United States
Environmental Protection
- 32 ''- '.
Environmental Monitoring
and Support Laboratory
PO Box 15027
Las Vegas NV 89114
EPA-60O 7-80-019
February 1980
Research and Development
Radiometric Method for
the Determination of
Uranium in Soil and Air
Interagency
Energy-Environment
Research
and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad categories
were established to facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously planned to foster
technology transfer and a maximum interface in related fields. The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY—ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the effort
funded under the 17-agency Federal Energy/Environment Research and Development
Program. These studies relate to EPA'S mission to protect the public health and welfare
from adverse effects of pollutants associated with energy systems. The goal of the Pro-
gram is to assure the rapid development of domestic energy supplies in an environ-
mentally-compatible manner by providing the necessary environmental data and
control technology. Investigations include analyses of the transport of energy-related
pollutants and their health and ecological effects; assessments of, and development of,
control technologies for energy systems; and integrated assessments of a wide range
of energy-related environmental issues.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161
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EPA-600/7-80-019
February 1980
RADIOMETRIC METHOD FOR THE
DETERMINATION OF URANIUM IN SOIL AND AIR:
Single-Laboratory Evaluation and
Interlaboratory Collaborative Study
by
V. R. Casella, C. T. Bishop, and A. A. Glosby
Environmental Assessment and Planning Section
Mound Facility
Miamisburg, Ohio 45342
Contract No. EPA-78-D-tf0143
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
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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 signify 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.
11
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FOREWORD
Protection of the environment requires effective regulatory
actions that 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
that 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
environment
• 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 soil and air. 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. ,Morgan
Director
Environmental Monitoring and Support Laboratory
Las Vegas
iii
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ABSTRACT
Results of a single-laboratory evaluation and an inter-
laboratory collaborative study of a method for determining
uranium isotopes in soil and air samples are presented. The
method is applicable to 10-gram soil samples and to both glass
fiber and polystyrene (Microsorban) air filter samples. Sample
decomposition is accomplished with a nitric-hydrofluoric acid
dissolution. After a solvent extraction step to remove most of
the iron present, the uranium is isolated by anion exchange
chromatography and electrodeposition. Alpha spectrometry is
used to measure the uranium isotopes.
Two soil samples, a glass fiber air filter sample, and a
polystyrene air filter sample were used to evaluate the method
for uranium concentrations ranging from a few tenths to about
one hundred disintegrations per minute per sample. Tracer
recoveries for the single-laboratory evaluation averaged 73%,
while the tracer recoveries for the collaborative study averaged
66%. Although the precision of the collaborative study results
did not approach counting statistics errors, the measured uranium
concentrations for these samples agreed to within 5% of the
reference concentrations when the uranium concentration was
greater than one disintegration per minute per gram of soil or
one disintegration per minute per air filter.
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CONTENTS
FOREWORD iii
ABSTRACT iv
LIST OF TABLES vi
ACKNOWLEDGEMENTS vii
INTRODUCTION 1
SUMMARY 2
CONCLUSIONS 2
CRITERIA 3
CHOICE OF METHOD 4
PREPARATION OF REFERENCE MATERIALS 4
SINGLE-LABORATORY EVALUATION 5
INTERLABORATORY COLLABORATIVE STUDY 8
DISCUSSION OF RESULTS 14
REFERENCES 21
APPENDIX 1: Tentative Method for the Determination of
Uranium Isotopes in Soil and Air Samples. . 23
APPENDIX 2: .Collaborative Study Instructions -
Uranium in Soil and Air 43
APPENDIX 3: Data on Uranium-232 Tracer 44
APPENDIX 4: Laboratories Participating in the
Uranium in Soil and Air Collaborative
Study 45
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LIST OF TABLES
No. Page
1. Single-Laboratory Evaluation Concentrations
and Recoveries for Sample 1 (Glass Fiber Filter)... 6
2. Single-Laboratory Evaluation Concentrations and
Recoveries for Sample 2 (Reference Soil) 6
3. Single-Laboratory Evaluation Concentrations and
Recoveries for Sample 3 (Microsorban Filter) 7
4. Single-Laboratory Evaluation Concentrations and
Recoveries for Sample 4 (Diluted Pitchblende Ore) . . 7
5. Collaborative Study Results for Sample 1 (Glass
Fiber Filter - Reference Concentration: U-238
=0.21 dpm/filter; U-234 =0.24 dpm/fliter;
U-236 = 1.32 dpm/f ilter) 9
6. Collaborative Study Results for Sample 2
(Reference Soil - Reference Concentration:
U-238 =1.91 dpm/gram; U-234 =2.77 dpm/gram;
U-235 = 0.098 dpm/gram) 10
7. Collaborative Study Results for Sample 3
(Microsorban Filter - Reference Concentration:
U-238 = 22.7 dpm/filter; U-234 = 43.8 dpm/
filter; 1.90 dpm/filter) 11
8. Collaborative Study Results for Sample 4
(Diluted Pitchblende Ore: U-238 = 20.54
dpm/gram; U-234 = 20.54 dpm/gram; U-235 =
0.89 dpm/gram) 12
9. Summary of Results for Uranium-In-Soil and
Air Collaborative Study 15
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
VI
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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 the Charles A. Phillips, Paul E. Figgins
and Harold W. Kirby for helpful discussions and suggestions.
Acknowledgement is also given to the following laboratories
which provided materials used in this study: Environmental
Measurements Laboratory, New York, N. Y.; Environmental Moni-
toring and Support Laboratory, U.S. EPA-Las Vegas, Nevada; and
the Radiological and Environmental Sciences Laboratory, Idaho
Falls, Idaho.
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INTRODUCTION
With the increased operations of nuclear power plants and
with projections that even greater production of nuclear energy
will be necessary to meet future energy demands (Lee, et al.,
1977), the determination of uranium in environmental samples
is becoming more important. Production of nuclear energy
involves many processes which could be sources of unacceptable
releases of uranium or other radioactive materials into the
environment, including uranium mining, uranium milling, con-
version of uranium to uranium hexafluoride, enrichment, fuel
fabrication, reactor power plant operations and fuel reprocessing.
Additional sources of releases may also occur during transportation
and waste management of the radioactive materials.
The objective of this study was to choose and evaluate a
method which could be recommended for measuring uranium isotopes
in environmental soil and air samples. Fluorometric procedures
(ASTM, 1977a; Danielsson et al., 1973) are most commonly used
for the determination of small concentrations of natural uranium;
however, such measurements are only indicative of uranium-238 due
to its extremely low specific activity. In many cases, uranium-
234 is not in equilibrium with uranium-238 in soils and ores
(Sill, 1977; NCRP, 1975), and environmental samples may be en-
riched in uranium-235. The concentrations of these isotopes
should be measured. Isotopic data are of considerable help in
understanding both biological and geological processes and are
also necessary to assess the lung dose resulting from exposure
to uranium-containing materials.
In addition to being an isotopic method, the recommended
method would have to be applicable to a wide variety of soil
samples found in the United States and to air samples collected
on polystyrene or glass fiber filters. The method would also
have to produce results of sufficient accuracy and precision,
be free from interferences, be cost-effective, and be applicable
for routine analyses.
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SUMMARY
This report presents the results of a single-laboratory
evaluation and interlaboratory collaborative study of a
candidate method for the determination of uranium in air and
soil. The method was chosen on the basis of a literature
search and a preliminary laboratory evaluation of currently
available methods. Reference soil samples and both glass fiber
and polystyrene air filter samples were analyzed in a single-
laboratory evaluation done at Mound Facility to show that
criteria previously established for the method were met. After
the single-laboratory evaluation, a copy of the procedure
(Appendix I) and the reference samples were sent to fourteen
other laboratories for analysis by the present method. Uranium-
232 tracer which had been standardized at Mound was also supplied
to the laboratories so that all laboratories would be using the
same tracer. Eight laboratories had submitted results after about
a 7-month period, and a statistical evaluation of the collaborative
study was carried out.
