ASTM C1221-92(2004)
(Test Method)Standard Test Method for Nondestructive Analysis of Special Nuclear Materials in Homogeneous Solutions by Gamma-Ray Spectrometry
Standard Test Method for Nondestructive Analysis of Special Nuclear Materials in Homogeneous Solutions by Gamma-Ray Spectrometry
SIGNIFICANCE AND USE
This test method is a nondestructive means of determining the nuclide concentration of a solution for special nuclear material accountancy, nuclear safety, and process control.
It is assumed that the nuclide to be analyzed is in a homogeneous solution (Practice C 1168).
The transmission correction makes the test method independent of matrix and useful over several orders of magnitude of nuclide concentrations. However, a typical configuration will normally span only two to three orders of magnitude.
The test method assumes that the sample-detector geometry is the same for all measured items. This can be accomplished by requiring that the liquid height in the sidelooking geometry exceeds the detector field of view defined by the collimator. For the uplooking geometry, a fixed sample fill height must be maintained and vials of identical radii must be used unless the vial radius exceeds the field of view defined by the collimator.
Since gamma-ray systems can be automated, the test method can be rapid, reliable, and not labor intensive.
This test method may be applicable to in-line or off-line situations.
SCOPE
1.1 This test method covers the determination of the concentration of gamma-ray emitting special nuclear materials dissolved in homogeneous solutions. The test method corrects for gamma-ray attenuation by the sample and its container by measurement of the transmission of a beam of gamma rays from an external source (Refs. (1), (2), and (3)).
1.2 Two sample geometries, slab and cylinder, are considered. The sample container that determines the geometry may be either a removable or a fixed geometry container. This test method is limited to sample containers having walls or a top and bottom of equal transmission through which the gamma rays from the external transmission correction source must pass.
1.3 This test method is typically applied to radionuclide concentrations ranging from a few milligrams per litre to several hundred grams per litre. The assay range will be a function of the specific activity of the nuclide of interest, the physical characteristics of the sample container, counting equipment considerations, assay gamma-ray energies, sample matrix, gamma-ray branching ratios, and interferences.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazards, see Section 9.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation: C1221 – 92 (Reapproved 2004)
Standard Test Method for
Nondestructive Analysis of Special Nuclear Materials in
Homogeneous Solutions by Gamma-Ray Spectrometry
This standard is issued under the fixed designation C1221; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope C982 Guide for Selecting Components for Energy-
Dispersive X-Ray Fluorescence (XRF) Systems
1.1 This test method covers the determination of the con-
C1133 Test Method for Nondestructive Assay of Special
centration of gamma-ray emitting special nuclear materials
Nuclear Material in Low-Density Scrap and Waste by
dissolved in homogeneous solutions. The test method corrects
Segmented Passive Gamma-Ray Scanning
for gamma-ray attenuation by the sample and its container by
C1168 Practice for Preparation and Dissolution of Pluto-
measurement of the transmission of a beam of gamma rays
nium Materials for Analysis
from an external source (Refs. (1), (2), and (3)).
E181 TestMethodsforDetectorCalibrationandAnalysisof
1.2 Two sample geometries, slab and cylinder, are consid-
Radionuclides
ered. The sample container that determines the geometry may
2.2 ANSI Standards:
be either a removable or a fixed geometry container. This test
ANSI N15.20 Guide to Calibrating Nondestructive Assay
method is limited to sample containers having walls or a top
Systems
and bottom of equal transmission through which the gamma
ANSI N15.35 Guide to Preparing Calibration Material for
rays from the external transmission correction source must
NondestructiveAssaySystemsthatCountPassiveGamma
pass.
Rays
1.3 This test method is typically applied to radionuclide
ANSI N15.37 Guide to the Automation of Nondestructive
concentrations ranging from a few milligrams per litre to
Assay Systems for Nuclear Material Control
several hundred grams per litre. The assay range will be a
ANSI/IEEE 645 Test Procedures for High-Purity Germa-
function of the specific activity of the nuclide of interest, the
nium Detectors for Ionizing Radiation
physical characteristics of the sample container, counting
2.3 U.S. Nuclear Regulatory Commission Regulatory
equipment considerations, assay gamma-ray energies, sample
Guides:
matrix, gamma-ray branching ratios, and interferences.
