EPA-600/4-76-054
October 1976
Environmental Monitoring Series
INTERLABORATORY INTERCOMPARISON OF
POLONIUM-210 MEASUREMENTS
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Las Vegas. Nevada 89114
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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 five series. These five 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 five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and instrumentation for the identification and quantification of environmental
pollutants at the lowest conceivably significant concentrations. It also includes
studies to determine the ambient concentrations of pollutants in the environment
and/or the variance of pollutants as a function of time or meteorological factors.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/4-76-054
October 1976
INTERLABORATORY INTERCOMPARISON OF
POLONIUM-210 MEASUREMENTS
by
L. 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 constitute
endorsement or recommendation for use.
ii
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INTRODUCTION
The Quality Assurance Branch at the Environmental Monitoring and Support
Laboratory in Las Vegas/ Nevada, has maintained an active interlaboratory
intercomparison study of radioactivity measurements of environmental media
for the last 3 years (1,2,3). Over one hundred State laboratories, Federal
laboratories, commercial environmental monitoring laboratories, national
laboratories of other countries, nuclear power facilities, and university
laboratories have participated in these studies during this time.
The Quality Assurance Branch has also distributed, upon request, cali-
brated samples of selected radionuclides to these laboratories for use in
calibrating their instruments and evaluating their analytical techniques.
In October 1975 the Radioactivity Section of the National Bureau of
Standards delivered 40 alpha-particle test solutions of polonium-210 to the
Quality Assurance Branch. They also supplied a Report of Calibration for
these solutions (Appendix A).
Thirty-nine test solutions were sent to laboratories which have used
EPA's quality assurance services in the past. These laboratories agreed to
analyze the test solutions for activity and purity and return a test report
form similar to that used by the National Bureau of Standards (NBS) (4).
Twenty-four of these laboratories did return the test report; five more
indicated that they were unable to perform the analysis during the time
requested, in April, Reports of Calibration were sent to those which had
received the test solutions. The participants are listed in Table 1.
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TABLE 1. LIST OF PARTICIPANTS, ALPHA-PARTICLE TEST SOLUTION
POLONIUM-210*
1. Public Service Company of Colorado, Fort St. Vrain Nuclear Station,
Platteville, Colorado
2. General Electric Company, Vallecitos Nuclear Center, Pleasanton,
California
3. U.S. Food and Drug Administration, Winchester Engineering and
Analytical Center, Winchester, Massachusetts
4. Illinois Department of Public He'alth, Division of Laboratories,
Springfield, Illinois
5. South Carolina Department of Health and Environmental Control, Division
of Radiological Health, Columbia, South Carolina
6. Accu-Labs/CDM Limnetics, Wheatridge, Colorado
7. State Hygienic Laboratory of Iowa, Iowa City, Iowa
8. National Radiation Laboratory, Christchurch, New Zealand
9. Washington State Department of Social and Health Services, Environmental
Laboratories Unit, Seattle, Washington
10. Michigan Department of Public Health, Division of Radiological Health,
Lansing, Michigan
11. New York State Health Department, Radiological Sciences Laboratory,
Albany, New York
12. Nebraska State Department of Health, Radiation Health Laboratory,
Lincoln, Nebraska
13. Hazen Research, Inc., Golden, Colorado
14. Connecticut State Health Laboratories, Hartford, Connecticut
15. U.S. Environmental Protection Agency, Eastern Environmental Radiation
Facility, Montgomery, Alabama
16. Wisconsin State Division of Health, Department of Health and Social
Services, Madison, Wisconsin
17. Vermont State Health Department, Divison of Occupational Health,
Barre, Vermont
18. Los Alamos Scientific Laboratory, H-5 Division, Los Alamos, New Mexico
19. University of Washington, College of Fisheries, Laboratory of Radiation
Ecology, Seattle, Washington
20. Eberline Instrument Corporation, Albuquerque, New Mexico
21. Emory University, Physics Department, Atlanta, Georgia
22. Health and Welfare Canada, Radiation Protection Bureau, Ottawa, Ontario,
Canada
23. U.S. Energy Research and Development Administration, Health and Safety
Laboratory, Analytical Chemistry Division, New York, New York
24. LFE Environmental Analysis Laboratories, Technical Services Department,
Richmond, California
* The order in which participants are listed in this table does not correspond
to the order in which results are listed in Table 2.
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EXPERIMENTAL DETAILS
Each participant analyzed the test solution by the method(s) of his
choice. Some of the variations in the methods used are described in four
categories.