CONCLUSIONS
The requirments set forth in the criteria for the method
(defined in next section) were satisfied by the present pro-
cedure for the determination of uranium isotopes in soil and
air. Chemical recoveries averaged 787o for the single-laboratory
evaluation at Mound and 66% for the multilaboratory collaborative
study. Uranium activities in the range of a few tenths of a
disintegration per minute (dpm) were measured and, when the
uranium concentrations were greater than one dpm per gram of
soil or one dpm per air filter, the average deviation from the
reference concentration was about 5%. The relative standard
deviations of the collaborative results among the laboratories
averaged about 10% for concentration levels exceeding one dpm
per gram of soil or one dpm per filter. Plutonium, americium,
polonium and thorium tracers (30 to 300 dpm) were used to show
that these elements did not interfere with the uranium analysis.
The single-laboratory and interlaboratory evaluations showed
that the present method provides a relatively simple and accurate
means of determining uranium in soil and air samples.
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CRITERIA
Criteria for the present method were established based on
a literature review of published methods for determining uranium
in soil and air samples and the environmental data obtained using
these methods.
The criteria were as follows:
1. The method will be a radiometric method yielding
isotopic information, rather than a chemical method
giving only total uranium.
2. The method will be applicable to up to 10 grams of
a wide variety of soil samples found in the U.S.
and shall also be applicable to air samples collected
on polystrene or glass fiber filters.
3. The method will be capable of determining highly
insoluble forms of uranium.
4. The method will reflect cost effectiveness by
emphasizing simplicity of equipment, reagents and
procedures.
5. The chemical yield of the method will be 50% or
better.
6. The sensitivity of the method with 10-gram soil
samples or air filter samples will be 0.10 dpm/g
or dpm/filter, respectively.
7. Plutonium, americium, polonium, and thorium tracers
will be used in testing the method to give assurance
that isotopes of these elements do not interfere
with the uranium analysis.
8. The single-laboratory relative standard deviation of
the method, not including the counting statistics
error, will be ^570 or better.
9. The accuracy of the method will be dependent upon
the accuracy of the tracer activity U-232, which
is expected to be about 1.5%, the accuracy in the
measurement of the amount of tracer added, and
the counting errors.
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CHOICE OF METHOD
Three methods are commonly used for the initial decomposi-
tion of environmental samples: acid leach, acid dissolution,
and fusion. Since the acid dissolution and fusion methods
provide more rigorous decomposition of the sample matrix than
the acid leach method, it was decided to omit the acid leach
method from further consideration. A recent comparison of acid
dissolution and fusion methods for the analysis of plutonium in
soil (Whittaker and Grothaus, 1979) has strongly indicated that
the two methods are equivalent, even for highly refractory forms
of plutonium. This study showed that the acid dissolution method
was less time-consuming and more economical than the fusion
method; therefore, an acid dissolution method, similar to that
used for the measurement of plutonium in soil (USAEC, 1974),
was chosen for the present method.
A method for the measurement of uranium isotopes in water
has been recently developed at Mound Facility (Bishop et al,
1978) through an Interagency Agreement with the EPA's Environ-
mental Monitoring and Support Laboratory-Las Vegas (EMSL-LV).
Several of the analytical techniques used in the uranium-in-water
method were found to be applicable to the measurement of uranium
isotopes in soil and air samples. After sample decomposition by
an acid dissolution procedure, the uranium could be concentrated
by coprecipitation with iron hydroxide and isolated by anion
exchange chromatography in a hydrochloric acid medium, prior to
electrodeposition onto a stainless steel slide for alpha pulse
height analysis. However, soil and air samples usually contain
a great deal more iron than water samples, making it necessary
to remove the bulk of this iron before the ion exchange separa-
tion to prevent overloading of the anion exchange column with
ferric ions. Extracting the hydrochloric acid sample solution
with isopropyl ether (Morrison and Freiser, 1957) before passing
this solution through the ion exchange column was found to be an
effective way to remove most of the iron from the sample solution.
PREPARATION OF REFERENCE MATERIALS
Two air filters and two soil samples were prepared as
reference materials for the single-laboratory evaluation and
the collaborative study. The first simulated air sample,
referred to as Sample 1, was prepared by pipeting 250 A of a
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diluted uranium-236 standard solution onto a 70-mm diameter glass
fiber filter and drying in an oven at 120°C. Based on the stand-
ardization of the U-236 standard solution by the National Bureau
of Standards (NBS), the activity deposited onto each prepared
filter was 1.33 dpm. The uncertainty of the calibration of the
standard solution was reported by the NBS to be 0.94 percent. A
second simulated air sample, referred to as Sample 3, was pre-
pared by placing 40.0 mg of a standard diluted pitchblende ore
between the layers of a rectangular Microsorban filter (100 mm
x 125 mm) and sealing the filter in a plastic bag. When these
samples were analyzed, both the plastic bag and the filter were
ignited to ensure that no sample would be lost by removing the
filter from the plastic bag. The diluted pitchblende ore was
obtained from the EPA's EMSL-LV and had a uranium-238 concentra-
tion of about 560 dpm/g. The diluted ore was prepared by the
Radiological and Environmental Services Laboratory, U. S. Depart-
ment of Energy, Idaho Falls, Idaho by diluting an extensively
characterized primary unaltered pitchblende ore in secular
equilibrium with a background soil (Sill, 1977).
The first reference soil sample, referred to as Sample 2,
was blended at the EMSL-LV and analyzed by Mound and EMSL-LV.
Uranium concentrations of the isotopes U-238 and U-234 in dpm/g
were, respectively, 1.91 ± 0.06 and 2.78 ± 0.08 from Mound's
analyses and 1.89 ± 0.07 and 2.77 ± 0.05 from the analyses done
at EMSL-LV using their method. The second reference soil sample,
referred to as Sample 4, was prepared by physically hand-mixing
2 grams of a standard pitchblende ore (Sill, 1977) with 100 grams
of a soil of a known uranium content, and then blending this
mixture with about 500 additional grams of the same soil. The
blending was carried out in a Patterson/Kelly twinshell blender
for a total of about 96 hours. The soil of known uranium content
was obtained from Environmental Measurements Laboratory, U. S.
DOE, New York, N. Y. During the blending of the soil, duplicate
5-gram samples were taken for analysis at approximately 30 hours,
48 hours and at the end of the sample period, and the measured
average concentrations of U-238 and U-234 in dpm/g for these
samples were, respectively, 20.30 and 20.14 (30 hrs), 20.81 and
20.51 (48 hrs), and 21.30 and 20.86 (96 hrs).
SINGLE-LABORATORY EVALUATION
A single-laboratory evaluation of the present method was
performed at Mound Facility in order to determine if the
criteria that had been established for the method had been met
before proceeding with the interlaboratory collaborative study,
The reference materials described in the previous section were
used to evaluate the method, and the results of the single-
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TABLE 1. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 1 (Glass Fiber
Filter)3
Sample
1A
IB
1C
ID
Avg.
Ref .
U-238
(dpm/ filter)
0.184
0.249
0.193
0.200
0.207 ± 0.029
U-234
(dpm/filter)
0.227
0.293
0.207
0.214
0.235 ± 0.039
U-236
(dpm/filter)
1.38
1.44
1.28
1.40
1.38 ± 0.07
1.32 ± 0.03
Recovery
%
93
101
85
77
89 ± 10
TABLE 2. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 2 (Reference Soil)
Sample
2A
2B
2C
2D
2E
2F
2G
2H
21
2J
2K
2L
Avg.
U-238
(dpm/ gram)
1.78
1.87
1.90
1.90
1.93
1.90
1.92
2.01
1.99
1.94
1.90
1.89
1.91 ± 0.06
U-234
(dpm/ gram)
2.69
2.66
2.81
2.76
2.77
2.83
2.64
2.86
2.89
2.79
2.81
2.76
2.77 ± 0.08
U-235
(dpm/ gram)
0.109
0.087
0.097
0.091
0.099
0.100
0.093
0.103
0.089
0.102
0.100
0.096
0.098 ± 0.007
Recovery
%
62
75
73
77
79
71
78
58
86
75
83
66
74 ± 8
aErrors in Tables 1 through 4 represent one standard deviation.
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TABLE 3. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 3 (Microsorban
Filter)
Sample
t
U-238
(dpm/filter)
U-234
(dpm/filter)
U-235
(dpm/filter)
Rejected by ASTM test.
Recovery
3A
3B
3C
3D
3E
3F
3G
3H
31
Avg.
