xvEPA
United States
Environmental Protection
Agency
Environmental Monitoring
and Support Laboratory
PO Box 15027
Las Vegas NV 89114
EPA-600 7-78-105
June 1978
Research and Development
Intercomparison of
Plutonium-239
Measurements
Interagency
Energy-Environment
Research
and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad categories
were established to facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously planned to foster
technology transfer and a maximum interface in related fields. The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY—ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the effort
funded under the 17-agency Federal Energy/Environment Research and Development
Program. These studies relate to EPA'S mission to protect the public health and welfare
from adverse effects of pollutants associated with energy systems. The goal of the Pro-
gram is to assure the rapid development of domestic energy supplies in an environ-
mentally-compatible manner by .providing .the necessary environmental data and
control technology. Investigations include analyses of the transport of energy-related
pollutants and their health and ecological effects; assessments of, and development.of,
control technologies for energy systems; and integrated assessments of a wide range
of energy-related environmental issues.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161
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EPA-600/7-78-105
June 1978
INTERCOMPARISON OF
PLUTQNIUM-239 MEASUREMENTS
by
Lee H. Ziegler
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
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. Mention of trade names or commercial products does not consti-
tute endorsement or recommendation for use.
11
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FOREWORD
Protection of the environment requires effective regulatory actions which
are based on sound technical and scientific information. This information
must include the quantitative description 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 tran-
scends the media of air, water, and land. The Environmental Monitoring and
Support Laboratory-Las Vegas contributes to the formation and enhancement of a
sound monitoring data base for exposure assessment through programs designed
to:
• develop and optimize systems and strategies for moni-
toring 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 describes an interlaboratory study measuring the activity of
aqueous solutions of plutonium-239. The study was funded under the 17-agency
Federal Energy/Environment Research and Development Program. The data from
these measurements are useful in evaluating the state of the art of existing
measurement techniques which in turn provides valuable input into the establish-
ment of standards and guides, and enforcement activities. The Quality Assurance
Branch at the U.S. Environmental Protection Agency's Environmental Monitoring
and Support Laboratory in Las Vegas encourages the development and implementa-
tion of quality control procedures at all levels of sample collection, analysis,
data handling and reporting of environmental radiation measurements . and can
provide further assistance upon request.
George B Morgan
Director
Environmental Monitoring and Support Laboratory
Las Vegas
iii
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INTRODUCTION
The Quality Assurance Branch at the Environmental Monitoring and Support
Laboratory in Las Vegas, Nevada, has maintained an active quality assurance
program for the last five years. One major activity of the branch in this
program has been repetitive interlaboratory intercomparison studies of radio-
activity measurements of environmental media (1, 2, 3, 4, 5). Another major
activity of the branch has been the calibration and distribution of calibrated
radioactivity samples (6). Over 150 State laboratories, Federal laboratories,
commercial environmental monitoring laboratories, national laboratories of
other countries, nuclear power facilities, and university laboratories have
participated in these programs during this time.
The Quality Assurance Branch in Las Vegas has maintained a continuing
intercomparison1studies program with the National Bureau of Standards through-
out its existence (7). One phase of this program has been the occasional
distribution of calibrated radioactivity standards to laboratories partici-
pating in the Quality Assurance Branch's programs. A previous distribution of
an aqueous polonium-210 solution was done as an intercomparison study (8).
This report describes an intercomparison study on measurement of activity of
aqueous solutions containing plutonium-239.
These intercomparison studies provide information about the accuracy that
monitoring laboratories produce when measuring the activities of aqueous
solutions. Also, they are intended to survey the methodology and equipment
currently used by these monitoring laboratories.
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EXPERIMENTAL
In April, 28 calibrated solutions of plutonium-239 were distributed as
unknowns to 28 laboratories which had agreed to participate in an intercom-
parison study (Appendix) . The calibrated solutions were prepared by gravimetric
dilutions of a plutonium standard obtained from a commercial vendor. Since
the dilutions were made in 100-ml volumetric flasks, aliquots of two dilutions
were distributed. One dilution had an activity on December 1, 1973 of 18.63
disintegrations per second per gram of solution, while the other dilution had
an activity of 18.46 disintegrations per second per gram of solution. The
impurities, expressed as a percentage of the activity of the plutonium-239 on
December 1, 1973, were:
Plutonium-238 + Americium-241 (alpha). 0.5%
Plutonium-240 (alpha)....3.62%
Plutonium-241 (beta) <11%
The activities of the impurities were not included in the activities give^i
above for the plutonium-239 solutions. Consequently, the total alpha-particle
emission rate of the calibrated solution would then be 1.04 times the certified
activity value.
