United States
Environmental Protection
Agency
Environmental Monitoring
and Support Laboratory
PO Box 15027
Las Vegas NV 89114
EPA-600 7-79-093
April 1979
Research and Development
c/EPA
Radiometric Method
for the Determination
of Uranium in Water:
Single-Laboratory
Evaluation and
Interlaboratory
Collaborative Study
Interagency
Energy-Environment
Research
and Development
Program Report
»
•
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EPA-600/7-79-093
April 1979
RADIOMETRIC METHOD FOR THE
DETERMINATION OF URANIUM IN WATER:
Single-Laboratory Evaluation and
Interlaboratory Collaborative Study
by
C. T. Bishop, V. R. Casella, and A. A. Glosby,
Environmental Assessment and Planning Section
Mound Facility
Miamisburg, Ohio 45342
Contract No. EPA-IAG-D6-0015
Project Officer
Paul B. Hahn
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
-------
DISCLAIMER
This report has been reviewed by the Environmental Moni-
toring and Support Laboratory-Las Vegas, U. S. Environmental
Protection Agency, and approved for publication. Approval does
not signifiy that the contents necessarily reflect the views
and policies of the U. S. Environmental Protection Agency, nor
does mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
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FOREWORD
Protection of the environment requires effective regulatory
actions which are based on sound technical and scientific infor-
mation. This information must include the quantitative descrip-
tion and linking of pollutant sources, transport mechanisms,
interactions, and resulting effects on .man and his environment.
Because of the complexities involved, assessment of specific
pollutants in the environment requires a total systems approach
which transcends the media of air, water, and land. The Envi-
ronmental Monitoring and Support Laboratory-Las Vegas contributes
to the formation and enhancement of a sound integrated monitoring
data base for exposure assessment through programs designed to:
' develop and optimize systems and strategies for
monitoring pollutants and their impact on the
envi r onmen t
' demonstrate new monitoring systems and technologies
by applying them to fulfill special monitoring needs
of the Agency's operating programs.
This report presents the results of a single-laboratory
evaluation and an interlaboratory collaborative study of a
method for measuring uranium in water. Such studies are
extremely useful as they demonstrate the state-of-the-art of
the analytical methodology which will ultimately provide the
information for decisions associated with environmental standards
and guidelines. Collaborative studies also allow each partici-
pating laboratory to critically evaluate its capabilities in
comparison with other laboratories and often document the need
for taking corrective action to improve techniques. For further
information, contact the Methods Development and Analytical
Support Branch, Monitoring Systems Research and Development
Division, Environmental Monitoring and Support Laboratory,
Las Vegas, Nevada.
George B. Morgan
Director
Environmental Monitoring and Support Laboratory
Las Vegas
ill
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ABSTRACT
The results of a single-laboratory evaluation and an inter-
laboratory collaborative study of a method for determining
uranium in water are reported. The method consists of coprecipi-
tation of uranium with ferrous hydroxide, a nitric-hydrofluoric
acid dissolution if the sample contains sediment, separation of
the uranium by anion exchange chromatography, and electro-
deposition, followed by alpha pulse height analysis.
•
Four reference samples, ranging from 1 to 2,000 disintegra-
tions per minute per liter, were prepared for evaluating the
method. These samples consisted of two actual environmental
samples, a substitute ocean water sample, and a sample containing
sediment. Measured uranium concentrations for these samples
agreed to within 5% of the reference concentrations, while tracer
recoveries averaged about 70%. The precision of the collaborative
study results approached counting statistics errors for the three
water samples which did not contain sediment.
IV
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CONTENTS
FOREWORD iii
ABSTRACT iv
LIST OF TABLES vi
ACKNOWLEDGEMENTS viii
INTRODUCTION 1
SUMMARY 1
CONCLUSIONS 2
CRITERIA 3
CHOICE OF METHOD 4
PREPARATION OF REFERENCE MATERIALS . 5
SINGLE-LABORATORY EVALUATION 6
INTERLABORATORY COLLABORATIVE STUDY 9
DISCUSSION OF RESULTS 16
REFERENCES 21
APPENDIX 1: Tentative Method for the Determination of
Uranium Isotopes in Water (By a
Coprecipitation Anion Exchange Technique). . 23
APPENDIX 2: Collaborative Study Instructions - Uranium
in Water 45
APPENDIX 3: Data on Uranium-232 Tracer 47
APPENDIX 4: Laboratories Participating in the Uranium
in Water Collaborative Study 48
v
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LIST OF TABLES
No. Page
1. Single-Laboratory Evaluation Concentrations
and Recoveries for Sample 1 (Uranium
Processing Facility Effluent) 7
2. Single-Laboratory Evaluation Concentrations
and Recoveries for Sample 2 (Mound Facility
Effluent) 7
3. Single-Laboratory Evaluation Concentrations
and Recoveries for Sample 3 (Substitute
Ocean Water) 8
4. Single-Laboratory Evaluation Concentrations
and Recoveries for Sample 4 (Sample
Containing Sediment) 8
5. Collaborative Study Results for Sample 1 (Uranium
Processing Facility Effluent - Reference Concen-
trations : U-238 = 2085 dpm/1; U-234,-233 = 1610
dpm/1; U-235,-236 = 130 dpm/1) 10
6. Collaborative Study Results for Sample 2 (Mound
Facility Effluent - Reference Concentrations:
U-238 = 0.10 dpm/1; U-234,-233 = 13.62 dpm/1;
U-235,-236 = 0.102 dpm/1) 11
7. Collaborative Study Results for Sample 3
(Substitute Ocean Water - Reference Concentrations:
U-238 =1.73 dpm/1; U-234,-233 =1.73 dpm/1; U-235,
-236 = 0.080 dpm/1) 12
8. Collaborative Study Results for Sample 4 (Sample
Containing Sediment - Reference Concentrations:
U-238 =56.2 dpm/sample; U-234,-233 =56.2 dpm/
sample; U-235,-236 = 2.63 dpm/sample) 13
9. Summary of Uranium-in-Water Collaborative Study
Results 15
vi
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LIST OF TABLES (Cont'd)
10. t-Test for Systematic Errors in Collaborative
Study Results 18
11. Overall Standard Deviation of Collaborative Study
Results and Standard Deviations Expected from
Counting Statistics Errors 20
vii
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ACKNOWLEDGEMENTS
The authors would like to thank all those individuals from
the participating laboratories involved in the collaborative
study (cf. Appendix 4).
Several people at Mound Facility provided support for the
present study. Thanks are due to Warren E. Sheehan, F. Keith
Tomlinson and Billy M. Farmer for providing the necessary sample
counting services and to Charles A. Phillips, Paul E. Figgins
and Bobby Robinson for helpful discussions and suggestions.
viii
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INTRODUCTION
This study was designed to choose and evaluate a method
which could be recommended for measuring uranium isotopes in
environmental water samples and in aqueous discharges from
nuclear facilities. The determination of uranium in environ-
mental samples is becoming more important with the increased
operations of nuclear power plants and the mining and milling
of uranium ores. Isotopic uranium analysis can be used to
determine uranium-234/uranium-238 ratios in environmental
samples and for monitoring effluents from U-235 enrichment
plants. Other non-naturally produced uranium isotopes found
in aqueous samples can be identified and measured. Examples
are U-234 produced from decay of plutonium-238, and U-233
which will be produced in large quantities if thorium-232 is
converted to U-233 in breeder reactors.
For recommendation, the method would have to be applicable
to a variety of water samples in the concentration range of a
few tenths to several thousand disintegrations per minute per
liter. The method would also have to produce results of
sufficient precision and accuracy, be free of interferences
from other alpha-emitting radionuclides, and be applicable to
the routine analysis of large numbers of samples.
SUMMARY
A candidate method to determine the concentration of
uranium isotopes in water has been developed at the Mound
Facility, Miamisburg, Ohio. This report presents the results
of a single-laboratory evaluation and interlaboratory collabora-
tive study of this method. Support for this work was provided by
EPA's Environmental Monitoring and Support Laboratory-Las Vegas,
Nevada under the terms of an "Interagency Agreement."
After an extensive literature search of currently available
methods and preliminary laboratory testing, a method was chosen
for further evaluation. Criteria were established for the
method, subject to EPA approval, and a single-laboratory eval-
uation was used to confirm that these criteria were met. The
single-laboratory evaluation was performed using actual waste-
water samples from Mound Facility and from a uranium processing
-------
facility and with samples prepared for the subsequent inter-
laboratory collaborative test.
A copy of the procedure (Appendix I) and duplicates of four
different water samples were sent to eleven laboratories which
had agreed to participate in the collaborative study. Two of
these samples were taken from actual effluents discharged to the
environment and the third sample was "substitute ocean water" to
which a known amount of uranium was added. The fourth sample
consisted of "diluted pitchblende ore" of a known uranium con-
centration which was added to a liter of deionized water. The
participants were also supplied with a standard U-232 tracer to
eliminate error due to standardization of the tracer by the
participating laboratories. Eight laboratories had submitted
results after a 5-month period. Data from seven of these lab-
oratories were acceptable and a statistical evaluation of the
collaborative study was carried out.
CONCLUSIONS
The single-laboratory evaluation demonstrated that the
uranium-in-water procedure met the requirements set forth in
the criteria established for the method. Chemical recoveries
averaged about 70%, and the accuracy and precision of the method
were shown to be acceptable. Interlaboratory collaborative study
results agreed with the reference values to within 5% for the
determinations of higher level samples where counting statistics
errors were not a major factor. The precision of the results
approached that of counting statistics for the water samples
not containing sediment. Although the precisions observed for
the sample containing sediment were somewhat higher than counting
statistics error, good agreement with the reference values was
obtained. Uranium activities as low as 0.1 disintegrations per
minute per liter (dpm/1) were measured, and plutonium, thorium,
americium and polonium tracer activities (10 to 100 dpm) and
lead (15 mg) did not interfere with the uranium determinations.
The method was shown to be applicable for water samples to which
"diluted pitchblende ore" was added. However, in order to show
that the present procedure is applicable to a particular environ-
mental water sample containing sediment, it would be advisable to
analyze the water portion of the sample by the present method
and the sediment by an appropriate uranium-in-soil method and to
compare the sum of these determinations with the analysis of the
total sample by the present procedure.