23.1
22.2
23.0
21.8
23.7
19.5
22.3
23.0
25.5
22.7 ± 1.6
48.5
41.4
47.5
40.3.
29. 2T
41.5
44.2
.40.2
46.5
43.8 ± 3.4
1.91
1.86
2.00
1.82,
1.48T
1.85
1.85
1.88
1.99
1.90 ± 0.07
91
67
91
89
86
86
77
90
83
84 ± 8
TABLE 4. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 4 (Diluted
Pitchblende Ore)
Sample
4A
4B
4C
4D
4E
4F
Avg.
Ref .
U-238
(dpm/gram)
20.32
20.02
20.32
21.39
21.25
21.30
20.77 ± 0.61
20.54 ± 0.23
U-234
(dpm/gram)
20.39
19.86
19.90
21.20
20.92
20.77
20.51 ± 0.55
20.54 ± 0.23
U-235
(dpm/gram)
1.02
1.03
1.02
1.18
1.05,
1.42T
1.06 ± 0.07
0.89 ± 0.02
Recovery
%
88
42
88
25
80
70
66 ± 26
Rejected by ASTM test.
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laboratory evaluation of these samples are summarized in Tables
1 through 4. Reference values for Samples 1 and 4 were calculated
from the concentrations of the standard materials used in the
preparation of these samples and are given in Tables 1 and 4.
Since reference values were not known for Samples 2 and 3, the
average uranium concentrations determined in the single-laboratory
evaluation for these samples were used as reference concentrations
in the subsequent collaborative study. An ASTM-recommended criterion
(ASTM 1977a), which is discussed in the next section of this report,
was used for rejection of outliers.
Four duplicate analyses were performed on a soil sample of
known uranium concentration, obtained from Environmental Measure-
ments Laboratory, New York, to test the present procedure for
interferences from other radionuclides. The following tracers
were added for these analyses: Po-210 (87 dpm) and U-236 (10 dpm);
Pu-236 (93 dpm), Am-241 (258 dpm) and U-236 (10 dpm); Th-228
(38 dpm) and U-236 (10 dpm); and for one duplicate determination
no tracers were added to ensure that there were no alpha peaks in
the areas of interest. The final spectra from these analyses
showed that no plutonium and thorium could be detected (<0.1%),
while only very small peaks were observed for polonium (<0.370)
and americium ( and the uranium tracer recovery
for each of the analyses. Since Mound and EPA personnel decided
in previous studies (Bishop et al., 1978, 1979) that determin-
ations which had chemical recoveries less than 2070 were unaccept-
able, data listed in these tables with such low recoveries were
rejected as questionable and omitted from further consideration.
Outliers were rejected on the basis of an ASTM-recommended
criterion for rejection (ASTM 1977b).
8
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VO
TABLE 5. COLLABORATIVE STUDY RESULTS FOR SAMPLE 1 (Glass Fiber Filter
- Reference Concentration: U-238 =0.21 dpm/filter; U-234 =
0.24 dpm/filter; U-236 =1.32 dpm/filter)a
U-238b X" ± Si
X U-234b X ± Sn-
X" U-236b
X i Si X Recovery
Lab (dpm/filter) (dpm/filter) XRgf (dpm/filter) (dpm/filter) XRgf (dpm/filter) (dpm/filter) XRgf ?„
1 0.17*0.01 ---c
2 ~~~
, 0.14*0.03 n 17+n ns
J 0.21±0.04 U.I/-U.UD
, 0.70*0.07 , 7n+o ,nt
* 1.69±0.09 i-^u-u./u
5 ~~~
, 0.36*0.03 o o1+n n7
0 0.26*0.02 u.ji-u.u/
7 0.26±0.05 n 9o+n n,
' 0.20±0.03 u.zj-u.ut
8 0.075±0.023 n nsfi+n oo
8 0.041±0.014 °-058±0-02
0.81 0.10±0.01
1.18±0.18*
""" 0.51±0.07
n ftl 0.13±0.03 n 9s+n 10
°-81 0.38±0.05 0-"-0.18
,- -,, 0.66±0.07 -, , s+n fiqt
D' IL 1.6410.09 J-.u-u.D^
, ,0 0.4910.04 n /fl+o 10
L'48 0.3210.02 0.4010.12
, in 0.2010.05 n 7n+n nn
1>iu 0.2010.03 u.^u-u.uu
- 0 no 0.00710.007 Q 027+0 028
^ U'":° 0.04610.015 u-uz/-u-uze
0.42 1.3210.03
2.13 ""
, n, 1.2210.09
L'U^ 1.5010.10
, ?Q 0.7610.07
•^ 1.3H0.08
1.2310.04
1.1910.06
-, A7 1.2510.06
il&/ 1.3H0.05
n ft, 1.2810.12
U'8J 1.2010.08
n ,, 1.6010.14
Uliz 1.2410.10
1.00 80
17
51
1.3610.20 1.03 11
JO
1.0410.391" 0.79 g^
1. 2H0.03 0.92 8°
1.2810.04 0.97 7£
1.24±0.06 0.94 g°
1.4210.25 1.08 7g
aWhere S. is the experimental (within laboratory) standard deviation; X is the average of replicate
results; and XR ^ is the reference concentration (dpm/filter). 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.
*Rejected because uranium tracer recovery was less than 20%.
Rejected by ASTM test.
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TABLE 6. COLLABORATIVE STUDY RESULTS FOR SAMPLE 2 (Reference Soil
- Reference Concentration: U-238 =1.91 dpm/gram; U-234
=2.77 dpm/gram; U-235 = 0.098 dpm/gram)
Lab
1
2
3
4
5
6
7
8
U-238 X ± Si
(dpm/gram) (dpm/gram)
1.86±0.03 , 89. o Q4
1.92±0.03 I-**-"-"*
1.67±0.05 , Sfl+f) OQ
2.08±0.08 1-88*0.29
1.94±0.06 1 aa+0 oq
1.82±0.06 L-88±0-09
1.75±0.05 , 76+Q 0,
1.76 + 0.04 l-'°-u-UJ-
1.85 + 0.03 , R,+n n,
1.87±0.03 1-86±0.02
1.84+0.03 -, Rs + f) n?
1.86±0.03 i-8510-02
1.48±0.03f
1.72±0.08 . 97+Q ..
2.21±0.11 ^'-U--"
X U-234
XRef (dPm/gram)
0 nn 2.71+0.04
u'vy 2.75±0.03
q. 2.78±0.08
U'ya 2.96+0.10
n go 2.64±0.07
u'y° 2.68+0.09
„„ 2.52+0.06
u'y/ 2.53+0.06
0 9? 2.70+0.04
U'y/ 2.74+0.04
0 9? 2.65+0.04
u>y/ 2.68+0.04
0.78 2.27+0.05
l Q3 2.47+0.11
L-UJ 3.49+0.17
X ± Si X U-235 X + Si X Recovery
(dpm/gram) XRgf (dpm/gram) (dpm/gram) XRgf ?„
2.73±0.03 0.99 ""
2.87±0.13 1.04
2.66±0.03 0.96 Q' 110+0 ' 010 °-110±0-001 l-12
2.53+0.01 0.91 o 102+0 007 °-090±0-018 °-92
2.72+0.03 0.98 o'l03+o'o05 °-106±0-004 i-08
2.67±0.02 0.96 o'083+o'o05 °-076±0-011 ° • 78
0.80 0.072±0.005 --- 0.62
2.98+0.72 1.08 o'o89+o'oiO °-083±0-009 °-85
85
89
70
45
40
28
76
78
68
70
67
69
74
88
60
t
Rejected by ASTM test.
