EPA-600/4-75-014
October 1975
Environmental Monitoring Series
RADIATION QUALITY ASSURANCE
INTERCOMPARISON STUDIES
1974-1975
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 identifi-
cation 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 Information Service, Springfield, Virginia 22161.
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EPA-600/4-75-014
October 1975
RADIATION QUALITY ASSURANCE INTERCOMPARISON STUDIES
1974-1975
by
Quality Assurance Branch
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
ROAP Numbers 22ADB/22AAJ
Program Element 1HA327
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 Vegass U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
Effective June 293 1975, the National Environmental Research Center-Las
Vegas (NERC-LV) was designated the Environmental Monitoring and Support Labo-
ratory-Las Vegas (EMSL-LV). This Laboratory is one of three Environmental
Monitoring and Support Laboratories of the Office of Monitoring and Technical
Support in the U.S. Environmental Protection Agency's Office of Research and
Development.
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CONTENTS
Page
Introduction 1
Procedures 3
Results 8
Summary and Conclusions 11
References 13
APPENDIX. Questionnaire Supplied with Unknown Samples
in the EPA-NBS Traceability Studies 14
FIGURES
1. 4-inch by 4-inch Nal Well Crystal Coupled to a
Multichannel Analyzer 5
2. Ge(Li) Coaxial Detector Coupled to a Channel
Analyzer Using a Linear Amplifier 6
TABLES
1. Results of Direct Traceability Studies 9
2. Results of Indirect Traceability Studies 9
3. Results of Intercomparison Studies with the HSL
(Samples Prepared by EPA - Measured by HSL) 10
4. Results of Intercomparison Studies with the HSL
(Samples Prepared by HSL Measured by EPA) 11
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RADIATION QUALITY ASSURANCE INTERCOMPARISON STUDIES
1974-1975
INTRODUCTION
The Quality Assurance Branch of the Technical Support Laboratory
at the U.S. Environmental Protection Agency's (EPA) National Environ-
mental Research Center-Las Vegas (NERC-LV) prepares and distributes
calibrated low-level radioactive solutions to federal, state, and pri-
vate laboratories involved in environmental radiation monitoring and
surveillance. These solutions are utilized for both the calibration
of counting instruments and chemical yield determinations. Since the
laboratories using these samples must have confidence in their accuracy,
the QA Branch has instituted a continuing intercomparison studies pro-
gram with the National Bureau of Standards (NBS), the goal of these
studies being to establish the traceability of the EPA's calibrated
radiation samples to the NBS.
The expression "traceability to NBS," although appearing frequently
in guidelines and procedures referring to the measurement of radioactive
materials, has not been adequately defined in the guidelines and appears
to be a much misunderstood term. In many areas of metrology, trace-
ability to the NBS can be readily established in a direct manner. A
standard is obtained from the NBS and, by using the NBS prescribed pro-
cedures, the instrument of interest is calibrated and its precision and
accuracy documented. For many measurements (e.g., voltage measurements
using standard cells) such a procedure is sufficient to establish trace-
ability to the NBS. However, since the activity of all radionuclides
decreases with time, it is not possible to duplicate a measurement of
the same material at different times. Therefore, the measurement of
radioactive materials and the establishment of their traceability to
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the NBS require a different approach. Moreover, many gaps still exist
in our knowledge concerning the half-lives and decay schemes of many
radionuclides. Consequently, to obtain traceability to the NBS in the
measurement of radionuclide activity each radionuclide must be assayed
on an individual basis. Cavallo, et al. (1), have defined the expres-
sion "traceable to NBS" and indicated how both direct and indirect
traceability to NBS may be obtained.
"Direct traceability to the national radioactivity
measurements system (NRMS) exists when any 'outside'
laboratory prepares a batch of calibrated radio-
activity standards and submits several randomly
selected samples to the national standardizing
laboratory for confirmation and verification
Indirect traceability to the NRMS exists when the
national laboratory provides 'unknown1 calibrated
radioactivity samples to one or more measurement
laboratories, who in turn make measurements of
activity that agree within certain specified limits
with those of the national laboratory. Thus we can
have 1%, 5%, etc., traceability.... Indirect
traceability only means that the 'lower level'
laboratory has the potential to make measurements
that are consistent within the NRMS...."