From the conclusions presented, the authors believe that the
method described in this report provides a relatively simple and
accurate means of determining uranium isotopes in water.
-------
CRITERIA
Criteria were established for the present method based on
the information obtained from a review of published methods used
for the determination of uranium in water.
The criteria were as follows:
1. The method will be an alpha pulse-height analysis
method, rather than a chemical method giving only
total uranium.
2. Simplicity of equipment, reagents and procedure will
be emphasized to reflect cost effectiveness.
3. The chemical yield of the method will be 50% or
greater.
4. The method will apply to filtered water samples and
to water samples containing sediment.
5. The method shall be applicable to up to 20 liters
of fresh water or seawater.
6. Plutonium, americium, thorium, lead and polonium
tracers will be used in testing the method to give
assurance that isotopes of these elements do not
interfere with the uranium analysis.
7. The sensitivity of the method with 1-liter samples
will be 0.1 dpm/1 or better.
8. The single-laboratory relative standard deviation of
the method, not including the counting statistics
error, will be 5% or better.
9. The accuracy of the method will be dependent upon the
pipetting accuracy, the accuracy of the tracer
(U-232) to be used, and the counting errors. The
overall uncertainty of the tracer is expected to
be about 1.5%.
-------
CHOICE OF METHOD
One of the criteria for the method was that alpha pulse-
height analysis should be used for detection of the uranium
isotopes. Prior to alpha pulse-height analysis, the uranium
had to be preconcentrated from solution, separated from the
other elements present, and prepared for counting.
For preconcentration of uranium from water samples, three
procedures are commonly used: coprecipitation, adsorption on
charcoal, or ion exchange. Of these three methods, coprecipita-
tion was chosen because it was the easiest and least time con-
suming, although cation exchange gives high recoveries for
samples of up to 600 liters (Veselsky 1974) . While several
coprecipitation methods could have been used (Hodge et al.,
1974; Edwards, 1968), coprecipitation of the uranium with
ferrous hydroxide had been previously shown* to give high
recoveries and, therefore, was selected as a means of precon-
centrating the uranium. For effective coprecipitation of the
uranium, it is essential that carbon dioxide be removed from the
sample prior to precipitation and that carbonate-free reagents
(fresh ammonium hydroxide) are used to prevent the formation of
a carbonate complex ion of uranium in basic solution. To make
the procedure applicable to water samples containing sediment,
an acid dissolution, similar to that used in a soil analysis
(USAEC, 1974), was added to the procedure to analyze such samples
Ion exchange chromatography was found to be an extensively
used and easily implemented means of isolating the uranium for
subsequent electrodeposition on stainless steel slides (Korkisch,
et al., 1974, 1975a, 1975b, 1976). An electrodeposition pro-
cedure similar to those previously published (Puphal and Olsen,
1972; Talvitie, 1971) was shown to give good results in a method
for determination of plutonium in water (Bishop et al., 1978).
This procedure was shown to work well for uranium also, and
electrodeposition time could be reduced from 2 hours to 1 hour.
As previously stated, alpha pulse-height analysis, using a
silicon surface barrier detector, was used for counting the
uranium activity which was electrodeposited onto stainless steel
slides. Uranium-232 was chosen for use as a tracer because its
alpha energy is considerably higher than other uranium isotopes
of interest in environmental samples.
*Sill, C. W., private communication, Health Services Laboratory,
Department of Energy, Idaho Falls, Idaho. 1977
-------
PREPARATION OF REFERENCE MATERIALS
Four reference materials were prepared for procedure eval-
uation and also for use in the collaborative study. Two water
samples were taken from actual water discharged to the environ-
ment and, after filtration through Whatman GF/C paper, they were
acidified to 0.5M with concentrated nitric acid. The first
environmental sample, labeled 77-1 and referred to as Sample 1,
was a wastewater sample from a uranium processing facility.
This sample had a uranium-238 concentration of about 2,000 dpm/1
and also contained other natural radioisotopes in addition to
the uranium isotopes. The second environmental sample, labeled
77-2 and referred to as Sample 2, was wastewater discharged from
Mound Facility. Although the primary contaminant in this water
was plutonium-238, it also contained uranium-233 at concentra-
tions of about 10 dpm/1. The reference concentrations for these
samples were obtained by many repeated determinations and appro-
priate statistical analysis.
The other two materials were prepared by adding a substance
of known uranium concentration to water. The third sample,
labeled 77-3 and referred to as Sample 3, was "substitute ocean
water" to which a known amount of uranium was added. This sample
was prepared by adding a standard uranium solution to substitute
ocean water prepared according to an ASTM procedure (ASTM, 1977a).
The standard solution was made by dissolving dried (900°C for
1 hour) National Bureau of Standards (NBS) uranium oxide (NBS
SRM #950a) in nitric acid, and then diluting it to give a con-
centration of about 500 dpm/1. The known concentration of this
solution was verified by electrodepositing an aliquot with a
U-236 solution which had been standardized for Mound by the NBS.
About 90 kg of the substitute ocean water was transferred to a
30-gallon polyethylene container. Weighed amounts of concen-
trated nitric acid (32 ml/liter of water), the uranium standard
solution, and saturated lithium chloride solution were added to
the water. This solution was mixed for 4 hours with a peri-
staltic pump having a flow rate of 4 liters/min. The lithium
concentration was periodically determined by atomic absorption
spectroscopy and complete mixing was verified. Lithium was
added because it has a very good sensitivity in atomic absorption
analysis and only a small amount had to be added to the water
samples. Subsequently 1-liter samples were pumped into poly-
ethylene containers and stored.
-------
The fourth sample, labeled 77-4 and referred to as Sample 4,
consisted of individually prepared 0.100-gram samples of diluted
pitchblende ore added to about a liter of deionized water. Each
sample was preserved with 32 ml of concentrated nitric acid and
shaken vigorously. The entire sample was transferred to a beaker
when it was to be analyzed. This ore was supplied by the Envi-
ronmental Monitoring and Support Laboratory-Las Vegas, Nevada,
and the uranium concentration had been determined at the Health
Services Laboratory, Idaho Falls, Idaho.
SINGLE-LABORATORY EVALUATION
The method was evaluated at Mound Facility before the
multilaboratory collaborative study was begun. Also, since the
concentration of the uranium isotopes in Samples 1 and 2 were
unknown, these samples were analyzed many times in order to
obtain reference values for the uranium concentrations. The
results of these analyses are summarized in Table 1 through 4.
The average uranium recovery observed for multiple analysis of
the four samples was 71 ± 10%. The average values determined
for Samples 1 and 2 were used for the reference values in the
subsequent collaborative study. However, since Samples 3 and 4
were prepared from standards of known uranium concentrations,
the concentrations calculated from the known values were used
as reference values. A few analyses of Samples 3 and 4 were
carried out to assure that the present method was capable of
analyzing these samples, and these results are also listed. An
ASTM-recommended criterion, which is discussed in the next
section of this report, was used for rejection of outliers
(ASTM, 1977b).
Thorium-230, polonium-210, plutonium-236 and americium-243
tracers were used in evaluating the procedure foi. effective
chemical separation of the uranium from these elements. When
each of the four tracers (10 to 100 dpm) was added to the samples
which were analyzed for uranium by the present procedure, it was
found that no detectable tracer (<170) was observed in the final
alpha spectrum. When stable lead (15 milligrams) was added to
the sample, no detectable lead (<17o) was found by atomic absorp-
tion spectroscopy in the final solution to be electrodeposited.
The uranium recovery efficiency of the ferrous hydroxide
coprecipitation procedure was evaluated for up to 20-liter water
samples. Even though 500 mg of iron was used for coprecipitation
of uranium from 20-liter samples, tracer recoveries were less
consistent, ranging from 10 to 66%, and lower, yielding an
average recovery of about 35%, than for 1-liter samples.
6
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TABLE 1. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 1 (Uranium
Processing Facility Effluent)
Sample
1A
IB
1C
ID
IE
IF
1G
Avg.
U-238
(dpm/1)
2003
2093
2119
2070
2133
2081
2091
2085 ± 42
U-234,-233
(dpm/1)
1553
1598
1577
1596
1644
1638
1663
1610 ± 40
U-235,-236
(dpm/1)
117
114
96
128
154
150
150
130 ± 22
Recovery
%
92
86
90
84
82
75
84
85 ± 6
TABLE 2. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 2 (Mound Facility
Effluent)
_
Sample
2A
2B
2C
2D
2E
2F
2G
2H
21
2J
2K
2L
Avg.
U-238
(dpm/1)
0.024
0.11
0.042
0.12
0.065
0.23
0.086
--a
__a
__a
0.14
0.10
0.10 ± 0.06
U-234,-233
(dpm/1)
13.90
12.89
11.36*
13.69
13.17
12.87
13.68
14.14
14.14
13.86
14.02
13.65
13.62 ± 0.46
U-235,-236
(dpm/1)
0.10
0.097
0.053
0.13
0.019
0.12
0.097
__a
__a
__a
0.19
0.11
0.102 ± 0.048
Recovery
%
61
86
94
71
54
75
75
81
60
31
79
91
72 ± 18
*Rejected by ASTM test.
aAlpha spectrum not completely resolved.
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TABLE 3. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 3 (Substitute
Ocean Water)
Sample
3A
3B
3C
3D
Avg. 1
Ref . 1
U-238 U-234,-233
(dpm/1) (dpm/1)
1.75
1.76
1.72
1.71
.73 ± 0.03 1
.73 ± 0.02 1
1.65
1.72
1.73
1.71
.70 ± 0.04
.73 ± 0.02
U-235,-236
(dpm/1)
0.110
0.086
0.065
0.081
0.086 ± 0.019
0.080 ± 0.002
Recovery
(%)
54
65
64
82
66 ± 12
TABLE
4. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 4 (Sample
Containing Sediment)
Sample
4A
4B
Avg . 56 .
Ref. 56.
U-238
(dpm/1)
54.2
59.0
6 ± 3.4 57.
2 ± 0.4 56.
U-234,-233
(dpm/1)
56.6
59.2
9 ± 1.7
2 ± 0.4
U-235,-236
(dpm/1)
2.71
__a
2.71
2.63 ± 0.08
Recovery
(%)
65
61
63 ± 3
Alpha spectrum not completely resolved.
