United States
Environmental Protection
Age;
Environmental Monitoring
and Support Laboratory
P.O. Box 15027
Las Vegas NV 89114
EPA-600/7-78-122
June 1978
Research and Development
&EPA
Anion Exchange Method
for the Determination
of Plutonium in Water:
Single-Laboratory
Evaluation and
Interlaboratory
Collaborative Study
Interagency
Energy-Environment
Research
and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad categories
were established to facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously planned to foster
technology transfer and a maximum interface in related fields. The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY—ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the effort
funded under the 17-agency Federal Energy/Environment Research and Development
Program. These studies relate to EPA'S mission to protect the public health and welfare
from adverse effects of pollutants associated with energy systems. The goal of the Pro-
gram is to assure the rapid development of domestic energy supplies in an environ-
mentally-compatible manner by providing the necessary environmental data and
control technology. Investigations include analyses of the transport of energy-related
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of energy-related environmental issues.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161
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EPA-600/7-78-122
June 1978
ANION EXCHANGE METHOD FOR THE
DETERMINATION OF PLUTONIUM IN WATER:
Single-Laboratory Evaluation and
Interlaboratory Collaborative Study
by
C. T. Bishop, A. A. Glosby, R. Brown, and C. A. Phillips
Environmental Assessment and Planning Section
Mound Facility
Miamisburg, Ohio 45342
Contract No. EPA-IAG-D6-0015
Project Officer
Erich W. Bretthauer
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
Monitoring and Support Laboratory-Las Vegas, U. S. Environmental
Protection Agency, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the U. S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
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 Environ-
mental Monitoring and Support Laboratory-Las Vegas contributes
to the formation and enhancement of a sound integrated monitoring
data base for exposure assessment through programs designed to:
• develop and optimize systems and strategies for
monitoring pollutants and their impact on the
environment
- demonstrate new monitoring systems and technologies
by applying them to fulfill special monitoring needs
of the Agency's operating programs.
This report presents the results of a single-laboratory
evaluation and an interlaboratory collaborative study of a
method for measuring plutonium in water. Such studies are
extremely useful as they demonstrate the state of the art of the
analytical methodology which will ultimately provide the infor-
mation for decisions associated with environmental standards and
guidelines. Collaborative studies also allow each participating
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, Environ-
mental Monitoring and Support Laboratory, Las Vegas, Nevada.
Geoj _
Director
Environmental Monitoring and Support Laboratory
Las Vegas
iii
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ABSTRACT
This report gives the results of a single-laboratory eval-
uation and an interlaboratory collaborative study of a method for
determining plutonium in water. The method was written for the
analysis of one-liter samples and involves coprecipitation, acid
dissolution, anion exchange, electrodeposition, and alpha pulse
height analysis. The complete method is given in the first
appendix to the report. •
After the single-laboratory evaluation of the selected
method, four samples were prepared for the collaborative study.
There were two river water samples, a substitute ocean water
sample, and a sample containing sediment. These samples con-
tained plutonium-239 and plutonium-238 at concentrations ranging
from 0.42 to 28.9 dis/min/liter.
Standard deviations of the collaborative study plutonium
concentrations ranged from 57, to 13%. In three cases standard
deviations agreed with what was expected from counting statistics.
It is believed that hydrolysis occurred in the river water samples
resulting in errors greater than what was expected from counting
statistics.
IV
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CONTENTS
FOREWORD iii
ABSTRACT iv
LIST OF FIGURES vi
LIST OF TABLES vii
ACKNOWLEDGEMENTS ix
INTRODUCTION 1
SUMMARY 2
CONCLUSIONS AND RECOMMENDATIONS . 3
CRITERIA 5
CHOICE OF METHOD 6
PREPARATION OF- REFERENCE MATERIALS 7
SINGLE-LABORATORY EVALUATION 9
INTERLABORATORY COLLABORATIVE STUDY 15
DISCUSSION OF RESULTS 30
REFERENCES 38
APPENDIX 1: Tentative Method for the Determination
of Plutonium-239 and Plutonium-238 in
Water (By a Coprecipitation Anion
Exchange Technique) 42
APPENDIX 2: Collaborative Study Instructions
- Plutonium in Water 62
APPENDIX 3: Questionnaire on Collaborative Study .... 63
APPENDIX 4: Data on Plutonium-242 Tracer 64
APPENDIX 5: Laboratories Participating in the
Plutonium in Water Collaborative Study ... 65
APPENDIX 6: Table of Rejected Results 67
v
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LIST OF FIGURES
No.
1.
2.
3.
4.
Sample 1 (river water) plutonium concentrations
measured in collaborative study
Sample 2 (river water) plutonium concentrations
measured in collaborative study
Sample 3 (substitute ocean water) plutonium
concentrations measured in collaborative study . ,
Least squares fit to Sample 1 (river water)
plutonium-239 concentrations as a function of time
31
31
32
32
VI
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LIST OF TABLES
No. Page
1. Reference Samples for Plutonium-in-Water
Collaborative Study 10
2. Alpha Energies of Isotopes of Interest in the
Plutonium-in-Water Study 12
3. Single-Laboratory Evaluation Concentrations and
Recoveries for Sample 1 (River Water) 13
4. Single-Laboratory Evaluation Concentrations and
Recoveries for Sample 2 (River Water) 13
5. Single-Laboratory Evaluation Concentrations and
Recoveries for Sample 3 (Substitute Ocean Water) ... 14
6. Single-Laboratory Evaluation Concentrations and
Recoveries for Sample 4 (Sample Containing Sediment). 14
7. Collaborative Study Plutonium-239 Results for
Sample 1 (River Water - Reference Concn = 28.9
dis/min/liter) 17
8. Collaborative Study Plutonium-238 Results for
Sample 1 (River Water - Reference Concn = 9.94
dis/min/liter) 18
9. Collaborative Study Plutonium-239 Results for
Sample 2 (River Water - Reference Concn = 0.966
dis/min/liter) 19
10. Collaborative Study Plutonium-238 Results for
Sample 2 (River Water - Reference Concn = 7.51
dis/min/liter) 20
VII
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LIST OF TABLES (Cont'd)
11. Collaborative Study Plutonium-239 Results for
Sample 3 (Substitute Ocean Water - Reference
Concn =4.44 dis/min/liter) 21
12. Collaborative Study Plutonium-238 Results for
Sample 3 (Substitute Ocean Water - Reference
Concn =0.53 dis/min/liter) 22
13. Collaborative Study Plutonium-239 Results for
Sample 4 (Sample Containing Sediment - Reference
Value = 0.42 dis/min) 23
14. Collaborative Study Plutonium-238 Results for
Sample 4 (Sample Containing Sediment - Reference
Value = 0.02 dis/min) 24
15. Summary of Plutonium-in-Water Collaborative
Study Results 26
16. t-Test for Systematic Errors in Collaborative
Study Results 36
17. Overall Standard Deviation of Collaborative Study
Results and Standard Deviations Expected From
Counting Statistics Errors 37
viii
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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 5). Special thanks are due to Paul B. Hahn
of the U.S. Environmental Protection Agency's Environmental
Monitoring and Support Laboratory, Las Vegas, Nevada, who
worked with the authors on all phases of this study. Also
thanks are due to Isabel M. Fisenne of the U.S. Department of
Energy's Environmental Measurements Laboratory, New York,
New York, and Michael Hiatt of the U.S. Environmental Protection
Agency's Environmental Monitoring and Support Laboratory,
Las Vegas, Nevada, for their assistance in checking the standards
used in this study.
At Mound many individuals assisted in making this collab-
orative study a success. Thanks are due to Warren E. Sheehan,
F. Keith Tomlinson, and Billy M. Farmer for counting many
samples. We would like to thank Bob Robinson, Harold Kirby and
Vito R. Casella for many helpful discussions and suggestions.
Finally, the advice and assistance given by Pyrtle W. Seabaugh,
Clifford R. Rudy, and Louise A. Gibson in regard to statistical
calculations are acknowledged.
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INTRODUCTION
Although most of the plutonium released into rivers or other
bodies of water is eventually deposited and adsorbed onto sedi-
ments, there is still a need to determine environmental levels of
plutonium in fresh water and ocean water. Such determinations
need to be made on natural waters, on waters near an area where
contamination is suspected, and on water streams entering the
environment from facilities handling plutonium. Very low levels
of plutonium can be found almost anywhere in the world because
of fallout from atmospheric testing of nuclear weapons. It has
been estimated that about 300 kilocuries of plutonium-239 have
been distributed throughout the world mainly as a result of fall-
out from the explosions of large nuclear weapons (Harley, 1971).
Concentrations of plutonium above fallout levels are likely
to be found around facilities working with plutonium-239* for
weapons use or around facilities working with plutonium-238 for
heat sources. Waters around the area of underground nuclear
weapons testing and waters in the vicinity of waste disposal sites
should also be analyzed for plutonium. Likewise since nuclear
reactors produce some plutonium-239 and breeder reactors will pro-
duce even more, waters near these reactors and the nuclear fuel
reprocessing plants for these facilities will also have to be
monitored for plutonium.
"Maximum permissible concentrations" of plutonium in water
for occupational exposures have been recommended by the Interna-
tional Commission on Radiological Protection and the National
Council on Radiation Protection and Measurement. The U.S. Atomic
Energy Commission in turn set "radiation concentration guides"
for nonoccupational exposures (i.e., allowable concentrations in
unrestricted areas). For the isotopes of plutonium, this value
was 11.1 disintegrations per minute per milliliter (dis/min/ml)
in water. In this study, water samples having plutonium con-
centrations a few orders of magnitude below this concentration
were analyzed.
^Whenever this report refers to the determination of plutonium-
239, plutonium-240 is also included since the alpha peaks of
these isotopes cannot be resolved.
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To establish a suitable method for determining plutonium
in water, the U.S. Environmental Protection Agency wanted an
evaluation of a particular method that was capable of deter-
mining plutonium at concentrations between 0.1 and 30 dis/min/
liter. This evaluation was carried out by an extensive single-
laboratory evaluation followed by a collaborative study involving
18 laboratories.
SUMMARY
The purpose of this report is to present the results of a
single-laboratory evaluation and a collaborative study of a
tentative method for the determination of plutonium in water.
The method is very similar to a method developed for ocean water
(Wong, 1971) that has been used by many different laboratories
involved in the analysis of plutonium in water at environmental
levels. The method was selected after a literature search and
a preliminary laboratory evaluation.
The single-laboratory evaluation was carried out at the
U.S. Energy Research and Development Administration's (ERDA's)
Mound Laboratory* in Miamisburg, Ohio. Mound Facility did the
single-laboratory evaluation and conducted the collaborative
study for the EPA under the terms of an "Interagency Agreement"
with the U.S. Environmental Protection Agency's (EPA's) Environ-
mental Monitoring and Support Laboratory at Las Vegas, Nevada.
The single-laboratory evaluation was carried out using actual
waste-water samples from Mound Facility and with samples pre-
pared for the collaborative study. Criteria that were estab-
lished for the method were checked in the single-laboratory
evaluation.
Twenty-three laboratories agreed to participate in the
collaborative study and at the end of five months, 18 labor-
atories had submitted results. Data from 14 of these labor-
atories have been evaluated in this report. Duplicates of four
different samples were sent to the laboratories participating
in the collaborative study. The first two samples were river
water samples to which known amounts of plutonium-239 and
plutonium-238 had been added. The third sample was a subs-titute
ocean water sample also spiked with known amounts of plutonium.
*Since the completion of this work, ERDA has become part of
the U.S. Department of Energy, and Mound Laboratory has been
renamed Mound Facility. The ERDA was formerly the U.S. Atomic
Energy Commission.
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The fourth sample was prepared by adding a National Bureau of
Standards (NBS) river sediment sample containing a known amount
of plutonium-239 to deionized distilled water. All participa-
ting laboratories were supplied with a standard plutonium-242
tracer to eliminate any variance in results due to standard-
ization of the tracer.
The procedure, "Tentative Method for the Determination of
Plutonium-239 and Plutonium-238 in Water (By a Coprecipitation
Anion Exchange Technique)," and specific collaborative study
instructions were sent to each participating laboratory. These
are given in this report in Appendices 1 and 2. After the
study was completed, a questionnaire was sent to all the
participants to obtain additional information about the
collaborative study. A copy of this questionnaire is given in
Appendix 3; some of the responses are also given with the
questionnaire.
CONCLUSIONS AND RECOMMENDATIONS
Single-laboratory evaluation of the plutonium in water
procedure chosen for the collaborative study demonstrated that
the method met the criteria that were established prior to
beginning the study. Accuracy and precision obtained in
analyzing 1-liter water samples having plutonium-239 and
plutonium-238 concentrations from 0.5 to 30 dis/min/liter were
generally good. A negative bias averaging 127o was observed
when analyzing two of the collaborative study samples; however,
this bias is believed to be due to a hydrolysis of the samples
that occurred rather than to an inaccuracy in the analytical
method being evaluated. Precisions approached that of counting
statistics for some of the samples in both the single-laboratory
evaluation and in the collaborative study. Counting statistics
precisions were generally in the range of 3 to 13%.
Single-laboratory evaluation of the procedure also showed
that the method is applicable to sample volumes up to 20 liters.
Chemical yields in analyzing a variety of samples were generally
greater than 8070, and yields for the four collaborative study
samples determined in the single-laboratory evaluation averaged
85%. The use of uranium, thorium, americium, and polonium
tracers indicated that isotopes of these elements did not
interfere with the determination of plutonium.
The interlaboratory collaborative study results generally
indicated good agreement (better than 107o) with the reference
plutonium concentrations in the range of 0.4 to 30 dis/min/liter.
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For one sample where the plutonium-238 concentration was only
0.02 dis/min/liter, collaborative study results averaged 0.10
dis/min/liter, indicating a possible blank problem at plutonium
concentrations this low. Like the single-laboratory evaluation
data, the collaborative study data also indicated that the
plutonium concentrations in the river water samples were de-
creasing with time. For samples having plutonium concentrations
in the range of 4 to 30 dis/min/liter, "combined within-laboratory
standard deviations" of the results averaged 5.7%; in the 0.4
to 1 dis/min/liter plutonium concentration range this average was
11.17o. The precision of the method between laboratories in the
plutonium concentration range of 4 to 30 dis/min/liter averaged
6.470; in the 0.4 to 1 dis/min/liter plutonium concentration
range, this average was 5.57o.
