Inductively Coupled Plasma-Atomic Emission Spectrometry
(ICP-AES) in Support of Nuclear Haste Management*
by
CONP-840101—2
DE84 005267
Edmund A. Huff and E. P h i l i p Horwitz***
Chemical Technology Division
**Cheriiistry Division
Argonne National Laboratory
9700 South Cass Avenue
Argonne, I I . 60439
To be presented at the
1984 Winter Conference
on Plasma Spectrochemistry
January 2-6, 1984
The submitted manuscript has been authored
by a contractor of the U. S. Government
under contract No. W-3M09-ENG-33.
Accordingly, the U. S. Government retains e
nonexclusive, royalty-fret; license to publish
or reproduce the published form ol this
contribution, or allow others to do so, for
U. S. Government purposes.
*This work was performed under the auspices of the U.S. Department of Energy.
INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY
(ICP-AES) IN SUPPORT OF NUCLEAR WASTE MANAGEMENT
Edmund A. Huff and E. Philip Horvdtz
Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439 U.S.A.
DISCLAIMER
This report was prepared as an account of work sponsored by an agency of the United States
Government. Neither the United States Government nor any ageccy thereof, nor any of their
employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or
process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark,
manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views
and opinions of authors expressed herein do not' necessarily state or reflect those of the
United States Government or any agency thereof.
ABSTRACT
Simulated complex n u c l e a r waste s o l u t i o n s
are c h a r a c t e r i z e d by I n d u c -
t i v e l y Coupled Plssiiia-Atoiiiic Emission Spectrometry (ICP-AES).
The system uses
an ICP source focused on both a polychromator and a computer-controlled
scanning monochromator
allows
for
for
simultaneous
intensity
measurements.
and sequential
This
instrumentation
measurements of liquid
extraction
distribution coefficients needed in the development of process flow sheets for
component separations.
A large number of elements are determined rapidly with
adequate sensitivity and accuracy.
The focus of this investigation centers on
the analysis of nuclear fission products.
1. INTRODUCTION
One of the areas in nuclear technology that has to bo addressed before
this energy option becomes a viable alternative to traditional sources is the
management and processing of nuclear fuels and associated waste streams.
Currently, the well established PUREX (Hutonium Uranium Recovery by Detraction) process is used almost exclusively in production facilities, and is
based on the selective liquid-liquid extraction of uranium and plutonium by
tri-butyl phosphate (TBP) from a nitrate medium.
However, all of the ameri-
cium (III) as well as a small portion of the neptunium and plutonium remain in
the raffinate.
This has prompted renewed interest in the synthesis and
evaluation of new, more efficient, stable extractants for the recovery of
actinide (III) ions from nuclear processing streams. A review of this subject
has bean published by SCHULTZ and NAVRATIL [1]. The Separations Group in the
Chemistry Division, Argonne National Laboratory, has been investigating the
preparation and properties of neutral bifunctional organophosphorus extractants [2,3,4].
As a consequence, distribution ratios for a large number of
elements, comprised of fission products (90-100 and 135-145 mass numbers),
corrosion products, and process contaminants, have to be evaluated in diverse
extraction systems.
Table 1 summarizes structural and nomenclature informa-
tion on selected components.
Traditionally, this data has been obtained by
radiometric or standard chemical analysis techniques, an approach that is
labor intensive, generates radioactive waste, and is of limited multielement
capability.
Inductively Coupled Plasma-Atomic
Emission Spectrometry
(ICP-AES),
because of the simultaneous or rapid sequential measurement capability and
excellent sensitivity, particularly for the rare earths fission products, was
selected as the method to support the activities in the Separations Chemistry
Group.
The determination of rare earth elements in geological [5,6,7] and
mineralogical [8] matrices have been reported.
In addition, impurities in
lanthanum [9] and yttrium [10] have been studied by ICP~A£S.
The objective of this paper is to demonstrate the applicability and the
versatility of a combined polychromator-computer controlled scanning monochromator system to the analysis of complex, simulated nuclear waste streams.
A typical waste composition is presented in Table Z.
2.