8
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INTERLABORATORY COLLABORATIVE STUDY
On the basis of the single-laboratory evaluation, a multi-
laboratory collaborative study was carried out to validate the
effectiveness of the proposed method under a variety of user
conditions. The procedure to be used and specific collaborative
study instructions were sent to the participating laboratories.
Subsequently, about 250 ml of the sample from the uranium proc-
essing facility and duplicate 1-liter portions of the other three
reference samples were also sent, together with standard U-232.
tracer to be used in the analyses. In a previous study (Bishop,
et al., 1978), Mound and EPA personnel agreed that analyses
which had tracer recoveries of less than 20% would be considered
questionable and the resulting data would be omitted from further
consideration. Such an extremely low recovery would indicate
that there was something seriously wrong with that particular
analysis.
After several months, eight of the eleven laboratories which
had been sent samples completed the analyses, while more pressing
commitments made it impossible for the other laboratories to do
the study. Each laboratory was randomly assigned a number from
1 to 8 and the collaborative study results are listed in Tables
5 through 8. Also presented in each of these tables are averages
of the replicate results, X; the experimental standard deviations,
S^; the ratios of the average value to the known value,
and the uranium tracer recovery for each of the analyses.
In these tables, determinations which had chemical recoveries of
<^ 207o were rejected as unacceptable results, and outliers were
rejected on the basis of an ASTM recommended criterion for re-
jection (ASTM, 1977b).
For this rejection criterion, with n observations listed in
order of increasing magnitude by xi <_ xa £ xa <_ ... <_ xn, if the
largest value xn is in question, then Tn is calculated as follows:
Tn = (xn - x)/s (1)
where:
Tn = test criterion
x = arithmetic average of all n values
-------
TABLE 5. COLLABORATIVE STUDY RESULTS FOR SAMPLE 1 (Uranium Processing
Facility Effluent - Reference Concentrations: U-238 = 2085
dpm/1; U-234,-233 = 1610 dpm/1; U-235,-236 = 130 dpm/1)
Lab
1
T
4
5
6
7
8
U-238b'd X ± Si X
(dpm/1) (dpm/1) X^
2153 ±
2109 ±
1800 ±
2000 ±
2164 ±
2080 ±
2161 ±
2040 ±
1 QAn +
2170 ±
2220 ±
2180 ±
1960 ±
75 2131 ± 31 1.02
80*
170*
37 c 1.04
37 2121 ± 57 1.02
97* c n aa
,r + 0.88
^3 2195 ± 35 1.05
44
Ig7 2070 ± 156 0.99
U-234,-233b X ± Si X
(dpm/1) (dpm/1) XRef
1670
1702
1500
1600
1734
1638
1662
1550
1630
1660
1840
1520
+ £3 1686 ± 23 1.05
± 64
± 70*
± 140*
±31 1.08
* 3® 1650 ± 17 1.02
± 76* 0 gi
j. 0 0 T U . 7 1.
- JO
* 35 1645 ± 21 1.02
* gg1 1680 ± 226 1.04
U-235,-236b X ± Si X Recovery
(dpm/1) (dpm/1) XRef (%)
1 O Q -J- 1 ^
}23 - 15 n5 ± 12 0_89
74 ± 10*
96 ± 22*
111 + 7'o 103 * 1:L °'79
IOC + Q Q
1JJ-O.^ i/o + 1-1 Tin
150 ± 7.9 ~ "
7fi 7 ?fi 87 ± 12 °'67
/O I 10
72
60
19
9
98
91
88
10
48
90
87
53
76
f\ ^_
Where Si is the experimental (within laboratory) standard deviation; X is the average of replicate
results; and XR ^ is the reference concentration (dpm/1). This also applies to Tables 6 through 8.
The error given here is the error associated with one-sigma counting statistics. This statement
also applies to Tables 6 through 8.
°When only one uranium concentration was determined, or if one value was rejected, no average or
standard deviation is tabulated. This also applies to Tables 6 through 8.
Laboratory 2 did not analyze Sample 1.
*Rejected because uranium tracer recovery was less than 2070.
^'Rejected by ASTM test.
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TABLE 6. COLLABORATIVE STUDY RESULTS FOR SAMPLE 2 (Mound Facility
Effluent - Reference Concentrations: U-238 =0.10 dpm/1;
U-234,-233 = 13.62 dpm/1; U-235,-236 = 0.102 dpm/1)
Lab
1
2
Q
4
5
6
7
8
0
0
0
0
0
0
?
0
0
0
0
0
U-238 X + Si X
(dpm/1) (dpm/1) XRef
:^-;H230.074±0.040.7
:io+o:o4 °-i4±o-o6 1.4
.21±0.10*
.20+0.07*
.03 + 0 I?1"
.10+0.02 1.0
:iO+0:02 0.13+0.04 1.3
•[ll™l 0.15±0.04 1.5
U-234, -233 X + Si X U-235,-236 X ± Si X Recovery
(dpm/1) (dpm/1) ^Ref (dpm/1) (dpm/1) XRef
13.70±0.43 ,3 S7+0 ,„ n QQ 0.037±0.017 Q Q^+0 001 0 33
13.43±0.43 13.b7±0.x9 0.99 o.033±0.017 ° -0-3-3-0 -uui ° • ^
13.73±0.48 ,, /1+n ,, n Qfi 0.069±0.025 n nA/ +n nn7 n Ao
13.08+0.70 13.41±0.46 0.98 0. 058+0. 033 0-064±0.007 0.63
15±1*
15 + 1*
14 i^+n 4? i 04
13.46+0.34 0.99
13.86+0.44
14.01 + 0.48 ,,, 89 + 0 T3 , 02
•i-i pft + n ^n ij.oy-u.j.j i.uz
13.72±0.32
^'"in'ot 13.52±0.02 0.99
13.57+0.62 13 20tQ 53 „ „ 0.033 + 0.024 . 024 + Q QU . 2-
12.82 + 0.52 J-J-^U-U.DJ u.y/ Q. 013 + 0. 013 u -U^^-0 -Ui^ u-^^
(/»)
67
69
90
46
11
18
37
77
39
29
69
68
83
78
31
40
"Rejected because uranium tracer recovery was less than 20%.
"^Rejected by ASTM test.
-------
N>
TABLE 7. COLLABORATIVE STUDY RESULTS FOR SAMPLE 3 (Substitute Ocean
Water - Reference Concentrations: U-238 =1.73 dpm/1;
U-234,-233 = 1.73 dpm/1; U-235,-236 = 0.080 dpm/1)
Lab
1
2
4
5
6
7
8
U-238
(dpm/1)
1.59*0.11
1.71+0.12
1.44+0.11
1.71+0.15
1.9*0.4*
1.7*0.2*
2.10+0.15*
1.75+0.14
1.70*0.13
1.61*0.21*
1.52+0.12
1.88*0.10
1.66+0.08
1.90+0.10
1.78+0.16
1.62+0.15
X * Si
(dpm/1)
1.65*0
1.58*0
1.73*0
1.70±0
1.78*0
1.70*0
.08
.19
.04
.25
.17
.11
X
XRef
0.95
0.91
1.00
0.98
1.03
0.98
U-234, -233
(dpm/1)
1
I
I
1
2
1
1
1
1
I
1
1
1
1
1
.54±0.11
.86*0.12
.80*0.13
.76*0.15
.1*0.4*
.8*0.2*
.52*0.17*
.84+9.14
.61*0.12
.83*0.22*
.63*0.12
.69*0.11
.67*0.08
.76+0.09
.78*0.16
.51*0.15
X + Si
(dpm/1)
1.70*0.23
1.78*0.03
1.73*0.16
1.66*0.04
1.72*0.06
1.65*0.19
X
XRef
0.98
1.03
1.00
0.96
0.99
0.95
U-235,-236
(dpm/1)
0
0
0
0
0
0
0
0
0
.146*0.036
.032+0.017
.037*0.034
.088*0.035
.033*0.017
.033*0.015
.085*0.020
.077*0.034
. 107*0 .040
X + Si X Recovery
(dpm/1) XRef (%)
0.089*0.068 1.11 54
0.063*0.036 0.79 ^
1
17
1ft
0.033*0.000 0.41 g°
11
30
61
1 06 85
1.06 ?6
0.092+0.021 1.15 gg
c
Rejected because uranium tracer recovery was less than 207o.
-------
TABLE 8. COLLABORATIVE STUDY RESULTS FOR SAMPLE 4 (Sample Containing
Sediment - Reference Concentrations: U-238 =56.2 dpm/sample;
U-234,-233 = 56.2 dpm/sample; U-235,-236 = 2.63 dpm/sample)
Lab
1
2
•3
4
5
6
7
8
U-238 X ± Si
(dpm/ (dpm/
sample) sample)
58.6+1.4 SR s+n .
58.9±1.4 58.8i0.2
55.8±12.4*
57.5+2.3
57±3*
57±2*
si ^+1 •*
56.U1.5 -, 1+n ,
56.0+1.8 56.1±0.1
57.2+1.8
54.7±1.5 55.5+1.5
54.5+1.2
57.9±1.4 ? 7+Q ,
57.4±1.4 3/-/-U-4
40.0±3.4*
5-1. 0±1. 2
U-234,-233
X (dpm/
XRef sample)
1 Q5 58.5±1.4
i-U:> 58.3±1.4
, n9 6-5.0±14.3*
i.uz 57-9±2.3
54±3*
58 ±2*
0 91 50 7+1 3
1 00 53.3+1.4
57.0±1.8
54.3±1.7
0.99 54.9+1.5
53.2±1.2
l Q3 55.8±1.3
i-UJ 56.9±1.4
0 91 41.2+3.5*
u'yi 50.7±1.4
X ± Si _ U-235, -236
(dpm/ X (dpm/
sample) XRef sample)
9 fii +n is
58.4±0.1 1.04 2:43+0:14
, 03 4.44±1.8*
i-UJ 3.50+0.27
3.3±0.3*
2.6±0.2*
0 90
55.2±2.6 0.98 2"91+o'l7
54.1+0.9 0.96
56.4±0.8 1.00 2.90:0.15
0 9fi 1.48±0.4*
U'JU 2.41±0.1
X + Si
(dpm/ X Recovery
sample) XRef W
2.62±0.23 1.00 ^g
T oo 1.6
i.jj 51
13
18
57
2.77±0.17 1.05 ^g
21
36
61
2.90+0.00 1.10 fZ
oU
n oo 17
0.92 56
'Rejected because uranium tracer recovery was less than 2070.