Based on the responses to a questionnaire answered by all
laboratories participating in the collaborative study, it is
believed that only one laboratory of the 14 that were evaluated
in this report deviated considerably from the procedure that was
being evaluated. This was a deviation in the electrodeposition
technique. The average plutonium recovery observed for the 14
laboratories was 6970. In general, the laboratories participating
in the study believed the method was a good method, and nine
laboratories answered yes to the question, "Do you believe that
this would be a good reference method for plutonium in water?"
On the basis of the experience and results of this study,
the following recommendations can be made:
1. For samples that are to be stored for longer than
a few weeks, acid should be added to a concentration
of greater than 0.1 N at the time of collection. In
view of the absence of any definite data, a concen-
tration greater than 0.5 N acid is suggested.
2. The tracer employed should be obtained from the
National Bureau of Standards or should be standard-
ized either against an NBS standard or with an
instrument calibrated with an NBS standard.
3. Either plutonium-242 or plutonium-236 should be used
as the tracer depending upon the concentrations and
the isotopes to be determined in the water samples to
be analyzed.
4. If the water sample contains sediment to which highly
refractory plutonium is attached, it would be advisable
to separate this sediment and analyze it by an appro-
priate plutonium-in-soil procedure.
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5. If plutonium (VI) is possibly present in a water
sample, a step to assure reduction to plutonium
(IV) should be added before the coprecipitation
with ferric hydroxide.
CRITERIA
An environmental plutonium standard for water has not yet
been established, so quantitative values for accuracy, precision,
sensitivity, etc., are likewise not established at a specific
concentration. Nonetheless, certain criteria were established
for the "plutonium-in-water" method to be chosen for collabor-
ative study, based on previously published information on the
determination of "environmental levels" of plutonium in water.
The criteria established were as follows:
1. The method shall be applicable to a routine
determination requiring relatively inexpensive
equipment, and being of such a nature that many
samples could be analyzed simultaneously in a
relatively short period of time.
2. The accuracy of the method will be dependent
upon the pipetting or weighing accuracy.
3. The single-laboratory relative standard deviation
of the method, /not including the counting statistics
error, will be 5% or better at plutonium concen-
trations of 3 dis/min/liter.
4. The sensitivity of the method with 1-liter samples
will be 0.1 dis/min/liter or better.
5. The method shall be applicable to up to 20 liters
of fresh water or ocean water.
6 . The chemical yield of the method shall be 50%. or
greater.
7. Uranium, americium, thorium, and polonium must not
interfere with the analysis.
8. The method shall be applicable to water samples
containing sediment.
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These criteria were used as guidelines in the literature
search for a suitable method, and were also evaluated once a
method was chosen and tested in the single-laboratory evaluation.
CHOICE OF METHOD
The literature search uncovered several potentially good
procedures for the determination of plutonium in water
(Livingston et al., 1975a; Scott and Reynolds, 1975; Hodge and Gurney,
1975; McDowell et al., 1974; Golchert and Sedlet, 1972; Harley,
1972; Wong, 1971; Talvitie, 1971; Kooi and Hollstein, 1962).
In addition, to ensure that this information was up to date,
several laboratories known to be presently involved in measuring
plutonium in environmental samples were contacted by phone.
Chemists at these laboratories provided useful information on
the determination of plutonium in water and some references not
yet appearing in the abstract journals were obtained (Wong
et al., 1976; Button et al., 1976).
Although a number of the methods probably could have met
the criteria established, time did not allow the evaluation of
all these methods. From an examination of the literature,
however, it appeared that many investigators were using an iron
hydroxide coprecipitation-anion exchange technique (Wong, 1971)
to determine plutonium in water. Several authors of papers
presented at the "Transuranium Nuclides in the Environment"
symposium at San Francisco in 1975 (IAEA, 1976) referred to
this method or a similar method. Also, in the published results
of a plutonium-in-seawater-and-seaweed intercalibration study
in which seventeen laboratories participated (Fukai and Murray,
1975), it was pointed out that "with the exception of one method,
all the procedures reported by the laboratories for plutonium
analysis used coprecipitation of iron hydroxide followed by
separation of plutonium using anion exchange columns."
A recent study (Wong et al., 1976), however, indicated that
a manganese dioxide coprecipitation was superior to the iron
hydroxide coprecipitation. On the basis of what was found in
the literature search, the iron hydroxide coprecipitation method
and the manganese dioxide coprecipitation method were chosen for
laboratory evaluation.
A decision also had to be made as to which plutonium tracer
would be used in the procedure and in the collaborative study.
The procedure was written such that either plutonium-242 or
plutonium-236 could be used as the tracer depending upon the
nature of the sample being analyzed. For the collaborative
study, however, it was desired to use only one tracer. The
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results of a "Plutonium-in-Soil Collaborative Test" (Hahn et al.,
1977) suggested that a common tracer be provided to all partici-
pating laboratories to avoid uncertainties introduced by each
laboratory standardizing its own tracer.
For this collaborative study, plutonium-242 was chosen for
three reasons. First of all, at the time this study was under-
taken, plutonium-242 was available as a standard reference
material from the National Bureau of Standards (NBS). The
purity of the NBS tracer is very high; NBS Standard Reference
Material 4334 showed a (Pu-238 + Am-241)/Pu-242 activity ratio
of ca 0.0002 in March 1975. A second reason for choosing
plutonium-242 was the discussion in the recent publication
"Plutonium-242 vs Plutonium-236 as an Analytical Tracer" (Kressin
et al., 1975). This publication concluded that plutonium-242 is
the better of the two tracers primarily because of its longer
half life of 3.87 x 10s yr. A third reason for choosing
plutonium-242 as a tracer rather than plutonium-236 was Mound
Facility's own experience with plutonium-236 in determining
small, amounts of plutonium-238. Even though it has been pointed
out that plutonium-236 contains less than 0.01?0 of either
plutonium-238 or plutonium-239 (Sill, 1975), its alpha particle
energy of 5.77 MeV is higher than the alpha energies of plutonium-
238 and plutonium-239. Thus, when an electrodeposited sample is
less than perfect, tailing of the 5.77-MeV plutonium-236 peak
into the 5.50-MeV plutonium-238 peak can sometimes occur. The
4.90-MeV alpha energy of plutonium-242, however, falls below
even the 5.16-MeV alpha energy of plutonium-239, so that this
tracer would cause no tailing interference.
Although plutonium-242 was recommended and used in the
present study, in certain applications, plutonium-236 would be
the preferred tracer to use. If, for example, one were analyzing
water containing relatively high concentrations of plutonium-239,
it would be advisable to use plutonium-236 tracer. Certainly,
in situations where the concentration of plutonium-239 is
completely unknown and where the plutonium-238 is not the isotope
of greatest interest, plutonium-236 is definitely the preferred
tracer.
PREPARATION OF REFERENCE MATERIALS
Four reference materials were prepared for the collaborative
study. Three of the samples were prepared by adding standard
solutions of plutonium-238 and plutonium-239 to filtered river
water or to substitute ocean water. The fourth sample was
prepared by adding NBS river sediment (SRM #4350) to deionized
distilled water; these sediment samples were prepared individually
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The plutonium-238 that was used to prepare the standard
solution was taken from the plutonium-238 that is used to make
plutonium-238 heat sources at Mound Facility. This has the
following approximate composition in weight percent (Abrahamson
et al., 1969): Pu-236, 0.0001%; Pu-238, 80%; Pu-239, 16%:
Pu-240, 3.0%; Pu-241, 0.72%; Pu-242, 0.14%. Based on this com-
position, it would be expected that greater than 99.9% of the
alpha activity of this material is due to the plutonium-238. An
alpha pulse-height analysis of this plutonium-238 showed that
less than 0.2% of the alpha activity was due to plutonium-239 in
the sample. The plutonium-239 used to prepare the standard was
taken from an NBS isotopic standard (SKM #948). This material
had the following composition in weight percent as of September
1, 1972: Pu-238, 0.011%; Pu-239, 91.540%; Pu-240, 7.944%;
Pu-241, 0.472%; Pu-242, 0.033%. The plutonium-238 in this
sample did contribute significantly to the total alpha activity.
Four independent alpha pulse-height analyses showed that
'2.9 ± 0.1% (la) of the alpha activity was due to plutonium-238.
Before the plutonium-238 and plutonium-239 isotopes were
prepared as a standard solution, the americium-241 produced by
the decay of the plutonium-241 impurity in both of these isotopes
was removed by anion exchange. The presence of americium-241 is
especially undesirable because its principal alpha energy is the
same as that of plutonium-238. After ion exchange, the samples
were taken to near dryness and diluted with 1 M nitric acid to
a concentration of about 45 dis/min/ml for the plutonium-238
and about 90 dis/min/ml for the plutonium-239.
The solutions of plutonium-238 and plutonium-239 were
standardized at Mound Facility by liquid scintillation counting
and by alpha pulse-height analysis comparison to an NBS pluto-
riium-242 standard. The samples were also sent to the Energy
Research and Development Administrationsfs Health and Safety
Laboratory in New York. The data from all three standardizations
showed good agreement and the specific activities of the pluto-
nium-23.8 and plutonium-239 solutions were 45.7 ± 0.3 dis/min/g
and 89.3 ±0.6 dis/min/g respectively, where the error given is
one standard deviation based on the multiple determinations made
of the standard solution concentrations. Later counting results
obtained by the U.S. Environmental Protection Agency's Environ-
mental Monitoring and Support Laboratory in Las Vegas, Nevada,
confirmed these specific activities.
The first two reference materials were prepared from a
50-gallon (189-liter) water sample taken from the Great Miami
River about 25 miles (40 kilometers) upstream from Mound Facility
at Miamisburg, Ohio. Analysis of this water showed that the
plutonium-238 and plutonium-239 concentrations were both less
than 0.01 dis/min/liter, a factor of 100 to 1,000 times lower
than the concentration to which they were later spiked. This
8
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river water was filtered with Whatman GF/C paper to remove the
suspended matter. The third reference material was substitute
ocean water prepared according to a method recommended by the
American Society for Testing and Materials (ASTM, 1976a).
River water or substitute ocean water samples of about 8
kilograms (kg) were weighed to within 1 gram in 2-gallon (7.6-liter)
Nalgene aspirator bottles and transferred to a 30-gallon (114-liter)
polyethylene drum liner to give a total of about 80 to 90 kg
of water. A weighed amount of concentrated nitric acid, in the
amount of 5 ml per liter of water, was then added to the water
through one of the two screw cap tops on the drum liner, to yield
an acid concentration of about 0.1 N after mixing. Weighed
amounts of the plutonium-239 and plutonium-238 standard solutions
were then added to the acidified water. Finally a few grams of
saturated copper nitrate solution were added to the river water
samples, and a few grams of saturated lithium chloride solution
were added to the substitute ocean water sample. These metals
served as a "tracer" to determine when complete mixing had
occurred.
All three samples were mixed for 4 hours or longer using
peristaltic pumps. Confirmation of complete mixing was obtained
by atomic absorption analysis for copper or lithium in 2-ml
samples taken approximately every 30 minutes. Copper and lithium
salts were chosen since these metals have a very good sensitivity
in atomic absorption analysis and only a small amount had to be
added to the water samples. Copper could not be used with the
substitute ocean water since it already contained a small amount
of copper.
The plutonium-238 and plutonium-239 concentrations were
computed based on what was added to each solution and these
values are summarized in Table 1. The errors given represent
an estimate of the total error involved in computing that con-
centration. The values in parentheses for Samples 1 through 3
are experimentally determined values which will be explained
later in the report.
SINGLE-LABORATORY EVALUATION
As mentioned earlier, two procedures were chosen for labora-
tory evaluation. These procedures were used in analyzing on-
site water samples at Mound Facility known to contain plutonium-
238. The procedures were modified slightly in progressing from
one sample to the next in an attempt to improve the recovery of
the plutonium-242 tracer, and to simplify the procedure to make
it as "cost effective" as possible. After several samples were
-------
TABLE 1. REFERENCE SAMPLES FOR PLUTONIUM-
IN-WATER COLLABORATIVE STUDY
Sample
No.
1
2
3
4
Type
Sample
River Water
River Water
Substitute
Ocean Water
River Sediment
Expected
Pu-239
(dis/min/liter)a
31.6 ± 0.6
(31.6)b
1.07 ± 0.02
(1.13)
4.44 ± 0.04
(4.22)
0.42 ± 0.04
Expected
Pu-238
(dis/min/liter)a
10.7 ± 0.2
(10.7)
9.60 ± 0.19
(8.47)
0.53 ± 0.01
(0.55)
0.02
in Distilled
Water
lFor Sample 4, the numbers represent the dis/min/sample.
'The numbers in parentheses are experimentally determined
from collaborative study data and will be explained later.
analyzed, only one method was chosen for further evaluation.
This method, a modification of the ferric hydroxide coprecip-
itation method, showed greater than 8070 recovery of the plutonium
and was a relatively simple laboratory procedure. The manganese
dioxide coprecipitation procedure gave plutonium recoveries as
good or even better, but it had the disadvantage of being more
time consuming. Also, it was more difficult to use because of
the pH control required, and it produced a poorly compacted
precipitate compared to the ferric hydroxide precipitate.
In studying both of the above methods, the technique of
using two tracers (Livingston et al., 1975b) was used in
optimizing conditions for a satisfactory electrodeposition
procedure. Procedures similar to a few recently published
(Puphal and Olsen, 1972; Talvitie, 1972), were used in electro-
plating the plutonium for alpha pulse-height analysis. By
adding plutonium-236 tracer just prior to the electrodeposition,
it was possible to evaluate the electrodeposition efficiency in
addition to the overall recovery efficiency of the entire
analysis. It was found from these studies that electrodeposition
of plutonium from 1 M ammonium sulfate which was initially
10
-------
adjusted to a pH of about 2 gave electrodeposition recoveries of
better than 90%. Samples were electroplated onto stainless steel
slides at 1.2 amps at about 45 C for 1.5 to 2.0 hours. Again,
other electrodeposition procedures may give recoveries just as
good, but the present procedure proved to work well for a
number of different samples.
The plutonium recovery efficiency of the ferric hydroxide
coprecipitation procedure was further evaluated using substitute
ocean water samples and 20-liter water samples. Plutonium-242
tracer recoveries from these samples were still much greater
than 507o. To make the procedure applicable to water samples
containing sediment, an acid dissolution step similar to a
dissolution used in soil analysis (Peters, 1975; USAEC, 1974)
was added to the procedure to analyze such samples.