Addressing the question of using standards in establishing trace-
ability, Cavallo, et al. (1), state:
"If an 'outside' laboratory regularly uses NBS
radioactivity standards to calibrate its measuring
equipment, this does not, in our view, constitute
traceability. Only when that laboratory can
measure the activity of an unknown sample and send
back values that agree with our values within a
certain specified range of error do we consider
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that traceability has been established. And that
condition can be achieved without using a single
NBS radioactivity standard."
PROCEDURES
Utilizing the approach suggested by Cavallo, et al. (1), the
Quality Assurance Branch, NERC-LV, initiated a program designed to
establish both "direct" and "indirect" traceability of radioactive
nuclides to the NBS within plus or minus 5 percent at the 1 sigma con-
fidence level. NBS personnel reviewed the objectives of the EPA's
calibrated sample distribution program, inspected the laboratory,
facilities, and instrumentation available at the NERC-LV, then outlined
the program required to establish the desired 5 percent traceability.
The first phase of the program involved direct traceability studies
wherein radioactive solutions, prepared and calibrated by the QA staff,
were submitted to the NBS for their measurements. The samples submitted
were 5-milliliter (ml) aqueous solutions of manganese-54, zinc-65,
strontium-89, strontium-90, and cobalt-60 with activity levels ranging
from 237 disintegrations per minute per gram (dps/g) to 2210 dps/g.
These samples were selected at random from the inventory of the EPA's
calibrated sample distribution program.
The second phase of the program, an indirect traceability study,
required that radioactive solutions prepared by the NBS be measured by
the QA staff. Since the initiation of this phase of the study, the NBS
has submitted 11 different radionuclides for analysis. These include
strontium-89, strontium-90, mercury-203, chromium-51, cesium-137,
cadmium-109, selenium-75, carbon-14, iron-59, silver-llOm, and
cesium-134. Measurements have been completed and the results reported
to NBS for strontium-89, strontium-90, mercury-203, chromium-51,
cesium-137, cadmium-109, and selenium-75. Work is currently in pro-
gress on carbon-14, iron-59, silver-llOm, and cesium-134.
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In addition to the NBS traceability studies, the Quality Assurance
staff has participated in intercomparison studies with the Energy Re-
search and Development Administration's (ERDA) Health Services Labora-
tory (HSL) at Idaho Falls, Idaho. These studies were deemed necessary
since the EPA's radiation quality assurance program involves the par-
ticipation of federal, state, and private laboratories, many of which
also participate in the quality control programs of ERDA. It is,
therefore, essential that the measurements being made and the calibrated
samples being distributed by the two Federal agencies involved in en-
vironmental radiation monitoring be in close agreement. To ascertain
whether such agreement exists, calibrated samples were exchanged by
the two laboratories. The Quality Assurance Branch, NERC-LV, submitted
calibrated samples of 15 different radionuclides for measurement by the
HSL and the HSL submitted 8 different radioactive solutions to the
NERC-LV for analysis.
The measurement of the samples supplied by the NBS requires, in
addition to the measurement of activity, a qualitative and quantitative
analysis of radionuclide impurities and a rigorous analysis of errors.
A questionnaire, typical of those which accompany each NBS sample, is
shown in the Appendix.
The counting instruments utilized for the routine calibration of
low-level radioactive samples and for the traceability studies with the
NBS include:
1. A 4-inch by 4-inch Nal well crystal coupled to a 400 channel
Technical Measurements Corporation Model 404c multichannel
analyzer. (Figure 1)
2. A 16% efficient Ge(Li) coaxial detector coupled to a Nuclear
Data 4096 channel analyzer using an Ortec Model 452 linear
amplifier. (Figure 2)
3. A Beckman LS-100 liquid scintillation counter.
The measurement of the gamma emitting radionuclides in the indirect
traceability studies involved the determination of the total activity of
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Figure 1. 4-inch by 4-inch Nal Well Crystal
Coupled to a Multichannel Analyzer
Figure 2. Ge(Li) Coaxial Detector Coupled to a Channel
Analyzer Using a Linear Amplifier
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the ampul supplied by the NBS and the activity per gram of solution.