Besides the calibrated solution, the laboratories were sent one alpha-
particle test solution prepared by the National Bureau of Standards with an
accompanying report of calibration. A form on which laboratories could report
their results and describe the methodology used was also sent to the partici-
pating laboratories. This form is similar to that used by the National Bureau
of Standards (7) and was used in a previous study (8). The alpha-particle
test solution was intended to be used as a calibration standard by the indi-
vidual laboratories.
By early August, 17 of the laboratories had measured the activity of the
plutonium-239 unknown and reported their results. In late August, Calibration
Certificates prepared by the Environmental Protection Agency (6) for the
calibrated plutonium-239 unknown were sent to all 28 laboratories. The 17
laboratories who returned results are listed in Table 1.
Fifteen laboratories reported that they looked for impurities using
spectroscopy. One laboratory also measured the beta activity of the solution.
Six laboratories indicated that they observed plutonium-238 in the range of
0.1 nuclear transformations per second per gram (nts 1q 1) to 0.4_nts q l,
in general agreement with the certified value of 0.5% or 0.09 nts *q 1. One
laboratory indicated they observed plutoniuin*242, but they did not quantify
the activity of this radionuclide. Six laboratories indicated that they
looked for, but did not find the impurities in the solution. A comparison of
the mean value of the measurements obtained by the laboratories that did not
detect impurities showed no significant difference from that of the laboratories
which did report impurity levels.
2
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TABLE 1. LIST OF PARTICIPANTS, ALPHA-PARTICLE TEST SOLUTION
PLUTONIUM-239
Quality Assurance Program
Eastern Environmental Radiation
Facility
P. O. Box 3009
Montgomery, AL 36109
State of Connecticut Health
Laboratories
Environmental Chemistry Section
10 Clinton Street
Hartford, CT 06101
Midwestern Facility
Eberline Instrument Corporation
245 Roosevelt Road
West Chicago, IL 60185
State Hygienic Laboratory
The University of Iowa
Medical Laboratory Building
Iowa City, IA 52242
Winchester Engineering and
Analytical Center
U.S. Food & Drug Administration
109 Holton Street
Winchester, MA 01890
Nuclear Facilities and Contract
Control Section
Division of Radiological Health
Bureau of Environmental and
Occupational Health
Michigan Department of Public Health
3500 N. Logan St., P.O. Box 30035
Lansing, MI 48909
I
Eberline Instrument Corporation
Albuquerque Laboratory
P.O. Box 3874
Albuquerque, NM 87110
Group, H-5, Industrial Hygiene
University of California
Los Alamos Scientific Laboratory
P.O. Box 1663, MS 486
Los Alamos, NM 87544
The order in which participants are listed in this table does not correspond
to the order in which results are listed in Table 2 and Figure 1.
Sroup H-8
University of California
Los Alamos Scientific Laboratory
P.O. Box 1663
Los Alamos, NM 87544
Radiological Sciences Laboratory
New York State Health Department
30 Russell Road
Albany, NY 12206
Mound Laboratory
Monsanto Research Corporation
P.O. Box 32
Miamisburg, OH 45342
State of Oregon Health Division
Radiation Control Section
1400 S.W. 5th Avenue
Portland, OR 97201
Radiation Management Corporation
3508 Market Street
Philadelphia, PA 19104
South Carolina State Department of
Health and Environmental Control
2600 Bull Street
Columbia, SC 29201
Lynchburg Research Center
P.O. Box 1260
Lynchburg, VA 24505
Radiochemistry Division
United States Testing Company, Inc.
.2800 George Washington Way
Richland, WA 99352
Laboratory of Radiation Ecology
104 Fisheries Center
University of Washington
Seattle, WA 98105
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Six laboratories used alpha spectrometers and six laboratories used gas
flow proportional counters. One laboratory used a zinc sulfide phosphor.
Four laboratories did not indicate the type of detector they used. The mean
value of the measurements obtained by those laboratories using alpha spectro-
meters was about the same as that value of those laboratories using gas flow
proportional counters.
Four laboratories used plutonium-242 as a tracer. One laboratory used
plutonium-236 as a tracer. Six laboratories indicated they electroplated
their counting sources while five laboratories indicated they prepared their
sources by evaporating the solution onto planchets. One laboratory precipi-
tated the plutonium using lanthanum trifluoride (La FS). The mean value of
the measurements made by laboratories using tracers was not significantly
different from that of laboratories that did not use tracers. There was no
significant difference between the results of the laboratories that electro-
plated their sources and those that evaporated their sources.