-------
TABLE 7. COLLABORATIVE STUDY RESULTS FOR SAMPLE 3 (Microsorban Filter
- Reference Concentration: U-238 = 22.7 dpm/filter; U-234 =
43.8 dpm/filter; 1.90 dpm/filter)
U-238 X i Si
X
U-234
X + S-- X
U-2:
Lab (dpm/filter) (dpm/filter) XR ^ (dpm/filter) (dpm/filter) XR f (dpm/fi
i 22
1 21
9 23
24
3 22
J 24
/ 18
4 23
5 21
5 19
, 22
6 24
7 19
' 20
8 19
8 20
.2±0
.4 + 0
.2il
.9il
.7iO
.1 + 0
.7±0
.4iO
.6iO
.0±0
.4tO
.9+0
.2±0
.7 + 1
.9 + 2
.4+1
~2 21.810.6
.0
.5*
J 23.4H.O
.5 ,, 1+, ,
.6 ^J-.i-J.J
•3 20.3H.8
•5 9 T 7 + 1 Q
.4 23.7U.8
.5
.0*
.8*
.1
0.96 £2
31
1.02 39
i m 43
i-UJ 46
0.93 33
0.90 23
1.04 £5;
0.85 33^;
0 90 35'
0.90 33
.2
.1
.0
.7
.0
Q
Q
10
H
12
iO
iO
+ ?
.OiO
.7
4
,2
4
7
iO
10
11,
15.
il.
.4
.2
. 1*
.9
.8
;S
.6
!e
.9
.7*
,0*
,8
43.3H.3 0.99
n 71
2
. 2
38.917.1 0.69 J
31.3H0.9 0.72 ]_
43.9,3.1 1.00 };
1
1 .
0.77 ]_'
.1610.
.5810.
.50+0.
.8810.
.5010.
.02+0.
.9310.
,65iO.
71 + 0.
7410.
0310.
46iO.
J5 X + Si
.Iter) (dpm/filt
10 2.3710.30
10 1 69+Q 2?
11
06 l 26+Q 34
05
10 1 79+0 90
06 i./y-u-^u
11
20*
26*
13
X R
er) XRef
1.25
0.89
0.66
0.94
0.90
0.77
.ecovery
7»
99
107
34
17
31
17
73
70
30
72
1553
11
*Rejected because uranium tracer recovery was less than 20%.
-------
TABLE 8. COLLABORATIVE STUDY RESULTS FOR SAMPLE 4 (Diluted Pitchblende
Ore: U-238 = 20.54 dpm/gram; U-234 = 20.54 dpm/gram; U-235 =
0.89 dpm/gram)
U-238 X + Si
Lab (dpm/gram) (dpm/gram)
, 22.00±0.24 ,, nrm ,,
1 19.99±0.21 zJ--uu-J--^
, 19.24±1.14*
z 21.74+0.63
3 |5;5£S;ff 21.60±0.88
4 10.91tO.42"
, 20.22+0.32
D 18.77±0.81*
6 20:49*0:25 20-17t0.46
7 16.43±0.30f
o 17. 68 ±2. 91*
0 21.14+2.48*
X U-234 X + Si
XRef (dPm/8rani) (dpm/gram)
, n9 21.36*0.23 9n ri+1 91
i-u/ 19.65±0.21 ^u^1-1'^1
, n, 20.39±1.20*
i'Ub 21.56±0.63
, ns 20.44+0.54 ,, ns+n R,
^^ 21.66iO.53 21'05±0-86
10.81±0.42f
n QR 20.29+0.32
18.46+0.80*
n qft 19.50±0.31 ,q qi+n s?
u'yo 20.31+0.25 J-^-^J--u.3/
16.55±0.031t
18.07+2.97*
20.16±2.37*
_X U-235 X ± Si
XRef (dPm/gram) (dpm/gram)
1.00 ""
1.05 :::
, n, 1.56±0.07 , ,1+n nR
1.45±0.06 J--3i-u.uo
0.63t0.05
n QQ
1.07±0.08*
°'97 O'.95±o!o2 0-93 + 0.02
0.96±0.03
0.96±0.20*
1.53±0.21*
X Recovery
XRef 7o
92
94
13
52
63
72
24
46
6
0.89 g^
0.91 76
7
9
^Rejected because uranium tracer recovery was less than 207o.
'Rejected by ASTM test.
-------
For this rejection criterion, with n observations listed in
order of increasing magnitude by Xj <_ x2 < x3 < . . . <_ x , if the
largest value xn is in question, then Tn Ts caTculated Ss follows
Tn = Cxn - x)/s (1)
where:
T = test criterion
n
x" = arithmetic average of all n values
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:
T! = (x - Xl)/s (2)
If the Tn or T1 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 570 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 for each
laboratory was used to calculate the grand average value for the
collaborative study. Uranium-235 concentrations reported by the
laboratories were divided by 0.844 because only 84.470 of the
total alpha branches from uranium-235 are included in a well-
resolved spectrum of natural uranium (Sill, 1977). The
laboratory calculations were checked to ensure that this
correction had not been made previously.
In general, the procedure evaluated at Mound was followed
by the participating laboratories, but a few minor deviations
were made. Since Laboratory 5 did not have the necessary counting
equipment and since the alpha pulse height analysis system at
Laboratory 4 was being repaired, the slides from these labora-
tories were counted at Mound and the resulting spectra were sent
back to these laboratories to be analyzed as described in the
procedure. Laboratory 1 used silver slides, rather than the
stainless steel slides recommended in the procedure. The only
laboratory that deviated considerably from the procedure was
Laboratory 2. This laboratory used an ammonium oxalate procedure
for electrodeposition rather than the ammonium sulfate procedure
13
-------
given in the present method. Three out of the eight deter-
minations reported by Laboratory 2 had tracer recoveries of less
than 207o and had to be rejected, while the average uranium-232
recovery for this laboratory was only 377o. Previous experience
at Mound has indicated that an ammonium sulfate procedure gen-
erally gives better yields than an ammonium oxalate procedure.
DISCUSSION OF RESULTS
A summary of the collaborative study results is given in
Table 9. In this table, the grand averages or the average
collaborative study concentrations (Xc) and the standard
deviations (Sd) of the individual laboratory averages are
presented for the uranium isotopes measured for each sample.
These statistics were calculated as follows (Youden and Steiner
1975):
(3)
Sd = (^1 -^c; ] (4)
where:
Xi = average of duplicate results for
laboratory i for the given sample
n = number of laboratories providing
results for the given sample
The precision standard deviation or the combined within-laboratory
standard deviation, Sr, and the standard deviation of the system-
atic errors or the precision of the method between laboratories,
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:
Sr = (Ed2/2n) (5)
where:
d = the absolute difference between the
duplicates
14
-------
TABLE 9. SUMMARY OF RESULTS FOR URANIUM-IN-SOIL
AND AIR COLLABORATIVE STUDY*
Tabulated Quantity
Sample
1
1
1
2
2
2
3
3
3
4
4
4
Isotope
U-238
U-234
U-236
U-238
U-234
U-235
U-238
U-234
U-235
U-238
U-234
U-235
Xc
0.19
0.25
1.31
1.87
2.68
0.090
21.6
37.9
1.70
20.95
20.66
1.01
Sd
0.09
(47%)
0.18
(72%)
0.08
(6.1%)
0.06
(3.2%)
0.21
(7.8%)
0.016
(18%)
1.7
(7.9%)
5.7
(15%)
0.40
(24%)
0.74
(3.5%)
0.65
(3.1%)
0.37
(37%)
S
0.05
(26%)
0.11
(44%)
0.15
(12%)
0.17
(8.9-1
0.28
(10%)
0.010
(11%)
1.9
(8.8%)
6.1
(16%)
0.28
(16%)
1.0
(4.8%)
0.92
(4.5%)
0.06
(6.0%)
sb
0 07
(33%)
0.16 •
(647.)
0.07
(2.6%)
0.014
(16%)
1.0
(4.6%)
3.7
(9.8%)
0.35
(21%)
0.22
(1.0%)
0.00
(0%)
0.37
(37?=)
Y +9 7
"Ref " bRef /0
0.21 ± 0.03
0.24 ± 0.04
1.32 ± 0.03
1.91 ± 0.06
2.77 ± 0.08
0.098 = 0.007
22.7 - 1.6
43.8 = 3.4
1.90 - 0.07
20.54 - 0.23
20.54 - 0.23
0.89 - 0.02
Difference
9.5
4.2
0.8
2.1
3.2
8.2
4.9
13
11
2.0
0.6
13
"'The tabulated quantities are defined as: X - collaborative study
average concentration, S^ - standard deviation of the laboratory
averages, Sr - precision standard deviation or combined within-
laboratory averages, S^ - standard deviation of the systematic errors,
^Ref - SRef - reference concentration and standard deviation of the
reference concentration.