The selection of the counting instrument(s) and the method(s) of analy-
sis used for the studies were made on an individual basis.
The measurements of cesium-137, cadmium-109, and selenium-75 were
done on the Ge(Li) system while chromium-51 and mercury-203 were meas-
ured using a Nal system. Determination of the total activity per ampul
was accomplished by making replicate measurements of each of the ampuls
supplied by the NBS. To determine the activity per gram of solution,
each NBS ampul was opened, diluted, and 5-ml aliquots of the dilution
prepared and counted. The gamma emission rate of each of these aliquots
was then determined by comparing their gamma-emission rates with those
of the appropriate standard(s).
For cesium-137 an NBS cesium-137 standard, calibrated for emission
rate, was utilized. The activity of the chromium-51 sample was deter-
mined using a chromium-51 standard (Amersham-Searle) calibrated for
activity. In the case of cadmium-109, a cadmium-109 standard (Labora-
toire de Metro!ogie des Rayonnements lonisants), calibrated for activity,
as well as an NBS mixed radionuclide standard, calibrated for emission
rate, was employed. The gamma emission rate of mercury-203 was deter-
mined using a mercury-203 standard (Amersham-Searle) calibrated for
activity. The activity of selenium-75 was determined by comparing the
gamma emission rate using a mercury-203 standard (Amersham-Searle), an
NBS cobalt-57 standard, and an aliquot of an Amersham-Searle cobalt-57
standard, all of which were calibrated for activity.
In addition to the gamma-emitting samples, a sample containing a
mixture of strontium-89 and strontium-90 was submitted by the NBS. The
activities per gram of solution for both strontium-89 and strontium-90
were measured on a Beckman LS-100 liquid scintillation counter. The
LS-100 was standardized using strontium-89 and strontium-90 standards
obtained from Amersham-Searle. The Cerenkov method of counting was
employed both for standardization and sample analysis of strontium-89
and yttrium-90 (2). The unknown strontium-89 and strontium-90 mixture
was received from the NBS in a sealed glass ampul. The ampul was opened
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and the contents transferred to a tared 100-ml volumetric flask. The
flask and sample were weighed, diluted using strontium-yttrium carrier
in 0.1N nitric acid solution and reweighed.
Five-tenths gram portions of the unknown NBS sample and the
strontium-89-90 mixture were measured using the LS-100. Five-tenths
gram portions of a known yttrium-88 and 0.5 ml of a known strontium-85
sample were measured using a Nal well counter. The yttrium-88 and
strontium-85 were used for yield determination. The yttrium was pre-
cipitated as a hydroxide three successive times for separation of the
strontium from the yttrium. The yttrium-88 was then counted using the
well counter and the yttrium-90 (of the known and NBS unknown) was
counted using the LS-100. The supernate of the NBS known and
strontium-85 samples were evaporated to approximately 10 ml and fuming
nitric acid was added to drop out the strontium nitrate. This step
was repeated. The strontium-85 was then counted in the well counter
and the strontium-89 in the LS-100. The counting efficiency using
Cerenkov radiation was 51 percent for yttrium-90, 0.1 percent for
strontium-90, and 26 percent for strontium-89.
The procedures used in the preparation and measurement of the EPA's
calibrated radioactive samples which were submitted to the NBS in the
direct traceability studies, and to HSL in the intercomparison study,
have been previously described (3).
RESULTS
The results of the direct traceability studies are summarized
in Table 1. These data indicate that the measurements of the five
radionuclide solutions prepared by the EPA's QA staff, MERC-LV, and
submitted to the NBS for assay were well within the desired plus or
minus 5%. In no case did the difference between the EPA's values and
those of the NBS [(NBS-EPA)/NBS x 100] exceed 2.4£.