-------
s = the estimate of the population standard
deviation based on the sample data
Alternately if xi rather than xn is the doubtful value, the
criterion is as follows:
Ti = (x - xi)/s (2)
If the Tn or TI value exceeds the critical value, the measure-
ment in question may be rejected. Critical values of T for
various levels of significance are given in the ASTM reference
(ASTM, 1977b) . A 5% two-sided level of significance was employed
in deciding whether or not to reject a given measurement in the
present study.
When a laboratory had made only one determination or when
one of the duplicates had been rejected, the one acceptable
value was used as the laboratory average. The average value of
each laboratory was used in calculating the average collabora-
tive study value. Reference values for Samples 1 and 2 were
obtained from the single-laboratory evaluation. All data
received from Laboratory 3 had tracer recoveries of £ 20%;
therefore, data from only seven laboratories were included in
this study. Only 84.470 of the total alpha branches from U-235
are included in a well-resolved spectrum of natural uranium
(Sill, 1977). Since this correction was not included in the
collaborative study instructions, the uranium-235 concentrations
reported by the laboratories were divided by 0.844. The labora-
tory calculations were checked to ensure that this correction
had not been made previously.
A summary of the collaborative study results is given in
Table 9. In this table, average isotopic concentrations that
were determined in the collaborative study for each sample are
listed along with corresponding reference concentrations. The
estimated standard deviations for the reference concentrations,
sRef' an(* t^ie estimated collaborative study standard deviations,
Sjj, are also given in Table 9.
The precision standard deviation or the combined within-labora-
tory standard deviation, Sr, and the standard deviation of ;the
systematic errors or the precision of the method between labora-
tories, 85, are also given in Table 9. The precision standard
deviation is estimated according to Youden's Formula (3) (Youden
and Steiner, 1975) as follows for duplicate determinations:
S = (Zd2/2n)% , (3)
14
-------
TABLE 9. SUMMARY OF URANIUM-IN-WATER
COLLABORATIVE STUDY RESULTS*
Tabulated
Sample Isotope XR ^
1
1
1
2
2
2
3
3
3
4
4
4
U-238
U-234
U-235
U-238
U-234
U-235
U-238
U-234
U-235
U-238
U-234
U-235
2085
,-233 1610
,-236 130
.-233
,-236
,-233
,-236
,-233
,-236
0
13
0
1
1
0
56
56
2
.10
.62
.102
.73
.73
.080
.2
.2
.63
Quantity
X
c
2136
1679
112
0
13
0
1
1
0
55
54
2
(dpm/1,
SRef
42
40
22
.12
.60
.040
.69
.71
.073
.4
.8
.84
0.06
0.46
0.048
0.02
0.02
0.002
0.4
0.4
0.08
47
36
24
0
0
0
0
0
0
3
3
0
dpm for Sample 4)
Sd
Sr
Sb
86
115
12 22
.03
.32
.021
.07
.05
.025
.1
.1
.41
0.04
0.33
0.010
0.16
0.14
0.045
0.8
1.4
0.19
0.01
0.22
0.020
-
-
-
3.0
2.9
0.. 39
*The
*c
tabulated quantities
- collaborative study
are defined as: XR £
average concentration
- reference concentration,
, SR £ - standard deviation
of
the reference value, S, - standard deviation of the laboratory averages,
Sr - precision standard deviation or combined within-laboratory standard
deviation, S, - standard deviation of the systematic errors or precision
of the method between laboratories.
15
-------
where: d = the absolute difference between the
duplicates
n = the number of collaborating laboratories
reporting duplicates
The standard deviation of the systematic error, S^, is computed
from the other two standard deviations according to Youden's
Formula (4) (Youden and Steiner, 1975) :
V = V ' Sr2/2 (4)
It can be seen from Table 9 that the within-laboratory
standard deviation, S,., is the most significant source of error
for Samples 1 and 3 of the collaborative study, while the
between-laboratory standard deviation, S^,, is insignificant,
except for the U-235, -236 determinations of Sample 1. These
results can be explained from the data given in Tables 5
through 7. There is a large difference between some of the
duplicates, especially for laboratory 8, when compared to the
other results, which gave a large value of Sr calculated from
equation (3). Since there was a limited amount of duplicate
data, a large difference in one of the duplicates resulted in
a large value of Sr and a corresponding low value for S^
(equation 4). For Samples 2 and 4 and the U-235, -236 deter-
minations in Sample 1, there were no unusually large differences
in the duplicate data which would cause the within-laboratory
deviation to be so large that the between-laboratory deviation
could not be determined. Therefore, the between-laboratory
deviation, Su, was found to be a main contributor to the
experimentally observed standard deviation, S^, for these
determinations.
DISCUSSION OF RESULTS
From the comparison of the average collaborative study
uranium concentrations with the reference values shown in Table
9, there appears to be good agreement of the data for all four
samples. To determine whether the average collaborative study
concentrations agree with the reference values, the t-test was
used. Two equations were used in applying the t-test. The
first relationship applies to a situation in which the average
of the measured value and the average of the reference value
each shows a significant standard deviation; this equation is
as follows (Walpole and Myers, 1972):
16
-------
(5)
where :
t = test criterion
X"c = average of collaborative test results
X,, £ = average reference value
S = estimated standard deviation of collaborative
test results
nc = number of collaborating laboratories
SR £ = estimated standard deviation of reference
concentration
n-n f = number of determinations made in obtaining
the reference value
The second relationship applies to a situation in which
the error in the reference value is considered to be negligible;
or, in other words, the reference value is considered to be the
true mean. This equation is as follows (Youden and Steiner,
1975):
t •
where :
R = the reference value considered to be the
true mean
Other quantities are defined as in equation (5)
Equation (5) was used to calculate the t values for
Samples 1 and 2, and equation (6) was applied to obtain t values
for Samples 3 and 4. The calculated values of t for the four
reference samples and the data used to calculate these values
are given in Table 10 . Critical values of t (tpr^t) , determined
for a 5/0 level of significance, are also given for comparison
to the calculated t values. When t is less than tcr^t, it can
be said that the two means agree. It can be seen in Table 10
17
-------
TABLE 10. t-TEST FOR SYSTEMATIC ERRORS IN
COLLABORATIVE STUDY RESULTS
Tabulated Quantity3
Sample
1
1
1
2
2
2
3
3
3
4
4
4
Isotope
U-238
U-234,
U-235,
U-238
U-234,
U-235,
U-238
U-234,
U-235,
U-238
U-234,
U-235,
-233
-236
-233
-236
-233
-236
-233
-236
V
2136 ±
1679 ±
112 ±
0.12 ±
13.60
0.040
1.69 ±
1.71 ±
0.073
55.4 ±
54.8 ±
2.84 ±
± S
c
47
36
24
0.03
±0.32
± 0.021
0.07
0.05
± 0.025
3.1
3.1
0.41
X
Ref * SRef
2085 ± 42
1610 ± 40
130 ± 22
0.
13
0.
1.
1.
0.
56
56
2.
10 ± 0.06
.62 ± 0.46
102 ± 0.048
73
73
080
.2
.2
63
nc
5
5
4
5
7
3
6
6
5
7
7
5
nRef
7 1
7 3
7 1
9 0
12 1
9 2
1
0
1
0
1
1
t
.94
.12
.22
.43
.24
.55
.40
.98
.92
.68
.20
.47
t
2
2
2
2
2
2
2
2
2
2
2
2
crit
.23
.23
.26
.18
.11
.23
.57
.57
.78
.45
.45
.78
The tabulated quantities are defined in the text.
18
-------
that all results from the collaborative study agree with the
reference values, except the U-234, -233 determination in
Sample 1 and the U-235, -236 determination in Sample 2.
Since the U-235, -236 concentration in Sample 2 was very
low and since only three collaborative study results were
obtained, the data appear to be inadequate to ascertain if there
is a bias in this case. However, for the U-234, -233 determina-
tion in Sample 1, there definitely appears to be a bias in
either the single-laboratory evaluation, which was used to
arrive at the reference value, or the collaborative study results
An objective of the present study was to determine if the
precision of the measured uranium concentrations approached the
precision expected from counting statistics. The standard
deviations expected from counting statistics errors were cal-
culated from the total counts and total counting time of each
duplicate determination which were supplied by the participating
laboratories. They are given in Table 11, along with the
standard deviation of the uranium concentrations determined in
each sample. It can be seen that the errors calculated from
the collaborative study approach the errors expected from
counting statistics for Samples 1, 2 and 3. However, for
Sample 4, which contained sediment, the collaborative study
error was found to be about a factor of 2.5 higher than the
error expected from counting statistics. Thus, when the present
procedure is applied to water samples which do not contain
sediment, the precision of the results approaches counting
statistics errors.
The collaborative study results shown in Table 11 agree to
within 57o of the reference values, except when the very low
uranium concentrations resulted in high errors due to counting
statistics. These low-level determinations showed that as
little as 0.1 dpm/1 could be detected by this method.
In conclusion, the uranium-in-water procedure used in the
present study gave good results for both the single-laboratory
and multilaboratory evaluations. It is believed that this
method provides a relatively simple, cost effective means of
accurately determining uranium isotopes in water.
19
-------
TABLE 11. OVERALL STANDARD DEVIATION OF COLLABORATIVE
STUDY RESULTS AND STANDARD DEVIATIONS
EXPECTED FROM COUNTING STATISTICS ERRORS
Sample
Number Isotope
1 U-238
1 U-234,
-233
1 U-235,
-236
2 U-238
2 U-234,
-233
2 U-235,
-236
3 U-238
3 U-234,
-233
3 U-235,
-236
4 U-238
4 U-234,
-233
4 U-235,
-236
Avg Uranium
Concn (dpm/1)
2136
1610
112
0.12
13.60
0.040
1.69
1.71
0.073
55.4
54.8
2.84
Std Deviations
Std Dev Expected From
of Data Counting Statistics
(dpm/1) (dpm/1)
±47
(2.3%)
±36
(2.1%)
±24
(21%)
±0.03
(25%)
±0.32
(2.4%)
±0.021
(53%)
±0.07
(4.1%)
±0.05
(2.9%)
±0.023
(32%)
±3.1
(5.5%)
±3.1
(5.5%)
±0.41
(14%)
±47
(2.3%)
±40
(2.4%)
±10
(9%)
±0.02
(17%)
±0.33
(2.4%)
±0.016
(40%)
±0.09
(5.2%)
±0.09
(5.2%)
±0.020
(27%)
±1.3
(2.3%)
±1.3
(2.3%)
±0.16
(5.6%)
20
-------
REFERENCES
American Society for Testing and Materials, 1977 Annual
Book of ASTM Standards, Part 31, Designation: D 1141-75,
p. 47, Philadelphia, Pa., 1977a.