2.1
EXPERIMENTAL
Apparatus
The ICP-AES measurements were performed on a spectrometer system that
incorporated a 29-channel polychromator and a computer controlled scanning
monochrornator {Instruments S.A., Inc., Metuchen, N.J.) both focused on a
single plasma excitation source. Table 3 lists the instrumentation and Table
4 details the operating conditions.
2.2
Reagents
2.2.1
Standards
Standards for the determination of Al, Ba, Cd, Cr, Fe, Mo, N1,
Sr, and Zr were obtained commercially (Spex Industries, Metuchen, N.J.)
as 6N_ hydrochloric acid solutions. These stock solutions were diluted
e»nd adjusted to 0.3N_ hydrochloric acid to provide the required calibration standards.
Standards for Pd, Rh, and Ru were prepared by the sealed tube
dissolution [11] of spectrographically characterized high-purity metals
and appropriate dilution into mixed working standards.
Individual rare earth metal oxides were dissolved in nitric acid
and the metal content of each stock standard was determined by EDTA
titrations.
Mixed working standards, containing Ce, Eu, La, N d , P r ,
Sm, and Y at concentrations proportional to their respective detection
limits were prepared by dilution of the stock matrices.
2.2.2
Extractants
The preparation and purification of the extractants used in this
investigation have been described in earlier publications [2,3,4].
They were dissolved in diethyl benzene {mixture of isomers, Aldrich
Chemical Co., Milwaukee, WI) to the appropriate moiarity.
2.2,3 Synthetic High Level Liquid Waste (HLLW) Solutions
The fission product portion of the waste solution was prepared
by combining stock solution standards in ratios expected for a typical
process stream of spent reactor fuel. Corrosion products (Cr, Fe, Ni)
and process contaminants (Al, Ha) were prepared separately and combined
to give the composition shown in Table 2.
2.3
Procedures
2.3.1
Extraction
HLLW aliquots were adjusted to the aqueous phase composition to
be studied.
Portions of these solutions (4-5 mL) were extracted by an
equal volume of a preequilibrated organic phase in an extraction tube.
Constant temperature was maintained during the extraction. The phases
were then allowed to separate and a known quantity (3-4 mL) of the
aqueous phase was withdrawn, transferred to a volumetric flask, and
made up to volume at 0.2^ nitric acid. An accurately measured aliquot
(2-4 mL) of the loaded organic phase was then pipetted into a separate
extraction tube and scrubbed three times (using an organic to aqueous
phase ratio of 0.33) with 1. 5M_ HN03-0.1MI H2C2O4, water, and 0.514
Ma2C03-0.01M NajCjO^
The aqueous phases were combined into a volu-
metric flask and diluted to volume. The acidity was adjusted at O.2f4
nitric acid.
2.3.2
ICP-AES Analysis
Table 5 lists wavelengths, detection limits, and concentration
ranges for the elements in the polychromator array that were used in
this study.
They represent those lines generally selected because of
sensitivity and freedom from spectral interferences.
Profiles with
single element standards were used to verify their applicability to
the snatn'ces under study and, except for cadmium, did not require
interference corrections. The spectral overlap of iron on cadmium was
observed and corrections were made off-line, an approach consistent
with accuracy requirements.
Table 6 summarizes the analytical conditions for elements
determined on the scanning raonochromator. The analytical wavelengths
were evaluated and selected so that no spectral interference corrections were necessary at the concentration levels of interest, except
for palladium at 342.124 nm. This line was strongly interfered with by
the 342.121 nm chromium emission and could not be used in the presence
of this analyte.
Analyses were performed using the 2-point calibration approach
with the standards listed in Tables 5 and 6, after initially calibrating the system with a full set of standards. The following four sets
of element combinations were used:
1. Al, Ba $ Cd, Cr, Fe, Mi, Sr, Zr\
2. Mo.
3. Ce, Eu, La, Nd, Pr, Sim, Y.
4. Pd, Rh, Ru.
Measurements were made in triplicate and required as a minimum
25 mL of solution.
Element concentraions exceeding the values of the
high standard were determined from appropriately diluted samples.