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Table 1. RESULTS OF DIRECT TRACEABILITY STUDIES
EPA Measured NBS Measured
Activity Activity
Nuclide (dps/g) (dps/g) EPA/NBS
60Co .2210 ± 6%* 2196 ± 1.3%* 1.006
54Mn 2059 ± 9% 2066 ± 2.7% .997
65Zn 2200 ± 9% 2213 ± 2.3% .994
89Sr 237 ± 9% 239.2 ± 3.6% .989
90Sr 1179.3 ± 9% 1152 ± 2.5% 1.024
* Total error
A comparison of the data obtained by the EPA with that of the NBS
in the indirect traceability studies is shown in Table 2. The measure-
ments of the NBS solutions made by the EPA are in good agreement with
those of the NBS as indicated by the EPA/NBS ratios. With the exception
of selenium-75, the differences between NBS measurements and EPA meas-
urements range from minus 2.8 percent to plus 3 percent for cadmium-109.
Table 2, RESULTS OF INDIRECT TRACEABILITY STUDIES
EPA Measured NBS Measured
Nuclide Activity3 Activity9 EPA/NBS
109Cd 1.16xl05YS-1g-1±5.6%, 1 .igexlO^s'V1!! .88% .970
1.23xl05YS'1g'1±1.5%D 1.028
75Se 36yCi g-1+20% 39.19±1.03yCi g'1 .919
-15%
189yCi±ll% 199.36yCi±2.6% .951
89Sr 90.08nts-1g~1±12% 90.36nts"1g~1±3% .997
90Sr 5.17nts'1g-1±3% 5.1nts~V1±3% 1.00
203Hq 85.1yCi g-1±13% 83.14yCi g-:±l% 1.024
51Cr 32.3yCi g-1±4.27% 31.81yCi g~l±1.5% 1.015
137Cs 1.22yCi g~1±2.4% 1.24yCi g-z±2.7% .981
a Uncertainties at 99.7% CL
b From total activity of source
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The data obtained from the interchange of samples between the
NERC-LV and HSL are summarized in Tables 3 and 4. As with the NBS
studies, there is generally good agreement between the measurements
of the 16 different radionuclides made by the two laboratories.
Table 3. RESULTS OF INTERCOMPARISON STUDIES WITH THE HSL
(Sample Prepared by EPA - Measured by HSL)
Nuclide
EPA Measured
Activity
(dpm g"1)
HSL Measured
Activity
(dpm g"1x
EPA/HSL
22Na
46Sc
5"Mn
58Co
60Co
63Ni
65Zn
85Sr
89Sr
90Sr
103Ru
106Ru
124Sb
137Cs
140Ba
1
4
1
1
2
3
1
7
4
1
1
2
5
3
2
.73
.31
.81
.38
.47
.51
.81
.92
.77
.14
.37
.59
.57
.81
.07
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
104
104
104
10"
104
104
104
103
103
105
10"
104
104
104
104
1
4
1
1
2
3
1
8
4
1
1
2
5
3
2
.69 ±
.30 ±
.91 ±
.38 ±
.47 ±
.37 ±
.91 ±
.07 ±
.66 ±
.17 ±
.40 ±
.45 ±
.27 ±
.90 ±
.03 ±
0.04
0.05
0.02
0.01
0.04
0.03
0.04
0.07
0.09
0.02
0.02
0.07
0.04
0.01
0.03
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
10"
104
104
104
104
104
104
103
103
105
104
104
104
104
104
1
1
0
1
1
1
0
0
1
0
0
1
1
0
1
.03
.00
.95
.00
.00
.04
.95
.98
.02
.97
.98
.06
.06
.98
.02
Uncertainties at ± la CL
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Table 4. RESULTS OF INTERCOMPARISON STUDIES WITH THE HSL
(Samples Prepared by HSL - Measured by EPA)
EPA Measured HSL Measured
Activity Activity
Nuclide (dpm g"1) (dpm g"1) EPA/HSL
137Cs 3.44 x 10" ± 3% 3.44 x 10" 1.00
5"Mn 4.88 x 10" ± 3% 4.99 x 10" .978
65Zn 1.02 * 10** ± 4% 1.08 x 10* .944
88Y 3.09 x 10" ± 2% 3.11 x 10" .994
60Co 3.48 x 10" ± 2% 3.54 x 10" .983
90Sr 2.10 ± 0.02 x 10" 2.26 ± 0.05 x 10" .929
89Sr* 3.43 ± 0.08 x 10" 4.92 ± 0.07 x 10" *
Uncertainties at la CL
* +5.18 x io3 strontium-90 contamination.