In order to determine the effectiveness of the chemical
separation, isotopic tracers of uranium, americium, thorium,
and polonium were used in evaluating the procedure for effective
chemical separation of the plutonium from these elements. The
isotopes used for these tracer studies and their alpha energies
are given in Table 2. All the plutonium isotopes of interest
in this study and their alpha energies are also given in
Table 2. Americium-241 is also given in Table 2 to show that
this isotope must be removed to determine plutonium-238 in a
sample, since the alpha peaks of these two isotopes cannot be
resolved by alpha pulse-height analysis. When each of the four
tracers (thorium actually consisted of a mixture of thorium-228
and thorium-229) was added to samples which were analyzed for
plutonium, using the proposed coprecipitation-ion exchange
procedure, it was found that no detectable amount of tracer
came through and thus there was no interference in determining
the plutonium isotopes. This is consistent with what would have
been expected based on the ion exchange behavior of these
elements (Korkisch, 1969). No quantitative data on ion exchange
distribution coefficients were obtained since such data already
exist for the pure elements (Korkisch, 1969), and are likely to
be slightly different for different environmental samples.
Plutonium determinations of the four samples that were sent
to the laboratories participating in the collaborative study
were also carried out at Mound Facility. The results of these
analyses are summarized in Tables 3 through 6. The date that
the analysis was performed is given in these tables because it
is believed that the plutonium concentrations in Samples 1 and 2
are decreasing with time. This phenomenon will be discussed at
greater length later in the report. The reason for the selected
averages given in Tables 3 and 4 will be explained later. The
average plutonium recovery observed for multiple analyses of all
four samples was 86 ± 10%. This plutonium recovery is about the
same as that reported in a single-laboratory evaluation of a
11
-------
plutonium in soil method (Hahn et al., 1977) where the recovery
was 88 ± 7%.
Mound Facility had observed a plutonium-238 blank as high
as 0.2 dis/min/liter during the present study. For this reason
no plutonium-238 concentrations are reported for Sample 4. Even
the plutonium-238 concentrations given for Sample 3 may be
slightly high since no blank was subtracted.
TABLE 2. ALPHA ENERGIES OF ISOTOPES OF INTEREST
IN THE PLUTONIUM-IN-WATER STUDY
Isotope
Alpha Energy in MeV (Abundance)
Pu-236
Pu-238
Am-241
Th-228*
Po-210
Am-243
Pu-239
Pu-240
Pu-242
Th-229
U-236
5.77 (69%), 5.72 (31%)
5.50 (72%), 5.46 (28%)
5.49 (85%), 5.44 (13%)
5.43 (71%), 5.34 (28%)
5.31 (100%)
5.28 (87%), 5.23 (11.5%)
5.16 (88%), 5.11 (11%)
5.17 (76%), 5.12 (24%)
4.90 (76%), 4.86 (24%)
5.05 (7%), 4.97 (10%), 4.90 (11%), 4.84 (58%)
4.81 (11%)
4.49 (76%), 4.44 (24%)
Underlined isotopes are those used as tracers to evaluate
the effectiveness of the chemical separation.
12
-------
TABLE 3. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 1 (River Water)
Sample Date Pu-239 Pu-238 Pu Recovery
Number Analyzed (dis/min/liter) (dis/min/liter) (%)
1 C 09-30-76 29.35 ± 0.62a 9.72 ± 0.24 65
1 G 10-28-76 29.74 ± 0.71 10.44 ± 0.29 84
1 H 10-28-76 29.96 ± 0.31 11.04 ± 0.14 92
1 I 11-22-76 28.37 ± 0.23 9.47 ± 0.09 89
1 J 11-22-76 28.24 ± 0.25 9.35 ± 0.10 105
1 K 11-22-76 27.95 ± 0.25 9.42 ± 0.11 65
1 P 02-15-77 24.10 ± 0.38 8.06 ± 0.16 84
1 R 02-23-77 22.99 ± 0.29 7.78 ± 0.12 92
1 U 08-29-77 22.55 ± 0.56 7.68 ± 0.24 71
1 V 08-29-77 21.34 ± 0.62 7.15 ± 0.26 71
Avg of Oct/Nov 28.85 ± 0.93b 9.94 ± 0.76 87 ± 15
1976 Results
aThis error is the one sigma counting statistics error.
This is the standard deviation of the plutonium concentrations
used to compute the average.
TABLE 4. SINGLE-LABORATORY EVALUATION CONCENTRATIONS
AND RECOVERIES FOR SAMPLE 2 (River Water)
Sample Date Pu-239 Pu-238 Pu Recovery
Number Analyzed (dis/min/liter) (dis/min/liter) (%)
2 A
2 B
2 C
2-1
2-2
2-3
2-4
2 D
2 E
11-09-76
11-09-76
11-09-76
11-29-76
11-29-76
11-29-76
11-29-76
02-15-77
02-15-77
1.031
0.953
0.937
0.966
0.992
0.893
0.989
0.909
0.825
± 0.072
± 0.061
± 0.061
± 0.032
± 0.035
± 0.029
± 0.036
± 0.039
± 0.038
7.91
7.65
7.92
7.29
7.30
7.32
7.21
6.98
7.29
±0.25
± 0.21
± 0.22
± 0.11
±0.12
± 0.11
±0.12
±0.14
±0.15
71
86
85
93
81
95
77
84
84
Avg of first 0.966 ± 0.044 7.51 ± 0.31 84 ± 9
seven values
13
-------
TABLE 5. SINGLE-LABORATORY EVALUATION. CONCENTRATIONS AND
RECOVERIES FOR SAMPLE 3 (Substitute Ocean Water)
Sample Date Pu-239 Pu-238 Pu Recovery
Number Analyzed (dis/min/liter) (dis/min/liter) (%)
3 A
3 B
3 C
3 D
3 E
3 G
3 H
3 I
11-15-76
11-15-76
11-15-76
02-23-77
02-23-77
04-28-77
04-28-77
04-28-77
4.25
4.25
4.09
4.35
4.40
4.17
4.49
4.22
± 0.07
± 0.07
± 0.07
± 0.08
± 0.08
±0.15
±0.14
±0.11
0.533 ±
0.583 ±
0.548 ±
0.622 ±
0.536 ±
--
0.560 ±
0.581 ±
0.022
0.023
0.022
0.026
0.024
-
0.041
0.034
85
95
92
88
84
72
82
89
Avg of 4.28 ± 0.13 0.566 ± 0.032 86 ± 7
all values
TABLE 6. SINGLE-LABORATORY EVALUATION CONCENTRATIONS AND
RECOVERIES FOR SAMPLE 4 (Sample Containing Sediment)
Sample Date Pu-239 Pu-238 Pu Recovery
Number Analyzed (dis/min/sample) (dis/min/sample)
4 A 11-08-76 1.409 ± 0.019a -- 73
4 B 11-08-76 0.433 ± 0.011 -- 86
4 C 12-09-76 0.430 ± 0.009 -- 93
4 D 12-09-76 0.448 ± 0.011 -- 94
Avg of B,C,D 0.437 ± 0.010 -- 91 ± 4
aReject, ASTM test.
No plutonium-238 concentrations were determined for Sample 4
because of blank problems.
14
-------
INTERLABORATORY COLLABORATIVE STUDY
Duplicate 1-liter portions of Samples 1,2, 3 and 4 were
sent to 23 laboratories that had previously indicated an in-
terest in participating in the plutonium-in-water collaborative
study. In addition to the procedure to be used (cf. Appendix 1)
each laboratory was also sent specific collaborative study
instructions (cf. Appendix 2). Each participating laboratory
was also sent the same standard plutonium-242 tracer to use in
analyzing the water samples.
The standard tracer, labeled MD-2, consisted of NBS SRM
4334 Plutonium-242 Alpha Particle Solution Standard accurately
diluted with 5M nitric acid by a mass dilution. The activity
of the undiluted solution was 21.41 ± 1.07o nuclear transitions
per second per gram as stated by the National Bureau of
Standards. This activity was used to calculate the activity
of the diluted tracer which was found to be 77.0 dis/min/g
or 89.6 dis/min/ml. The error in this value is also believed
to be about 1.0% since negligible errors were introduced in the
mass dilution. The 77.0 dis/min/g plutonium-242 tracer was
checked by the EPA in Las Vegas and by ERDA's Environmental
Measurements Laboratory; their values agreed within experimental
error to the value computed from the dilution. A copy of the
"Data on Plutonium-242 Tracer" that was sent to each partici-
pating laboratory with the tracer is given in Appendix 4.
A list of the 18 laboratories that completed the plutonium-
in-water collaborative study is given in Appendix 5. Each lab-
oratory that submitted results was randomly assigned a laboratory
number. Before evaluating any of the results it was agreed
upon by the authors and by the EPA Environmental Monitoring and
Support Laboratory in Las Vegas that any result having a tracer
recovery of less than 20% would be considered unacceptable.
The 20% recovery value is an arbitrarily selected number, but
it was believed that some value should be chosen such that if
the recovery was below this number, there was probably something
seriously wrong with that particular analysis, and the results
should be considered questionable.
Plutonium-242 tracer recoveries from laboratories 2, 4, and
18 averaged 5.870, 3.2%, and 14% respectively, so consequently
these data were considered unacceptable. Although one recovery
reported by laboratory 18 was 22.5%, the data for that partic-
ular analysis were also rejected as an outlier on the basis of
15
-------
a statistical test described later. The data submitted by
these laboratories are given in Appendix 6 as a "Table of
Rejected Results." This table also includes the results from
laboratory 6. Reported plutonium-242 recoveries from this
laboratory averaged 67%; however, there were computational
errors in the data as submitted. Also, from the total number
of counts submitted it was clear that the samples were not
counted for the required 1,000 minutes.
Acceptable results are reported according to isotope and
sample number in Tables 7 through 14. In these tables an
asterisk (*) in column 2 beside the plutonium concentration
indicates that this -value is rejected because of a chemical
recovery of less than 20%. A cross (t) beside the plutonium
concentration indicates that this value is rejected as an
outlier on the basis of an ASTM recommended criterion for
rejection (ASTM, 1976b).
For this rejection criterion, with n observations listed
in order of increasing magnitude by Xi £ x2 <_ x3 <_ ... £ x ,
if the largest value x is in question, then T is calculated
as follows: n n
= (xn - x)/s (1)
where:
T = test criterion
x = arithmetic average of all n values
s = the estimate of the population standard
deviation based on the sample data
Alternately if xi rather than xn is the doubtful value, the
criterion is as follows:
Tj = (x - Xl)/s (2)
If the T or TI value exceeds the critical value then the
measurement in question may be rejected. Critical values of
T for various levels of significance are given in the ASTM
reference (ASTM, 1976b). A 57o two-sided level of significance
was employed in deciding whether or not to reject a given
measurement in the present study.
The average of the duplicate values is given in column 3,
and the estimated standard deviation is given in column 4. The
ratio of the average value to the reference value for each
laboratory is given in the fifth column. The reference values
used for Samples 3 and 4 are the expected plutonium-239 and
16
-------
TABLE 7. COLLABORATIVE STUDY PLUTONIUM-239 RESULTS
FOR SAMPLE 1 (River Water - Reference
Concn =28.9 dis/min/liter)
Lab
1
3
5
7
8
9
10
11
12
13
14
15
16
17
Pu-239a Avg Concn
(dis/min/liter) (dis/min/liter)
26.9 ±0.9
28.2 ± 0.9
28.0 ± 0.6
25.9 ± 0.5
21.0 ± 0.6
20.9 ± 1.0
26.8 ± 1.4
27.7 ± 1.0
28.0 + 0.7
31.3 ± 1.0
27.9 ± 0.7
28.7 ± 0.8
30.7 ± 1.1
34.3 ± 1.3
23.9 ± 0.6
25.8 ± 0.6
22.7 ± 0.7
23.0 ± 1.6
24.3 ± 1.0
24.4 ± 0.7
30.5 ± 0.7
29.4 ± 0.7
30.6 ± 0.9
28.9 ± 0.6
24.5 ± 0.7
23.5 ± 0.7
25.7 + 0.4
24.1 ± 0.6*
27.5
27.0
21.0
27.2
29.6
28.3
32.5
24.9
22.9
24.4
30.0
29.8
24.0
-b
Std Deviation Ratio Avg
(dis/min/liter) to Reference
0.9
1.4
0.1
0.6
2.3
0.6
2.6
1.4
0.2
0.1
0.8
1.2
0.7
~
0.95
0.94
0.73
0.94
1.03
0.98
1.13
0.86
0.79
0.85
1.04
1.03
0.83
0.89
Pu Recovery
62
78
60
64
31
33
30
56
84
51
•79
70
62
55
81
82
86
95
57
36
92
90
63
83
96
90
29
12
aThe error given here is the error associated with one sigma counting statistics.
This statement also applies to Tables 8 through 14.
bWhen only one plutonium concentration was determined, or if one value was
rejected, no average or standard deviation is tabulated. This statement also
applies to Tables 8 through 14.
*Reject, yield <20%.
17
-------
TABLE 8. COLLABORATIVE STUDY PLUTONIUM-238 RESULTS
FOR SAMPLE 1 (River Water - Reference
Concn = 9.94 dis/min/liter)
Lab
1
3
5
7
8
9
10
11
12
13
14
15
16
17
Pu-238 Avg Concn
(dis/min/liter) (dis/min/liter)
9.15 ± 0.38
9.25 ± 0.35
8.92 ± 0.23
8.61 ± 0.21
6.72 ± 0.29
6.84 ± 0.53
9.07 ± 0.56
8.62 ± 0.39
8.94 ± 0.29
10.5 ± 0.4
8.92 ± 0.28
11.31 ± 0.37
10.97 ± 0.47
14.56 ± 0.631'
7.57 ± 0.23
8.56 ± 0.25
7.57 ± 0.33
7.32 ± 0.64
8.95 ± 0.45
8.53 ± 0.28
10.3 ±0.3
9.81 ± 0.28
10.9 ± 0.4
9.54 ± 0.22
7.83 ± 0.30
7.82 ± 0.29
8.64 ± 0.17
7.65 ± 0.25*
9.20
8.77
6.78
8.85
9.73
10.1
.