3. RESULTS AMD DISCUSSION
Table 7 compares the prepared nomine! composition of the experimental
fission product solution with results obtained by ICP-AES analysis.
general, the agreement is good except for rhodium and zirconium.
In
Uncertainty
and instability of stock solutions was probably the reason for this discrepancy.
In order to assess potential interferences for the matrix under study,
the standard additions approach was used to evaluate fission product recoveries and analytical reproducibility.
Table 8 lists the results. It is appar-
ent that at the concentration levels studied, the data are self-consistent and
of acceptable accuracy.
Extraction efficiency in immiscible systems is determined by the ratio
of element contents in the organic and aqueous phases.
In order to ensure
control over experimental variables, material balances between starting and
final solution concentrations have to be assessed.
information for a typical experimental system.
Table 9 presents this
In light of uncertainties
associated with back-extraction procedures, potential chemical changes, and
manipulation of small volumes, the data provide good agreement with expected
results. Tables 10 and 11 [12] compare experimental distribution ratios for a
large number of elements in three extraction systems. Radiochemical actinide
measurements are included, since the objective of these studies is the
development of flowsheets for the isolation and purification of transuranic
elements. The data show that trivalent actinides can be selectively separated
from corrosion products and fission products other than the lanthanides.
Palladium and ruthenium show some partitioning; however, a complete separation
in these systems can be achieved by multiple extraction and scrubbing [12].
Preliminary experiments for the determination of the entire series of.
rare earths were performed in anticipation of basic studies with those elements. Interference studies allowed the lanthanides, yttrium, and scandium to
be arranged into three groups as shown in Table 12. Table 13 compares ICP-AES
results with dat s reported by radiochemical and spectrophotometrfc analysis
techniques [13], The reported results are normalized in light of the use of
different dilutents for the two experiments and uncertainties in analytical
measurement techniques.
•
4. CONCLUSION
It has been shown that the 1CP-AES analytical method can be successfully applied to the characterization of complex matrices prevailing in the
nuclear process industry.
The approach provides multielement analyses with
good detectibility and adequate accuracy to quickly identify trends in liquidliquid extraction separations. A considerable saving in time and materials is
realized, although the current need for back-extraction is still a time-intensive step.
The direct analysis of organic phases would bo advantageous but
has as yet not been developed.
The combined polychroroator-scanning monochromator system provides the
versatility needed for complex matrices not usually analyzed.
It allows for
the selection of wavelengths that are free from spectral interferences, does
not significantly increase analysis time, and the consumption of analyte is
not excessive.
LI.CRATURC CITATIONS
[1]
,
»
W. W, SCHULZ and J. D. NAVRATIL, Recent Developments in Separation
(edited by N. N. Lei), Vol. VII, p. 31, CRC Press, Inc., Boca Raton,'
Florida (1981).
[2] D. G. KALIKA, t. P. HORWITZ, L. KAPLAN, and A. C. MUSCATELLO, SepiJ Sci.
Technol. .16,1127 (1981).
[3]
; ,
E. P. HORMITZ, D. G. KALINA, I. KAPLAN, G. W. MASON, and H. DIAMOND /
Sep. Sci. Techno!. 17., 1261 (1982).
[4]
E. P. HORWITZ, D. G. KALINA, and A. C. MUSCATELLO, Sep. Sci. Techno!Vi
.16,403 (1981).
[5] I. B. BRENNER, A. E. WATSON, T. W. STEELE, E. A. JONES, and M.-GOHCALVES,
Spectrochim. Acta JGB.,785 (1981).
[5] J. G. CROCK and F. E. LICHTE, Anal. Chem. 54_,1329 (1982). "-"•
[7]
A. BOLTON, J. HWANG, and A. VANDER VOET, Spectrochim. Acta 38B_,T65
(1983).
[8]
J. A. C. BROEKAERT, F. LE1S, and K. LAQUA, Spectrochim., Aita 34B.73 3
(1979).
[9] H. SHI I and K. SATOH, Talanta JO,111 (1983).