DETECTORS USED
Six laboratories used internal gas flow proportional counters, nine
laboratories used gas flow proportional counters, three laboratories used
silicon surface barrier detectors, two laboratories used alpha-particle
scintillation detectors, and one laboratory used a Frisch grid alpha-particle
spectrometer. One laboratory used two detectors. Four laboratories did not
indicate the detector used.
DILUTION OF SOLUTION
Nine laboratories did not dilute the solution and ten laboratories did
dilute the solution. Five laboratories gave no indication of their prepara-
tion.
PREPARATION OF SOLUTION
Twelve laboratories prepared their solutions for counting by evaporating
them on planchets, three laboratories prepared their solutions by electro-
plating the polonium onto planchets, two laboratories absorbed the polonium
on silver disks, three laboratories precipitated polonium from their solu-
tions and counted the filters, one laboratory used a hydrogen gas disposition,
and three laboratories did not indicate how they prepared their counting
sources.
CALIBRATION STANDARDS USED
Six laboratories indicated they used more than one radionuclide to
calibrate their counting instrument. Fourteen laboratories indicated they
used only one radionuclide. Four laboratories did not indicate which, or how
many, radionuclides were used to calibrate their counting instruments. Four
laboratories used polonium-210 sources, three laboratories used lead-210,
four laboratories used plutonium-239, six laboratories used americium-241,
two laboratories used gadolinium-148, two laboratories used thorium-230, two
laboratories used polonium-208, one laboratory used neptunium-237, and one
laboratory used plutonium-240.
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RESULTS
The results reported by the 24 participants are given in Table 2 and
Figure 1 as ratios of the participant's reported value of activity, corrected
for decay to the date of calibration, to the NBS-calibrated activity value.
This ratio is denoted as (x/NBS). For each x/NBS ratio, Figure 1 shows the
linear sum of the random counting error at the 99-percent confidence level
plus the linear sum of the estimated limits of systematic errors (as bars) as
reported by the participant.
TABLE 2. RESULTS OF INTERLABORATORY INTERCOMPARISON
OF POLONIUM-210 MEASUREMENTS
Participant x/NBS
Uncertainty
Uncertainty
Participant
1 1.00
2 0.60
3 0.91
4 0.98
5 0.62
6 0.36
7 0.96
8 0.76
10 0.95
14 1.37
15 1.04
16 0.96
± 3.3
*
± 8
± 1.7
*
± 7
± 2.3
± 10
± 6.1
± 3.6
± 4
± 10
17
18
19
20
21
22
23
24
25
26
27
28
0.91
0.48
1.02
1.02
0.28
0.33
0.82
0.47
0.95
1.02
1.01
0.76
*
+ 21, - 9
± 4.6
± 13
*
± 1.8
± 7.7
± 10
± 1
± 28
± 7.6
± 7.2
* Not determinable
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7
6
5
4
3
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1
2
3
4
5
6
7
8
10
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
REPORTED VALUE
NBS CERTIFIED VALUE
.1 .2 .3 .4 .5 .6 .7 .8 .9 1.01.11.21.31.41.51.61.71.8
i i i i i i
j i i i i i i i
0 .1 .2 .3 .4 .5 .6 .7 .8 .9 1.01.11.21.31.41.51.61.71.8
Figure 1. Reported results for the polonium-210 radioactivity test solution.
Participants in this intercomparison are listed in Table 1. The
bars are total estimated uncertainties (random plus estimated
systematic errors). Uncertainties could not be determined for
laboratories 2, 5, 17 and 21.
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DISCUSSION
The x/NBS activity ratios have a range from 0.28 to 1.37. Thirteen of
the participants reported values within ± 10 percent of the certified value
of activity. Ten of the eleven who reported values more than 10 percent from
the known value reported values that were lower than the known value.
Averages and standard deviations for each of the previously noted dif-
ferences in methodology were computed (e.g., those who diluted their test
solutions versus those who did not, as well as those who did not indicate
dilution or nondilution). Inspection of these averages and standard devia-
tions showed nothing significant. It was felt by the author that the sample
size was so small that further statistical testing was not warranted. As a
group, those participants who did not indicate complete experimental details
and who filled out the test report form sloppily, tended to have values much
below the NBS value for activity. Eight of the 24 participants considerably
underestimated the magnitude of their systematic errors. There is no obvious
correlation between total estimated errors and agreement with the NBS value.
The bias for low values of activity may have been due to the high volatility
of polonium (5).
SUMMARY
A total of 24 laboratories, representing power reactors, industry, State
health organizations, national laboratories of foreign countries, Federal
laboratories, and environmental consultant groups tested their measurement
techniques on samples containing polonium-210. Only 54 percent of the
reported results fell within ± 10 percent of the corresponding NBS values.
