ASTM C1030-95(2001)
(Test Method)Standard Test Method for Determination of Plutonium Isotopic Composition by Gamma-Ray Spectrometry
Standard Test Method for Determination of Plutonium Isotopic Composition by Gamma-Ray Spectrometry
SCOPE
1.1 This test method is applicable to the determination of isotopic abundances in isotopically homogeneous Pu-bearing materials. This test method may be applicable to other plutonium-bearing materials, some of which may require modifications to the described test method.
1.2 The procedure is applicable to sample sizes ranging from a few tenths of a gram up to the maximum sample weight allowed by criticality limits.
1.3 Because 242 Pu has no useful gamma-ray signature, its isotopic abundance is not determined. Isotopic correlation techniques may be used to estimate its relative abundance (Refs 1, 2).
1.4 This test method has been demonstrated in routine use for isotopic abundances ranging from 94 to 70% 239 Pu. This test method has also been employed for isotopic abundances outside this range.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: C 1030 – 95 (Reapproved 2001)
Standard Test Method for
Determination of Plutonium Isotopic Composition by
Gamma-Ray Spectrometry
This standard is issued under the fixed designation C 1030; 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 181 General Methods for Detector Calibration and Analy-
sis of Radionuclides
1.1 This test method is applicable to the determination of
E 267 Test Method for Uranium and Plutonium Concentra-
isotopic abundances in isotopically homogeneous Pu-bearing
tions and Isotopic Abundances
materials. This test method may be applicable to other
2.2 ANSI Standards:
plutonium-bearing materials, some of which may require
ANSI N15.22 Plutonium-Bearing Solids—Calibration
modifications to the described test method.
Techniques for Calorimetric Assay
1.2 The procedure is applicable to sample sizes ranging
ANSI N15.35 Guide to Preparing Calibration Material for
from a few tenths of a gram up to the maximum sample weight
Nondestructive Assay Systems that Count Passive Gamma
allowed by criticality limits.
Rays
1.3 Because Pu has no useful gamma-ray signature, its
isotopic abundance is not determined. Isotopic correlation
3. Summary of Test Method
techniques may be used to estimate its relative abundance
2 3.1 Relative intensities of gamma-rays from a plutonium
(Refs 1, 2).
sample are determined from a gamma-ray spectrum obtained
1.4 This test method has been demonstrated in routine use
with a high-resolution Ge detector.
for isotopic abundances ranging from 94 to 70 % Pu. This
3.2 The atom ratio, N /N , for isotopes i and j is related to the
i j
test method has also been employed for isotopic abundances
relative counting intensities, I and I , for the gamma-rays of
i j
outside this range.
energy D and E by:
i j
1.5 The values stated in SI units are to be regarded as the
standard. N I e
i i j
5 C · (1)
ij
N e I
1.6 This standard does not purport to address all of the j i j
safety concerns, if any, associated with its use. It is the
1/2
responsibility of the user of this standard to establish appro-
T B
i j
C 5 · (2)
ij 1/2
priate safety and health practices and determine the applica-
B
T i
j
bility of regulatory limitations prior to use.
where:
2. Referenced Documents
e = relative detection efficiency for a gamma-ray at
energy E,
2.1 ASTM Standards:
1/2
T = half-life, and
C 697 Test Methods for Chemical, Mass Spectrometric, and
B = gamma-ray branching intensity (usually expressed
Spectrochemical Analysis of Nuclear-Grade Plutonium
as the gamma-ray emission probability per disinte-
Dioxide Powders and Pellets
gration).
C 698 Test Methods for Chemical, Mass Spectrometric, and
3.3 The conversion factors, C , are computed from known
Spectrochemical Analysis of Nuclear-Grade Mixed Oxides ij
half-lives and gamma-ray branching intensities.
((U, Pu)O )
3.4 The relative detection efficiency, e, is a function of
C 982 Guide for Selecting Components for Energy-
gamma-ray energy and results from the combined effects of
Dispersive X-Ray Fluorescence (XRF) Systems
detector response, attenuation due to absorbers and container
walls, and self-absorption within the sample for gamma-rays of
differing energies. The relative detection efficiencies are deter-
This test method is under the jurisdiction of ASTM Committee C26 on Nuclear
Fuel Cycle and is the direct responsibility of Subcommittee C26.10 on Nondestruc-
mined for each sample from the observed gamma spectrum.
tive Assay.
Current edition approved Sept. 10, 1995. Published November 1995. Originally
published as C 1030 – 84. Last previous edition C 1030 – 89.