8.07
7.45
8.74
10.1
10.2
7.83
_
Std Deviation Ratio Avg
(dis/min/liter) to Reference
0.07 0.93
0.22 0.88
0.08 0.68
0.32 0.89
1.12 0.98
1.7 1.02
1.10
0 70 0.81
0.18 0.75
0.30 0.88
0.36 1.02
0.95 1.03
0.01 0.79
0.87
Pu Recovery
62
78
60
64
31
33
30
56
84
51
79
70
62
55
81
82
86
95
57
36
92
90
63
83
96
90
29
12
Reject, ASTM test
*Reject, yield <20%
18
-------
TABLE 9. COLLABORATIVE STUDY PLUTONIUM-239 RESULTS
FOR SAMPLE 2 (River Water - Reference
Concn = 0.966 dis/min/liter)
Lab
1
3
7
8
9
10
11
12
13
14
15
16
17
Pu-239 Avg Concn Std Deviation
(dis/min/liter) (dis/min/liter) (dis/min/liter)
0
1
1
0
1
0
0
0
1
1
1
0
0
0
0
0
0
0
1
0
1
0
0
0
0
0
.93 ±
.03 i
.05 i
.92 ±
.22 ±
.84 i
.79 i
.83 ±
.12 ±
.02 ±
.17 i
.98 ±
.83 ±
.99 ±
.85 i
.68 i
.94 t
.86 ±
.13 i
.93 t
.00 ±
.93 *
.82 ±
.92 ±
.87 ±
.83 ±
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.08
.09
.07
.06
.12
.18*
.06
.06
.10
.07
.11
.10
.06
.08
.08
.10
.09
.11
.007
.06
.06
.06
0.07
0
0
0
.08
.03
.03
0.
0.
_
0.
1.
1.
0.
0.
0.
1.
0.
0.
0.
98
99
81
07
08
91
77
90
03
97
87
85
0
0
0
0
0
0
0
0
0
0
0
0
.07
.09
.03
.07
.13
.11
.12
.06
.14
.05
.07
.03
Ratio Avg
to Reference
1
1
1
0
1
1
0
0
0
1
1
0
0
.01
.02
.26
.84
.11
.12
.94
.80
.93
.07
.00
.90
.88
Pu Recovery
a>
69
72
45
40
50
16
102
95
65
79
62
62
72
70
69
53
91
53
94
96
80
79
98
76
68
70
*Reject, yield <20%
Laboratory 5 did not provide results for this sample
19
-------
TABLE 10. COLLABORATIVE STUDY PLUTONIUM-238 RESULTS
FOR SAMPLE 2 (River Water - Reference
Concn =7.51 dis/min/liter)
Lab
1
3
7
8
9
10
11
12
13
14
15
16
17
Pu-238 Avg Concn Std Deviation
(dis/min/liter) (dis/min/liter) (dis/min/liter)
7
8
8
7
8
7
7
7
8
8
8
8
7
7
7
6
7
6
8
8
7
7
7
7
7
7
.90
.58
.42
.11
.29
.70
.59
.63
.59
.18
.21
.12
.69
.78
.10
.65
.80
.90
.33
.16
.50
.59
.63
.61
.22
.25
i 0
t 0
i 0
± 0
± 0
± 0
± 0
± 0
± 0
± 0
± 0
± 0
± 0
± 0
± 0
* 0
± 0
± 0
± 0
+ 0
± 0
± 0
± 0
± 0
± 0
± 0
.31
.32
.25
.23
.40
.69*
.23
.25
.36
.27
.38
.38
.23
.29
.28
.38
,33
.40
.25
.24
.22
.23
.29
.31
.10
.10
8.
7.
-
7.
8.
8.
7.
6.
7.
8.
7.
7.
7.
24
77
61
39
17
74
88
35
25
55
62
24
0.
0.
-
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
48
93
03
29
06
06
32
64
12
06
01
02
Ratio Avg
to Reference
1
1
1
1
1
1
1
0
0
1
1
1
0
.10
.03
.10
.01
.12
.09
.03
.92
.98
.10
.01
.01
.96
Pu Recovery
69
72
45
40
50
16
102
95
65
79
62
62
72
70
69
53
91
53
94
96
80
79
98
76
68
70
*Reject, yield <20%
Laboratory 5 did not provide results for this sample
20
-------
TABLE 11. COLLABORATIVE STUDY PLUTONIUM-239 RESULTS
FOR SAMPLE 3 (Substitute Ocean Water -
Reference Concn =4.44 dis/min/liter)
Pu-239
Lab
I
3
5
7
8
9
10
11
12
13
14
15
16
17
Avg Concn
(dis/min/ liter) (dis/min/liter)
4
4
4
3
5
6
4
3
3
3
4
4
.40
.48
33
.89
.31
.9
.08
.94
.7
.73
.45
.37
4.04
4
4
4
3
4
4
3
4
4
4
4
3
4
4
.32
.17
.11
.76
.29
.10
.60
.22
.35
.37
.18
.98
.55
.15
'. 0
1 0
1 0
1 0
' 0
1 1
• 0
1 0
'. 0
' 0
< 0
* 0
! 0
' 0
' 0
1 0
1 0
' 0
1 0
' 0
1 0
' 0
' 0
' 0
> 0
* 0
i 0
.20 4.44
.18
.16 4.11
.16
.33!
. 8"
.22 4.01
.21
. 5'*
.10
.17 4.41
.22
.19 4.18
.20
16 4.14
.17
.22 4.03
.39
.22 3.85
.25
/
.17
.11 4.36
.09
.24 4.08
.20
.08 4.35
.06
Std Deviation Ratio Avg Pu
(dis/min/liter) to Reference
0.06 1
0.31 0
0 .10 0
0
0.06 0
0.20 0
0.04 0
0.37 0
0.35 0
0
0 .01 0
0 14 0
0.28 0
.00
.93
.90
.84
.99
.94
.93
.91
.87
.95
.98
.92
.98
Recovery
(7.)
80
93
38
34
35
2
61
69
8
92
81
48
90
89
92
83
80
77
90
60
94
62
104
61
78
54
80
''Reject, ASTM test
*Reject, yield <20%
21
-------
TABLE 12. COLLABORATIVE STUDY PLUTONIUM-238 RESULTS
FOR SAMPLE 3 (Substitute Ocean Water -
Reference Concn = 0.53 dis/min/liter)
Lab
1
3
5
7
8
9
10
11
12
13
14
15
16
17
Pu-238 Avg Concn Std Deviation Ratio Avg
(dis/min/liter) (dis/min/liter) (dis/min/liter) to Reference
0.41 ±0.05 0.46
0.51 t 0.05
0.45 i 0.05 0 44
0.42 ± 0.05
0.41 ± 0.08
2.4 -t 0.9*
0.52 ± 0.07 0.58
0.64 ± 0.03
0.2*0.1*
0.54 ± 0.03
0.58 t 0.05 0.62
0.65 ± 0.07
0.48 ± 0.06 0.50
0.51 ± 0.06
0.64 ± 0.05 0.56
0.48 ± 0.05
0.54 t 0.08 0 46
0.38 t 0.11
0.45 ± 0.06 0.52
0.58 ± 0.09
0.55 ± 0.05
0.47 ± 0.03 0.49
0.51 ± 0.03
0.51 ± 0.007 0 46
0.41 ± 0.05
0.54 + 0.02 0.50
0.46 ± 0.02
0.07 0.87
0.02 0.83
0.77
0.08 1.09
1.02
0.05 1.17
0.02 0.94
0.11 1.06
0.11 0.87
0.09 0.98
1.04
0.03 0.92
0.07 0.87
0.06 0.94
Pu Recovery
(%)
80
93
38
34
35
2
61
69
8
92
81
48
90
89
92
83
80
77
90
60
94
62
104
61
78
54
80
*Reject, yield <20%
22
-------
TABLE 13. COLLABORATIVE STUDY PLUTONIUM-239 RESULTS
FOR SAMPLE 4 (Sample Containing Sediment
- Reference Value =0.42 dis/min)
Lab
1
3
7
8
10
11
12
13
14
15
16
17
Pu-239 Avg Value Std Deviation
(dis/min) (dis/min) (dis/min)
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.04
.54
.41
.47
.36
.40
.36
.49
.42
.42
.41
.44
.37
.36
.33
.41
.43
.67
.75
.40
.44
.49
.34
4
+
+
+
+
+
±
+
+
+
4.
+
±
+
+
+
+
±
+
+
±
+
+
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.081"
.05
.05 0.44 0.04
.04
.06 0.38 0.03
.05
.03 0.43 0.09
.05
.06 0.42 0.00
.06
.06 0.42 0.03
.06
.05
.09 0.35 0.02
.06
.05 0.42 0.01
.05
.04!
.04f
.05 0.42 0.03
.05
.02
.04*
Ratio Avg
to Reference
1
1
0
1
1
1
0
0
1
1
1
.29
.05
.90
.02
.00
.00
.88
.83
.00
.
.00
.17
Pu Recovery
(%)
93
91
38
34
50
61
64
74
75
65
38
54
72
28
66
86
72
61
83
93
83
87
14
"^Reject, ASTM test
*Reject, yield <20%
Laboratories 5 and 9 did not provide results for this sample
23
-------
TABLE 14. COLLABORATIVE STUDY PLUTONIUM-238 RESULTS
FOR SAMPLE 4 (Sample Containing Sediment
- Reference Value =0.02 dis/min)
Lab
1 0
0
3 0
7 0
0
8 0
0
10 0
0
11 0
0
12 0
13 0
0
14 0
0
15 0
0
16 0
0
17 0
0
Pu-238 Avg Value Std Deviation
(dis/min) (dis/min) (dis/min)
.005
.021
.13 i
.12 *
.25 i
.02 ±
.02 i
.06 i
.12 <
.09 i
.07 i
.03 i
.17 i
.39 ±
.04 >
.04 t
.20 t
.04 i
.07 ±
.09 ±
.14 i
.16 t
i 0.010 0.01 0.01
.1 0.027
0.03
0.04 0 19 0.09
0.05
0.01 0.02 0.00
0.01
0.02 0.09 0.04
0.03
0.03 0.08 0.02
0.02
0.01
0.06 0.28 0.16
0.06
0.01 0.04 0.00
0.01
0.02 0.12 0.11
0.01
0.02 0.08 0.01
0.02
0.01
0.02*
Ratio Avg
to Reference
0.
6.
9.
1.
4.
4.
1.
14
2.
6.
4.
6.
5
5
5
0
5
0
5
0
0
0
8
Pu Recovery
93
91
38
50
61
64
74
75
65
38
54
72
28
66
86
72
61
83
93
83
87
14
*Reject, yield <20%
Laboratories 5 and 9 did not provide results for this sample
24
-------
plutonium-238 concentrations based on what was added (cf. Table
1). The reference values used for Sample 1 are the averages of
the second through the sixth values determined at Mound Facility
(cf. Table 3). For Sample 2 the average of the first seven
values determined at Mound was used as the reference. As stated
earlier the single-laboratory evaluation showed that the pluto-
nium concentrations in Samples 1 and 2 had decreased with time.
Only values determined during the time span that collaborative
laboratories made their determinations were used in obtaining
a reference value. Finally, the last column gives the pluto-
nium recovery based upon the amount of plutonium-242 tracer
used in the analysis.
A summary of the data for each sample and each isotope is
given in Table 15. The first row gives the average plutonium
concentration as determined from the laboratory averages taken
from Tables 7 through 14. When a laboratory had made only one
determination or when one of the duplicates had been rejected,
the one acceptable value was used in computing the overall
laboratory average given in Table 15. The estimated standard
deviation, S,, was also calculated from the laboratory
averages. Tnese values are given in the second row of Table
15. Also the relative standard deviation in percent is given
in parentheses under the standard deviations in row two and in
other rows where a standard deviation is listed.
Two other standard deviations are also given in Table 15.
These are the precision standard deviation, or the combined
within-laboratory standard deviation, S , and the standard
deviation of the systematic errors or trie precision of the
method between laboratories, S, . The first of these values
is estimated according to Youden's Formula (3) (Youden and
Steiner, 1975) as follows for duplicate determinations:
Sr = (Zd2/2n)% (3)
where:
d = the absolute difference between the
duplicates
n = the number of collaborating laboratories
reporting duplicates
The standard deviation of the systematic errors, Sb is computed
from the other two standard deviations according to Youden's
Formula (4) (Youden and Steiner, 1975):
25
-------
TABLE 15. SUMMARY OF PLUTONIUM-IN-WATER COLLABORATIVE STUDY RESULTS
ho
Plutonium Concentrations
dis/min/ liter (dis/min for
Quantity Sample 1
Tabulated Pu-239
Avg Pu Concn 26.8
(14 labs)
Sd ±3.2
(%) (12%)
Sr 1.2
(%) (4.6%)
Sb 3.1
(%) (12%)
Reference Value 28.9
Estimated Error ±0.9
(%) (3.1%)
Pu-238
8.96
±1.18
(13%)
0.70
(7.9%)
1.07
(12%)
9.94
±0.76
(7.6%)
Sample 2
Pu-239
0.96
±0.12
(13%)
0.09
(9 . 6%)
0.10
(10%)
0.966
±0.044
(4.6%)
Pu-238
7.78
±0.47
(6.0%)
0.38
(4.9%)
0.39
(5.0%)
7.51
±0.31
(4.1%)
or Error
Sample 4)
Sample 3
Pu-239
4.15
±0.21
(5.1%)
0.22
(5 . 2%)
0.14
(3.4%)
4.40
±0.09
(2%)
Pu-238
0.51
±0.059
(12%)
0.073
(14%)
0.028
(5.5%)
0.53
±0.01
(2%)
Sample 4
Pu-239
0.42
±0.053
(12%)
0.040
(9.8%)
0.045
(11%)
0.42
±0.036
(8.5%)
Pu-238
0.10
±0.08
(77%)
0.07
( 72%)
0.06
(62%)
0.02
% Difference -7.1% -9.9%
Avg Pu Recovery 66 ± 21%
-1.09% +3.6%
72 ± 17%
-5.7% -4.8%
75 ± 19%
0% +400%
65 ± 20%
S, = standard deviation of the laboratory averages.
S = precision standard deviation, or combined within laboratory standard deviation,
S, = standard deviation of the systematic errors, or precision of the method
between .laboratories.
% Difference = percent difference between the reference value and the average
of the 14 laboratories.
-------
^Also given in Table 15 are the reference values described
previously. The absolute estimated errors of these reference
values and these values expressed as a percent are also given.