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RESULTS
The results reported by the 17 participants are given in Table 2 and
Figure 1 as ratios of the participants reported mean values of alpha activity,
corrected for decay to the date of calibration, to the EPA-calibrated activity
value. This ratio is denoted as (X/EPA). For each X/EPA ratio presented in
Figure 1, the linear sums of the random counting error at the 99 percent
confidence level/ plus the linear sums of the estimated limits of systematic
error as reported by the participants, are shown as an error bar.
TABLE 2. RESULTS OF THE PLUTONIUM-239 MEASUREMENTS
Laboratory
Code Letter
A
B
C
D
E
F
G
H
I
X/EPA
Ratio
1.020
1.007
0.894
0.823
1.037
0.932
1.049
1.111
1.811
Uncertainty
(%)
5
7
*
6
2
17
10
6
7
Laboratory
Code Letter
J
K
L
M
N
O
P
Q
X/EPA
Ratio
1.028
1.002
1.025
1.153
1.103
4.563
1.439
0.914
Uncertainty
(%)
3
10
6
7
4
6
*
*
* Uncertainties could not be determined for laboratories C, P and Q.
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Reported Value
EPA Value
5 .6 7 8 .9 1.0 1 1 1.2 1.3 1.4 1.5
•o
o
o
>
o
o
.o
J3
.5 .6 .7 .8 .9 1.0 1.1 1.2 1.3 1.4 1.5
Figure 1. Reported results for the plutonium-239 radioactivity unknown solu-
tion. Participants in this intercomparison are listed in Table 1. The bars
are total estimated errors (random plus estimated systematic errors). Uncer-
tainties could not be determined for laboratories C, P and Q. Results from
laboratory O are not included.
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DISCUSSION
Twenty-eight laboratories received an alpha-particle test solution pre-
pared by the National Bureau of Standards for use as a calibration standard.
Fifteen laboratories reported values within ± 20% of the EPA-certified value.
Two laboratories data differed from the EPA-certified value by more than 20%,
consequently, these data were not used in analyzing the results of this study.
Comparisons between the various methodologies were made by examining the mean
values and the standard deviation of each group. Inspection of these averages
and standard deviations showed nothing significant. It was felt by the
author that the sample size was so small that further statistical testing was
not warranted.
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INFERENCES
1. Environmental Monitoring and Support Laboratory. Environmental Radio-
activity Laboratory Intercomparison Studies Program FY 1977. EPA-600/4-
77-001 January 1977. U.S. Environmental Protection Agency, Las Vegas,
Nevada. 1977. 17 pp.
2. Jarvis, A. N. , and D. G. Easterly. Preliminary Milk Report. EPA-680/4-
75-007 June 1975. U.S. Environmental Protection Agency, Las Vegas,
Nevada. 1975. 36 pp.
3. Jarvis, A. N., R. F. Smiecinski, and D. G. Easterly. The Status and
Quality of Radiation Measurements of Water. EPA-600/4-76-017 April
1976. U.S. Environmental Protection Agency, Las Vegas, Nevada. 1976.
23 pp.
4. Easterly, D. G., R. R. Kinnison, A. N. Jarvis, and R. F. Smiecinski. The
Status and Quality of Radiation Measurements for Air. EPA-600/4-77-043
October 1977. U.S. Environmental Protection Agency, Las Vegas, Nevada.
1977. 32 pp.
5. Easterly, D. G., R. R. Kinnison, A. N. Jarvis, and R. F. Smiecinski.
Status and Quality of Radiation Measurements Food and Human Urine. EPA-
600/4-77-047 October 1977. U.S. Environmental Protection Agency,
Las Vegas, Nevada. 1977. 33 pp.
6. Ziegler, L. H., Radioactivity Standards Distribution Program FY 1977.
EPA-600/4-76-053 October 1976. U.S. Environmental Protection Agency,
Las Vegas, Nevada. 1976. 10 pp.
7. Environmental Monitoring and Support Laboratory. Radiation Quality
Assurance Intercomparison Studies 1974-1975. EPA-600/4-75-014 October
1975. U.S. Environmental Protection Agency, Las Vegas, Nevada. 1975.
20 pp.
8. Ziegler, L. H. Interlaboratory Intercomparison of Polonium-210 Measure-
ments. EPA-600/4-76-054 October 1976. U.S. Environmental Protection
Agency, Las, Vegas, Nevada. 1976. 9 pp.
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APPENDIX
U.S. DEPARTMENT OF COMMERCE
NATIONAL BUREAU OF STANDARDS
WASHINGTON, D.C. 20234
REPORT OF CALIBRATION
PLUTONIUM-239
Alpha-Particle Solution Standard
prepared for
Environmental Protection Agency
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada
This standard consists of carrier-free plutonium-239 in 4.1 grams of 5.0 molar
nitric acid in a flame-sealed borosilicate-glass ampoule.