[10]
R. NI-CHUNG, C. WU-MIN, J. ZU-CHENG, and Z. Yun-E, Spectrochim. Acta,
388_,175 (1983).
[11] E. WICHERS, W. G. SCHLECHT, and C. L. GORDON, J. Res. NatV. Bur. Std.
^3,363 (1944).
[12] E. P. HORWITZ, H. DIAMOND, and D. G. KALINA, Plutonium Chemistry (Edited
by W. T. Carnall and G. R. Choppin), p. 433, American Chemical Society^
Washington, D.C. (1983).
[13] E. P. HORWITZ, A. C. MUSCATELLO, D. G. KALINA, and L. KAPLAN, Sep. Sci.
Technol. 16,417 (1981).
{
:
V
o
^ork performed underthe auspices of the U.S.-Department of Energy.
•The use of trade names is solely for descriptive purposes and does not coristittite endors|raent by the U.S. Department of Energy.
AY
5
Table 1. Abbreviations, structures and nomenclature of
CHP and CMPO extractanfcs
Abbreviation
Extractant
0
II
DHDECMP
Nomenclature
0
II
P-CH2-C-N(C2H5)2
Dihexyl-N.N-diethylcarbamoylmethyl phosphonate
HHDECMP
Hexyl h e x y l - N } N diethylcarbamoylmethylphosphonate
O*D[IB]CMPO
0
0
n
11
P-CH2-C-N[CH2-CH(CH3)232
n-OctyKphenyU-N.Ndi i sobutylcarbamdylmethyl phosphine o.xide
Table 2.
Element
Al
Ba
Cd
Cr
Fe
Mo
Ni
Concentration
(yg mL~M
16400
5.4
5.9
710
8500
230
420
Composition of synthetic I!
Element
Ha
Pd
Rh
Ru
Sr
Ir
Concentration
(ng niL-l)
5000
110
32
110
50
310
Element
Concentration
(yg mL-1)
Ce
Eu
La
fid
Pr
Sra
Y
«HLLW = High Level Liquid Waste.
''Ag, Cs, Rb, Se, and Te were also present at trace concentrations.
160
11
77
2G0
75
54
29
Table 3.
A.
B.
C.
Instrumentation
Power and Nebulizer System
Generator
Plasma-Therm Model HFP-2500, 27.12 MHz with
3-turn copper load c o i l .
Hebulizer
Meinhard Model TR-30-02 concentric.
Torch
Conventional Plasma-Therm Model T1.0 quartz,
20 mm o . d .
Spray Chamber
Plasma-Therm Model SC--2 double b a r r e l .
Spectrometers
Polychrornator
Instruments S. A , , Inc. Model J-Y48P 1-meter
Paschen-Runge with 2500 grooves mm~l holographic concave g r a t i n g . 20 \im entrance and
50 vim e x i t s l i t s . Hamamatsu R3Q0 and R306'
photomultiplier tubes, 28 channels.
Monochromator
Instruments S. A., Inc. Model J-Y37 0.64 meter
(Czerney-Turner with stepping motor drive and
c o n t r o l l e r , 1800 grooves turn"1 holographic
plane g r a t i n g , 1C ym entrance and e x i t s l i t s ,
Hamamatsu R955 photomultiplier tube.
Purging
Spectrometers and optical interfaces purged
with nitrogen at 3 L
^
Computer Systeiii
Computer
Terminals
D i g i t a l Equipment Corp. PDP-11/23 with 256K
byte of memory, dual RL-02 d i s k s .
D i g i t a l Equipment Corp. DEC W r i t e r - I l l hard
copy and DEC YT-100 video with graphics capa-
bility.
Software
Instruments S. A., Inc. supplied analytical
software run by the DEC RT-11 operating
system.
