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

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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 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

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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.

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                           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%.

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                       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

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              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.

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     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

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       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.

-------
         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

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                           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

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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

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     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

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     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

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         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

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         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

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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

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     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

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     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

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     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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