2 4
The boldface numbers in parentheses refer to the list of references at the end of Annual Book of ASTM Standards, Vol 12.02.
this standard. Available from the American National Standards Institute, 11 W. 42nd St., 13th
Annual Book of ASTM Standards, Vol 12.01. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 1030
TABLE 1 Gamma-Ray Interferences Due to Uranium in (Pu, U)O
4. Significance and Use 2
Materials
4.1 The determination of isotopic composition by gamma-
Branching
ray spectrometry is a nondestructive technique and when used
Energy Intensity
Isotope
with other nondestructive techniques, such as calorimetry or (keV) (%g/disinte-
gration)
neutron coincidence counting, can provide a totally destructive
143.77 10.7 U
plutonium assay necessary for material accountancy and safe-
163.36 4.85 U
guards needs.
185.72 56.1 U
4.2 Since gamma-ray spectrometry systems are typically
202.12 1.07 U
205.31 4.87 U
automated, the routine use of the test method is fast, reliable,
and is not labor intensive. Since the test method is nondestruc-
tive, requiring no sample preparation, it does not create waste
disposal problems.
affect the isotopic abundance determination. This is especially
4.3 This test method assumes that the isotopic composition
important for samples having high americium concentrations.
of plutonium in the sample being measured is homogeneous.
Summing of the intense 59.5-keV transition with other intense
4.4 The Pu abundance is not measured by this test method
gamma radiations produces spurious spectral peaks (3). Thin
and must be estimated from isotopic correlation techniques,
cadmium absorbers shall be placed on the front face of the
stream averages, historical information, or other measurement
detector to keep the height of the 59.5 keV gamma-ray peak
techniques.
equal to or less than the height of the most intense peaks in the
241 241 241 239
4.5 A daughter product of Pu is Am. The Am/ Pu
100-keV region.
atom ratio can also be determined by means of this test method
(assuming a homogeneous isotopic distribution of plutonium
6. Apparatus
and Am) and is necessary for the correct interpretation of a
6.1 Germanium Detector (with liquid nitrogen supply),
calorimetric heat measurement.
Preamplifier and High-Voltage Supply—Energy resolution of
4.6 The isotopic composition of a given batch or sample of
the detector for spectra collected below 400 keV should be
plutonium is an attribute of that sample and, once determined,
better than 600 eV full-width-at-half-maximum (FWHM) at
can be used in subsequent inventory measurements to verify
122 keV. Purchase specifications of 550 eV or less should
the identity of a sample within the measurement uncertainties.
ensure a working resolution of 600 eV or better. These
detectors are generally intrinsic, planar Ge of a few cubic
5. Interferences
centimeters active volume. For the energy regions above 400
5.1 Due to the finite resolution of even the best quality of
keV, a large volume Ge detector with an active volume of 40
germanium detectors, the presence of other gamma-emitting cm or greater and with resolution of 2.0 keV or better at 1332
sources must be assessed for their effects on the isotopic
keV is preferred.
abundance determination. 6.2 Linear Amplifier, Analog-to-Digital Converter (ADC),
5.1.1 The germanium detector used for the spectral mea- Multichannel Pulse-Height Analyzer (MCA)—The ADC-MCA
surements shall be adequately shielded from other nearby combination shall be capable of at least 4K channel conversion
plutonium sources. Background spectra shall be collected to and storage. More detailed descriptions of these components
ensure the effectiveness of detector shielding and to identify can be found in Guide C 982.
the background radiations. 6.3 High count rate applications require the use of pile-up
5.1.2 If fission products are present in the sample being rejection circuitry. Digital stabilization may be desirable for
measured, they will contribute additional gamma-ray spectral long count times or poor environmental control to ensure the
peaks. These peaks occur mainly in the 500 to 800-keV energy quality of the spectral data.
range and may affect the intensity determination of plutonium 6.4 Because of the complexity of plutonium spectra, data
and americium peaks in this region. These high-energy reduction is usually performed by computer. Several software
gamma-rays from fission products also produce contributions codes are available that perform the spectral analysis and
to the Compton background below 500 keV that decrease the isotopic abundance calculations on a computer (Refs 4–9).
precision for peak intensity determination in this region. 6.5 All of the above apparatus is commercially available.
Electronic modules are either NIM standard or NIM compat-
5.1.3 For mixed plutonium-uranium oxide samples, the
appropriate corrections for the spectral peaks produced by ible. Many gamma-ray spectrometry systems are interfaced to
a computer. This permits the isotopic abundance determination
uranium gamma emission shall be applied. The main interfer-
procedure to be automated.
ences due to uranium are listed in Table 1.
5.1.4 Other interference-producing nuclides can be rou-
7. Precautions
tinely present in plutonium-bearing materials. The gamma rays
from these nuclides must be assessed for their interference 7.1 Safety Precautions—Plutonium-bearing materials are
effects on the multiplets used for the plutonium isotopic
both radioactive and toxic. Use adequate laboratory facilities
analysis and the proper spectral corrections applied. Some of and safe operating procedures in handling samples containing
these interfering nuclides would include: Np and its daugh-
these materials. Safe handling practices are outlined in Refer-
233 239 243 233
ter Pa, Np, Am, and U. ences (10-12).