SUMMARY AND CONCLUSIONS
Direct and indirect traceability studies with the MBS, as well as
intercomparison studies with the HSL, have been conducted by the EPA's
Quality Assurance Branch, NERC-LV. Direct traceability studies have
been made for five radionuclides: manganese-54, cobalt-60, zinc-65,
strontium-89, and strontium-90. In addition, indirect traceability
studies with the NBS have been made for seven radionuclides: chromium-
51, selenium-75, strontium-89, strontium-90, cadmium-109, cesium-137,
and mercury-203. As indicated by EPA/MBS ratios, all of the EPA
measurements, with the exception of the activity per unit mass deter-
mination of selenium-75, have agreed with those of the NBS within the
desired plus or minus 5 percent.
Intercomparison studies, involving the exchange and measurement
of calibrated radioactive samples by the HSL and the NERC-LV indicate
good agreement between the two laboratories. With the exception of
zinc-65 and strontium-90, the measurements of the two laboratories
do not differ by more than plus or minus 5 percent.
10
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These results indicate that the QA Branch, NERC-LV, has the
facilities, instruments, staff, and expertise required to measure
aqueous solutions of nine different radionuclides to within plus or
minus 5 percent of the NBS values. The traceability studies with NBS
are on a continuing basis. Measurements of four additional radionuclide
solutions prepared by NBS (carbon-14, iron-59, silver-HOm, and
cesium-134) are currently in progress.
11
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REFERENCES
Cavallo, L. M., et al.s "Needs for Radioactivity Standards and
Measurements in Different Fields," Nuol. lustrum. Methods,
112(1J2):5) K. Siegbahn-Uppsala, ed, North-Holland Pub. Co.,
Amsterdam, September/October 1973.
Randolph, R. B., "Determination fo Strontium-90 and Strontium-89
by Cerenkov and Liquid-Scintillation Counting," Int. J. Appl.
Radiat. Isotopes, 26:9, 1975.
Radioactivity Standards Distribution Program, 1973-1974,
EPA-680/4-73-001a, National Environmental Research Center,
Las Vegas, Nevada, 1974.
12
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APPENDIX. QUESTIONNAIRE SUPPLIED WITH UNKNOWN SAMPLES
IN THE EPA-NBS TRACEABILITY STUDIES
U.S. DEPARTMENT OF COMMERCE
[Manorial Bureau of Standards
V.'3sn,r,g:on. Q C. 20234
Instruction Sheet
I. Questionnaire
A. Please read questionnaire through before proceeding.
B. Quantify material as soon aa possible after receipt.
C, Please answer questions, fill in blanks or add any information
you feel might be helpful in diagnosing difficulties or be
helpful to other participants.
D. A certificate will be issued upon return of questionnaire,
therefore the sainple can also be used as a standard reference
material.
E. Please return your completed questionnaire before , November 151
to the
Radioactivity Section
National Sureau of Standards
Room C-114, Rad P
feshington, D.C. 20234
F. Enclosed is a copy of a t-distribution table for your use.
II. Measurement
A. Check for radlonuclidic irrpurities, id-ntify and qaar.tify.
B. Determine activity of the sample.
C. Make corrections for the ir-puri; ie s.
D. Enter results on cue st ior.r.aire .
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AIF-NBS Quality Assurance Program
Round ix: October, 1974
IRON-59
Questionnaire
I. Impurities
A. Did you identify (a) radionuclidic impurity (ies)?_
B. What is (are) the impurity (ies) and the relative amount (s)7
C. How did you identify and measure the impurity(ies)?
D. List the half-life(s) and other decay scheme parameters used in
pv^ Inat in pp t"hp irnnm—f f-v fsl .
evaluating the impurity(s).
14
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II. Calibration P-esulcs: Activity per groj) of soluClon.