The total number of alpha particles emitted by plutonium-239 plus impurities
per second per gram of solution on October 1, 1976 was
*99.42 ± 1.0%*.
A master solution of carrier-free plutonium-239 was calibrated by depositing
weighed aliquots on platinum disks and counting the dried deposits in the NBS
"medium-geometry11, def ined-solid-angle (ft 3? 0.4 steradians) , alpha-particle counter
with scintillator detector. This standard was then prepared by quantitative mass
dilutions of that master solution. Confirmatory measurements of the diluted solu-
tions were made using both the "medium-geometry" counter and a liquid-scintillation
counter. The measurements of the diluted and master solutions agreed to within
0.2%.
The uncertainty in the alpha-particle-emission rate, 1.0 percent, is the linear
sum of 0.2 percent, which is the limit of the random error in the def ined-solid-
angle, alpha-particle-counter measurements of the master solution at the 99-percent
confidence level (3.17 Sm, where Sm is the standard error computed from 11 deter-
minations), and 0.8 percent, which is the linear sum of the estimated upper limits
of conceivable systematic errors associated with these measurements and the dilutions.
Other isotopes of Plutonium, as 'well as americium-241, are present in this solution
standard. No attempt was made at NBS to determine the quantities of these impurities.
However, the composition of the starting material has been extensively studied and
intercompared and the reported composition is given on the reverse side of this
report.
For the Director,
A
W. B. Mann, Uiief ~
Radioactivity Section
Center for Radiation Research
December 8, 1976
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Appendix (continued)
The composition of plutonium mixture Pu-1 circulated for intercomparison and
used as the'starting material for this standard is given below:
Isotope
Pu-238
Pu-239
Pu-240
Pu-241
Am-241
Total
Weight fraction on
December W, 197^
8.32 x 10~6
8.45 x 10"6
0.992602
0.992642
7.311 x 10" 3
7.263 x 10~3
9.028 x 10~5
8.633 x 10~5
6.1 x 10~7
6.7 x 10"7
1.000012
1.000000
Laboratorub
LASL
LLL
LASL
LLL
LASL
LLL
LASL
LLL
LASL
LLL
LASL
LLL
Half life0
( 11 ears)
87.79
24146
6537
14.35
434.1
Average relative a-particle
emission rate .an
October 1, 197 6a
0.0023
1.0000
0.0270
(0.1358 6~)
0.0004
1.0297
Note that, because the amount of americium-241 is still increasing and, to
some extent, compensates for the decay of the plutonium, the total alpha-
particle-emission rate will remain within 0.2% of the certified value for
more than 100 years.
a. Date of purification.
b- LASL Las Alamos Scientific Laboratory, Las Alamos, New Mexico.
LLL = Lawrence Livermore Laboratory, Livermore, California.
t. The half lives used are taken from appendix B, American•National
Standard Calibration Techniques for the Calorimetric Assay of
Plutonium Bearing Solids Applied to Nuclear Materials Control,
N15.22 1975, except for the half life of plutonium-239, which
is the value calculated from the composition data above and the
measured total alpha-particle-e-mission rate.
d. Date of calibration.
10
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/7-78-105
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
INTERCOMPARISON OF PLUTONIUM-239 MEASUREMENTS
5. REPORT DATE
June 1978
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
Lee H. Ziegler, Quality Assurance Branch
Monitoring Systems Research and Development Division
8. PERFORMING ORGANIZATION REPORT NO
. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas, Nevada 89114
10. PROGRAM ELEMENT NO.
INE625
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Rnvironmental Protection Agency- Las Veaas, NV
Office of Research and Development
Environmental Monitorina and Sunnort Laboratory
Las Vegas, Nevada 89114
13. TYPE OF REPORT AND PERIOD COVERED
final
14. SPONSORING AGENCY CODE
EPA/600/07
15. SUPPLEMENTARY NOTES
16. ABSTRACT
In 1977 the U.S. Environmental Protection Agency distributed calibrated solutions
of plutonium-239 to laboratories interested in participating in an intercomparison
study of plutonium analysis. Participants were asked to perform a quantitative
radioactivity analysis of the solution. The results reported by all the partici-
pating laboratories are given here. Eighty-eight- percent of the reported activity
values were within ± 20 percent of the activity value certified by the Environmental
Protection Agency.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Held/Group
plutonium
calibration
radioactivity
reliability
intercalibration
intercomparison
National Bureau of
Standards
07 B
14 D
18 B, H
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
16
20. SECURITY 'CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
PREVIOUS EDITION IS OBSOLETE
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