5.2 Count-rate and coincident summing effects may also 7.2 Technical Precautions:
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 1030
A
TABLE 2 Energies and Gamma-Ray Branching Intensities of
7.2.1 Preclude or rectify counting conditions that may
Prominent Pu and Am Spectral Peaks
produce spectral distortions. Use pulse pile-up rejection tech-
Energy Branching Intensity
niques if high count rates are encountered. Use absorbers when
Isotope
(keV) (g/disintegration, %)
appropriate to reduce the intensity of the 59.5 keV gamma-ray
59.54 0.359 Am
of americium (see 5.2). Temperature and humidity fluctuations
−5 241
125.29 4.08 3 10 Am
in the measurement environment may cause gain and zero- −5 239
129.29 6.26 3 10 Pu
−6 241
148.57 1.87 3 10 Pu
level shifts in the gamma-ray spectrum. Employ environmental
−6B 238
152.68 9.37 3 10 Pu
controls or digital stabilization, or both, in this case. Failure to
−6 240
160.28 4.02 3 10 Pu
C −7 241 237
isolate the electronic components from other electrical equip-
164.48 4.53 3 10 Pu- U
−7 241
6.67 3 10 Am
ment or the presence of noise in the AC power may also
−6 239
203.54 5.60 3 10 Pu
produce spectral distortions.
C −6B 241 237
208.00 5.16 3 10 Pu- U
−6 241
7.2.2 The alpha decay branch of Pu proceeds through the
7.91 3 10 Am
237 237
C −8 241 237
335.44 2.39 3 10 Pu- U
daughter U, which in turn decays to Np with a half-life of
−6 241
4.96 3 10 Am
6.75 days. About eight weeks are required for secular equilib-
−6 239
345.01 5.59 3 10 Pu
C −8 241 237
rium to be achieved. If less than eight weeks have elapsed since
368.61 1.05 3 10 Pu- U
241 −6 241
2.17 3 10 Am
separation, use gamma rays produced by the parent, Pu, for
−5 239
375.04 1.57 3 10 Pu
isotopic abundance determinations; for example, the 148.57
−5 239
413.71 1.49 3 10 Pu
−7 240
keV peak. However, gamma rays arising from decay of the
642.48 1.245 3 10 Pu
237 −7 239
645.97 1.49 3 10 Pu
daughter, U, can be used for relative efficiency calculations.
−6 241
662.42 3.64 3 10 Am
7.2.3 Preferably, do not include high-Z absorbers in sample
−8 239
717.72 2.74 3 10 Pu
−6 241
packaging. As little as ⁄8in. (0.32 cm) of lead surrounding the
721.99 1.96 3 10 Am
plutonium will absorb the majority of the useful gamma rays in A
Branching intensities from Ref 15, except where noted.
B
the 100 to 200-keV region and invalidate the measurement. Branching intensity from “Handbook of Nuclear Data for Safeguards,” INDC
(NDS)-248, Nuclear Data Section, IAEA, Vienna, Austria, 1991.
7.2.4 The isotopic composition of all the plutonium in the
C 241 237 241
Produced in decay of Pu- U and Am, total intensity will be a function
sample must be the same. The technique does not apply to
of the abundances of these two isotopes.
nonuniform mixtures of different isotopic composition. How-
ever, the physical distribution of the plutonium within the
measured fundamental constants and as an aid in identifying
sample may be nonuniform with no adverse effect on the
possible spectral interferences.
results.
241 239
8.2.2 Working reference materials traceable to the National
7.2.5 The Am/ Pu atom ratio must be uniform in all the
Institute of Standards and Technology (NIST) reference mate-
plutonium in the sample, in order to obtain reliable specific
rials may be used to verify the overall correct operation of the
power measurements to use in interpreting calorimetry results.
spectrometry system and data reduction techniques, and also as
Certain types of Pu materials with nonhomogeneous Am-Pu
an aid in identifying interferences. Currently available NIST
distributions (salt residues) have been shown to be amenable to
isotopic reference materials (SRMs NIST-946, NIST-947, and
assay by this test method with slight modifications (13, 14).
NIST-948) are usually not suitable for direct use as reference
These materials have a low density salt matrix containing most
standards in all cases due to the small plutonium mass of the
of the americium while most of the plutonium is dispersed
materials. Working reference materials traceable to the NIST
throughout this matrix as high density localizations or free
standard reference materials should be prepared and validated
metal shot.
by other analysis techniques (see Test Methods C 697, C 698,
7.2.6 Plutonium-bearing materials, especially plutonium
and E 267).
fluoride compounds, should not be stored in the vicinity of, or
8.3 Measurement Control:
on, the germanium detectors. High energy neutrons emitted by
8.3.1 A measurement control program shall be established
these materials can produce trapping centers in the
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