Regulatory Guide 5.9, Rev. 2, Guidelines for Germanium
1.4 This standard does not purport to address all of the
Spectroscopy Systems for Measurement of Special
safety concerns, if any, associated with its use. It is the
Nuclear Materials
responsibility of the user of this standard to establish appro-
Regulatory Guide 5.53, Rev. 1, Qualification, Calibration,
priate safety and health practices and determine the applica-
and Error Estimation Methods for Nondestructive Assay
bility of regulatory limitations prior to use. For specific
hazards, see Section 9.
3. Terminology
2. Referenced Documents 3.1 Fordefinitionsoftermsusedinthistestmethod,referto
3 Terminology C859.
2.1 ASTM Standards:
C859 Terminology Relating to Nuclear Materials
4. Summary of Test Method
4.1 Manynuclearmaterialsspontaneouslyemitgammarays
ThistestmethodisunderthejurisdictionofASTMCommitteeC26onNuclear
with energies and intensities characteristic of the decaying
Fuel Cycle and is the direct responsibility of Subcommittee C26.10 on Non-
nuclide. The analysis for these nuclear materials is accom-
Destructive Assay.
plished by selecting appropriate gamma rays and measuring
CurrenteditionapprovedJune1,2004.PublishedJuly2004.Originallyapproved
their intensity to identify and quantify the nuclide.
in 1992. Last previous edition approved in 1998 as C1221-92 (1998). DOI:
10.1520/C1221-92R04.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this test method. Withdrawn. The last approved version of this historical standard is referenced
For referenced ASTM standards, visit the ASTM website, www.astm.org, or on www.astm.org.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
Standards volume information, refer to the standard’s Document Summary page on 4th Floor, New York, NY 10036.
the ASTM website. Available from U.S. Nuclear Regulatory Commission,Washington, DC 20555.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1221 – 92 (2004)
4.1.1 The gamma-ray spectrum of a portion of solution is
obtained with a collimated, high resolution gamma-ray detec-
tor.
4.1.2 Count-rate-dependent losses are determined and cor-
rections are made for these losses.
4.1.3 A correction factor for gamma-ray attenuation in the
sample and its container is determined from the measurement
of the transmitted intensity of an external gamma-ray source.
The gamma rays from the external source have energies close
to those of the assay gamma rays emitted from the sample.
Figs.1and2illustratetypicaltransmissionsource,sample,and
detector configurations. Gamma rays useful for assays of U
and Pu are listed in Table 1.
4.1.4 The relationship between the measured gamma-ray
intensity and the nuclide concentration (the calibration con-
NOTE 1—The sample geometry in this case is a slab. (Not to scale.)
stant) is determined by use of appropriate standards
FIG. 2 Schematic of an Uplooking Configuration
(ANSIN15.20, ANSIN15.35, USNRC Regulatory Guide
5.53, Rev. 1).
TABLE 1 Suggested Nuclide/Source Combinations
4.2 In the event that the total element concentration is
Count
desired and only one isotope of an element is determined (for
Peak Peak Peak
Transmission Rate
Nuclide Energy Energy Energy
example, Pu), the isotopic ratios must be measured or
Source Correction
(keV) (keV) (keV)
estimated.
Source
235 169 241
U 185.7 Yb 177.2 Am 59.5
5. Significance and Use 198.0
239 75 133
Pu 413.7 Se 400.1 Ba 356.3
5.1 Thistestmethodisanondestructivemeansofdetermin- 239 57 109
Pu 129.3 Co 122.1 Cd 88.0
ing the nuclide concentration of a solution for special nuclear 136.5
material accountancy, nuclear safety, and process control.
5.2 It is assumed that the nuclide to be analyzed is in a
homogeneous solution (Practice C1168).