15
-------
n = the number of collaborating laboratories
reporting duplicates
The standard deviation of the systematic error, Su, is computed
from the other two standard deviations according to Youden's
Formula (4) (Youden and Steiner, 1975):
2 =
- S 2/2
r
(6)
Also given in Table 9 are the reference concentrations and
estimated errors of these concentrations. Reference values
for Samples 2 and 3 were obtained from the single-laboratory
evaluation. The "% difference" given in Table 9 is the percent
difference between the reference value and the average reported
value.
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):
t =
where:
X.
c
SRef
Xc - XRef
t =
Ref
d
-d + -Ref
Ref
n
(7)
test criterion
average of collaborative test results
average reference value
estimated standard deviation of
collaborative test results
n = number of collaborating laboratories
estimated standard deviation of
reference concentration
16
-------
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 = U:_^A
(8)
where:
R = the reference value considered to be the
true mean
Other quantities are defined as in equation
(7)
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 (tcj.j_t), determined for a 570 level of
significance, are also given for comparison to the calculated t
values. When t is less than tcrit, it can be said that the two
means agree. It can be seen in Table 10 that all results from
the collaborative study agree with the reference values, except
the U-234 determination in Sample 3. It should be pointed out
that three of the duplicate results reported by the laboratories
for Sample 3, which are given in Table 7, show large variations
in duplicate values for this determination, and relatively poor
precision was obtained for the U-234 concentration of Sample 3
in the single-laboratory evaluation given in Table 3. Since
only 40 mg of diluted pitchblende ore was added to the Micro-
sorban air filter, a homogeneity problem may be suspected;
however, the U-238 results show better precision than the U-234
results. It would be expected that U-238 and U-234 activities
would be in equilibrium for Sample 3 but, instead, the U-234
activity is about a factor of two greater than the U-238 activity.
This is evidence that the naturally occurring uranium series had
been altered in the preparation of this sample and may help
explain why the U-234 concentration appears to be less homogeneous
than the U-238 concentration. Blank determinations of the
polystyrene filters and plastic bags in which the samples were
sent to the participating laboratories showed that the unexpected
U-234/U-238 ratio was not caused from these materials. Although
the reason for the discrepancy between the reference value and
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
xc
0.19
0.25
1.31
1.87
2.68
0.090
21.6
37.9
1.70
20.95
20.66
1.01
+~ Sc
± 0.
± 0.
± 0.
± 0.
± 0.
± 0
± 1.
± 5.
± 0.
± 0
± 0
± 0.
09
18
08
06
21
.016
7
7
40
.74
.65
37
XRef
0.21
0.24
1.32
1.91
2.77
0.098
22.7
43.8
1.90
20.54
20.54
0.89
± SRef
± 0.
± 0.
± 0.
± 0.
± 0.
± 0
± 1.
± 3.
± 0.
± 0
± 0
± 0.
03
04
03
06
08
.007
3
4
07
.23
.23
02
nc nRef
5 4
6 4
6
7 12
8 12
6 12
8 9
8 8
6 8
5
5
4
0
0
0
1
1
1
1
2
1
1
0
0
t
.47
.13
.31
.40
.16
.17
.48
.51
.21
.24
.41
.65
crit
2.57
2.45
2.57
2.16
2.31
2.45
2.16
2.20
2.57
2.78
2.78
3.18
o ^^
The tabulated quantities are defined in the text.
18
-------
collaborative study value is not apparent, it is probably re-
lated to the reference sample, rather than the analytical method
used in the preparation of the collaborative study.
An additional 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 do not approach the error expected from counting statistics.
The average collaborative study error for determinations of
uranium activities above 1.0 pCi/g was found to be about 1070,
which is a factor of 3 higher than the error expected from count-
ing statistics. Standard deviations for reference samples with
the highest uranium concentrations and lowest counting errors
were found to be about 370, and this might be considered the lower
limit for the precision of the present method. The errors shown
in Table 11 for the determination of uranium in air (Samples 1
and 3) were somewhat higher than the errors for the determination
of uranium in soil (Samples 2 and 4), but this would be expected
since the counting errors for the air samples were also higher.
Some comments about the collaborative study were provided
by a few of the participating laboratories. One laboratory
commented that the procedure was not long or time-consuming,
while another laboratory indicated that even though the procedure
was good overall, they felt that it was very lengthy, especially
since only uranium isotopes are separated and analyzed. It was
pointed out by one of the participants that the uranium added to
the Microsorban air filters of Sample 3 appeared to differ from
one filter to its duplicate. Two suggestions for possible changes
in the procedure were expressed. These were to substitute an
ammonium iodide solution (100 mg per 10 ml 6M HC1) for the
hazardous hydriodic acid used in the anion exchange separation,
and to add the uranium tracer before ignition of the Microsorban
filters.
The single-laboratory and multilaboratory evaluations of the
present procedure showed that the method provides a relatively
simple, cost effective, and accurate means of determining
uranium isotopes in soil and air samples for uranium concentrations
of greater than a few tenths of a disintegration per minute.
19
-------
TABLE 11. OVERALL STANDARD DEVIATION OF COLLABORATIVE
STUDY RESULTS AND STANDARD DEVIATIONS
EXPECTED FROM COUNTING STATISTICS ERRORS"
Sample
Number
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
Average Uranium
Concentration
(dpm/g or
dpm/ filter)
0.19
0.25
1.31
1.87
2.68
0.090
21.6
37.9
1.70
20.95
20.66
1.01
Std Dev
of Data
(dpm/g or
dpm/f ilter)
0.09
(47%)
0.18
(72%)
0.08
(6.1%)
0.06
(3.2%)
0.21
(7.8%)
0.016
(18%)
1.7
(7.9%)
5.7
(15%)
0.40
(24%)
0.74
(3.5%)
0.65
(3.1%)
0.37
(37%)
Std Dev Expected
From Counting Statistics
(dpm/g or dpm/ filter)
0.02
(11%)
0.03
(12%)
0.06
(4.6%)
0.04
(2.1%)
0.05
(1.9%)
0.005
(5.6%)
0.6
(2.8%)
0.9
(2.4%)
0.09
(5.3%)
0.38
(1.8%)
0.38
(1.8%)
0.04
(4.0%)
20
-------
REFERENCES
American Society for Testing and Materials, 1977 Annual Book
of Standards, Part 31, Designation: D2907-75, P. 790,
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.
Bishop, C. T., V. R. Casella, and A. A. Glosby, "Radiometric
Method for the Determination of Uranium in Water: Single-
Laboratory Evaluation and Interlaboratory Collaborative Study,"
U. S. Environmental Protection Agency Report, EPA 600/7-79-093,
Las Vegas, NV, 1979.
Danielsson, A., B. Ronnholm, and L. Kjellstron, "Fluorometric
Method for the Determination of Uranium in Natural Waters,"
Talanta, 20, 185 (1973).
Lee, H., T. 0. Peyton, R. V. Steele, and R. K. White, "Potential
Radioactive Pollutants Resulting From Expanded Energy Programs,"
U.S. Environmental Protection Agency Report, EPA-600/7-77-082,
Las Vegas, NV, 1977.
Morrison, G. H., and H. Freiser, Solvent Extraction in Analytical
Chemistry, John Wiley and Sons, Inc., New York, N. Y., p. 212,
I9TT
NCRP Report No. 45, Natural Background Radiation in the United
States, November, 1975.
Sill, C. W "Simultaneous Determination of 238U, 234U, 230Th,
ZZbRa, and /luPb in Uranium Ores, Dusts, and Mill Tailings,:
Health Physics, 33, 393 (1977).
U. S. Atomic Energy Commission Regulatory Guide 5.4, Measurements
of Radiohuclides in the Environment, Sampling and Analysis of
Plutonium in Soil, May, 1974.
21
-------
Whittaker, E. L., and G. E. Grothaus, "Acid Dissolution Method
for the Analysis of Plutonium-239 and Plutonium-238 in Soil:
Evaluation of an Interlaboratory Collaborative Test and
Comparison with Results of a Fusion Method Test," U. S.
Environmental Protection Agency Report, EPA 600/7-79-081,
Las Vegas, NV, 1979.
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.
