
Outer wall
A
Inner wall
(c) Thermal stress distribution
PTSE-2A
403530C/)
C,)
25-
LI
20-
C,)
15-
0
0
10-
M
-o-
0.43
6- - A-
- 1.30
--
I
5-10
s---
0
Outer wall
o-
Time (nn)
-2.16
-3.03
I&- f
-
-A--A-A--
20
40
---
.0
60
A
-
*- 0
-*--0
80
Depth (%)
(d) Hoop stress distribution
Fig.3.4 continued from the previous page
30
& -67
100
Inner wall
PTSE-2A
150
100
CD)
U
F0
F-
50
0
-50
0
w
Oue wall
20
60
40
80
Depth (%)
(e) Total stress distribution
Fig.3.4 continued from the previous page
31
100
Inner wall
PTSE-2B: Imposed Conditions
600
12
500
10
400
8
a: 300
M
6
a:
Wj
200
4
100
2
0
Cf,
(0)
W
(L
0
0
0
1
4
3
2
7
6
5
Time (min)
(a) Transient conditions
PTSE-2B
600
500
0
-
%W,
a:
Hr
D:
<I
cc
Hi
400
a
-
-
'.
S
-
$-~
0.0
-
~-e
300
-0.98
e-
7ime
min)
200
- --- 4.05
-- -5.03
----m 6.01
---- 6.99
100
0
-2.03
---- - 3.0 1
I
II
0
20
Outer wall
60
40
80
Depth(%)
100
Inner wall
(b) Temperature distribution within the vessel wall
Fig. 3.5 Transient conditions and stress distributions in PTSE-2B
32
PTSE-2B
120
-1
- 0.7
90C/
U)
W
Time (min)
60-
-1.40
-- o- -6.29
C/
a:
-
-
30-
Ui
0 -30-
-60
-
0
20
40
~OEI6-~
80
60
Depth (%)
Outer wall
-0t
100
Inner wall
(c) Thermal stress distribution
PTS E-2B
40-
-
35-
-
30-
--
-
0.7
6-
2.8
Time (min)
-4.19
--- -5.59
25207
+,-
-
--
-
-
150
0
105 0 ~1
0
Outer wall
20
40
60
80
Depth (%)
(d) Hoop stress distribution
Fig.3.5 continued from the previous page
33
100
Inner wall
PTSE-2B
150
100
C')
50
C')
-j
F-
0
0
-50
0
Outer wall
20
60
40
80
Depth (%)
(e) Total stress distribution
Fig.3.5 continued from the previous page
34
100
Inner wall
YANKEE-SBLOCA: Imposed Conditions (Case 170)
600
3.0
500
2.5
400
2.0
M 300
1.5
a:
200
1.0
W
100
0.5
0
a:
0-
w
HL
0
'L
I
0
20
I
I
I
40
60
0.0
80
Time (min)
(a) Transient conditions
YANKEE - SBLOCA (Case 170)
10000
CV
1000.
100
0
10
CD
CM
0
20
40
60
80
100
Time (min)
(b) Surface heat transfer coefficient
Fig. 3.6 Transient conditions and stress distributions in Yankee SBLOCA (Case 170)
35
YANKEE - SBLOCA (Case 170)
550
500
450
0
9L
H
400
350
300
250
20 0
20
0
A
60
40
n
100
80
kD
h%
ep ( )
Inner wall
Outer wall
(c) Temperature distribution within the vessel wall
YANKEE - SBLOCA (Case 170)
60-
Time (m
50
-
40
-
-
24
-a-4
,
30-
8.