The estimated errors given for Samples 1 and 2 are the standard
deviations estimated from the multiple determinations used to
compute the average. For Sample 3, the errors represent an
estimate of the total uncertainty based on measurements of the
amount of plutonium-239 and plutonium-238 added to the sample.
For the plutonium-239 in Sample 4 the error given is the total
uncertainty of the plutonium-239 content of the NBS River
Sediment, since in preparing the collaborative test samples no
significant additional errors should have been introduced. The
"% difference" given in Table 15 is the percent difference
between the reference value and the average reported value.
Finally, the average plutonium recovery observed for a given
sample for all of the laboratories, together with the standard
deviation of these recoveries, is given in the last row of
Table 15.
After results of the collaborative study had been submitted,
a questionnaire was sent to each participant. Specific questions
about certain problem areas and general questions about the
plutonium-in-water procedure were asked. A summary of the
responses to the questions that could be answered by a "yes" or
"no", or by a specific number is given with the questionnaire
in Appendix 3. Only the 14 laboratories whose data were
evaluated in this report are included in the summary.
Considering the responses to the general questions that
were asked (Numbers 5 through 9), 9 of the 14 laboratories
reported that they did not deviate considerably from any part
of the procedures. Two laboratories responded with a definite
"yes" that they did deviate from the procedure, and three others
indicated that some changes were made. It is our judgment,
however, that only one of these five laboratories "deviated
considerably" from the procedure being studied. That laboratory,
number 7, used an ammonium oxalate procedure for electro-
deposition rather than the ammonium sulfate procedure that was
called for. Previous experience at Mound Facility has indicated
that an ammonium sulfate procedure generally gives better yields
than an ammonium oxalate procedure. It was observed that
laboratory 7 had an average plutonium recovery of 54 ± 127» (even
after rejecting one determination with a yield of 16%) compared
to the 14-laboratory average of 69 ± 20%.
The questionnaire also asked for good and bad points of
the procedure as well as general comments. The significant
good points given were as follows:
1. The procedure was well written and easy to follow.
27
-------
2. The procedure was straightforward, simple, and very
workable.
3. It brought together many good techniques into one
procedure.
4. It is a good procedure for large volume water samples.
5. The use of the preadjusted electrolyte for electro-
deposition is a good point; generally excellent
slides are produced.
6. High plutonium recoveries are generally obtained.
Significant bad points given by the participants were as
follows:
1. It would be preferable to routinely treat the initial
hydroxide precipitate with nitric and hydrofluoric
acids to ensure complete dissolution and the equili-
bration of the tracer with the sample activity.
2. The procedure should not be applied to water samples
containing sediment, but rather the sediment should be
separated and analyzed by a plutonium-in-soil procedure
3. The treatment of samples containing sediment required
considerable time and left much of the sample still
undissolved.
4. The ion exchange separation was too time consuming.
5. Some gassing occurred during the transition of the
resin from the nitrate form to the chloride form
possibly incurring some losses due to channeling.
6. Some samples went to dryness when evaporating the
sample effluent prior to electrodeposition and it
was difficult to redissolve such samples. It was
recommended that the sodium bisulfate and sulfuric
acid be added before these steps.
7. The thymol blue end point was difficult to observe.
In spite of the fact that an approximately equal number of
good and bad points about the procedure were received, 9 of the
14 laboratories believed that the method being evaluated would
be a good reference method for plutonium in water. Only one
laboratory responded with a definite no. This laboratory
submitted five bad points about the procedure although only
two of the bad points were considered valid for inclusion in
28
-------
the above list. These were items 3 and 4 in that list. The
other three bad points that this laboratory listed were as
follows: there is no equilibration of plutonium; iron is used
to carry the plutonium, so the plates are dirty and unusable
for mass spectrometric analysis if ever desired; there were
problems plating the samples because the plating solution
boiled away. The first comment is not considered valid since
in the procedure the sample is acidified, plutonium-242 tracer
is added, and the sample is mixed and heated for at least an
hour. The answer to the second comment is that although iron
is added as a carrier, it is later chemically separated from
the plutonium on the ion exchange column. Finally the last
problem can be eliminated by cooling the electrodeposition cell
Of the four remaining laboratories, one considered the
method for plutonium in water to be adequate while another
wanted to see the results of the collaborative test before
forming an opinion. A third laboratory did not believe that
the method was a good reference method for samples containing
suspended matter. And finally one laboratory had reservations
about the effectiveness of the ferric hydroxide precipitation
step of the procedure.
In response to question 9 on the questionnaire, several
general comments on the procedure were made. Most of these
comments are definitely worth mentioning and are as follows
in the order in which they would apply to the procedure:
1. Some of the activity could have adhered to the walls
of the cubitainer due to hydrolysis, and an acid
rinse of this container would be in order.
2. The use of plutonium-236 tracer is advisable when
determining relatively large amounts of plutonium-239.
3. To be consistent the iron carrier should be added as
a nitrate rather than as a chloride.
4. Platinum ware could be used in place of Teflon in
the acid dissolution.
5. It is suggested that the sediment be heated to fumes
of perchloric acid in a covered Teflon beaker, with
hydrochloric, nitric, and hydrofluoric acids added
as needed. Any excess perchloric acid is then
evaporated and if the small amount of perchlorate
ion would not interfere in the subsequent column work,
the residue in the Teflon beaker could be dissolved
in hydrochloric acid and passed through the column
as called for in the procedure.
29
-------
6. Whatman #2 filter paper was used in place of the
Whatman GF/A glass fiber filter in filtering any
dissolved sediment before beginning the ion
exchange.
7. After the plutonium is placed on the column and
rinsed with 8M nitric acid, conversion of the
column to the chloride form with 9-10 M hydro-
chloric acid may decrease the reaction rate
between the two acids thereby decreasing the
amount of gas formed.
8. In the first step of the electrodeposition, is all
the sulfuric acid necessary or could the 5% sodium
bisulfate monohydrate be prepared in 1M sulfuric
acid?
DISCUSSION OF RESULTS
When the first Mound Facility analyses of Samples 1, 2,
and 3 were performed, it could be seen that all the measured
plutonium concentrations were lower by about 107o on the
average than the expected plutonium concentrations (cf. Table 1
and Tables 3 through 5). No immediate explanation could be
given, but when some of the first collaborative study results
were received, it was observed that these results were also
lower than the concentrations expected from what was added to
the samples. Also when additional determinations were made
at a later date at Mound Facility, plutonium concentrations
were even lower than the previously determined values for
Samples 1 and 2.
To determine whether or not some systematic -error existed
in the collaborative study data, the "two-sample chart"
technique (Youden and Steiner, 1975) was used. Each sample
used in the collaborative study contained two isotopes, pluto-
nium-239 and plutonium-238; thus by plotting the plutonium-239
concentration against the plutonium-238 concentration for each
laboratory, a chart analogous to the two-sample chart is
obtained. This was done for the first three samples and the
charts are illustrated in Figures 1 through 3. A chart was
not prepared for Sample 4 since it had already been noted that
there was what was believed to be a serious blank problem in
measuring the very low plutonium-238 concentration in this
30
-------
u>
32 -
30 -
28 .
.1
E
Ts
'?• 26-
1
g
U
S
CM
3
Q_
24 -
22 -
20-
0°
O
o
0
o
o
o
, o
0°°
o
o
5 6
78 10 11
Pu-238 concn (dis/min/liter)
1.22-
1.14-
1.06 -
I0-9
8
O>
"
0.90 -
0.82 .
0.74
7.0
7.5
Pu-238 concon (dis/min/liter)
8.0
8.5
Figure 1. Sample 1 plutonium
concentrations measured
in collaborative study.
Figure 2. Sample 2 plutonium
concentrations measured
in collaborative study.
-------
u>
ro
5.0 -
1
TJ
5
4-0
3.5 -
3.0
0.3
00
o
o
o
0.4 0.5
Pu-238 concn (dis/min/liter)
0.6
35
O Collaborative study laboratory values
20
10
15
20
Time elapsed since sample preparation (weeks)
Figure 3. Sample 3 plutonium
concentrations measured
in collaborative study.
Figure 4. Least squares fit to
Sample 1 plutonium-239
concentrations vs. time
-------
sample. On the charts, a vertical line is drawn through the
average of the plutonium-238 concentrations and a horizontal
line is drawn through the average of the plutonium-239 concen-
trations. This divides each chart into four quadrants, and if
random errors are responsible for the scatter, the points
corresponding to the laboratories should be divided equally
among the four quadrants. In Figure 3, which corresponds to
Sample 3, this seems to be true. For Samples 1 and 2, however,
all but two of the points are found in the upper right or lower
left quadrant. This indicates that if a laboratory gets a high
(compared to the average) plutonium-239 concentration in the
water, the plutonium-238 concentration is also likely to be
high. The fact that the errors are random in Sample 3, yet not
in Samples 1 and 2, suggests that the systematic error may be
due to the samples rather than the laboratories.
A logical explanation to the decreasing plutonium concen-
trations with time is that the plutonium is hydrolyzing or
otherwise being adsorbed by the walls of the container. Perhaps
preservation of the samples by adjusting the acid concentration
to 0.1M nitric acid is not sufficient when samples are to be
stored for more than a few weeks. More definite evidence that
the plutonium concentration was decreasing with time was
obtained when the concentration was plotted as a function of
the time elapsed since the sample was prepared. One such plot
is shown in Figure 4 for the plutonium-239 in Sample 1. Although
there is considerable scatter in the points, a least squares
calculation verified a negative slope. Also in this case, the
extrapolated plutonium-239 concentration, 31.6 dis/min/liter,
corresponds exactly to the concentration expected from the
plutonium-239 added to the sample. Least squares fitting of
the remaining data from Samples 1, 2, and 3 also indicates that
hydrolysis or a similar reaction to remove plutonium is occurring
in Samples 1 and 2, but not 3. All the extrapolated plutonium-
in-water concentrations"are given in parentheses under the
expected values in Table 1. Agreement is very good in all cases
except for the plutonium-238 in Sample 2. A possible explanation
for the fact that the plutonium concentration in Sample 3 is not
decreasing, whereas it is in Samples 1 and 2, is that Sample 3
is a substitute ocean water sample containing relatively large
concentrations of salts which may be stabilizing the plutonium
in the aqueous phase.
When the average collaborative study plutonium concen-
trations tabulated in Table 15 are compared to the reference
values for the same samples, it is clear that there is definite
agreement on the plutonium-239 concentrations in Samples 2 and
4. For Sample 2, these concentrations are 0.96 vs. 0.966 dis/
min/liter, and for Sample 4, 0.42 vs. 0.42 dis/min/liter. On
the other hand, for Sample 4 the average plutonium-238 concen-
tration from the collaborative study was five times as high as
33
-------
the reference value, and these two values certainly do not
agree.
To determine whether the other average collaborative study
plutonium concentrations agree with the reference values, the
t-test was used on the data from the first three samples. Two
equations were used in applying the t-test. The first re-
lationship 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):
^i 9 «i 9 \ %
(5)
where:
t = test criterion
X = average of collaborative test results
X - average reference value
S = estimated standard deviation of collaborative
test results
n = number of collaborating laboratories
S = estimated standard deviation of reference
concentration
n = 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 =
c
where:
R = the reference value considered to be the
true mean
Other quantities are defined as in equation (5)
34
-------
Equation (5) was applied to Samples 1 and 2, and equation
(6) was applied to Sample 3 using the data from Table 15. The
quantities used in the calculations, the calculated value of t,
and the critical value of t (tcrit) are given in Table 16. The
critical value of t is for a 5% level of significance. When t
is less than tcrit. it can be said that the two means agree.
Thus, from the results in Table 16, it can be said that the
collaborative test .average does not agree with the reference
value in Samples 1 and 3 for plutonium-239. It has already
been suggested that hydrolysis may have occurred in Samples 1
and 2, and this could explain the discrepancy observed for the
plutonium-239 in Sample 1.
The Mound Facility data for Sample 3 (cf. Table 5), on the
other hand, seemed to indicate that no loss of plutonium occurred
from this substitute ocean water sample. However, it is be-
lieved that there is a possibility that some initial hydrolysis
occurred at the time the sample was prepared. If this is true,
the best reference value for Sample 3 might also be the average
of the single-laboratory evaluation values. These values are
given in the last two rows of Table 16. Using these data and
the average of the collaborative test concentrations, the t test
indicates agreement with the Sample 3 plutonium-239 concentra-
tions, but not with the plutonium-238 values. The error in the
plutonium-238 values, however, could readily be explained by
the fact that the 0.57 dis/min/liter value determined by Mound
Facility for Sample 3 is high because of the plutonium-238
blank problem.
One of the objectives of the present study was to gather
counting data from the laboratories participating in the
collaborative study and determine whether the precision of the
measured plutonium concentrations approached the precision
expected from counting statistics. The standard deviations of
the plutonium concentrations and the standard deviations ex-
pected from counting statistics are given in Table 17 for each
sample for both plutonium-239 and plutonium-238, except for
plutonium-238 in Sample 4. For Samples 1 and 2, the standard
deviation of the data exceeded the error expected from counting
statistics. This is to be expected in view of previous dis-
cussions in regard to a possible hydrolysis that occurred in
these two river water samples. The data for Samples 3 and 4,
however, show that the observed experimental standard deviation
was that which would be expected from the counting statistics
of the actual counting data. Thus, for the plutonium-in-water
procedure studied, the precision of the results does indeed
approach counting statistics.
The results of this study were summarized at the Twenty-
Third Annual Conference on Bioassay, Environmental, and
Analytical Chemistry (Bishop et al., 1977) and a few significant
35
-------
comments were made at that meeting that should be noted here.
It was pointed out that plutonium in the environment could be
present as plutonium (VI) (Larsen and Oldham, 1977) and the
procedure evaluated in this study did not account for this
possibility. Use of an appropriate reducing agent, such as
sodium bisulfite before coprecipitation would eliminate this
problem. Sodium bisulfite has been used in a recent soil
analysis procedure to reduce hexavalent plutonium (Hiatt, 1977).
A second comment made at the conference was that in order to
preserve samples for plutonium analysis, adjustment to 4N
hydrochloric acid was necessary to prevent any loss of plutonium
on storage. This unfortunately would require rather large
amounts of concentrated hydrochloric acid when analyzing large
samples. As an alternative, it has been suggested that adjust-
ment to IN nitric acid would be sufficient to preserve water
samples for plutonium analysis. This option would certainly
require considerably less acid.