5.5 Since gamma-ray systems can be automated, the test
5.3 The transmission correction makes the test method
method can be rapid, reliable, and not labor intensive.
independent of matrix and useful over several orders of
5.6 This test method may be applicable to in-line or off-line
magnitude of nuclide concentrations. However, a typical con-
situations.
figuration will normally span only two to three orders of
magnitude.
6. Interferences
5.4 The test method assumes that the sample-detector ge-
6.1 Radionuclides may be present in the sample, which
ometry is the same for all measured items. This can be
produce gamma rays with energies that are the same or very
accomplished by requiring that the liquid height in the side-
nearly the same as the gamma rays suggested for nuclide
lookinggeometryexceedsthedetectorfieldofviewdefinedby
measurement,countratecorrection,ortransmissioncorrection.
the collimator. For the uplooking geometry, a fixed sample fill
Thus,thecorrespondingpeaksinthegamma-rayspectrummay
height must be maintained and vials of identical radii must be
be unresolved and their areas may not be easily determined
usedunlessthevialradiusexceedsthefieldofviewdefinedby
unless multiplet fitting techniques are used. In some cases, the
the collimator.
nuclideofinterestmayemitothergammaraysthatcanbeused
foranalysisoralternativetransmissionorcountratecorrection
sources may be used.
6.1.1 Occasionally,asignificantamountof Npisfoundin
237 233
aplutoniumsample.The Npdaughter, Pa,emitsagamma
rayat415.8keVaswellasothergammaraysinthe300to400
keV region. These Pa gamma rays may interfere with the
analysis of Pu at 413.7 keV and at several other normally
useful Pugamma-rayenergies.Inthiscase,the Pugamma
ray at 129.3 keV may be a reasonable alternative. In addition,
the 398.7 keV gamma ray from Pa may interfere with the
transmission corrections based on the 400.7 keV Se gamma-
ray measurements. Multiplet fitting techniques can resolve
these problems.
169 235
6.1.2 Yb,usedasthetransmissionsourcefor Uassays,
NOTE 1—Thesamplegeometrymaybeeithercylindricaloraslab.(Not
emits a 63.1 keV gamma ray that may interfere with the
to scale.)
FIG. 1 Schematic of a Sidelooking Configuration measurementoftheareaofthepeakproducedbythe59.5keV
C1221 – 92 (2004)
gamma ray of Am, which is commonly used as the count schedules. These time-dependent backgrounds might not be
rate correction source. The 63.1 keV Yb gamma ray should detected if the background is checked at the same time each
day.
be attenuated by placing a cadmium absorber over the trans-
6.3 High-energy gamma rays from fission products in the
mission source. Cd may be a suitable alternative count rate
samplewillincreasetheComptonbackgroundanddecreasethe
correction source.
239 75
precision of gamma-ray intensity measurements in the lower
6.1.3 In the special case of Pu assays using Se as a
energy (<500 keV) region of the spectrum.
transmission source, random coincident summing of the 136.0
6.4 Low energy X- and gamma rays from either the trans-
and279.5keVgamma-rayemissionsfrom Seproducesalow
mission or count rate correction source may contribute signifi-
intensity sum peak at 415.5 keV that interferes with the peak
cantly to the total system electronic pulse rate causing in-
area calculation for the peak produced by the 413.7 keV
creased count rate losses and sum peak interferences. An
gamma ray from Pu. The effects of this sum peak interfer-
absorber should be fixed between the source and detector to
ence can be reduced by using absorbers to attenuate the
reduce the number of low energy X-rays detected.
radiation from the Se to the lowest intensity required for
transmission measurements of acceptable precision. The prob-
7. Apparatus
lem can be avoided entirely by making two separate measure-
7.1 General guidelines for selection of detectors and signal-
ments on each sample; first, measure the peak area of the
processing electronics are discussed in Guide C982 and NRC
transmission source with the sample in place and second,
Regulatory Guide 5.9, Rev. 2. Data acquisition systems are
measure the peak area of the assay gamma ray while the
considered in ANSIN15.37 and NRC Regulatory Guide 5.9,
detector is shielded from the transmission source.