Table 4, Operating Conditions
Forward R.F. Power
Reflected Power
Argon Flow Rates
Coolant Gas
Auxiliary Gas
Nebulizer Gas
Sample Uptake Rate
Observation Height
Integration TMme
Poiychromator
Monochromator
1.00 kW
<5 W
14 L ruin"*
0.8 L iirirr*0.8 L min" 1
2.6 mL mirr*
16 mm above load coil
10 sec
1 sec
Table !3. Analytical conditions (Polychromator)
Element
Wavelength (nm)
D.L.a{ng rnL"*)
C o n e . R a n g e (vg mL~M
Al
30S.215
9
0-4
Ba
233.527
1
0-4
Cd
226.502
1
0 - 4
Cr
267.716
2
0-4
Fe
238.204
2
0 - 4
Ho
202.030
6
0-5
Hi
231.604
5
0 - 4
Sr
407.771
0.2
0-4
Zr
343.823
1
0-4
detection "limit (D.L.) defined as 3 times the standard deviation of
the baseline noise.
Table 6. Analytical conditions (Monoch-".jRiator)
Element
a
Wavelength (mn)
D.L. a (ng ml.-1)
Cone. Range (yg ml**1
0-20
Ce
413.765
Eu
331.967
0,9
0 - 2
La
398.852
3
0-8
Md
406.109
16
0 •• 1 0
Pd
324.270
24
0-10
Pd
342.124
40
0-10
Pr
414.3.11
30
0 - 8
Rh
343.489
24
0-10
Ru
349.894
41
0 - 10
Sm
359.260
13
0 - 8
Y
371.030
20
0.5
0-4
Detection limit (D*L.) defined as 3 times the standard deviation of
the baseline noise.
Table 7.
Element
Fission product v^ste composition
Composition (ii<3 niL-1)
Found
Theoretical
Error {%)
Ba
332
344
+
3.6
Cd
17
18
+
5.9
Mo
680
678
-
0,3
Pd
282
292
+
3.6
Rh
77a
93
+ 20.8
Ru
299
316
+
5.7
Sr
163
170
+
4.3
Zr
724a
964
+ 33.2
Ce
492
488
-
Eu
34
34
La
254
246
-
3.2
Nd
816
786
-
3.7
Pr
239
233
-
2.5
Sm
177
168
- 5.1
Y
93
92
- 1.1
Composition of starting material is uncertain.
0.8
0
Table 8. Standard addition recoveries
Element
Concentration (u<j inL-1)
round
Initial
Added
Recovery {%)
Ba
0.06
3,46
3.52
100
Cd
0.06
0.19
0.27
110
Mo
2.23
6.80
9.09
100
Pd
1.12
2.92
3.99
98
Rh
0.24
"0.75
1.01
103
Ru
1.02
2.99
4.3.2
104
Sr
0.50
1.69
2.22
102
Zr
3.11
9.59
12.73
100
Ce
1.59
4.32
6.37
99
Eu
0.11
0.34
0.45
100
La
0.79
2.52
3.27
98
Nd
2.56
8.20
Pr
0.75
2.34
3.06
99
Sm
0.54
1.66
2.23
102
Y
0.29
0.95
1.21
97
11.3
107
Table 9. Extraction experiment recoveries
Found (yo)
Elercertt
Al
Taken
(yg)
65600
Aqueous
67000
Organic
25
Total
Recovery {%)
67000
102
Ba
21.6
25.2
< 1
25.2
117
Cd
23.6
21 - 7
< 1
21.7
92
Cr
2840
2990
< 2
2990
105
Fe
34000
33230
1580
34800
102
Mo
S20
860
100
960
104
Ni
1680
1740
<2
1740
104
Pd
440
291
D7
383
88
Rh
128
103
< 5
103
80
Ru
440
316
89
405
92
Sr
200
206
< 1
206
103
Ir
1240
1180
168
1350
109
Ce
640
136
545
681
106
Eu
44
0
34
43
98
La
308
89
238
327
106
Nd
1040
189
865
1050
101
Pr
300
56
258
314
105
Sm
216
40
173
213
99
Y
116
45
70
115
99
•
Table " 0 . D i s t r i b u t i o n r a t i o s from s y n t h e t i c HLLW SO^C
0.8M IIHDiLCMP
in DEB b
0.4M 04,D[IB]CMP0
in DEBC
< O.OO1
< 0.001
< 0.001
0.006
0.003
0.003
0.56
1.7
7.7
Zr
0.017
0.26
0.19
Mo
0.026
0.89
0.66
*Tc
0.50
1.4
1.2
Ru
0.14
0.26
0.083
Rh
< 0.04
0.11
0.10
0.62
0.19
Element
*Rb
O.8M DHDECMP
in DEBa
Sr
Y
0.077
Pd
Ag
< 0.5
_-
Cd
< 0.03
0.057
0.056
*Cs
< 0.001
< 0.001
< 0.001
Ba
< 0.007
< 0.007
< 0.007
Cr
< 0.09
< 0.09
< 0.09
Fe
< 0.03
0.08
0.08
Ni
< 0.2
< 0.2
*Radiochemical measurements.