Youden, ¥. 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 SOIL AND AIR SAMPLES
This appendix is a reprint of a procedure of the same title
by Vito R. Casella, Carl T. Bishop, Antonia A. Glosby, and
Charles A. Phillips of Mound Facility in Miamisburg, Ohio. The
report was prepared December 12, 1977, for the U. S. Environmental
Protection Agency under Contract No. EPA-78-D-X0143. 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-77-72-0001.
23
-------
PREFACE
The analytical procedure described in this document is a
tentative method for the determination of uranium isotopes
in soil and air samples. It is being collaboratively tested
according to an interagency agreement between the U. S.
Environmental Protection Agency (EPA) and the U. S. Department
of Energy (DOE). 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.
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 28
2. Summary 28
3. Interferences 29
4. Apparatus
4.1 Instrumentation 29
4.2 Laboratory Equipment 30
4.3 Labware 32
5. Standards, Acids, Reagents
5.1 Standards 33
5.2 Acids 33
5.3 Reagents 33
6. Calibration and Standardization
6.1 Standardization of the Uranium-232 Tracer Solution 34
6.2 Determination of Alpha Spectrometer Efficiency 34
7. Step by Step Procedure for Analysis
7.1 Acid Dissolution 35
7.2 Coprecipitation 36
7.3 Ether Extraction 37
7.4 Anion Exchange Separation 37
7.5 Electrodeposition 38
7.6 Alpha Pulse Height Analysis 39
8. Calculation of Results
8.1 Calculations of Uranium Concentrations 40
8.2 Calculation of Alpha Spectrometer Efficiency 40
8.3 Calculation of Uranium Recovery of the Chemical ^
Analysis
References 42
25
-------
1. SCOPE AND APPLICATION
1.1 General Considerations
This procedure applies to the determination of uranium
isotopes in soil or air filter samples. It has been
applied to soils from various parts of the U.S. and to
both fiber glass and polystyrene air filters. Analysis
of soils for uranium at levels greater than 0.01 dpm/g
can be performed using this method for 10 gram samples.
Although 10 g samples are recommended, it can be applied
to samples of up to 50g of soil.
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 operations,
but it should be utilized only after satisfactory results
are obtained by the analyst when replicate standard
samples are analyzed.
1.2 Minimum Detectable Activity
The minimum detectable concentration of a given uranium
isotope is dependent upon the size of the sample 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 of interest
is 5 counts in 1000 minutes, and the chemical recovery of
the uranium tracer is 80%. From the definition of the MDA,
26
-------
the sample count would have to be seven (ca. 3 x / 5)
in 1000 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 by this
procedure would be 0.03 d/m.
1.3 Sensitivity
Using the minimum detectable activity computed in the
last section and considering a 10 gram soil sample, the
lowest concentration of uranium-238, as mg U-238/g of
soil, that could be detected by this method would be:
0.034 d/m / (0.739 d/m/mg x lOg) = 0.0046 mg/g.
The lowest concentration of U-238 detectable per air filter
is the same as the MDA, i.e. 0.046 mg/filter.
The sensitivity of this isotopic method can be
compared (Bishop, 1977) to methods which determine
total uranium concentrations fluorometrically.
Although fluorometric methods are comparable in
sensitivity to counting methods for U-238 (natural
uranium), fluorometric methods could not detect
other uranium isotopes which are readily detect-
able by counting methods. This is because the
isotopic method can be used to detect much smaller
masses of these other uranium isotopes which have
high specific activities. The long lived isotopes
of uranium along with some of their properties
of interest to this procedure are given in Table
1.
PROPERTIES OF URANIUM ISOTOPES
OF INTEREST IN ENVIRONMENTAL SAMPLES
Half-Life
Isotope (Years)
U-232
U-233
U-234
U-235
U-236
U-238
72
1.62xlOv
2.47x10*
7. 1 xlO
8
2.39x10
4.51xl09
Specific
Activity
(dis/min/Mg)
4.75xl07
21,000
13,730
4.76
141
0.739
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
-------
] . 4 Precision and Accuracy
The precision of the method has not yet been evaluated,
but based on experience with a similar procedure for
uranium in water, the precision is expected to approach
that of counting statistics errors. The accuracy is
expected 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 a nitric acid-hydrofluoric
acid dissolution, coprecipitation of uranium with iron hydro-
xide, an ether extraction if the sample contains iron as a
major constituent, separation of uranium by anion exchange, and
electrodeposition of the uranium followed by alpha pulse height
ana lysis.
After adding uranium-232 tracer, organic matter is removed
from the sample by heating. Subsequently, the sample is
decomposed by a nitric acid-hydrofluoric acid digestion,
and the uranium is coprecipitated by making this solution
basic with ammonium hydroxide (carbonate free). The hydro-
xide precipitate is dissolved in 8 M hydrochloric acid,
which is extracted with isopropyl ether to remove the bulk
of the iron present. For samples with relatively low iron
concentrations, such as air filters containing little
particulate matter, this extraction can be omitted.
The 8 M hydrochloric acid solution is passed through an anion
exchange resin column. Uranium, polonium and bismuth will be
adsorbed on the resin while thorium and radium will pass through
the column. Plutonium and any unextracted iron are also retained
by the resin, but are eluted with 6 M HC1 containing hydrogen
iodide. The iodide ion reduces plutonium (IV) to plutonium (III)
and reduces the iron (III) to iron (II), and neither of these
ions are retained by the ion exchange resin in 6 M HC1. The'
uranium is eluted from the column with 1.0 M HC1, while any
zinc adsorbed on the column will remain. Electrodeposition of
the uranium onto a stainless steel slide is performed, and the
slide is counted by alpha pulse height analysis using a silicon
surface barrier detector.
28
-------
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 contained both uranium-233 and
uranium-234, it would be very difficult 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 (Ed-
wards, 1968). Protactinium-231 has the following alpha
energies in MeV, the abundance being given in parantheses:
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 deter-
mination of uranium-233 or uranium-234.
3.2 In determining very low levels of uranium isotopes in
environmental 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.
4. APPARATUS
4.1 Instrumentation
4.1.1 Alpha Pulse Height Analysis System - A system con-
sisting of a silicon surface barrier detector capable
of giving a resolution of 50 keV or better with
samples electrodeposited on flat mirror finished
29
-------
stainless steel slides is used. 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, 0-12 volts and 0-2 amps,is required
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 electrodeposi-
tion 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 electro-
deposition is 2 cm .
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, precision
± 0.1 g.
4.2.2 Balance - analytical, capacity 160 g, precision
+ 0.1 mg
4.2.3 Hot plate - magnetic stirrer and stirrer bar.
4.2.4 Centrifuge - capable of handling 100 ml or larger
centrifuge bottles.
30
-------
Micro bell gloss
(Sorgent-Welch
Cot. No. S-4930)
Liquid scintillation counting
polyethylene vial, 25 ml capacity,
with bottom cut off containing
electrolyte solution
Brass screw cap machined
to fit 25 ril polyethylene
vial, with 7/32" diameter by
1/2" long tube protruding
from base of cap
Platinum wire
anode
5/14" od glass
tub* added to bell glass
Rubber tubing carrying
cooling water out
Small rubber bulb
Stainless steel slide
3/4" in diameter
Stainless steel tubing,
3/8"odby 2 1/2" long,
electrical connection to cathode
mode here
Rubber stopper,
size 2
Rubber tubing carrying
cooling water in
Figure 1. Water Cooled Electrodeposition Apparatus
31
-------
4.3 Labware
4.3.1 Graduated cylinders - 25 ml to 100 ml.
4.3.2 Beakers - glass, 100 ml to 250 ml.
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 100 A and 1000A.
4.3.6 Centrifuge bottles - 250 ml.
4.3.7 Ion exchange columns - approximately 1.3 cm ID,
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
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.
32
-------
5. STANDARDS, ACID, 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 distilled
deionized water.
5.2.1 Nitric acid - concentrated (16 M).
5.2.2 Hydrochloric acid - concentrated (12 M, 8 M, 6 M,
1.0 M, 0.5 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.
5.3.1 Ferric chloride - in 0.5 M 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
slurrying this resin with 8 M HC1 and pouring it
onto a column of inside diameter approximately
33
-------
1.3 cm. The height of the column of resin should
be about 10 cm.