American Society for Testing and Materials, 1977 Annual
Book of ASTM Standards, Part 41, Designation!E 178-75,
p. 195, Philadelphia, Pa., 1977b.
Bishop, C. T., A. A. Glosby, R. Brown, and C. A. Phillips,
"Anion Exchange Method for the Determination of Plutonium
in Water: Single-Laboratory Evaluation and Interlaboratory
Collaborative Study," U. S. Environmental Protection Agency
Report, EPA-600/7-78-122, Las Vegas, NV, 1978.
Edwards, K. W., "Isotopic Analysis of Uranium in Natural
Waters by Alpha Spectrometry," Radiochemical Analysis of
Water, Geological Survey Water-Supply Paper 1696-F, U. S.
Government Printing Office, Washington, D. C~T, 1968.
Hodge, V. F., F. L. Hoffman, R. L. Foreman, and T. R. Folson,
"Simple Recovery of Plutonium, Americium, Uranium, and
Polonium from Large Volumes of Ocean Water," Anal. Chem.,
46, 1334 (1974).
Korkisch, J., and L. Goell, "Determination of Uranium in
Natural Waters After Anion-Exchange Separation," Anal. Chem.
Acta, ;7JL, 113 (1974).
Korkisch, J., and I. Steffan, "Determination of Uranium in
Sea Water After Anion-Exchange Separations," Anal. Chem.
Acta. 77_, 312 (1975a) .
Korkisch, J., and A. Soreo,"Determination of Seven Trace
Elements in Natural Waters After Separation by Solvent
Extraction and Anion-Exchange Chromatography," Anal. Chem.
Acta. 79, 207 (1975b).
Korkisch, J., and H. Krivanic, "Application of Ion-Exchange
Separation to Determination of Trace Elements in Natural
Waters-IX," Talanta, 23, 295 (1976).
21
-------
10. Puphal, K. W., and D. R. Olsen, "Electrodeposition of
Alpha Emitting Nuclides from a Mixed Oxalate-Chloride
Electrolyte," Anal. Chem., 44, 284 (1972).
11. Sill, C. W., "Simultaneous Determination of 238U, 23*U,
23oTh> 226Ra> and 2iopb in Uranium Ores, Dusts, and Mill
Tailings," Health Physics, 33, 393 (1977).
12. Talvitie, N. A., "Radiochemical Determination of Plutonium
in Environmental and Biological Samples by Ion Exchange,"
Anal. Chem.. 43, 1827 (1971).
13. U. S. Atomic Energy Commission Regulatory Guide 4.5,
Measurements of Radionuclides in the Environment, Sampling
and Analysis of Plutonium in Soil, May, 1974.
14. Veselsky, J., "An Improved Method for the Determination of
the Ratio 23"U/238U in Natural Waters," Radiochim. Acta.
21, 151 (1974).
15. Walpole, R. E., and R. H. Meyers, Probability and Statistics
for Engineers and Scientists, Macmillan Publishing Co., Inc.,
New York, N. Y., p. 197, 1972.
16. Youden, W. J., and E. H. Steiner, "Statistical Manual of
the Association of Official Analytical Chemists,"
Association of Official Analytical Chemists, Washington,
D. C., 1975.
22
-------
APPENDIX 1
TENTATIVE METHOD FOR THE DETERMINATION OF
URANIUM ISOTOPES IN WATER (BY A
COPRECIPITATION ANION EXCHANGE TECHNIQUE)
This appendix is a reprint of a procedure of the same
title by Carl T. Bishop, Vito R. Casella, Ralph Brown,
Antonia A. Glosby, and Bob Robinson* of Mound Facility in
Miamisburg, Ohio. The report was prepared February 14, 1977,
for the U. S. Environmental Protection Agency under Contract
No. EPA-IAG-D6-0015. Mound Facility is operated by Monsanto
Research Corporation for the U. S. Department of Energy^
under U. S. Government Contract No. EY-76-C-04-0053. The
procedure was prepared by Mound Facility for distribution
to participants in the interlaboratory collaborative study
and was designated as report number MLM-MU-77-61-0001.
^Present address is Battelle Pacific Northwest Laboratory,
Richland, Washington 99352
"^Formerly the U. S. Energy Research and Development
Administration
23
-------
PREFACE
The analytical procedure described itl this document is a tentative
method for the determination of uranium isotopes in water. It is
being collaboratively tested according to an interagency agreement
between the U. S. Environmental Protection Agency (USEPA) and the
U. S. Energy Research and Development Administration (USERDA)*.
Data from the collaborative test will be examined and information
on the precision and accuracy of the method will be obtained. A
final report describing the results of the collaborative study
will be prepared.
^Effective October 1, 1977 U. S. Energy Research and Development
Administration was designated the Department of Energy.
24
-------
CONTENTS
SECTIONS PAGE
1. Scope and Application
1.1 General Considerations 26
1.2 Minimum Detectable Activity 26
1.3 Sensitivity 27
1.4 Precision and Accuracy 29
2. Summary 29
3. Interferences 30
4. Apparatus
4.1 Instrumentation 31
4.2 Laboratory Equipment 31
4.3 Labware 33
5. Standards, Acids, Reagents
5.1 Standards 34
5.2 Acids 3£
5.3 Reagents 34
6. Calibration and Standardization
6.1 Standardization of the Uranium-232 Tracer Solution 35
6.2 Determination of Alpha Spectrometer Efficiency 36
7. Step by Step Procedure for Analysis
7.1 Coprecipitation 36
7.2 Acid Dissolution of Insoluble Residue 38
7.3 Anion Exchange Separation 39
7.4 Electrodeposition 40
7.5 Alpha Pulse Height Analysis 41
8. Calculation of Results
8.1 Calculation of Uranium Concentrations in Water 42
8.2 Calculation of Alpha Spectrometer Efficiency 42
8.3 Calculation of Uranium Recovery of the 43
Chemical Analysis
References 44
25
-------
I- SCOPE AND APPLICATION
1.1 General Considerations
This procedure applies to the determination of uranium
isotopes in fresh water and in seawater. It has been
applied to fresh water samples having a volume as high
as 20 liters. The volume of seawater that can be
analyzed by this method is limited by the fact that a
seawater sample must be boiled before analysis, thus
seawater analysis is usually limited to a few liters.
This method applies to soluble uranium as well as to
any uranium that might be present in suspended matter
in the water sample. When suspended matter is present,
a nitric acid-hydrofluoric acid dissolution step is
added to the procedure to assure that the uranium
present in the suspended matter completely dissolves.
The method described in this procedure can be carried
out by an experienced technician under the supervision
of a chemist who fully understands the concepts involved
in the analysis. It involves relatively simple oper-
ations, but it should be utilized only after satisfactory
results are obtained by the analyst when replicate stan-
dard samples are analyzed.
1.2 Minimum Detectable Activity
The minimum detectable concentration of a given uranium
isotope in water is dependent upon the volume of water
analyzed and the minimum detectable activity (MDA) of the
isotope. In a given laboratory situation this will also
depend upon the observed blank values (cf. Section 3).
The MDA is defined as that amount of activity which in the
same counting time, gives a count which is different from
the background count by three times the standard deviation
of the background count.
The MDA can be calculated from some typical parameters
that might be expected from the method described in this
procedure. Suppose a sample is counted for 1000 minutes
using a silicon surface barrier detector with a 25%
counting efficiency, the background in the energy region
26
-------
of interest is 5 counts in 1,000 minutes, and the chemical
recovery of the uranium tracer is 80%. From the defi-
nition of the MDA, the sample count would have to be
seven (ca. 3 x / 5 ), in 1,000 minutes, and to achieve this
count under the stated conditions would require 0.034 d/m
of activity. Thus, a typical MDA for a given uranium
isotope in water by this procedure would be 0.03 d/m.
1.3 Sensitivity
From the minimum detectable activity computed in the last
section, the sensitivity of this isotopic method can be com-
pared to that of a fluorometric method recommended by the
EPA for uranium in drinking water (ASTM, 1976) . This
fluorometric method is used for determining total uranium
in the concentration range from 0.005 to 50 mg/liter. The
method described in this procedure is an isotopic method,
in which uranium isotopes are detected by alpha pulse
height analysis. The long lived isotopes of uranium along
with some of these properties of interest to this procedure
are given in Table 1. Generally the fluorometric method
is able to detect only uranium-238 in environmental samples
TABLE 1
PROPERTIES OF URANIUM ISOTOPES
OF INTEREST IN ENVIRONMENTAL SAMPLES
Half-Life
Isotope (Years)
U-232
U-233
U-234
U-235
1
2
7
72
.62xl05
.47xl05
.1 xlO8
U-236
U-238
2.39x10
4.51xl09
Specific
Activity
(dis/min/pg)
4.75xl07
21,030
13,730
4.756
140.7
0.7393
Alpha Energies in MeV
(Abundance)
5.32 (68%),5.27 (32%)
4.82 (83%), 4.78 (15%)
4.77 (72%), 4.72 (28%)
4.58 (8%), 4.40 (57%)
4.37 (18%)
4.49 (76%), 4.44 (24%)
4.20 (75%), 4.15 (25%)
27
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since the mass concentrations of the other uranium
isotopes are not high enough to be determined by this
chemical method. It can be seen from Table 1, however,
that the specific activities of all of the other isotopes
of uranium are higher than the specific activity of
uranium-238. Thus, this isotopic method can be used to
detect much smaller masses of these other uranium isotopes,
because the measurement of the radioactivity is much more
sensitive for these isotopes with high specific activities.
