ASTM E692-00
(Test Method)Standard Test Method for Determining the Content of Cesium-137 in Irradiated Nuclear Fuels by High-Resolution Gamma-Ray Spectral Analysis
Standard Test Method for Determining the Content of Cesium-137 in Irradiated Nuclear Fuels by High-Resolution Gamma-Ray Spectral Analysis
SIGNIFICANCE AND USE
This test method uses a high-resolution gamma-ray spectrometer as a basis for measuring the gamma-ray emission rate of 137Cs-137mBa in a dilute nitric acid solution containing 10 mg/L of cesium carrier. No chemical separation of the cesium from the dissolved-fuel solution is required. The principal steps consist of diluting a weighed aliquot of the dissolved-fuel solution with a known mass of 1 M nitric acid (HNO3) and measuring the 662 keV gamma-ray count rate from the sample, then measuring the 662 keV gamma-ray count rate from a standard source that has the same physical form and counting geometry as the sample.
The amount of fuel sample required for the analysis is small. For a sample containing 1 mg of fuel irradiated to one atom percent fission, a net count rate of approximately 103 counts per second will be observed for a counting geometry that yields a full-energy peak efficiency fraction of 1 × 10-3. The advantage of this small amount of sample is that the concentration of fuel material can be kept at levels well below 1 g/L, which results in negligible self-absorption in the sample aliquot and a small radiation hazard to the analyst.
SCOPE
1.1 This test method covers the determination of the number of atoms of Cs in aqueous solutions of irradiated uranium and plutonium nuclear fuel. To minimize interference from short-lived fission products, the fuel should decay 4 months or more prior to the gamma-ray emission-rate measurement.
1.2 When combined with a method for determining the initial number of fissile atoms in the fuel, the results of this analysis allows atom percent fission (burnup) to be calculated. The determination of atom percent fission, uranium and plutonium concentrations, and isotopic abundances are covered in Test Methods E267 and E321.
1.3 Cs is not suitable as a fission monitor for samples that may have lost cesium during reactor operation. For example, a large temperature gradient enhances Cs migration from the fuel region to cooler regions such as the radial fuel-clad gap, or to a lesser extent, towards the axial fuel end.
1.4 The Cs distribution may be ascertained by an axial gamma-ray scan of the fuel element to be assayed. In a mixed-oxide fuel, comparison of the Cs distribution with the distribution of nonmigrating fission-product nuclides such as Zr or Ce would indicate the relative degree of Cs migration. A nonuniform Cs distribution should alert the analyst to the potential loss of the fission nuclide.
1.5 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E692–00
Standard Test Method for
Determining the Content of Cesium-137 in Irradiated Nuclear
Fuels by High-Resolution Gamma-Ray Spectral Analysis
This standard is issued under the fixed designation E 692; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 267 Test Method for Uranium and Plutonium Concentra-
tions and Isotopic Abundances
1.1 Thistestmethodcoversthedeterminationofthenumber
E 321 Test Method for Atom Percent Fission in Uranium
of atoms of Cs in aqueous solutions of irradiated uranium
And Plutonium Fuel (Neodymium-148 Method)
and plutonium nuclear fuel.When combined with a method for
determining the initial number of fissile atoms in the fuel, the
3. Summary of Test Method
results of this analysis allows atom percent fission (burnup) to
2 3.1 Cs is assayed by measuring the 662 keV gamma-ray
be calculated (1). The determination of atom percent fission,
emissionratefromtheisomerictransitionofitsmetastable2.6
uranium and plutonium concentrations, and isotopic abun-
137m
min Ba daughter, using a high-resolution germanium
dances are covered in Test Methods E 267 and E 321.
detector and multichannel pulse-height analyzer. Refer to Test
1.2 Csisnotsuitableasafissionmonitorforsamplesthat
Methods E 181.
may have lost cesium during reactor operation. For example, a
3.2 The number of atoms of Cs in a sample is computed
large temperature gradient enhances Cs migration from the
from the measured net gamma-ray count rate relative to the
fuel region to cooler regions such as the radial fuel-clad gap,
measured net gamma-ray count rate from a standard Cs
or, to a lesser extent, towards the axial fuel end.
solution.