C/)
-J
30 I
H/
0
-10
-20
-301
0
20
40
60
80
100
Depth (%)
Outer wall
Inner wall
(d) Thermal stress distribution
Fig.3.6 continued from the previous page
36
YANKEE-SBLOCA (Case 170)
15
12
Cn
9
0-
6
0
0
3
r
0
20
40
60
80
100
Depth (%)
Outer wall
Inner wall
(e) Hoop stress distribution
YANKEE -SBLOCA (Case 170)
120
100
Zl
U)
80
60
40
(I)
20
0
-
20 '
0
20
40
60
80
100
Depth (%)
Outer wall
Inner wall
(f) Total stress distribution
Fig.3.6 continued from the previous page
37
YANKEE - MSLB: Imposed Conditions (Case 971)
600
3.0
500
2.5
I- 400
2.0
a- 300
D
1.5
Ui
200
1.0
100
'0.5
j
0
'0.0
0
25
20
15
10
5
0
Time (min)
(a) Transient conditions
YANKEE - MSLB (Case 973)
10000
c~J
H
a)
a,
0
0
a,
C
Cu
H
Cu
a,
I
1 000
0
5
10
15
20
25
Time (min)
(b) Surface heat transfer coefficient
Fig. 3.7 Transient conditions and stress distributions in Yankee MSLB (Case 971)
38
YANKEE - MSLB (Case 971)
550
500
0
U-
w
450
400
D
aHr
350
300
2501 g
20000
a
---+-
0
20
40
Inner wall
60
80
100
Depth(%)
Outer wall
(c) Temperature distribution within the vessel wall
YANKEE - MSLB (Case 971)
60
-0
50 -J
C/)
5
Hj
Time (mi
c
2
30 -
-0o--
20 -
-x-
1 0-
11
-Z
0
W -10 -30
0
20
40
60
80
100
Depth (%)
Outer wall
Inner wall
(d) Thermal stress distribution
Fig.3.7 continued from the previous page
39
YANKEE - MSLB (Case 971)
15
12
Uf)
9
a.
6
0
0
0r 3
0
0
100
80
60
40
20
Depth (%)
Outer wall
Inner wall
(e) Hoop stress distribution
YANKEE - MSLB (Case 971)
120
100
80
U)
U)
60
C/)
40
-
20
0
-
20 '
'
20
60
40
80
100
Depth (%)
Outer wall
Inner wall
(f) Total stress distribution
Fig.3.7 continued from the previous page
40
YANKEE-MSLB: Imposed Conditions (Case 973)
0~
wL
600
3.0
500
2.5
400
2.0
300
1.5
w
c
200
1.0
W
w
100
0.5
Hr
'
'
0
0
I '
30
I
'
10
20
' I
' I
'
40
'
50
0.0
60
Time (min)
(a) Transient conditions
YANKEE - MSLB (Case 973)
10000
-.
I.-
1000
0
C-)
100
0
10
20
30
40
50
60
Time (min)
(b) Surface heat transfer coefficient
Fig. 3.8 Transient conditions and stress distributions in Yankee MSLB(Case 973)
41
YANKEE - MSLB (Case 973)
550
500
w-
450
Hr
400
D
0;C
wr
H
350
300
250
200
0
A
40
M
20
eP
Inner wall
80
60
+h
k0/t
(
100
4
)I
Outer wall
(c) Temperature distribution within the vessel wall
YANKEE - MSLB (Case 973)
60
50
40
C/,
C,, 30
w
CC,
20
-
10
wn 0
CC -1 0
HU
-20
-30
20
60
40
80
100
Depth (%)
Outer wall
Inner wall
(d) Thermal stress distribution
Fig.3.8 continued from the previous page
42
YANKEE - MSLB (Case 973)
15
12C,,
C,)
p
9-
Time (min)
6.0
I)
6-
0
0
1:
30
-
6-
-12.0
- -
A-
-
-o-
I
II I
20
0
I
aI
I
40
Ip
100
80
60
-42.0
I
-
I
Depth (%)
Outer wall
Inner wall
(e) Hoop stress distribution
YANKEE - MSLB (Case 973)
120
100
80
c/)
60
40
-
H/
0j
20
0
-
20
'
0
I
20
60
40
80
100
Depth (%)
Outer wall
Inner wall
(f) Total stress distribution
43
24.0
YANKEE-MSLB: Imposed Conditions (Case 974)
600
3.0
.