In conclusion, from the results of this collaborative study
it is believed that the plutonium-in-water procedure which was
evaluated would be a good analytical method. The method is
relatively simple and gave results of good precision and accu-
racy. Where statistical tests indicated a disagreement between
a collaborative test result average and the reference value,
it is believed that hydrolysis or some other phenomenon occur-
ring in the sample was the problem rather than the analytical
method itself.
TABLE 16. t-TEST FOR SYSTEMATIC ERRORS IN
COLLABORATIVE STUDY RESULTS
Tabulated
Sample Isotope X
± S
c
X
r
± S
Quantity
r
a
nc nr
t
tcrit
(or R)
1
1
2
2
3
3
3b
3b
Pu-239
Pu-238
Pu-239
Pu-238
Pu-239
Pu-238
Pu-239
Pu-238
26.77
8.96
0.958
7.77
4.15
0.50
4.15
0.50
± 3
± 1
± 0
± 0
± 0
± 0
± 0
± 0
.16
.18
.124
.47
.21
.06
.21
.06
28.9
9.94
0.966
7.51
4.40
0.53
4.28
0.57
± 0.
± 0.
± 0
± 0.
± 0.
± 0.
9
76
.044
31
13
03
14
14
13
13
13
13
13
13
5
5
7
7
8
7
2.22
2.11
0.21
1.48
4.29
1.80
1.75
3.48
2.11
2.11
2.10
2.10
2.18
2.18
2.09
2.10
aThe tabulated quantities are defined in the text.
^The second set of data for Sample 3 is given using Mound's
average, plutonium concentrations as the "reference values."
36
-------
TABLE 17. OVERALL STANDARD DEVIATION OF COLLABORATIVE
STUDY RESULTS AND STANDARD DEVIATIONS
EXPECTED FROM COUNTING STATISTICS ERRORS
Std. Dev.
Average Pu Std. Dev. Expected From
Sample Concentration of Data Counting Statistics
Number Isotope (dis/min/ liter) (%) (7.)
1 Pu-239 26.8 ±3.2
(127=)
1 Pu-238 8.96 ±1.18
(137.)
2 Pu-239 0.96 ±0.12
(137.)
2 Pu-238 7.78 ±0.47
(6.07.)
3 Pu-239 4.15 ±0.21
(5 . 1%)
3 Pu-238 O.'Sl ±0.059
(127.)
4 Pu-239 0.42a ±0.053
(127.)
±0.9
(3.3%)
±0.37
(4.27.)
±0.08
(8 . 37o)
±0.29
(3.87.)
±0.19
(4.77.)
±0.060
(127.)
±0.055
(137.)
lUnits here are dis/min/sample.
37
-------
REFERENCES
1. Abrahamson, S. G., D. G. Carfagno and B. R. Kokenge,
"Plutonium-238 Isotoptc Fuel Form Data Sheets," U.S.A.E.G.
Report MLM-1691, 1969.
2. American Society for Testing and Materials, 1976 Annual
Book of ASTM Standards, Fart 32, Designation!D 1141-75,
p. 48, Philadelphia, Pa., 1976a.
3. American Society for Testing and Materials, 1976 Annual
Book of ASTM Standards, Part 41, Standard Recommended
Practice for Dealing with Outlying Observations,
Designation: E178-75, p. 183, Philadelphia, Pa., 1976b.
4. Bishop, C. T., A. A. Glosby, R. Brown and C. A. Phillips,
"Collaborative Study of a Tentative Standard Method for
the Determination of Plutonium in Water." In Program
and Abstracts: Twenty-Third Annual Conference on Bioassay,
Environmental, and Analytical Chemistry, U.S. Energy
Research and Development Administration Report IDO-12083,
paper No. 1, 1977.
5. Fukai, R., and C. N. Murray, "Results of Plutonium Inter-
calibration in Seawater and Seaweed Samples," In Reference
Methods for Marine Radioactivity Studies II, Technical
Reports Series No. 169, International Atomic Energy Agency,
Vienna, p. 167, 1975.
6. Golchert, N. W., and J. Sedlet, "Radiochemical Determina-
tion of Plutonium in Environmental Water Samples,"
Radiochem. Radioanal. Letters, 12, 215 (1972)
7. Hahn, P. B., E. W. Bretthauer, P. B. Altring-er and N. F.
Mathews, "Fusion Method for the Measurement of Plutonium
in Soil; Single Laboratory Evaluation and Interlaboratory
Collaborative Test," U.S. Environmental Protection Agency,
Report EPA-600/7-77-078, Las Vegas, NV, 1977
8. Harley, J. H., "Radiochemical Determination of Plutonium
in Urine, Feces and Water." In HASL Procedures Manual,
U.S.A.E.G. Report HASL-300, 1972.
38
-------
9. Harley, J. H., "Worldwide Plutonium Fallout from Weapons
Tests." In Proceedings of Environmental Plutonium
Symposium, Los Alamos Scientific Laboratory Report
LA-4756, 1971.
10. Hiatt, M. H., "Simultaneous Analysis of Plutonium,
Americium and Curium in Soil,U.S. Environmental Protection
Agency,Las Vegas Nevada, (In preparation),
11. Hodge, V. F., and M. E. Gurney, "Semiquantitative
Determination of Uranium, Plutonium and Americium in
Sea Water," Anal. Chem., 47, 1866 (1975).
12. International Atomic Energy Agency, Transuranium Nuclides
in the Environment, Proceedings of the Symposium on
Transuranium Nuclides in the Environment Organized by
the United States Energy Research and Development
Administration and the International Atomic Energy Agency
held in San Francisco, 17-21 November 1975, Vienna, 1976.
13. Kooi, J., and V. Hollstein, "An Improved Method for the
Determination of Trace Quantities of Plutonium in Aqueous
Media-Method and Procedure," Health Physics, 8, 41 (1962).
14. Korkisch, J., Modern Methods for the Separation of Rarer
Metal Ions, Pergamon Press, New York, N.Y., pp. 28, 1969.
15. Kressin, I. K., W. D. Moss, E. E. Campbell and H. F. Schulte,
"Plutonium-242 vs. Plutonium-236 as an Analytical Tracer,"
Health Physics, 28, 41 (1975).
16. Larsen, R. P., and R. D. Oldham, "The Oxidation of Pu(IV)
to Pu(VI) by Chlorine-Consequences for the Maximum
Permissible Concentration of Plutonium in Drinking Water."
In Program and Abstracts. Twenty-Third Annual Conference
on Bioassay, Environmental, and Analytical Chemistry,
U.S. Energy Research and Development Administration Report
IDO-12083, paper No. 12, 1977.
17. Livingston, H. D., D. R. Mann and V. T. Bowen, "Analytical
Procedures for Transuranic Elements in Seawater and
Marine Sediments." In Analytical Methods in Oceanography,
Advances in Chemistry Series,No.147, p.124, American
Chemical Society, Washington, D. C. 1975a.
18. Livingston, H. D., D. R. Mann and V. T. Bowen, "Double
Tracer Studies to Optimize Conditions for the Radiochemical
Separation of Plutonium from Large Seawater Samples."
In Reference Methods for Marine Radioactivity Studies II,
Technical Reports Series No. 169, p. 69, International
Atomic Energy Agency, Vienna, 1975b.
39
-------
19. McDowell, W. J., D. T. Farrar and M. R. Billings,
"Plutonium and Uranium Determination in Environmental
Samples: Combined Solvent Extraction-Liquid Scintillation
Method," Talanta. 21, 1231 (1974).
20. Peters, R., "Determination of 238Pu and 239/240pu Activity,"
Los Alamos Scientific Laboratory, unpublished procedure,
1975.
21. Puphal, K. W., and D. R. Olsen, "Electrodeposition of
Alpha Emitting Nuclides from a Mixed Oxalate-Chloride
Electrolyte," Anal. Chem., 44, 284 (1972).
22. Scott, T. G., and S. A. Reynolds, "Determination of
Plutonium in Environmental Samples Part II, Procedures,"
Radiochem. Radioanal. Letters, 2_3, 275 (1975).
23. Sill, C. W. , "Some Problems in Measuring Plutonium in the
Environment," Health Physics, 29_, 619 (1975).
24. Sutton, D. C., G. Calderon and W. Rosa, "Determination of
Environmental Levels of Pu-239, 240, Am-241, Cs-137 and
Sr-90 in Large Volume Sea Water Samples," ERDA Health
and Safety Laboratory, New York, N. Y., HASL-307, 1976.
25. Talvitie, N. A., "Radiochemical Determination of Plutonium
in Environmental and Biological Samples by Ion Exchange,"
Anal. Chem.. 43, 1827 (1971).
26. Talvitie, N. A., "Electrodeposition of Actinides for
Alpha Spectrometic Determination," Anal. Chem. , 44, 280
(1972). ~~
27. U.S. Atomic Energy Commission Regulatory Guide 4.5,
Measurements of Radionuclides in the Environment, Sampling
and Analysis of Plutonium in Soil, May, 1974.
28. Walpole, R. E., and R. H. Myers, Probability and Statistics
for Engineers and Scientists, Macmillan Publishing Co.,
Inc., New York, N.Y., p. 197, 1972.
29. Wong, K. M., "Radiochemical Determinations of Plutonium in
Seawater, Sediments and Marine Organisms," Anal. Chem.
Acta, 56, 355 (1971).
30. Wong, K. M., G. S. Brown and V. E. Noshkin, "A Rapid
Procedure for Plutonium Separation in Large Volumes of
Fresh and Saline Water by Manganese Dioxide Coprecipitation,"
submitted for publication in the Journal of Radioanalytical
Chemistry, 1976.
40
-------
31. Youden, W. J., and E. H. Steiner, "Statistical Manual of
the Association of Official Analytical Chemists,"
Association of Official Analytical Chemists, Washington,
B.C., 1975.
41
-------
APPENDIX 1
TENTATIVE METHOD FOR THE DETERMINATION OF
PLUTONIUM-239 AND PLUTONIUM-238 IN WATER
(BY A COPRECIPITATION ANION EXCHANGE TECHNIQUE)
This appendix is a reprint of a procedure of the same title
by Carl T. Bishop, Ralph Brown, Antonia A. Glosby, Charles A.
Phillips and Bob Robinson* of Mound Facility in Miamisburg, Ohio
The report was prepared September 17, 1976, for the U. S.
Environmental Protection Agency under Contract No. EPA-IAG-D6-
0015. Mound Facility is operated by Monsanto Research Corpora-
tion 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 inter-
laboratory collaborative study and was designated as report
number MLM-MU-76-69-0002.
^Present address is Battelle Pacific Northwest Laboratory,
Richland, Washington 99352
42
-------
PREFACE
The analytical procedure described in this document is a method
for the determination of plutonium in water which 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.
Final USEPA and USERDA documents will be prepared describing
the results of the collaborative test.
In order to obtain a method for collaborative testing, the
scientific literature on the determination of plutonium in
water was first examined. Based on certain established
criteria, a method from the literature was chosen and tested.
Similar methods were tested and modifications were made until
a final procedure was established. One of the principal
criteria was that the method be cost effective. Thus the
method that was finally adopted uses techniques that are rela-
tively simple, and it is also designed to handle a large number
of samples. Also,the equipment and reagents are generally
common to the analytical laboratory.
43
-------
CONTENTS
SECTIONS PAGE
1. Scope and Application 4
2. Summary 5
3. Interferences 5
4. Apparatus 6
4.1 Instrumentation 6
4.2 Laboratory Equipment 8
4.3 Labware
5. Standards, Acids, Reagents 9
5.1 Standards 9
5.2 Acids 9
5.3 Reagents 9
Calibration and Standardization
10
6.1 Standardization of the Plutonium-242 Tracer 10
Solution
6.2 Determination of Alpha Spectrometer Efficiency 10
7. Step-by-Step Procedure for Analysis 11
7.1 Coprecipitation 11
7.2 Acid Dissolution of Insoluble Residue 13
7.3 Anion Exchange Separation 14
7.4 Electrodeposition ^
7.5 Alpha Pulse-Height Analysis 16
8. Calculation of Results 17
8.1 Calculation of Plutonium Concentrations 1?
8.2 Calculation of Alpha Spectrometer Efficiency 17
8.3 Calculation of Plutonium Recovery of the 18
Chemical Analysis
9. References 19
44
-------
WATER ANALYSIS PROCEDURE
1. Scope and Application
1.1 This procedure has been successfully tested and is applicable
to both fresh water and sea water samples. It can be
applied to sample volumes of a liter to 20 liters or more.
In laboratories where the background of the counters is
less than a count per 1000 minutes in the Pu-239, Pu-240,
or the Pu-238 regions, and where reagent blanks contribute
less than counter background, as little as a few femto-
curies of plutonium can be determined when the sample is
counted for a few days.
This method applies to soluble plutonium and to suspended
particulate matter containing plutonium. When the latter
situation occurs, an acid dissolution step is added to
the procedure to assure that all of the plutonium dissolves.
1.2 The minimum detectable concentration of plutonium in water
depends on the volume of water analyzed. The minimum
detectable activity (MDA). 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, can be estimated from
some typical parameters that might be expected from the
present procedure.
Consider a sample that is counted for 1000 minutes on an
alpha spectrometer having a 25% counting efficiency and
a five count per 1000 minute background in the energy
region of interest, and shows a 60% chemical recovery.
Based on the definition of the MDA, the sample count would
have to be 7 (^3 x /5~), and to achieve this count under
the conditions stated would require 0.045 d/m of
activity. Thus, a typical MDA for plutonium in water by
this procedure would be 0.05 d/m.
1.3 The precision of the method has not yet been extensively
evaluated, but it is expected to approach that of the
counting statistics errors. The accuracy is expected to
be within limits propagated from counting statistics and
the uncertainty in the specific activity of the tracer
used.
45
-------
1.4 This method was selected since it can be readily used
by a laboratory technician. It does not involve any
particularly sophisticated steps and after training by
a chemist who understands the chemistry and the counting
involved, the procedure can be routinely carried out by
a technician.
2. Summary
The procedure consists of a coprecipitation, an anion exchange
separation and electrodeposition, followed by alpha pulse
height analysis. More specifically, the sample is acidified
with nitric acid and plutonium-242 is added as a tracer before
any chemical separations are performed. Iron is added to the
water as iron (III) and the plutonium is coprecipitated with
the iron as ferric hydroxide by adding ammonium hydroxide.