To make a quantitative comparison between the above fluoro-
metric method and the present isotopic method, a particular
isotope has to be chosen for comparison. Since the fluoro-
metric method applies essentially to uranium-238, a com-
parison is made on the basis of this isotope. Using the
minimum detectable activity computed in Section 1.2 and
considering a 3- liter water sample, the lowest concentration
of uranium-238, in yg/ liter, that could be detected by the
isotopic method would be:
0.034 d/m/(0.739 ^™- x 3 liter)
*"^ O
= 0.015 yg/liter.
Comparing this number to the lower end of the concentration
range given for the ASTM fluorometric method, the isotopic
method is more sensitive by better than two orders of magni-
tude than the former method. On the other hand a sensitivity
of better than 0.05 yg/ liter has been reported for urani-
um-238 (Montgomery, 1977) using another fluorometric method
(Barker, 1965) .
Although fluorometric methods are comparable in sensitivity
to counting methods for uranium-238 (natural uranium) ,
fluorometric methods could not detect other uranium iso-
topes which are readily detectable by counting methods.
When determining uranium in water as a radioactive contami-
nant, it seems only logical that an isotopic method be the
preferred method of use.
28
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1.4 Precision and Accuracy
The precision of the method has not yet been evaluated,
but based on experience with a similar procedure for
plutonium in water, the precision is expected to approach
that of counting statistics errors. The accuracy is ex-
pected to be within the limits propagated from counting
statistics and the uncertainty in the specific activity of
the tracer used.
2. SUMMARY
The present procedure involves coprecipitation of uranium with
ferrous hydroxide, a nitric-hydrofluoric acid dissolution if
the sample contains sediment, separation of the uranium by anion
exchange in hydrochloric acid, electrodeposition and alpha pulse
height analysis.
The sample is acidified to pH 1 and uranium-232 (not normally
found in environmental samples) is added to serve as an isotopic
tracer before any additional operations are carried out. If the
sample is a seawater sample, or if it contains carbonate or bi-
carbonate ions, the sample must be boiled under acid conditions to
convert these ions to carbon dioxide gas which is then expelled
from the solution. Carbonate ions cannot be present during the
precipitation step since they complex the uranium and prevent its
coprecipitation . The uranium is coprecipiiated from the
sample by adding sodium bisulfite, iron chloride solution and ad-
justing the pH to 10 with concentrated ammonium hydroxide. The
ferrous hydroxide precipitate is dissolved in concentrated hydro-
chloric acid, or is subjected to an acid dissolution with concen-
trated nitric and hydrofluoric acids if the hydrochloric acid
fails to dissolve the precipitate.
The sample is adjusted to a concentration of 8 M in hydrochloric
acid and passed through an anion exchange resin column. The
uranium will be strongly absorbed on the resin at this hydro-
chloric acid concentration. Polonium and bismuth will also be
absorbed while thorium and radium will pass through the column.
Plutonium and iron are also retained by the resin, but are
eluted with 6 M HC1 containing hydrogen iodide. The iodide ion
reduces the plutonium (IV) to plutonium (III) and reduces the
iron (III) to iron (II) , and neither of these ions is retained
by the ion exchange resin in 6 M HC1. The uranium is eluted
from the column with 0.1 M HC1 and is then electrodeposited on
29
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a stainless steel slide for counting by alpha pulse height
analysis using a silicon surface barrier detector.
When uranium-232 is used as a tracer, the other isotopes of
uranium listed in Table 1 can be detected in the alpha spectrum
of an unknown sample. From the alpha energies given in Table 1
it can be seen that the alpha energy of uranium-232 is at least
0.50 MeV higher than the energy of any other uranium isotope.
Thus, there should be little interference from tailing of the
uranium-232 into the lower energy alpha peaks. If a sample con-
tained both uranium-233 and uranium-234, it would be very diffi-
cult to resolve these two peaks since their principal alpha
energies differ by only 0.05 MeV. The other uranium peaks can
be resolved if the resolution is good.
3. INTERFERENCES
3.1 The only possible alpha activity that may come through the
chemistry of the procedure is protactinium-231 (Edwards,
1968). Protactinium-231 has the following alpha energies
in MeV, the abundance being given in parentheses: 5.06 (10%),
5.02 (23%), 5.01 (24%), 4.95 (22%) and 4.73 (11%). Thus,
from Table 1, it can be seen that this protactinium-231
could possibly interfere with the determination of uranium-
233 or uranium-234.
3.2 In determining very low levels of uranium isotopes in en-
vironmental samples, detector backgrounds and laboratory
blanks must be accurately determined. Blank determinations
must be made in order to ascertain that the contamination
from reagents, glassware and other laboratory apparatus is
negligible compared to the sample that is being analyzed.
A blank determination should be made in exactly the same
way a sample determination is made. For accurate analyses
blank determinations should be consistent, and should be
an order of magnitude lower than activities obtained when
analyzing samples.
30
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4. APPARATUS
4.1 Instrumentation
4.1.1 Alpha Pulse Height Analysis System - A system
consisting of a silicon surface barrier detector
capable of giving a resolution of 50 keV or
better with samples electrodeposited on flat
mirror-finished stainless steel slides.
The resolution here is defined as the width of
the alpha peak in keV, when the counts on either
side of the peak are equal to one-half of the
counts at the maximum of the peak. The counting
efficiency of the system should be greater than
15% and the background in the energy region of
each peak should be less than 10 counts in 1000
minutes.
4.1.2 Electrodeposition Apparatus - A direct current
power supply, 0to 12 volts andOto2 amps, is re-
quired for the electrodeposition described in
this procedure. A disposable electrodeposition
cell is also recommended. An apparatus similar
to that shown in Figure 1 has been used in the
present procedure. In the present procedure,
the cell itself is surrounded by water, but the
water is not circulated. The electrodeposition
can be carried out without the water cooling.
The cathode is a stainless steel slide with a
polished mirror finish. The diameter of the slide
is 1.91 cm (3/4 in.) and the thickness is ca.
0.05 cm (0.02 in.). The exposed cathode area
during electrodeposition is 2 cm2.
The anode is a 1-mm diameter platinum wire with
an 8-mm diameter loop at the end above the cathode.
4.2 Laboratory Equipment
4.2.1 Balance - top loading, capacity 1200 g, pre-
cision + 0.1 g.
4.2.2 Hot plate - magnetic stirrer and stirrer bar.
31
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Micro bell glass
(Sargent-Welch
Cat. No. S-4930)
Liquid scintillation counting
polyethylene vial, 25 ml capacity,
with bottom cut off containing
electrolyte solution
Platinum wire
anode
5/16" od glass
tube added to bell glass
Brass screw cap machined
to fit 25 ril polyethylene
vial, with 7/32" diameter by
1/2" long tube protruding
from base of cap
Rubber tubing carrying
cooling water out
Small rubber bulb
Stainless steel slide
3/4" in diameter
Stainless steel tubing,
3/8" od by 2 1/2" long,
electrical connection to cathode
made here
Rubber stopper,
size 2
Rubber tubing carrying
cooling water in
Figure 1. Water Cooled Electrodeposition Apparatus
32
-------
4.2.3 Peristaltic pump with pumping capacity of 4
liters per minute (required only for samples
of several liters or greater).
4.2.4 Centrifuge - capable of handling 100 ml or
larger centrifuge bottles (a larger centrifuge
is required for handling 10 liter or larger
samples).
4.3 Labware
4.3.1 Graduated cylinders - 5 ml to 1,000 ml.
4.3.2 Beakers - glass, 100 ml to 2 liters.
4.3.3 Beakers - teflon, 250 ml with teflon covers.
4.3.4 pH paper - pH range 2 to 10.
4.3.5 Automatic pipettes - with disposable tips,
volumes between 100A and 1.000A.
4.3.6 Centrifuge bottles - 100 ml or greater (larger
bottles are required for 10 liter or larger
samples).
4.3.7 Ion exchange columns - approximately 1.3 cm i.d,
15 cm. long with 100-ml reservoir.
4.3.8 Pipettes - glass, Class A.
4.3.9 Disposable pipettes - 2-ml glass eye-dropper
type, with rubber bulb.
4.3.10 Dropping bottles.
4.3.11 Watch glasses.
4.3.12 Polyethylene washing bottles.
4.3.13 Glass stirring rods.
33
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4.3.14 Safety glasses or goggles.
4.3.15 Rubber gloves.
4.3.16 Crucible tongs - platinum tipped.
4.3.17 Beaker tongs.
4.3.18 Spatulas.
4.3.19 Heat lamp-mounted on ring stand for drying slides.
STANDARDS, ACIDS, REAGENTS
5. 1 Standards
5.1.1 Standardized uranium-232 solution.
5.2 Acids
Reagent grade, meeting American Chemical Society (ACS)
specifications; diluted solutions prepared with dis-
tilled deionized water.
5.2.1 Nitric acid - concentrated (16 M).
5.2.2 Hydrochloric acid - concentrated (12 M), 8 M, 6 M,
0.5 M, 0.1 M.
5.2.3 Sulfuric acid - concentrated (18 M), 1.8 M.
5.2.4 Hydrofluoric acid - concentrated (48% solution).
5.2.5 Hydriodic acid - concentrated (48% solution).
5.3 Reagents
Reagent grade, meeting ACS specifications; solutions
prepared with distilled deionized water.
34
-------
5.3.1 Ferric chloride - in 0.5 HC1 containing 10 mg
of iron per ml of solution.
5.3.2 Ammonium hydroxide - concentrated (15 M) , 1.5 M,
0.15 M. -
5.3.3 Anion exchange resin - Bio Rad AG1-X4 (100-200
mesh) chloride form. (Available from Bio Rad.
Laboratories, 3rd and Griffin Avenues, Richmond,
California, 94804). A column is prepared by
slurry ing this resin with 8 M HCL and pouring
it onto a column of inside diameter approximately
1.3 cm. The height of the column of resin should
be about 8 cm or greater for samples containing
suspended matter or for large volume samples.