5.3.4 Sodium hydrogen sulfate solution ca. 5% in 1 M
H SO ; dissolve 10 g of the NaHSO •H 0 in 100 ml
or water and then carefully add 100 ml of 2 M H SO .
4-i Tt
5.3.5 Preadjusted electrolyte - 1 M ammonium sulfate
adjusted to pH 3.5 with 15 M NH, OH and 18 M H SO
H- £ Q •
5.3.6 Thymol blue indicator, sodium salt (available
from Fisher Scientific Company) - 0.04% solution.
5.3.7 Ethyl alcohol - made slightly basic with a few drops
of 15 M NH OH 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
the specific activity of the uranium-232 solution could be
determined. Alternately, a freshly purified solution of
uranium-232 could be standardized by 2-rr counting. Weighed
aliquots of the solution free of hydrochloric acid could be
evaporated on platinum or stainless steel slides and counted
with a 2-n proportional counter. The efficiency of the 2-n
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 necessary.
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 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 concentration
of the unknown uranium isotope is calculated (cf. Section 8.1)
34
-------
A determination of the alpha spectrometer 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 particle counting efficiency is
then calculated as illustrated in Section 8.2.
7. STEP BY STEP PROCEDURE FOR ANALYSIS
7.1 Acid Dissolution
7.1.1 Weigh a representative 10.0 ± 0.1 grams of 100
mesh soil sample or the glass fiber filter(s)
and transfer to a casserole. If a Microsorban
(polystrene) filter(s) was used, place the
filter(s) into a 150-ml or 250-ml Pyrex beaker
and cover with a watch glass.
7.1.2 Add an appropriate quantity of uranium-232 tracer.
If the activity "is expected to be less than 1 dpm/g,
or is unknown, add 10 dpm of tracer. For higher
levels add as much uranium-232 tracer as the esti-
mated activity of uranium in the sample. If a
Microsorban filter(s) was used, add the uranium-232
tracer after Step 7.1.3.
7.1.3 Heat the casserole containing the soil sample or
glass fiber filter(s) at 600°C for four hours in
a muffle furnace; remove, and cool. If a Microsorban
filter(s) was used, place the Pyrex beaker in a
muffle furnace at 200°C for 1 hour. Increase the
temperature at 1 hr intervals to 300°C, 400°C and
550°C. Muffle for 2 or 3 hrs at 550°C or until only
a brown powdery ash remains . Remove and cool.
7.1.4 Transfer the sample to a 250-ml Teflon beaker,
rinsing the casserole with 10 ml portions of
16 M HNO- to a final volume of 60 ml of nitric
acid. For Microsorban filter(s) rinse the
beaker with 5 ml portions of 16 M HNC>3 to a
final volume of 30 ml of nitric acid.
35
-------
7.1.5 Carefully add 30 ml of 48% hydrofluoric acid
(20 ml for Microsorban filters), cover with a
teflon watchglass and heat on a hotplate with
frequent stirring for about 1 hr. Remove from
the hotplate and cool. (CAUTION: HF is very
hazardous. Wear rubber gloves, safety glasses
or goggles, and a laboratory coat. Avoid breathing
HF fumes. Clean up all spills and wash thoroughly
after using HF).
7.1.6 Carefully add 30 ml (20 ml for Microsorban filters)
each of 16 M HNO and HF (48%) and digest with some
stirring for an additional hour.
7.1.7 Remove from the hotplate and cool to room tempera-
ture. Slowly add 20 rnl of 12 M HC1 and heat on a
hotplate with some stirring until the solution has
evaporated to a liquid volume of approximately 10 ml.
7.1.8 Add 50 ml of distilled water and digest on a hot
plate with stirring for 10 minutes to dissolve the
soluble salts.
7.1.9 Cool and transfer the total sample into a 250-ml
centrifuge bottle with a minimum of distilled water
from a wash bottle. If any insoluble residue is
present, the sample should be centrifuged and the
supernate should be transferred into another centrifuge
bottle. This residue should be washed with 10 ml of
1.0 M HC1 which is added to the supernate. Discard
the insoluble residue. Proceed to section 7.2,
Coprecipitation.
7.2 Coprecipitation
7.2.1 Add 20 rag of iron as Fed in 0.5 M HC1 to the
centrifuge bottle and stir. (This step is usually
not necessary for soil samples containing iron).
o_
7.2.2 Add 15 M NH OH (CO free) while stirring to preci-
pitate the iron. Continue adding 15 M NH OH to raise
the pH to 9-10 as determined by pH paper, then add
5 ml in excess.
36
-------
7.2.3 Centrifuge for approximately 5 minutes, decant
and discard the supernate.
7.2.4 Dissolve the precipitate with a minimum of 12 M
HC1 and add 8 M HC1 to a volume of about 50 ml.
Transfer the solution to a 250-ml separatory funnel
using two 5-ml rinses of 8 M HC1 and proceed to
Section 7.3, Ether Extraction.
7.3 Ether Extraction
7.3.1 Add 60 ml of isopropyl ether to the separatory
funnel and shake the solution for two minutes.
Allow the phases to separate and then transfer
the aqueous phase (lower phase) to a second
separatory funnel. Add 5-ml of 12 M HCl to the
aqueous phase.
7.3.2 Repeat this ether extraction two more times. The
bulk of the iron is removed as evidenced by the
appearance of a yellow color in the organic phase.
(If the sample has a very high concentration of iron,
additional extractions may be necessary.)
7.3.3 Transfer the aqueous phase to a 150-ml beaker,
boil for 15 tnin, and proceed with Section 7.4,
Anion Exchange Separation.
7.4 Anion Exchange Separation
7.4.1 Condition the anion exchange resin column (prepared
as described in Section 5.3) by rinsing the column
with 4 column volumes of 8 M HCl.
7.4.2 Transfer the sample from Step 7.3.3 to the condi-
tioned anion exchange resin.
7.4.3 After the sample has passed through the column, elute
any unextracted iron (and plutonium if present) with
6 column volumes of 6 M HCl containing 1 ml of concen-
trated HI per 50 ml of 6 M HCl (freshly prepared).
37
-------
7.4.4 Rinse the column with an additional two column
volumes of 6 M HC1.
7.4.5 Elute the uranium with six column volumes of 1.0 M
HC1.
7.4.6 Evaporate the sample to about 20 ml and add 5 ml of
16 M HNO
O
7.4.7 Evaporate the sample to near dr^ness.
7.5 Electrodeposition
7.5.1 Add 2 ml of a 5% solution of NaHSCKH 0 in 1 M
H SO to the sample.
<£ T
7.5.2 Add 5 ml of 16 M HNO mix well and evaporate to
dryness, but do not Bake.
7.5.3 Dissolve the sample in 5 ml of the preadjusted elec-
trolyte (cf. Section 5.3), warming to hasten the
dissolution.
7.5.4 Transfer the solution to the electrodeposition
cell using an additional 5-10 ml of the electrolyte
in small increments to rinse the sample container.
7.5.5 Add three or four drops of thymol blue indicator
solution. If the color is not salmon pink, add
1.8 M HnSO (or 15 M NH^OH) until this color is
— 2t 4 — 4
obtainea.
7.5.6 Place the platinum anode into the solution so that
it is about 1 cm above the stainless steel slide
which serves as the cathode.
7.5.7 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.)
7.5.8 Continue the electrodeposition for a total of
1 hr.
38
-------
7.5.9 When the electrodeposition is to be terminated,
add 1 ml of 15 M NH.OH and continue the electro-
— 4
deposition for 1 min.
7.5.10 Remove the anode from the cell and then turn off the
power.
7.5.11 Discard the solution in the cell and rinse the
cell 2 or 3 times with 0.15 M NH4OH.
7.5.12 Disassemble the cell and wash the slide with
ethyl alcohol that has been made basic with NH^OH.
7.5.13 Touch the edge of the slide to a tissue to absorb
the alcohol from the slide.
7.5.14 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.)
7.6 Alpha Pulse Height Analysis
7.6.1 Count the samples for at least 1000 minutes or
longer if the detector efficiency is less than
15%, if the tracer recovery is low, or if the
unknown uranium activity is low.
7.6.2 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-236 and uranium-235, for example.)
7.6.3 Make the necessary background corrections. (The
background should be determined by a 4000 minute
or longer count.)