coolant
__
500
temperature
400
-~-
2.5
0
%-0
2.0
pressure
-
300
w
1.5
200
-
w
F- 100
--
01.0
W
w
0.5
0
0
20
Cc
100
80
60
Time (min)
40
120
(
0.0
(a) Transient conditions
YANKEE - MSLB (Case 974)
10000 cm
I-
10000
CD
100 I
0
, , , I
20
,
a
1
2
40
aI
I
a
I
60
A
I
a
80
I
a
I
100
I
t
I
120
Time (min)
(b) Surface heat transfer coefficient
Fig. 3.9 Transient conditions and stress distributions in Yankee MSLB (Case 974)
44
YANKEE-MSLB (Case 974)
600
-I
500-
0
wU
a:
400-
.
--
-0-
a
D~
wL
300-
HL
0
-0-- '* -
-,
0--
all,
20019- - -
100
I
0
20
--
- - 19
I
I
I
40
60
80
A
Inner wall
Depth(%)
100
Outer wall
(c) Temperature distribution within the vessel wall
YANKEE - MSLB (Case 974)
60
50
n
40
30
C/)
I
H-
20
10
0
10
20
30
0
20
40
60
80
100
Depth (%)
Outer wall
Inner wall
(d) Thermal stress distribution
Fig.3.9 continued from the previous page
45
YANKEE - MSLB (Case 974)
15
12
C/)
C/)
9
a:
l!6
0
0
3
0
0
100
80
60
40
20
+
Depth (%)
inner
Outer wall
wa
(e) Hoop stress distribution
YANKEE - MSLB (Case 974)
120
100
80
C/)
wU 60
a:
W
40
20
0
-n2e0 '
'l
20
60
40
80
Depth (%)
Inner wall
(f) Total stress distribution
Fig.3.9 continued from the previous page
46
100
Outer wall
(1) Acceptability of the experimental method of the PTSE to PTS analyses
In the PTSE tests, a flaw was implanted at the outer surface of the vessel and thermal
shock was introduced by cooling the outer surface of the vessel with internal pressure.
Therefore, tensile stress occurred at the outer surface of the vessel while the inner surface
was subject to compressive stress. In actual PTS events of nuclear reactors, thermal shock
occurs due to the cooling at the inside surface of the vessel with internal pressure. In this
case, tensile stress occurs at the inner surface of the vessel.
Because flaws grow and propagate when they are subject to the tensile stress, the
effect of thermal shock on the behavior of flaws are the same if the location of the flaws
and cooling are the same. Therefore, the effect of thermal shock on the crack behavior
observed in the PTSE is equivalent to the thermal shock effect on the behavior of flaws
present at the inner surface of the reactor vessel which are major concern of PTS.
The hoop stress both in PTSE and Yankee Rowe cases is tensile because the vessels
were internally pressurized. Also, the hoop stress does not significantly change for both
PTSE and Yankee Rowe cases along the depth of the vessel wall as shown in the hoop
stress figures in Section 3. Thus, the effect of internal pressure on the behavior of flaws is
the same regardless of the location of flaws.
As a conclusion, the experimental method employed in the PTSE tests is acceptable
for the investigation of the crack propagation which would occur in actual PTS events of a
reactor vessel.