5.3.4 Sodium hydrogen sulfite
5.3.5 Sodium hydrogen sulfate solution ca. 5% in
9 M H2S04; dissolve 10 g of the NaHS04-H20 in
100 ml of water and then carefully add 100 ml of
18 M H2S04.
5.3.6 Preadjusted electrolyte - 1 M ammonium sulfate
adjusted to pH 3.5 with 15 M NH40H and 18 M
5.3.7 Thymol blue indicator, sodium salt (available
from Fisher Scientific Company) - 0.04% solution.
5.3.8 Ethyl alcohol - ma'de slightly basic with a few
drops of 15 M NH4OH per 100 ml of alcohol.
6. CALIBRATION AND STANDARDIZATION
6. 1 Standardization of the Uranium-232 Tracer Solution
If a standard uranium-232 solution is not available, a
freshly purified sample of uranium-232 could be standard-
ized by mixing a known amount of another standard solution
such as uranium-236, with a known amount of the solution to
be standardized, mixing thoroughly and electroplating the
mixture. From an alpha pulse height analysis of the mixture
35
-------
the specific activity of the uranium-232 solution could
be determined. Alternately, a freshly purified solution
of uranium-232 could be standardized by 27r counting.
Weighed aliquots of the solution free of hydrochloric
acid could be evaporated on platinum or stainless steel
slides and counted with a 2 IT proportional counter. The
efficiency of the 2ir proportional counter can be accurately
determined with a National Bureau of Standards alpha-
particle standard. When using these standards, corrections
for resolving time and backscattering must be made if neces-
sary.
6.2 Determination of Alpha Spectrometer Efficiency
Determination of the alpha spectrometer counting efficiency
is not necessary to get an accurate concentration of the
uranium isotopes in the water sample being analyzed, since
the counting efficiency of the electroplated sample is the
same for the tracer uranium isotope and for the unknown
uranium isotope. This efficiency cancels out when the con-
centration of the unknown uranium isotope is calculated
(cf. Section 8.1). A determination of the alpha spectro-
meter counting efficiency is required to calculate the
uranium recovery of a particular analysis. To determine
this efficiency requires that one count an alpha particle
source of known alpha particle emission rate under the same
conditions that the samples are counted. The alpha par-
ticle counting efficiency is then calculated as illustrated
in Section 8.2.
7. STEP BY STEP PROCEDURE FOR ANALYSIS
7.1 Coprecipitation
7.1.1 Weigh or measure the volume of a 1-liter or
larger water sample.
7.1.2 If the sample has not been acidified, add 5 ml of
12 M HC1 per liter of sample.
36
-------
7.1.3 Mix the sample completely using a magnetic
stirrer for small samples, or a peristaltic or
other pump for larger samples. Check the
acidity with pH paper. If the pH is greater
than 1, add 12 M HC1 until it reaches this value.
7.1.4 Add standardized uranium-232 tracer with a cali-
brated pipette (or add a weighed amount of the
tracer) to give about 10 d/m of uranium-232.
7.1.5 Mix the sample for about 1 hour or longer if
the sample volume is greater than a few liters.
(If the sample volume is only a few liters, it is
advisable to heat the water to near boiling while
stirring.)
7.1.6 If the sample is a seawater sample or contains
carbonate ions, it must be boiled for about 5
minutes. The pH must be checked again after boiling
and, if it is greater than 1, 12 M HC1 must be added
to bring it back to 1.
7.1.7 Add about 250 mg of NaHSC>3 and 20 mg of iron as
FeCl3 in 0.5 M HC1 to a 1-liter sample. Add up
to 2 g of NaHS03 and up to 500 mg of iron for
larger samples.
7.1.8 Stir again for 10 minutes or longer if the sample
volume is greater than a few liters. (If the sample
volume is only a few liters or less, heat the sample
to boiling.)
7.1.9 Add 15 M NH^OH while stirring to precipitate the
iron. Continue adding 15 M NH^OH to raise the pH
to 9tolOas determined with pH paper.
7.1.10 Continue to stir the sample for 30 minutes, or
longer for samples with a volume greater than a few
liters, before allowing it to settle.
37
-------
7.1.11 After the sample has settled sufficiently,
decant the supernate, being careful not to
remove any precipitate. (If the analyst
wishes to continue immediately, the iron
hydroxide may be filtered out at this time.)
7.1.12 Slurry the remaining precipitate and super-
nate and transfer to a centrifuge bottle. If
larger samples of water are being analyzed, it
may be necessary to transfer the slurry to a
large beaker and allow it to settle again.
7.1.13 Centrifuge the sample and pour off the re-
maining supernate.
7.1.14 Attempt to dissolve the precipitate with a
minimum volume of 12 M HC1. If the precipitate
dissolves completely, add a volume of 12 M HC1
equal to twice the volume of the sample solution
and dilute to 100 to 150 ml with 8 M HC1, or
otherwise adjust the acidity to 8 M HC1. For a
sample that does dissolve, proceed to Section 7.3,
Anion Exchange Separation. If the sample does not
dissolve in the 12 M HC1, evaporate to dryness,
heat to 450°C for a few hours and proceed to the
next section, Section 7.2, Acid Dissolution of
Insoluble Residue.
7.2 Acid Dissolution of Insoluble Residue
7.2.1 Transfer the sample that did not dissolve in the
12 M HC1 to a 250-ml Teflon beaker and add 60 ml
of 16 M HN03 and 30 ml of 48% HF.
(CAUTION: HF is very hazardous. Wear rubber
gloves, safety glasses or goggles and a laboratory
coat. Avoid breathing any HF fumes. Clean up all
spills and wash thoroughly after using HF).
38
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7.2.2 Place the sample on a magnetic stirrer hot
plate, add a Teflon-coated stirring bar, (cover
with a Teflon sheet), and digest for about 2
hours while stirring. If the volur.e drops
below about 25 ml, add equal volumes of 16 M
HNO^ and 4870 HF (cooling the sample somewhaF
before adding).
7.2.3 Remove the sample from the hotplate and cool to
near room temperature (30to40°C). Add 20 ml of
12 M HC1 and slowly take the sample to dryness
on the hotplate. Remove the beaker from the
hotplate as soon as it has dried.
7.2.4 Cool the sample to near room temperature. Add
50 ml of 8 M HC1 and boil gently for a few minutes.
7.2.5 Filter through a Whatman No. 40 filter paper and
wash the paper with about 10 ml of 8 M HC1, com-
bining the wash water with the filtrate. Take
this solution and proceed with Section 7.3, Anion
Exchange Separation.
7.3 Anion Exchange Separation
7.3.1 Condition the anion exchange resin column (pre-
pared as described in Section 5.3) by rinsing the
column with 4 column volumes of 8 M HC1.
7.3.2 Transfer the sample from Step 7.1.14 or Step 7.2.5
to the conditioned anion exchange resin.
7.3.3 After the sample has passed through the column,
elute the iron (and plutonium if present) with six
column volumes of 6 M HC1 containing 1 ml of con-
centrated HI per 9 ml of 6 M HC1 (freshly prepared)
7.3.4 Rinse the column with two additional six column
volumes of 6 M HC1.
39
-------
7.3.5 Elute the uranium with six column volumes of
0.1 M HC1.
7.3.6 Evaporate the sample to about 20 ml and add 5 ml
of 16 M HN03.
7.3.7 Evaporate the sample to near dryness.
7.4 Electrodeposition
7.4.1 Add 2 ml of a 5% solution of NaHSO^t^O in
9 M H2S04 to the sample.
7.4.2 Add 5 ml of 16 M HNC>3, mix well and evaporate
to dryness, but do not bake.
7.4.3 Dissolve the sample in 5 ml of the preadjusted
electrolyte (cf. Section 5.3), warming to
hasten the dissolution.
7.4.4 Transfer the solution to the electrodeposition
cell using an additional 5 to 10 ml of the electro-
lyte in small increments to rinse the sample con-
tainer.
7.4.5 Add three or four drops of thymol blue indicator
solution. If the color is not salmon pink, add
1.8 M H2S04 (or 15 M NH^OH) until this color is
obtained.
7.4.6 Place the platinum anode into the solution so
that it is about 1 cm above the stainless steel
slide which serves as the cathode.
7.4.7 Connect the electrodes to the source of current,
turn the power on, and adjust the power supply to
give a current of 1.2 amps. (Constant current power
supplies will require no further adjustments during
the electrodeposition).
7.4.8 Continue the electrodeposition for 1 hour.
40
-------
7.4.9 When the electrodeposition is to be terminated,
add 1 ml of 15 M NH4OH and continue the electro-
deposition for 1 minute.
7.4.10 Remove the anode from the cell and then turn off
the power.
7.4.11 Discard the solution in the cell and rinse the
cell 2 or 3 times with 0.15 M HN40H.
7.4.12 Disassemble the cell and wash the slide with
ethyl alcohol that has been made basic with NIfyOH.
7.4.13 Touch the edge of the slide to a tissue to absorb
the alcohol from the slide.
7.4.14 Dry the slide, place it in a box and label for
counting. (The sample should be counted within a
week, since uranium-232 daughters grow into the
sample and possibly interfere with the determination
of certain other uranium activities.)
7.5 Alpha Pulse Height Analysis
7.5.1 Count the samples for at least 1,000 minutes or
longer if the detector efficiency is less than
15%, if the tracer recovery is low, or if the un-
known uranium activity is low.
7.5.2 Check the alpha pulse height analysis spectrum for
peaks at the uranium-233, uranium-234, uranium-235,
uranium-236 and/or uranium-238 alpha energies (see
Table 1) and determine the total counts in each peak.
Where two isotopes are close in energy, complete
resolution may not be possible. (This is the case
with uranium-234 and uranium-235, for example.)
7.5.3 Make the necessary background corrections. (The
background should be determined by a 4,000-minute
or longer count.)
7.5.4 Make a blank correction for each peak, if necessary.
41
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8. CALCULATION OF RESULTS
8. 1 Calculations of Uranium Concentrations in Water
By integrating the appropriate energy peak along with the
uranium-232 tracer peak, the concentrations of the corres-
ponding uranium isotope can be determined (cf . Table 1) .
This concentration is calculated as follows:
= Ci x At
Ct x Vs (8.1)
where X^ = the concentration of the unknown uranium
isotope in the water in disintegrations
per minute (d/m) per liter.
Cj_ = the net sample counts in the energy region
corresponding to the uranium isotope being
measured.
At = the activity of the uranium-232 tracer
added to the sample in d/m.