39
-------
7.6.4 Make a blank correction for each peak, if
necessary.
8. CALCULATION OF RESULTS
8.1 Calculations of Uranium Concentrations
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:
X. = C. x A
i __i t ,R .
C x W (8'1)
t s
where X. = the concentration of the unknown uranium
isotope in d/m/g of soil or d/m/ filter.
C. = the net sample counts in the energy region
corresponding to the uranium isotope being
measured.
A = the activity of the uranium-232 tracer added
to the sample in d/m.
C = the net sample counts in the uranium-232 tracer
energy region of the alpha spectrum.
W = the weight in grams of the soil sample taken
for analysis; W is omitted from this formula
o
(W =1) when the sample is an air filter.
S
8.2 Calculation of Alpha Spectrometer Efficiency
The absolute counting efficiency of the alpha spectrometer,
e, must be determined in order to calculate the uranium
recovery of the an-alytical procedure.
To determine this efficiency requires a standard source
of a known alpha particle emission rate:
40
-------
E = Rs/Ra (8.2)
where R = the net counting rate of the standard source
in the energy region of the alpha emitter of
interest in counts per minute.
R = the absolute alpha particle emission rate of
the alpha emitter of interest in alpha dis-
integrations per minute.
8. 3 Calculation of Uranium Recovery of the Chemical Analysis
The uranium recovery efficiency E (%) expressed in percent
is given by:
= Ct x 100% (g 3)
t x A xe
where t=the counting time in minutes and the other terms
are as defined in Sections 8.1 and 8.2.
41
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REFERENCES
F. Baltakmens, "Simple Method for the Determination of
Uranium in Soils by Two Stage Ion Exchange," Anal. Chem.,
47, 1147 (1975).
C. T. Bishop, V. R. Casella, R. Brown, A. A. Glosby,
C. A. Phillips and B. Robinson, "Tentative Method or
the Determination of Uranium Isotopes in Water (By a
Coprecipitation Anion Exchange Technique)." Unpublished
report MLM-MU-77-61-0001, Mound Laboratory, 1977.
K. W. Edwards, "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., 1968.
?. H. Essington and H. P. Patterson, "Determination of
38u, 233-234(j in Soil and Vegetation Samples (Tentative),"
Nevada Applied Ecology Group Procedures Handbook for Environ-
mental Transuranics, NVO-166, Vol. 1, p. 205, October 1976.
J. E. Gindler, "The Radiochemistry of Uranium," NAS-NS-3050,
National Academy of Sciences - National Research Council, 1962
J. Korkisch, "Modern Methods for the Separation of Rarer Metal
Ions," Pergamon Press, New York, 1969, P. 62.
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 9B1, p. 837, United Nations (1956).
N. A. Talvitie, "Electrodeposition of Actinides for Alpha
Spectrometric Determination," Anal. Chem. 44, 280 (1972).
U. S. Atomic Energy Commission, "Measurement of Radionuclides
in the Environment - Sampling and Analysis of Plutonium in
Soil," U. S. Atomic Energy Commission Regulatory Guide 4.5,
May, 1974.
42
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APPENDIX 2
COLLABORATIVE STUDY INSTRUCTIONS
URANIUM IN SOIL AND AIR
(January 1978)
1. Use the procedure "Tentative Method for the Determination
of Uranium Isotopes in Soil and Air Samples" by V. R. Casella
et. al., December 2, 1977.
2. If you have not analyzed samples using a procedure similar to
the one to be used in the collaborative study, a few known
samples should be analyzed before analyzing the collaborative
study samples.
3. Special reagents that you might not have on hand, such as the
ion exchange resin, will be furnished by Mound if you desire.
Contacts are given below.
4. Additional amounts of any sample are available if required.
Contacts are given below.
5. All samples should be analyzed in duplicate. For sample
78-4, analyze five grain aliquots rather than ten grams.
6. Uranium concentrations may bo as low as 0.5 dis/min/g or
0.5 dis/min/filter. Laboratory blanks should be determined
in your laboratory to be certain that they are not a problem
at these uranium concentrations.
7. Use the uranium-232 tracer, U-10, for this study. Data on this
tracer is attached to these instructions. Using 500X of this
tracer gives 10.4 dis/min of U-232.
8. When analyzing the Microsorban samples, do not remove the
filter from the plastic bag in which it is contained; ignite the
filter and bag together when beginning the analysis.
9. The water cooled electrodeposition apparatus shown in Figure 1
of the procedure is only an illustration. Water cooling is not
required, and any apparatus producing a suitable slide foi
alpha pulse height analysis is satisfactory.
10. Samples should be counted for 1000 minutes or at least long;
enough to accumulate 200 counts In an unknown alpha peak.
11. Report your results on the data sheet attached. Individual
counting data is requested so that the counting staizistice
error can be resolved from other experimental errors.
43
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APPENDIX 3
DATA ON URANIUM-232 TRACER
Isotope: U-232 I.D. No.: U-10
Date Prepared: 11/28/77
Specific Activity: 20.2 dis/min/gram (±2%)(on date prepared)
Density: 1.031 g/cm3 at 20°C
Acid Medium: 1 M HN03
Source: U.S. ERDA - Health and Safety Laboratory, purified by
ion exchange and standardized at Mound Facility.
Half Life: 72 years
Approximate Volume in Glass Ampoule: 6 ml
Opening Instructions: The constriction of the glass ampoule has
been previously scored and reinforced vrith
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.
Prepared At: Mound Facility
Monsanto Research Corporation
Miamisburg, Ohio 45342
44
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APPENDIX 4
LABORATORIES PARTICIPATING IN THE
URANIUM IN SOIL AND AIR COLLABORATIVE STUDY
Allied Chemical Corporation
Idaho Falls, Idaho
Argonne National Laboratory
Argonne, Illinois
Arkansas Department of Health
Little Rock, Arkansas
Eberline Albuquerque Laboratory
Albuqueque, New Mexico
LFE Environmental Analysis Laboratories
Richmond, California
Ohio State University
Columbus, Ohio
Reynolds Electrical and Engineering Co., Inc.
Las Vegas, Nevada
U. S. Energy Research and Development Administration
Environmental Measurements Laboratory
New York, New York
45
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
RADIOMETRIC METHOD FOR THE DETERMINATION OF URANIUM IN
SOIL AND AIR: Single Laboratory Evaluation and
Inter!aboratory Collaborative Study
5. REPORT DATE
February 1980
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
V. R. Casella, C. T. Bishop, and A. A. Glosby
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Monsanto Research Corporation
Mound Facility
P.O. Box 32
Miamisburg, Ohio 45342
10. PROGRAM ELEMENT NO.
INE833
11. CONTRACT/GRANT NO.
IAG-EPA-78-D-X0143
12. SPONSORING AGENCY NAME AND ADDRESS
U. S. Environmental Protection Agency—Las Vegas, NV
Office of Research and Development
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
13. TYPE OF REPORT AND PERIOD COVERED
4/1/77 ~ 10/1/78
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. DE-AC-04-76-DP00053
16. ABSTRACT
Results of a single-laboratory evaluation and an interlaboratory collaborative study
of a method for determining uranium isotopes in soil and air samples are presented.
The method is applicable to 10-gram soil samples and to both glass fiber and poly-
styrene (Microsorban) air filter samples. Sample decomposition is accomplished with a
nitric-hydrofluoric actd dissolution. After a solvent extraction step to remove most
of the iron present, the uranium is isolated by anion exchange chromatography and
electrodeposition. Alpha spectrometry is used to measure the uranium isotopes.
Two soil samples, a glass fiber air filter sample, and a polystyrene air filter sample
were used to evaluate the method for uranium concentrations ranging from a few tenths
to about one hundred disintegrations per minute per sample. Tracer recoveries for the
single-laboratory evaluation averaged 78 percent, while the tracer recoveries for the
collaborative study averaged 66 percent. Although the precision of the collaborative
study results did not approach counting statistics errors, the measured uranium
concentrations for these samples agreed to within 5 percent of the reference concen-
trations when the uranium concentration was greater than one disintegration per minute
per gram of soil or one disintegration per minute per air filter.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Uranium
Quantitative analysis
Quality assurance
Soil and air
68F
77B
99B, E
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
14
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-J (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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