1.3 A nonuniform Cs distribution should alert the
analyst to the potential loss of the fission product nuclide. The
4. Significance and Use
Cs distribution may be ascertained by an axial gamma-ray
4.1 This test method uses a high-resolution gamma-ray
scan of the fuel element to be assayed. In a mixed-oxide fuel,
spectrometer as a basis for measuring the gamma-ray emission
comparison of the Cs distribution with the distribution of
137 137m
95 144 rate of Cs- Ba in a dilute nitric acid solution containing
nonmigrating fission-product nuclides such as Zr or Ce
10 mg/L of cesium carrier. No chemical separation of the
would indicate the relative degree of Cs migration.
cesium from the dissolved-fuel solution is required. The
1.4 This standard does not purport to address all of the
principal steps consist of diluting a weighed aliquot of the
safety concerns, if any, associated with its use. It is the
dissolved-fuel solution with a known mass of 1 M nitric acid
responsibility of the user of this standard to establish appro-
(HNO ) and measuring the 662 keV gamma-ray count rate
priate safety and health practices and determine the applica-
from the sample, then measuring the 662 keV gamma-ray
bility of regulatory limitations prior to use.
count rate from a standard source that has the same physical
2. Referenced Documents form and counting geometry as the sample.
4.2 The amount of fuel sample required for the analysis is
2.1 ASTM Standards:
small. For a sample containing 1 mg of fuel irradiated to one
E 170 Terminology Relating to Radiation Measurements
3 atom percent fission, a net count rate of approximately 10
and Dosimetry
counts per second will be observed for a counting geometry
E 181 GeneralMethodsforDetectorCalibrationandAnaly-
-3
3 that yields a full-energy peak efficiency fraction of 1 3 10 .
sis of Radionuclides
The advantage of this small amount of sample is that the
E 219 Test Method for Atom Percent Fission in Uranium
3 concentration of fuel material can be kept at levels well below
Fuel (Radiochemical Method)
1 g/L, which results in negligible self-absorption in the sample
aliquot and a small radiation hazard to the analyst.
ThistestmethodisunderthejurisdictionofASTMCommitteeE-10onNuclear
Technology and Applications and is the direct responsibility of Subcommittee
E10.05 on Nuclear Radiation Metrology. The energy of the gamma ray is more precisely given in Reference (2) as
Current edition approved March 10, 2000. Published May 2000. Originally 661.657keV.Forsimplicity,allcitationsofthisenergyinthisstandardwillbegiven
published as E 692-79. Last previous edition E 692-98. as 662 keV.
2 5
The boldface numbers in parentheses refer to the list of references at the end of The half-life of this state is more precisely given in Reference (3) as 2.552 min.
this test method. Forsimplicity,allcitationsofthishalf-lifelistedinthisstandardwillbegivenas2.6
Annual Book of ASTM Standards, Vol 12.02. min.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E692
5. Precautions atoms per gram of standard should have been determined by
isotope-dilution mass spectrometry.An aliquot of not less than
5.1 Interferences from other gamma-emitting fission prod-
0.1 g of the standard solution, weighed to 6 0.1 mg, is diluted
ucts are lessened by the use of a germanium detector with a
tototalmassof10.00gwith1MHNO inasamplevial,which
minimum resolution of 3 keV full-width at half-maximum
is then flame-sealed. A series of working standards with
(FWHM) at 1332 keV, and by allowing 4 months or more for
different concentrations should be prepared so that a working
the sample to decay prior to measurement (4). Under these
standard may be selected that will have approximately the
conditions, the gamma rays nearest to the 662 keV gamma ray
137m 125
same number of Cs atoms as the sample to be measured.
of Ba will be the 637 keV gamma ray of Sb and the
697 keV gamma ray of Pr.
6. Apparatus
5.2 Aslight complication of this test method is that the 662
6.1 Germanium Detector, with minimum resolution capa-
keV gamma ray is superimposed on the Compton edge from
bilityof3keVFWHMat1332keV,andassociatedelectronics.
the766keVgammarayof Nbandfromthe796keVgamma
6.2 Multichannel Pulse-Height Analyzer, capable of a con-
ray of Cs, as shown in Fig. 1.
version ratio of 1 keV per channel (channel number versus
5.3 Thistestmethodrequiresaccuratelyweighinganaliquot
gamma-ray energy in kiloelectronvolts).
of the sample of fuel material containing sufficient Cs-
137m
Ba activity into a sample vial. In order to achieve the
7. Reagents and Materials
precision of which this test method is capable, the analyst
should exercise great care when preparing the sample. To 7.1 Cesium-137 Standard Solution—NBS SRM 4233, cer-
tified for Cs atoms per gram contents.
reduce the uncertainty associated with the sample quantity,
aliquots should be prepared by weighing to an accurac
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