After decantation and centrifugation, the ferric hydroxide
precipitate containing the coprecipitated plutonium is
dissolved and the solution is adjusted to 8M in HN03 for anion
exchange separation. When the sample fails to dissolve because
of the presence of insoluble residue, the residue is treated by
a rigorous acid dissolution using concentrated nitric acid
and hydrofluoric acids.
The sample is poured over an anion exchange column. The iron
and most other elements that might be present pass through the
column. Thorium is removed from the column with 12 M hydro-
chloric acid and then the plutonium is eluted by reducing it to
plutonium (III) with the iodide ion. The plutonium is elec-
trodeposited onto a stainless steel slide for counting by
alpha pulse-height analysis using a silicon surface barrier
detector. From the recovery of the plutonium-242 tracer, the
absolute amounts of plutonium-238 and plutonium-239 can be
calculated, and from the volume of sample analyzed the concentra-
tions of these two isotopes in the water sample can be calculated.
3. Interferences
3.1 The procedure is such that no other alpha-emitting radio-
isotopes should appear along with the plutonium in the
final counting step. The procedure has been tested with
uranium, americim, thorium and polonium isotopes to verify
the fact that these elements are separated out by anion
exchange, and thus do not electrodeposit with the plutonium.
46
-------
3.2 In determining low levels of plutonium in environmental
samples, it is essential to make blank determinations
to ascertain that the contamination from reagents, glass-
ware and other laboratory apparatus is negligible. A
blank value should be determined in exactly the same
way as a sample value.
4. Apparatus
4.1 Instrumentation
4.1.1 Alpha Pulse-Height Analysis System - The system
uses an ORTEC silicon surface barrier detector
and is 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 effi-
ciency 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 constant-current
power supply, 0-12 V, 0-2 A, is required for the
electrodeposition described in this procedure.
A disposable electrodeposition cell is also
required. 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 circu-
lated. The electrodeposition can be carried out
without the water cooling.
The cathode is a stainless steel slide pre-polished
to a mjrror finish. The diameter of the slide is
3/4" and the exposed cathode area during electro-
deposition is 2 cm2.
The anode is a 1 mm diameter platinum wire with an
8 mm diameter loop at the end, above the cathode
disk.
47
-------
Micro bell glass
(Sargent-Welch
Cot. No. S-4930)
Liquid scintillation counting
polyethylene vial, 25 ml capacity,
with bottom cut off containing
electrolyte solution
Brass screw cap machined
to fit 25 nl polyethylene
vial, with 7/32*' diameter by
1/2" long tube protruding
from base of cap
Platinum wire
anode
5/16" od glass
tube added to bell glass
Rubber tubing carrying
cooling water out
Stainless steet tubing*
3/8" od by 2 1/2" long,
electrical connection to cathode
mode here
Small rubber bulb
Stainless steel slide
3/4" in diameter
Rubber tubing carrying
cooling water in
Figure 1. Water Cooled Electrodeposition Apparatus
48
-------
4.2 Laboratory Equipment
4.2.1 Balance - top loading, capacity 1200 g, precision
±0.1 g
4.2.2 Hot plate - magnetic stirrer and stirrer bar
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 1000 ml
4.3.2 Beakers - glass, 100 ml to 2 liters
4.3.3 pH paper - pH range 2 to 10
4.3.4 Automatic pipets - with disposable tips, volumes
between 100X and 1000X
4.3.5 Centrifuge bottles - 100 ml or greater (larger
bottles are required for 10 liter or larger samples)
4.3.6 Ion exchange columns - approximately 1.3 cm i.d.,
15 cm long with 100 ml reservoir
4.3.7 Pipets - glass, class A
4.3.8 Disposable pipets - 2 ml glass eye-dropper type,
with rubber bulb
4.3.9 Dropping bottles
4.3.10 Watch glasses
4.3.11 Polyethylene washing bottles
4.3.12 Glass stirring rods
49
-------
4.3.13 Beaker tongs
4.3.14 Spatulas
4.3.15 Heat lamp - mounted on ring stand for drying slides
5. Standards, Acids, Reagents
5.1 Standards
5.1.1 National Bureau of Standards (NBS) plutonium-242 solution
(SRM #4334 or #4335) with the concentration certified to
+1% of its stated activity, or a dilution of this standard.
5.2 Acids - reagent grade, meeting American Chemical Society
(ACS) specifications; diluted solutions prepared from dis-
tilled deionized water.
5.2.1 Nitric acid - concentrated (16 M), 8 M
5.2.2 Hydrochloric acid - concentrated (12 M), 0.5 M
5.2.3 Sulfuric acid - concentrated (18 M). 1.8 M
5.2.4 Hydrofluoric acid - concentrated (48% solution)
5.2.5 Boric acid - powder or crystalline
5.3 Reagents - reagent grade, meeting ACS specifications,
solutions prepared from distilled deonized water
5.3.1 Ferric chloride - in 0.5 M HC1 to give 50 mg of iron
per ml of solution
5.3.2 Ammonium hydroxide - concentrated (15 M), 1.5 M,
0.15 M
5.3.3 Sodium nitrite
5.3.4 Anion exchange resin - Bio Had AG1-X8 (100-200 mesh)
chloride or nitrate form. (Available from Bio Rad
Laboratories, 3rd and Griffin Ave., Richmond, Calif.,
94804). A column is prepared by slurrying" this resin
with 8 M UNO3 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 larger volume samples.
The resin is then converted to the nitrate form by
passing 10 column volumes of 8 M HNO3 through the column.
50
-------
5.3.5 Ammonium iodide - 1 M. (prepare fresh weekly)
5.3.6 Sodium hydrogen sulfate - -v5% in 9 M H2 SO*, ; dissolve
10 g of the NaHSOi. in 100 ml of water and then
carefully add 100 ml of 18 M H2 SO., .
5.3.7 Preadjusted electrolyte - 1 M ammonium sulfate
adjusted to pH 3.5 with 15 M NH,, OH and 18 M H2 S04 .
5.3.8 Thymol blue indicator, sodium salt (available
from Fisher Scientific Company) - 0.04% solution.
5.3.9 Ammonium nitrate - 1% in 0.15 M NH..OH.
5.3.10 Ethyl alcohol - made slightly basic with a few
drops of 15 M NH^OH per 100 ml of alcohol.
6. Calibration and Standardization
6.1 Standardization of the Plutonium-242 Tracer Solution
This tracer is available from the National Bureau of
Standards (NBS) as SRM #4334 or #4335. The overall
uncertainty of the concentration of the plutonium-242
is ±1.0%.
If a laboratory desires to standardize its own solution,
aliquots of the solution could be mounted on slides and
counted with a 2w proportional counter. The efficiency
of the 2T counter must accurately be determined with an
NBS alpha point source, making corrections for
resolving time and backscattering if necessary.
6.2 Determination of Alpha Spectrometer Efficiency
An accurate determination of the alpha spectrometer
counting efficiency is not necessary to get an accurate
concentration of plutonium isotopes in the sample being
analyzed. This is because of the fact that when a
tracer is used, the counting efficiency is the same for
the tracer and the unknown plutonium isotopes, and is
not needed to calculate the unknown plutonium concen-
trations (cf. section 8.1).
10
51
-------
An approximate determination of the alpha spectrometer
counting efficiency is required to calculate the plu-
tonium recovery of a particular analysis. To determine
this efficiency requires that one count an alpha
particle source of a known alpha particle emission rate
under the same conditions that the samples are counted.
The alpha particle counting efficiency is then calculated
as illustrated in section 8.2.
7. Step By Step Procedure For Analysis
7.1 Coprecipitation
7.1.1 Weigh or measure the volume of a one liter or larger
water sample.
7.1.2 If the sample has not been acidified, add 5 ml of
16 M HN03 per liter of sample.
7.1.3 Mix the samples completely using a magnetic stirrer
for small samples, or a peristaltic or other pump
for larger samples. Check the acidity with pH
paper. If it is greater than 2, add 16 M HN03
until it reaches this value.
7.1.4 Add standardized Pu-242 tracer with a calibrated
pipet (or add a weighed amount of the tracer) to
give about 10 dis/min of Pu-242. If the Pu-238
or Pu-239 content of the sample is known to be
high, use Pu-236 tracer.
7.1.5. Mix the sample for about one 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 50-60°C while
stirring. )
7.1.6 Add 50 mg of iron as FeCl3 in 0.5M HC1 to a one
liter sample (or more iron, up to 1 gram, to a
sample of a few hundred liters).
7.1.7 Stir again for ten minutes or longer if the
sample volume is greater than a few liters. (If
52
-------
the sample volume is only a few liters or less,
heat the sample to boiling).
7.1.8 Add 15 M NH»OH while stirring to precipitate the
'iron. Add a slight excess of 15 M NH..OH to raise
the pH to 9-10 as determined with pH paper.
7.1.9 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.
7.1.10 After the sample has settled sufficiently, decant the
supernate, being careful not to remove any precipi-
tate. (If the analyst wishes to continue
immediately, the iron hydroxide may be filtered out
at this time).
7.1.11 Slurry the remaining precipitate and supernate and
transfer to a centrifuge bottle. If larger samples
of water are being analyzed, it is necessary to
transfer the slurry to a large beaker and allow it
to settle again.
7.1.12 Centrifuge the sample and pour off the remaining
supernate.
7.1.13 Dissolve the ferric hydroxide with a minimum of 16M
HN03« (If organic matter is present, it may be
necessary to treat the sample with 30% H202 and
16 M HNO3 to remove it.)
7.1.14 If the precipitate dissolves completely, add a
volume of 16 M HN03 equal to the volume of the sample
solution, dilute to 100-150 ml with 8 M HN03, and then
proceed to Section 7.3, Anion Exchange Separation.
If the precipitate does not dissolve in nitric acid,
proceed to section 7.2 Acid Dissolution of Insoluble
Residue.
12
53
-------
7.2 Acid Dissolution of Insoluble Residue
7.2.1 When the precipitate fails to dissolve in nitric
acid, add more 16 M HN03 to a total volume of
about 75 ml, transfer the entire sample to a
Teflon beaker, and add 75 ml of 48% HF- (CAUTION:
HF is extremely hazardous. Wear rubber gloves,
safety glasses or goggles and a lab coat. Clean
up all spills and wash thoroughly after using
HF. Avoid breathing any HF fumes.)
7.2.2 Add a Teflon coated stirring bar and heat on a
magnetic stirrer hot plate for about 4 hours at
a temperature near boiling. Add equal amounts of
16 M HN03 and 48% HF to keep the volume at about
150 ml.
7.2.3 Allow the mixture to cool, and decant the solution
into another teflon beaker.
7.2.4 Evaporate this solution to dryness.
7.2.5 While this solution is drying, add 75 ml of 12 M
HC1 and 2 g of H3BO3 to the undissolved residue.
Stir and let stand until the solution from the
previous step has evaporated to dryness.
7.2.6 Transfer the HC1-H3B03 mixture from the last step
to the dried sample, leaving any residue behind.
Rinse the residue once with water and transfer the
water to the sample.
7.2.7 Evaporate the sample in the Teflon beaker to about
10 ml.
7.2.8 Add 100 ml 16 M HN03 and boil to remove the HC1.
7.2.9 Evaporate the sample to a volume of about 50 ml.
13
54
-------
7.2.10 Remove from the hotplate, and add a volume of
distilled water equal to the volume of the sample.
7.2.11 Add 8 M HN03 to a volume of 150 ml, 1 g of H3B03
and allow the solution to cool.
7.2.12 Filter the solution through a Whatman GF/A glass
fiber filter and wash the filter a few times
with 8 M HN03. Discard any residue in the filter
paper and proceed with the analysis of the filtrate
according to step 7.3.1.
7.3 Anion Exchange Separation
7.3.1 To the solution from the coprecipitation procedure
or from the acid dissolution which should be 7-9 M
in nitric acid, add Ig of NaN02, heat to boiling
and cool.
7.3.2 Pass the sample solution through the prepared anion
exchange resin column (cf. Section 5.3.4) at a flow
rate no greater than 4 ml/min.
7.3.3 After the sample has passed through the column,
rinse the column with six column volumes of 8 M
HN03, again at a flow rate no greater than 4 ml/min.
7.3.4 Rinse the ion exchange resin column with six column
volumes of 12 M HC1 at a flow rate no greater than
2 ml/min.
7.3.5 Elute the plutonium with four column volumes of 12 M
HC1 containing 1 ml of 1 M NH,, I per 30 ml of the
12 M HC1* at a flow rate no greater than 2 ml/min.
7.3.6 Rinse the column with two portions of 12 M H Cl
equal to the volume of the column of resin at
maximum flow rate.
7.3.7 Evaporate the sample containing the plutonium to
about 20 ml and add 5 ml of 16 M HH03.
*Prepare fresh just before elution.
14
55
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7.3.8 Evaporate the sample to near dryness.
7.3.9 Add 20 ml of 16 M HN03 and evaporate to near dryness.
7.4 Electrodeposition
7.4.1 Add 2 ml of a 5% solution of NaHSO^'H20 in 9 M H2SO,,
to the.sample.
7.4.2 Add 5ml of 16 M HN03, 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 5.3.7), warming to hasten
the dissolution.
7.4.4 Transfer the solution to the electrodeposition cell
using an additional 5-10 ml of the electrolyte in
small increments to rinse the sample container.
7.4.5 Add three or four drops of thymol blue indicator
solution. If the color is not salmon pink, add
1.8 M H2SO^(or 1.5 M KH,,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 adjustment,
but others may require further adjustments during
the electrodeposition).
7.4.8 Continue the electrodeposition for a total of 1.5
to 2.0 hours.
7.4.9 When the electrodeposition is to be terminated,
add 1 ml of 15 M NH^OH and continue the electro-
deposition for 1 minute.
15
56
-------
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 3 times with 1% NH^N03 in 0.15 M NH^OH.
7.4.12 Disassemble the cell and wash the slide with
ethyl alcohol that has been made basic with
NH..OH.
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.
7.5 Alpha Pulse-Height Analysis
7.5.1 When the amount of Pu-238 is large compared.to the
amount of Pu-239 and/or Pu-242, and when the amount
of Pu-239 is large compared to the amount of Pu-242,
tailing can contribute to the counts in the lower
energy peaks. When this occurs, it is necessary
to make corrections. One way of making these
corrections is to prepare Pu-238 and Pu-239 sources
in the same manner in which the samples are prepared,
and determine the corrections from the alpha spectra
of the pure isotope.