Ct = the net sample counts in the uranium-232
tracer energy region of the alpha spectrum.
Vs = the volume in liters, of the water sample
taken for analysis.
8.2 Calculation of Alpha Spectrometer Efficiency
The absolute counting efficiency of the alpha spectro-
meter, e, must be determined in order to calculate the
uranium recovery of the analytical procedure..
To determine this efficiency requires a standard source
of a known alpha particle emission rate:
where Rs = the net counting rate of the standard source
in the energy region of the alpha emitter of
interest in counts per minute.
RJJ = the absolute alpha particle emission rate of
the alpha emitter of interest in alpha dis-
integrations per minute .
42
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8. 3 Calculation of Uranium Recovery of the Chemical Analysis
The uranium recovery efficiency E (%) expressed in per-
cent is given by:
= Ct x 1007° (8.3)
t X A£ XE
where t=the counting time in minutes. The other term'
are as defined in Sections 8.1 and 8.2.
43
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REFERENCES
1. C. T. Bishop, R. Brown, A. 'A. Glosby, C. A. Phillips and
B. Robinson "Tentative Method for the Determination of Plu-
tonium-239 and Plutonium-238 in Water (By a Coprecipitation
Anion Exchange Technique)," unpublished report MLM-M-76-69-002,
Mound Laboratory, 1976.
2. E. H. Essington and E. B. Fowler, "Nevada Applied Ecology Group,
Soils Element Activities for Period July 1, 1974 to May 1, 1975,"
in "Studies of Environmental Plutonium and Other Transuranics
in Desert Ecosystems, Nevada Applied Ecology Group Progress Re-
port," M. G. White and P. B. Dunaway, eds., NVO-159, p. 17, 1976.
3. "Microquantities of Uranium in Water by Fluorometry," in 1976
Annual Book of ASTM Standards, Water and Atmospheric Analysis,
Part 31, American Society for Testing and Materials, Phila-
delphia, PA. Designation: 02907-75, p-700, 1976.
\
4. F. Baltakmens, "Simple Method for the Determination of Uranium
in Soils by Two Stage Ion Exchange," Anal. Chem., 47, 1147
(1975).
5. J. Korkisch, "Modern Methods for the Separation of Rarer Metal
Ions," Pergamon Press, New York, 1969, p. 62.
6. K. W. Edwards, "Isotopic Analysis of Uranium in Natural Waters
by Alpha Spectroinetry," Radiochemical Analysis of Water,
Geological Survey Water Supply Paper 1696-F, U. S. Government
Printing Office, Washington, D. C.,1968-
7. F. B. Barker, "Determination of Uranium in Natural Waters,"
Radiochemical Analysis of Water, Geological Survey Water Supply
Paper 1696-C, U. S. Government Printing Office, Washington, D.C.,
1965.
8. J. E. Gindler, "The Radiochemistry of Uranium," NAS-NS-3050,
National Academy of Sciences - National Research Council, 1962.
9. K. A. Kraus and F. Nelson, "Anion Exchange Studies of the
Fission Products," Proceedings of the International Conference
on the Peaceful Uses of Atomic, Energy, Geneva, 1955, 7_, 113,
Session 9 Bl, p. 837, United Nations (1956).
10. D. M. Montgomery, private communication, 1977.
44
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APPENDIX 2
COLLABORATIVE STUDY INSTRUCTIONS-URANIUM IN WATER
(March 1977)
1. Use the procedure, "Tentative Method for the Determination
of Uranium Isotopes in Water (By a Coprecipitation Anion
Exchange Technique)." February 14, 1977.
2. If you have not used a procedure similar to the one
enclosed, it would be advisable to analyze a few known
samples before analyzing the test samples.
3. If you do not have the ion exchange resin or other
reagents needed for the analysis of the test samples,
Mound Facility will furnish them if you desire. Contacts
are given below.
4. " Use care in opening the samples. They were shipped in
collapsible containers and may tend to overflow when
opened. Samples may be less than 1 liter in volume, but
this does not matter; measure the weight or volume of
samples 77-1, 77-2 and 77-3. When analyzing sample 77-4,
quantitatively transfer the entire contents of the sample
to a larger beaker for analysis"
5. Additional amounts of any sample are available if a sample
is spilled, an obviously incorrect uranium concentration
is obtained, etc. Contacts are given below.
6. The coprecipitation step in the procedure (step 7.1) may
be omitted for sample 77-1; instead after weighing the
sample and adding the U-232 tracer, the sample should be
evaporated on a hotplate to dryness and about 20 ml of
8 M HC1 should then be added for the anion exchange
separation (step 7.3). Since the uranium concentration
for this sample is quite high (1,000-2,500 dis/min/liter),
only 5 to 25 ml are necessary for each determination.
Excess sample is provided so that practice runs can be made
if desired. Although only one container of sample 77-1
is provided, duplicate analyses should be determined.
45
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7. Sample concentrations of 77-2, 77-3 and 77-4 are in the
range 0.5 to 100 dis/min/liter; therefore, the total
sample (^1 liter) should be used for each analysis. Blanks
should be made in your laboratory to be certain that the
samples are not a problem at this uranium concentration.
8. We are requesting that the same tracer, U-7, be used by
all participants. Using 1 ml of this tracer gives the
approximate amount of U-232 called for in the procedure.
if you dilute the tracer supplied, keep in mind that it is
in a 1 M HNO^ solution.
9. In this collaborative test, the acid dissolution procedure
(Section 7.2) will be required only on sample 77-4.
10. The electrodeposition apparatus shown in Figure 1 of the
procedure is only an illustration. Your apparatus should
be similar, but not necessarily the same.
11. All samples should be counted for at least 1,000 minutes.
12. Individual counting data are requested so that the counting
statistics error can be resolved from other errors.
13. Sample 77-2 contains 0.3 dis/min/liter of U-232. An
appropriate tracer correction is necessary for determining
other uranium isotopes; that is, for equation 8.1 in the
procedure A' = A + 0.3V , where A' is the total activity
of U-232 fof this sample. u
14. Only one ampoule of U-232 tracer is provided (enough for
9 to 10 determinations), but more tracer will be provided
if necessary.
15. The densities may be required in order to report the results
in dis/min/liter. They are as follows: 77-1 (1.028 g/cm3),
77-2 (1.017 g/cm3) and 77-3 (1.040 g/cm3).
46
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APPENDIX 3
DATA ON URANIUM-232 TRACER
Isotope: U-232
Date Prepared: 1/25/77
I.D. No.: U-7
Specific Activity: 12.75 dpm/gram (±1.5%) (on date prepared)
13.15 dpm/cm3
Density: 1.031 g/cm3 at 20°C
Acid Medium: 1 M HNCU
Source: U. S. Department of Energy, Environmental Measurements
Laboratory, purified by ion exchange and standardized
at Mound Facility.
Half Life: 72 years
Opening Instructions:
Prepared At:
The constriction of the glass ampoule
has been previously scored and reinforced
with a blue ceramic band. It can readily
be broken without a file. The small
polyethylene bottle with the long narrow
neck, enclosed with the ampoule, may be
used to remove the tracer from the opened
ampoule and for weighing the amount of
tracer added to each sample.
Mound Facility
Monsanto Research Corporation
Miamisburg, Ohio 45342
47
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APPENDIX 4
LABORATORIES PARTICIPATING IN THE
URANIUM-IN-WATER COLLABORATIVE STUDY
Eberline Albuquerque Laboratory
Albuquerque, New Mexico
LFE Environmental Analysis Laboratories
Richmond, California
New York State Department of Health
Albany, New York
Teledyne Isotopes
Westwood, New Jersey
U. S. Department of Energy
Environmental Measurements Laboratory
New York, New York
U. S. Environmental Protection Agency
Environmental Monitoring and Support Laboratory - Cincinnati
Cincinnati, Ohio
U. S. Environmental Protection Agency
Environmental Monitoring and Support Laboratory - Las Vegas
Las Vegas, Nevada
Westinghouse Electric Corporation
Advanced Reactors Division
Madison, Pennsylvania
48
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
REPORT NO.
EPA-600/7-79-093
3. RECIPIENT'S ACCESSION NO.
TITLE AND SUBTITLE
RADIOMETRIC METHOD FOR THE DETERMINATION OF
URANIUM IN WATER: Single-Laboratory Evalu-
ation and Interlaboratory Collaborative Study
5. REPORT DATE
April 1979
6. PERFORMING ORGANIZATION CODE
AUTHOR!S)
G. T. Bishop, V. R. Casella, A. A. Glosby
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
Monsanto Research Corporation
Mound Facility
P. 0. Box 32
Miamisburg, OH 45342
10. PROGRAM ELEMENT NO.
1NE833
11. CONTRACT/GRANT NO.
EPA-IAG-D6-0015
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency - Las
Vegas, Nevada, Office of Research and
Development, Environmental Monitoring and
Support Laboratory, Las Vegas, Nevada 89114
13. TYPE OF REPORT AND PERIOD COVERED
11/15/76 - 6/15/78
14. SPONSORING AGENCY CODE
EPA/600/07
15. SUPPLEMENTARY NOTES
Mound Facility is operated by Monsanto Research Corporation for the
U.S. Department of Energy under Contract No. EY-76-C-04-0053.
16. ABSTRACT
The results of a single-laboratory evaluation and an inter-
laboratory collaborative study of a method for determining uranium in
water are reported. The method consists of coprecipitation of uranium
with ferrous hydroxide, a nitric-hydrofluoric acid dissolution if the
sample contains sediment, separation of the uranium by anion exchange
chromatography, and electrodeposition, followed by alpha pulse height
analysis.
Four reference samples, ranging from 1 to 2,000 disintegrations
per minute per liter, were prepared for evaluating the method. These
samples consisted of two actual environmental samples, a substitute
ocean water sample, and a sample containing sediment. Measured
uranium concentrations for these samples agreed to within 57<, of the
reference concentrations, while tracer recoveries averaged about 7070.
The precision of the collaborative study results approached counting
statistics errors for the three water samples which did not contain
sediment.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Uranium
Quantitative Analysis
Quality Assurance
Water
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI F;ield/Group
68F
77B
99A, E
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
60
20. SECURITY CLASS (This pagej
Unclassified
22. PR
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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