«HLLW - 2.9f[HN0 3 , 0.05M H2C2O4, 0/A = 1.0.
b
HLLW - 2.4f^ HW03s O.OGM_ H2C2O4, 0/A = 1.0.
C
HLLW - 2.4M HNO3, O.O75F[ H2C2O4, 0/A = 1.0.
iFrorn Ref. [ 1 2 ] .
< 0.6
< 0.2
Teb'le 11.
Element
D i s t r i b u t i o n r a t i o s from synthetic IILLW 5O°C5-
0.81-1 DHDECMP
in DHB a
0.8M HHDCO1P
in Dt".Bb
0.4H 0$l)[IB]CMP0
in DEB C
La
2.1
6.7
2.4
Ce
1.8
4.9
3.4
Pr
1.8
6.1
4.5
Nd
1.9
6.8
5.6
Sm
1.5
11.0
9.1
Eu
1.3
8.8
8.0
Gd
0.73
2.1
1.9
*Am
2.2
9.1
9.4
*Cm
1.7
6.8
7.2
*RadiocheRrica1 measurements.
a
HLLW - 2.9.M HN03s 0.05M H2C2O4, 0/A = 1 . 0 .
b
HLLW » 2 . W HNO3, 0.05H 112C204, 0/A = 1 . 0 .
C
HLLW - 2 . 4
iFrotn Ref. [12].
Table 12.
Multielement standards f o r Sc, Y, and the Rare Earths
Element
Group I
Wavelength
(nm)
D. L.
(ng rnL-1)
Eua
381.967
0 .4
Eu9
331.967
Er
337.271
4 .6
Ce
413.765
Pr
414.311
13
Gd
342.247
0.3
Sin
359.260
12
Lu
339.707
5.5
Tm
3*6.. 220
2 .0
Tb
350.917
6.6
Y
371.030
0 .7
Yb
369.419
0.3
Element
Wavelength
(nm)
D.L.
(ngri?L~l)
381.957
0.4
353.170
0.8
Ho
345.600
1.3
La
379.478
2.5
Nd
406.109
Sc
361.384
a
Element
12
0.3
Europium i s used as the normalizing element.
Group II
Wavelength
(nm)
D.L.
(ng nl~l)
0.4
17
Table 13. Cctfp;srat"fve chcrn'cal arn-j ICP-AES tlistribufcioi? r<jtios a
for the DiiDLCnP-UNO'? syrtc;a
tHstr-ibiitjo_n_ Ratio
Element
a
Che::i.b
ICP-AESC
'Distribution Ratio _* j
D11T.
(%)
Element
Chem.b
La
3.56
3.03
16.1
Dy
0.738
0.754
2.1
Ce
3.33
3.03
9.5
Ho
0.557
0.587
5.2
Pr
2.76
2.84
2.9
Er
0.429
0.431
0.5
Md
2.34
2.20
6.2
Tm
0.275
.0.312
12.6
5m
1.71
1.61
6.0
Vb
0.241
0.239
0.8
Eu
1.38
1.38
0
Lu
0.151
0.165
8.9
Gd
1.00
1.00
Y
0.302
0.303
0.3
Tb
0.820
0.917
11.2
Nonnalized on Gd,
b
DHDECMP dissolved in p-diisopropylbenzene [Ref.13].
C
Diff.
ICP--,AESC {%)
DHDECMP dissolved i n diethyl benzene.