7.5.2 Background corrections of course must also be made.
The background should be determined by at least a
4000 minute count and preferably longer if possible.
7.5.3 Count the samples for at least 1000 minutes, or
longer if the detector efficiency is less than 15%,
if the tracer yield is low, or if the unknown plu-
tonium activity is low.
7.5.4 Determine the total counts in the Pu-238, Pu-239
and Pu-242 energy regions, and make the
background and tailing, correction's if necessary.
16
57
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8. Calculation of Results
8.1 Calculation of Plutonium Concentrations
The concentration of plutonium-239 or plutonium-238 in
the aliquot of water taken for analysis is given by:
X. = C. x SA. x V.
1 i t t .„ ..
C xV (8'1)
t s
where X. = the concentration of plutonium-239 or
plutonium-238 in the water in disintegra-
tions per minute (d/m) per liter.
C = the net sample counts in the plutonium-239
or plutonium-238 energy region of the alpha
spectrum.
SA = the specific activity of the Pu-242 tracer
in d/m/ml.
V « the volume of the Pu-242 tracer added in ml.
C = the net sample counts in the plutonium-242
tracer energy region of the alpha spectrum.
V = the volume in liters of the water sample taken
s for analysis.
8.2 Calculation of Alpha Spectrometer Efficiency
The absolute counting efficiency of the alpha spectrometer,
E, must be determined in order to calculate the plutonium
recovery of the analytical procedure.
To determine this efficiency requires a standard source
of a known alpha particle emission rate:
e ' VRa (8.2)
where R = the net counting rate of the standard source
s in the energy region of the alpha emitter
of interest in counts per minute.
17
58
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R = the absolute alpha particle emission rate
of the alpha emitter of interest in alphas
per minute.
8.3 Calculation of Plutonium Recovery of the Chemical Analysis
The plutonium recovery efficiency expressed as a fraction,
E, will be given by:
-------
REFERENCES
1. D. C. Sutton, G. Calderon and W. Rosa, "Determination of
Environmental Levels of Pu-239,240, Atn-241, Cs-137 and
Sr-90 in Large Volume Sea Water Samples," ERDA Health and
Safety Laboratory, New York, N.Y., HASL-307, 1976.
2. H. D. Livingston, D. R. Mann and V. T. Bowen, "Analytical
Procedures for Transuranics Elements in Sea Water and Marine
Sediments," in Analytical Methods in Oceanography, Advances
in Chemistry Series, American Chemical Society, Washington,
D.C., 1975, p. 124.
3. I. K. Kressin, W. D. Moss, E. E. Campbell and H. F. Schulte,
"Plutonium-242 vs. Plutonium-236 as an Analytical Tracer,"
Health Physics, 28, 41 (1975).
4. T. G. Scott and S. A. Reynolds, "Determination of Plutonium in
Environmental Samples Part II Procedures," Radiochem. Radioanal.
Letters, 23, 275 (1975).
5. H. D. Livingston, D. R. Mann and V. T. Bowen, "Double Tracer
Studies to Optimize Conditions for the Radiochemical Separation
of Plutonium from Large Seawater Samples," in Reference Methods
for Marine Radioactivity Studies II, Technical Reports Series
No. 169, International Atomic Energy Agency, Vienna, 1975. p.69.
6. R. J. Budnitz, "Plutonium: A Review of Measurement Techniques
for Environmental Monitoring," IEEE Trans. Nucl. Sci. 21, 430
(1974).
7. Measurements of Radionuclides in The Environment Sampling & Analysis
of Plutonium in Soil, U.S. Atomic Energy Commission Regulatory
Guide 4.5, May, 1974.
8. N. W. Golchert and J. Sedlet, "Radiochemical Determination of
Plutonium in Environmental Water Samples," Radiochem. Radioanal.
Letters, 12, 215 (1972).
9. N. A. Talvitie, "Electrodeposition of Actinides for Alpha
Spectrometric Determination," Anal. Chem., 4^,280 (1972).
10. K. W. Puphal and D. R. Olsen, "Electrodeposition of Alpha
Emitting Nuclides from a Mixed Oxalate-Chloride Electrolyte",
Anal. Chem., 44, 284 (1972).
19
60
-------
11. K. M. Wong, "Radiochemical Determinations of Plutonium in
Sea Water,Sediments and Marine Organisms," Anal. Chim. Acta.
5£, 355 (1971).
12. National Bureau of Standards Handbook 80, "A Manual of
Radioactivity Procedures", Superintendent of Documents, Wash-
ington, D.C. 1961.
13. C. W. Sill, F. D. Hindman and Jesse I. Anderson, Health
Services Laboratory, USERDA, Idaho Falls, Idaho Simultaneous
Determination of Alpha-Emitting Nuclides of Radium through
Californium in Large Environmental and Biological Samples,"
to be published.
14. D. Curtis and R. Peters, Los Alamos Scientific Laboratory,
Los Alamos, New Mexico, private communication.
20
61
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APPENDIX 2
COLLABORATIVE STUDY INSTRUCTIONS - PLUTONIUM IN WATER
(September 1976)
1. Use the procedure "Tentative Method for The Determination
of Plutonium-239 and Plutonium-238 in Water (By a
Coprecipitation Anion Exchange Technique)." September 17,
1976.
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 Laboratory
will furnish them if you desire. Contacts are given below.
4. Use care in opening the samples. They were shipped in
collapsable containers and may tend to spurt out when opened.
Samples may be less than one liter in volume, but this does
not matter; measure the weight or volume of samples 1, 2 and
3. When analyzing sample 4, quantitatively transfer the
entire contents of the sample to a large beaker for analysis.
5. Additional amounts of any sample are available if a sample is
spilled, an obviously incorrect plutonium concentration is
obtained, etc. Contacts are given below.
6. Sample concentrations may be as low as 0.2 dis/min/liter.
Blanks should be made in your laboratory to be certain that
they are not a problem at this plutonium concentration.
7. We are requesting that the same tracer, MD-2, be used by all
participants. Using 100X of this tracer gives the approximate
amount of Pu-242 called for in the procedure. If you dilute
the tracer supplied, keep in mind that it is in a 5M HNOa
solution.
8. In this collaborative test, the acid dissolution.procedure
(Section 7.2) will be required only on sample 4.
9. The electrodeposition apparatus illustrated in Figure 1 of the
procedure is only an illustration. Your apparatus should be
similar, but not necessarily the same.
10. All samples should be counted for at least 1000 minutes.
11. Individual counting data is requested so that the counting
statistics error can be resolved from other errors.
12. Any comments you wish to make on the collaborative test and
the procedure would be appreciated.
62
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APPENDIX 3
QUESTIONNAIRE ON COLLABORATIVE STUDY OF
TENTATIVE METHOD FOR THE DETERMINATION
OF PLUTONIUM-239 AND PLUTONIUM-238 IN WATER
January, 1977
Laboratory Contact
1. When (to the nearest week) were the chemical analyses performed?
5-17 weeks after sample preparation
Yes No
2. Did you make a blank correction? 4 TO" If so, what were the values in
d/m/1 for Pu-239? 0.01 - 0.08 For Pu-238? 0 - 0 05
YesNo"
3. a) Did you dilute the Pu-242 tracer that was supplied? 5 ~9"
b) If you diluted the tracer, did you make corrections in the specific activity
of the tracer because of a change in density? Yes-5. No-0
Yes No
c) If you pipeted the tracer, was the volume of the pipet calibrated? ~7 "T
4. Was the 1M NH^I that you used less than two weeks old? Yes-14. No-0
Yes No Other
5. Did you deviate considerably from any part of the procedure? 2 ~9~ 3
If so, what were these deviations? (answer on other side)
6. What were the good points of this procedure? (answer on other side)
7. What were the bad points of this procedure? (answer on other side)
8. Do you believe that this would be a good reference method for plutonium
in water? Yes-9, No-1, Other-4
9. Any other comments that you might have would be appreciated.
63
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APPENDIX 4
DATA ON PLUTONIUM-242 TRACER
Isotope: Pu-242 I.D. No.: MD-2
Date Prepared: 8/30/76
Specific Activity: 77.0 dis/min/gram (±1.0%) (on date prepared)
Density: 1.164 g/cm3 at 20°C
Acid Medium: 5M HN03
Source: National Bureau of Standards
Standard Reference Material 4334
Plutonium-242 Alpha-Particle
Solution Standard diluted (by mass dilution) with 5M HN03
Half Life: 3.9 x 105 years
Approximate Volume in Glass Ampoule: 2 ml
Opening Instructions: 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 poly-
ethylene bottle with the long narrow neck,
enclosed with the ampoule, may be used to
remove the tracer from the opened ampoule.
Prepared At: Mound Facility
Monsanto Research Corporation
Miamisburg, Ohio 45342
64
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APPENDIX 5
LABORATORIES PARTICIPATING IN THE
PLUTONIUM IN WATER COLLABORATIVE STUDY
Argonne National Laboratory
Occupational Health and Safety
Argonne, Illinois
Colorado Department of Health
Occupational and Radiological Health Division
Denver, Colorado
Food and Drug Administration
Winchester Engineering and Analytical Center
Winchester, Massachusetts
Lawrence Livermore Laboratory
Environmental Evaluations Group
Livermore, California
Los Alamos Scientific Laboratory
Group H-8 Environmental Studies
Los Alamos, New Mexico
LFE Environmental Analysis Laboratories
Richmond, California
Mound Laboratory, Monsanto Research Corporation
Nuclear Operations Analytical*
Miamisburg, Ohio
New York State Department of Health
Albany, New York
Reynolds Electrical & Engineering Co., Inc.
Environmental Sciences Department
Las Vegas, Nevada
Rocky Flats, Rockwell International
Environmental Sciences
Golden, Colorado
Sandia Laboratories
Division 3311
Albuquerque, New Mexico
*This analytical group was entirely separate from the group
that conducted the study, i.e. the Environmental Evaluation Group.
65
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U. S. Air Force
McClellan Central Laboratory
McClellan Air Force Base, California
U. S. Energy Research and Development Administration*
Health Services Laboratory
Idaho Falls, Idaho
U. S. Energy Research and Development Administration*
Health and Safety 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
U. S. Testing Company, Inc.
Richland, Washington
Westinghouse Electric Corporation
Advanced Reactors Division
Madison, Pennsylvania
Now the U.S. Department of Energy
the Environmental Measurements Laboratory
66
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APPENDIX 6
TABLE OF REJECTED RESULTS
Data Reported
Laboratory Number
Sample 1
Pu Recovery
Pu-239 (dis/min/liter)
Pu-238 (dis/min/liter)
Sample 2
Pu Recovery
Pu-239 (dis/min/liter)
Pu-238 (dis/min/liter)
Sample 3
Pu Recovery
Pu-239 (dis/min/liter)
Pu-238 (dis/min/liter)
Sample 4
Pu Recovery
Pu-239 (dis/min)
Pu-238 (dis/min)
Average Recovery
2
3.7%, 6.3%
26.1, 290.6
6.6, 22.5
3.2%, 5.9%
0, 31.1
6.5, 0
4.1%, 15.5%
123.5, 5.8
0, 0
4%, 4%
242, 115
10, 10.4
4
4.7%, 4.3%
15.2, 18.7
5.68, 5.46
3.5%, 3.1%
0.5, 1
5.0, 5.1
3.3%, 3.1%
2.9, 2.8
0.3, 0.2
2.0%, 1.4%
0.0, 0.3
0.1, 3
6
21.8%, 52.5%
23.5, 21.6
7.08, 6.7
23.5%, 66.5%
.2.0, 0.83
6.59, 5.95
127.6%, 79.6%
3.29, 3.15
0.063, 0.313
94.1%, 67.9%
0.662, 0.588
0, 0
18
12.9%, 9.0%
38.7, 34.4
13.6, 11.1
14.7%, 8.7%
3.1, 4.8
9.0, 10.4
11.8%, 22.5%a
6.1, 6.1
0.6, 0.8
15.7%, 12.8%
2.6, 1.9
0.13, 0.23
5.8%
3.2%
67%c
14%
aRejected on the basis of an ASTM test for outliers.
^Laboratory rejected because of computational errors.
67
*U.S. GOVERNMENT PRINTING OFFICE: 1978 - 785-975/1232 Region No. 9-1
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TECHNICAL REPORT DATA
(P.lease read Instructions on the reverse before completing)
. REPORT NO.
EPA-600/7-78-122
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
ANION EXCHANGE METHOD FOR THE DETERMINATION OF
PLUTONIUM IN WATER: Single-Laboratory Evalu-
ation and Interlaboratory Collaborative Study
5. REPORT DATE
June 1978
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
C. T. Bishop, A. A. Glosby, R. Brown and
C. A. Phillips
8. PERFORMING ORGANIZATION REPORT NO.
MLM-2425
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Monsanto Research Corporation
Mound Facility
P. 0. Box 32
Miamisburg, Ohio 45342
10. PROGRAM ELEMENT NO.
1NE625
11. CONTRACT/GRANT NO.
EPA-IAG-D6-0015
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency-Las Vegas
Office of Research and Development
Environmental Monitoring & Support Laboratory
Las Vegas, Nevada 89114
13. TYPE OF REPORT AND PERIOD COVERED
5/20/76 - 6/17/77
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
This report gives the results of a single-laboratory evaluation and an
interlaboratory collaborative study of a method for determining pluto-
nium in water. The method was written for the analysis of 1-liter
samples and involved coprecipitation, acid dissolution, anion exchange,
electrodeposition, and alpha pulse-height analysis. The complete
method is given in the first appendix to the report.
After the single-laboratory evaluation of the selected method, four
samples were prepared for the collaborative study. There were two river
water samples, a substitute ocean water sample, and a sample containing
sediment. These samples contained plutonium-239 and a plutonium-238 at
concentrations ranging from 0.42 to 28.9 dis/min/liter.
Standard deviations of the collaborative study plutonium concentrations
ranged from 5% to 13%. In three cases standard deviations agreed with
what was expected from counting statistics. It is believed that
hydrolysis occurred in the river water samples resulting in errors
greater than what was expected from counting statistics.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Plutonium
Quantitative Analysis
Quality Assurance
Water
07B
14B, D
8. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
80
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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