These results are similar to the results of an interlaboratory intercompari-
son of a strontium-89, strontium-go-yttrium-go radioactivity test source
conducted by the National Bureau of Standards (6).
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REFERENCES
1. National Environmental Research Center. Environmental Radioactivity
Laboratory Intercomparison Studies Program 1975. EPA-680/4-4-75-002b
May 1975. U.S. Environmental Protection Agency, Las Vegas, Nevada,
1975. 19 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. 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.
5. Kahn, B., G. R. Choppin, and J. C. V. Taylor. Users Guide for Radio-
activity. National Academy of Sciences - National Research Council,
Washington D. C., 1967. 43 pp.
6. Coursey, B. M., J. R. Noyce, and J. M. R. Hutchinson. Interlaboratory
Intercomparisons of Radioactivity Measurements using National Bureau of
Standards Mixed Radionuclide Test Solutions. NBS Technical Note 875.
August 1975. U.S. Department of Commerce, Washington D. C. 14 pp.
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APPENDIX
(REV. 12-83)
U.S. DEPARTMENT OF COMMERCE
NATIONAL BUREAU OF STANDARDS
WASHINGTON, D.C. 20234
REPORT OF CALIBRATION
Alpha-Particle Test Solution
Polonium-210
prepared for
U. S. Environmental Protection Agency
Las Vegas, Nevada
This test solution consists of carrier-free polonium-210 in approximately
3.3 grams of approximately 2 molar nitric acid in a flame-sealed borosili-
cate-glass ampoule.
The number of alpha particles emitted per second per gram of solution at
1200 EST September 23, 1975, was
*164.4 ± 0.9%*.
This test solution was calibrated by means of liquid-scintillation counting
Confirmatory measurements were performed on sources that were deposited
and dried on platinum discs, using the NBS O.Srr defined-solid-angle alpha-
particle counter. The mean of these agreed with the calibration value
to within 0.1 percent.
The uncertainty in the alpha-particle-emission rate, 0.9 percent, is the
linear sum of 0.1 percent, which is the limit of the random error at the
99-percent confidence level (2.70 S^, where ^ is the standard error comput
ed from 47 determinations), and 0.8 percent, which is the estimated upper
limit of conceivable systematic errors.
A half life of 138.378 ± 0.007 days is suggested
The alpha-particle spectrum of an evaporated source prepared from this
test solution was examined over the energy region of 4.0 to 8.0 MeV with
a silicon surface-barrier detector system, and no alpha-particle-emitting
impurities were detected. The detection limits for alpha particles from
contaminants can be expressed as a percentage of the alpha-particle-emission
rate of polonium-210 on the calibration date. For contaminant alpha parti-
cles with energies less than 5.3 MeV the detection limit would be approxi-
mately 0.1 percent, and for those with energies greater than 5.3 MeV the
detection limit would be approximately 0.01 percent.
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- 2 -
The gamma-ray-emission rate due to contaminants in this test solution over
the energy region of 0.01 to 1.85 MeV is estimated to be less than 2 gamma
rays per second per gram of solution on the calibration date.
The emission rate from this test solution of beta particles with energies
greater than 0.15 MeV is estimated to be less than 2 beta particles per
second per gram of solution on the calibration date.
(a) M. B. Lewis, Nuclear Data Sheets, B5(6). 631 (1971).
For the Director,
W. B. Mann, Chief
Radioactivity Section
Center for Radiation Research
November 21, 1975
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/4-76-054
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
INTERLABORATORY INTERCOM?ARISON
MEASUREMENTS
5. REPORT DATE
October 1976
OF POLONIUM-210
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Lee H. Ziegler, Quality Assurance Branch
Monitoring Systems Research and Development Division
8. PERFORMING ORGANIZATION REPORT NO.
9. 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.
EHE625
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13. TYPE OF REPORT AND PERIOD COVERED
final
14. SPONSORING AGENCY CODE
EPA-ORD, Office of Energy,
Minerals and Industry
15. SUPPLEMENTARY NOTES
16. ABSTRACT
In 1975 the U.S. Environmental Protection Agency distributed calibrated solutions
of polonium-210 to laboratories interested in participating in an intercomparison
study of polonium-210 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. Fifty-four percent of the reported activity
values were within ± 10 percent of the activity value certified by the National
Bureau of Standards.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group
polonium
calibration
radioactivity
reliability
intercalibration
intercomparison
National Bureau of
Standards
07 B
14 D
18 B, H
8. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
UNCLASSIFIED
21. NO. OF PAGES
12
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
•&GPO 789- 861-1977
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