Rev. 2. It is recommended that the system have the following
239 241
6.1.4 In Pu solutions with high activities of Am
components:
or U, or both, the Compton continuum from intense 208.0
7.1.1 High Resolution, Germanium, Gamma-Ray
keV gamma rays may make the 129.3 keV gamma ray from
Detector—A coaxial-type detector with full width at half
Pu unusable for assays. Also, the 416.0 keV sum peak that
maximum (FWHM) resolution typically less than 850 keV at
resultsfrompileupofthe208.0keVgammaraysmayinterfere
122keVandlessthan2.0keVat1333keVmaybeusedforthe
with the 413.7 keV gamma ray from Pu. Use an absorber
analysis. A planar-type detector with resolution typically less
(for example, 0.5 to 0.8 mm of tungsten) between the detector
than600keVFWHMat122keVmayalsobeused.Thestated
and sample to attenuate the 208.0 keV gamma rays. This will
resolutions are for guidance only. The selection of detector
attenuatetheintensityofthelowerenergygammaraysandalso
type, coaxial or planar, should be based on the usual consid-
reduce the sum peak interference. The resulting Pu assay
erations of efficiency and resolution required for the specific
will be based on the 413.7 keV gamma ray.
application. Test procedures for detectors are given in Test
6.1.5 X-rays of approximately 88 keV from lead in the Methods E181 and ANSI/IEEE 645.
shielding may interfere with the measurement of the 88.0 keV 7.1.2 Nuclear Spectroscopy Amplifier—The amplifier capa-
gamma-ray peak when Cd is used as the count rate correc-
bilities should include selectable pulse shaping time constants,
tion source. Graded shielding (4) is required to remove the pole zero adjustment, active gated baseline restoration, and
interference. pulse pileup rejection.Adiscussion of these functions is found
in Guide C982.
6.2 Peaks may appear in the spectrum at gamma-ray ener-
7.1.3 Oscilloscope, required for proper adjustment of the
gies used for analysis when there is no sample present. This
various amplifier controls and troubleshooting the electronics.
may be caused by excessive amounts of radioactive material
The oscilloscope should have selectable time bases ranging
storedinthevicinityofthedetectororbycontaminationofthe
from 1 ms/cm to 0.5 µs/cm (20 MHz) and selectable vertical
instrument. This can cause variable and unacceptably high
sensitivities ranging from 5 V/cm to 10 mV/cm.
backgrounds leading to poor measurement quality.
7.1.4 High Voltage Bias Supply,equippedwithcontinuously
6.2.1 Remove unnecessary radioactive material from the
adjustablevoltagecontrolwithavoltagerangecompatiblewith
vicinity and also restrain movement of radioactive material
the requirements of the above detector.
around the assay area during measurements. Shielding should
7.1.5 Count-Rate Meter, to monitor the total electronic
be provided that completely surrounds the detector with the
pulse rate in the system for acceptable rate. It should be
exception of the collimator opening. Shielding opposite the
compatible with the output of the above amplifier.
detector on the far side of the sample will also reduce the
7.1.6 Multichannel Analyzer (MCA)—An MCA with a
amount of ambient radiation incident on the detector.
minimumof4096datachannelsisrecommended.Theanalyzer
6.2.2 Use sample containers that are free of outer surface
should operate using a Wilkinson type analog-to-digital con-
contamination. Remove any contamination from the instru-
verter(ADC)withaminimumADCclockrateof100MHz,or
mentthatmayinterferewithanalyses.Itmaynotbepossibleto
afixedconversiontimeADCwithamaximumconversiontime
completelydecontaminatein-lineinstrumentation.Inthiscase,
of 10 µs. Anti-coincidence gating for pulse-pile-up rejection,
the contamination should be minimized to the extent practical.
compatible with the above amplifier, and signal level discrimi-
6.2.3 The measurement of background should be made at nation may be required. Analyzer control, data transfer, and
various times during the day. Varying backgrounds can be
dataanalysisbycomputerarerecommended.Spectrumdisp
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