A. Mlcrocuries per gram of solution at 1200 EST October 24
13, Uncertainty In the yalue of the activity i
1, The standard error,
Z. The 99% confidence lirr.:'.-, (.tn-l) (standard error), Is
measure-
f/on
source!s
(s).
3. The total estimated ;y - t^tnat ic error is
which is comprised c-"
7, due to
_?„ due to
70 due to
70 due to
_ana
_and
_and
and
combined?
15
-------
( 4 )
5. How are the random and systematic errors combined?
Ill, Method of Calibration; Activity per gram of solution,
A, Describe calibration technique used. Please be explicits Your
description could be very important in the analysis of the results.
Use the reverse side of this sheet if necessary,.
16
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B.
'our activi
C. List corrections made and order of magnitude (and, uncertainties).
D. Please describe in detail the technique(s) used for preparing
your counting source (s).
1. How many sources did you prepare?
2. Kow ir.any sources did you measure?
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If i± standard was used (for comparison or efficiency determination,
etc.) please give the following information:
1. Uiat standard was used?
2. Chemical form
3. Physical form
4. Accuracy statement supplied with standard
5. Describe your use of this standard
IV. Calibration Results. Total activity in the ampoule^
A. Microcuries in ampoule at 1200 EST October 24
3. Uncertainty in the value of the activity is .
1. The standard error is
2. The 99% confidence limit is based on
measurements of/on source (s)«
3. The total estimated systematic error is which
is comprised of
% due to and
_7o due to and
7° due to and
7, due to
4. How are the systematic errors combined?
-------
( 7 )
5. How are the random and systematic errors combined?
V. Method of Calibration. Total activity in the ampoule.
A. Describe calibration technique used. Please be explicit.
Your description could be very Important in the analysis of
the results. Use the reverse side of this sheet if necessary.
B. Please list the decay scheme parameters (with their uncertainties)
used in determining your activity value.
19
-------
( 8 )
C0 List corrections made and order of magnitude.,
D. If a standard was used (for comparison or efficiency determina-
tion, etc.) please give the following information:
1. Uiat standard was used?
2. Chemical form
3. Physical form
4. Accuracy statement supplied with standard
5. Describe your use of this standard
20
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TECHNICAL REPORT DATA
(Please read Inslructions on the reverse before completing)
1 REPORT NO.
EPA-600/4-75-014
3. RECIPIENT'S ACCESSI Of* NO.
4 TITLE AND SUBTITLE
RADIATION QUALITY ASSURANCE INTERCOMPARISON STUDIES
1974-1975
5. REPORT DATE
October 1975
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
Quality Assurance Branch
'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.
1HA327
11. CONTRACT/GRANT NO.
in-house report
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13 TYPE OF REPORT AND PERIOD COVERED
Interim 1974-1975
14.
SPONSORING A
EPA-ORD, "
INCY CODE
ice of Monitor-
ing and Technical Support
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The Quality Assurance Branch of the Monitoring Systems Research and Development
Division at the U.S. Environmental Protection Agency's Environmental Monitoring
and Support Laboratory-Las Vegas prepares and distributes calibrated low-level
radioactive solutions to Federal, State, and private laboratories involved in
environmental radiation monitoring and surveillance. These solutions are utilized
for both the calibration of counting instruments and chemical yield determinations.
Since the laboratories using these samples must have confidence in their accuracy,
the Quality Assurance Branch has instituted intercomparison studies with the
National Bureau of Standards and with the Energy Research and Development Adminis-
tration Health and Service Laboratory. The results of the studies conducted during
1974 and 1975 are described.
17.
j.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
quality assurance
quali ty control
radioactivity
calibra ting
standards
i sotopes
radiochemistry
b. IDENTIFIERS/OPEN ENDEDTERMS
traceability
c. COSATI I-'ield/Group
07E
14B
14D
18B
18H
S DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19 SECURITY CLASS /This Report/
unclassified
21. NO. OF PAGES
28
10 SECURITY CLASS {This page/
unclassified
22. PRICE
EPA Form 2220-1 (9-73)
O 967-369
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