(2) Properties of Material
One of the key factors determining the impact of PTS is the material toughness
generally indicated by the reference nil-ductility temperature (RTNDT). Table 4.1 shows a
comparison of RTNDT's among the PTSE and Yankee Rowe Reactor material summarized
from Table 2.2, 2.3, 2.4, and 2.5. As noticed in Table 4.1, the RTNDT of the Yankee
Rowe is higher than the material tested in the PTSE. Thus, the Yankee Rowe Reactor
Vessel is considered to be more vulnerable to pressurized thermal shock than the material
tested in the PTSE. However, as mentioned in Section 2.3.5 and 2.3.6 of Ref.2, the exact
RTNDT of the PTSE-2 insert could not be defined because the insert did not achieve 68 J
even on the upper shelf (the RTNDT is defined as T68 - 33 OK where T68 is the temperature
at which the charpy V-notch impact energy is 68 J). The RTNDT of PTSE-2 shown in
Table 4.1 is the value obtained from the specimen presumed to have the same property of
47
the insert material. As observed by comparing the pretest material properties with the
posttest material properties (see Table 2.3, 2.4, and Fig.2.8), it is believed that the insert
material may have had lower toughness than the pretest material which has an RTNT of
210 OF. Ref.2 explains the change of material property before and after the tests in two
reasons: plastic deformation occurring in the tests and the regional non-uniformity of the
material from which the pretest specimen and insert were manufactured. If the nonuniformity of the material is the major reason of the discrepancy in material properties
between the insert and pretest specimen, then, the RTNDT of the PTSE-2 insert would be
closer to the estimated RTNT of the Yankee Rowe Reactor Vessel. Further investigation
on the RTNT of the PTSE-2 insert is recommended.
Table 4.1 A comparison of RTNT between PTSE and Yankee Rowe
RTrDT (OF)
PTSE-1
PTSE-2
Yankee Rowe
196.3
(pretest)
210.2
275-350
(3) Magnitude of stress
As noticed in Table 4.2, the magnitude of stress incurred by PTS is much smaller for
the Yankee Rowe cases than for the PTSE cases. We may characterize the PTSE tests in
contrast to the Yankee Rowe PTS as high toughness material with high stress versus low
toughness material with low stress. It is hard to conclude whether or not flaws in the
Yankee Rowe Reactor Vessel would propagate when PTS occurs based on the results of
the PTSE alone because the toughness of the Yankee Rowe Reactor Vessel is not the same
as the material used in the PTSE. In order to address the applicability of the PTSE results
to the Yankee Rowe PTS consequence, further study is required on the relationship
between toughness and applied stress regarding the crack behavior, i.e., whether and how
much toughness and applied stress can be compensated with each other.
48
Table 4.2 Comparisons of the maximum stresses between PTSE and Yankee Rowe PTS
Case
Thermal Stress (ksi)
Hoop Stress (ksi)
Total stress (ksi)
PTSE-1A
PTSE-1B
PTSE-1C
PTSE-2A
PTSE-2B
100.1
106.8
102.6
111.4
12.2
24.3
38.5
25.6
102.1
98.2
26.2
98.9
SBLOCA (Case 170)
MSLB (Case 971)
MSLB (Case 973)
MSLB (Case 974)
32.5
58.1
46.2
5.8
11.7
11.5
40.3
69.4
58.8
38.6
7.4
47.8
116.6
124.2
128.0
Note: for the Yankee Rowe cases, the maximum stresses shown above are for the reactor
vessel wall excluding the clad region.
(4) Effect of warm prestressing
Warm prestressing effect was recognized through the series of the PTSE, i.e., no
crack propagation under decreasing K, although K, > KIC. This observation is considered
to help identify the transients important for PTS. For instance, main steam line break
accident is considered to be a more serious event for PTS than small break LOCA, because
pressure is more likely back up during the course of transients in main steam line break.
Also, development of an operating procedure to limit unnecessary pressure surge is
recommended to reduce the impact of PTS.
49
References
1. Bryan, R. H. et al, "Pressurized-Thermal-Shock Test of 6-in.-Thick Pressure Vessels.
PTSE- 1: Investigation of Warm Prestressing and Upper-Shelf Arrest ", NUREG/CR4106, Oak Ridge National Laboratory, April 1985.
2. Bryan, R. H. et al, "Pressurized-Thermal-Shock Test of 6-in.-Thick Pressure Vessels.
PTSE-2: Investigation of Low Tearing Resistance and Warm Prestressing ",
NUREG/CR-4888, Oak Ridge National Laboratory, December 1987.
3. Simoien, F. A. et al, "VISA-II - A Computer Code for Predicting the Probability of
Reactor Pressure Vessel Failure ", NUREG/CR - 4486, Pacific Northwest Laboratory,
March 1986.
50