ASTM C1415-01
(Test Method)Standard Test Method for 238Pu Isotopic Abundance by Alpha Spectrometry
Standard Test Method for <sup>238</sup>Pu Isotopic Abundance by Alpha Spectrometry
SCOPE
1.1 This test method covers the use of alpha spectrometry for determining the 238Pu isotopic abundance in plutonium samples. It is particularly useful for samples in which the 238Pu content is less than 1% of the total plutonium content. For such samples, mass spectrometric results are less reliable than those from alpha spectrometry because of interference from any 238U isobar remaining after ion exchange.
1.2 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)
Designation: C 1415 – 01
Standard Test Method for
238 1
Pu Isotopic Abundance By Alpha Spectrometry
This standard is issued under the fixed designation C 1415; 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.
238 239 240
1. Scope alpha activity due to Pu and that due to Pu + Pu. The
239 240
abundance of Pu and Pu is determined by mass spectrom-
1.1 This test method covers the use of alpha spectrometry
238
etry (see Test Methods C 697) on a separate portion of the
for determining the Pu isotopic abundance in plutonium
238
purified sample.
samples. It is particularly useful for samples in which the Pu
content is less than 1 % of the total plutonium content. For such
4. Significance and Use
samples, mass spectrometric results are less reliable than those
238
238
4.1 This test method is used when the determined of Pu
from alpha spectrometry because of interference from any U
isotopic abundance is required for plutonium samples.
isobar remaining after ion exchange.
1.2 This standard does not purport to address all of the
5. Interferences
safety concerns, if any, associated with its use. It is the
241 241
Am is always present as a result of Pu decay and is a
responsibility of the user of this standard to establish appro-
direct interference that must be removed prior to the determi-
priate safety and health practices and determine the applica-
238 230 232
nation of Pu. The very small amount of Th and Th
bility of regulatory limitations prior to use.
which could be present causes insignificant interference with
238
the determination of Pu at the level of uncertainty of this test
2. Referenced Documents
method. Other nuclides that would interfere, such
2.1 ASTM Standards:
238 243 245 249
as U, Am, Cm, and Bk, are removed by the anion-
C 697 Test Method for Chemical, Mass Spectrometric, and
exchange separation. Any residual uranium, while it does not
Spectrochemical Analysis of Nuclear-Grade Plutonium
2 directly interfere with the alpha-pulse height determination,
Dioxide Powders and Pellets
can raise the salt content of the sample. A high salt content can
C 1168 Practice for Preparation and Dissolution of Pluto-
2 decrease the resolution of the alpha spectra, and, consequently,
nium Materials for Analysis
3
decrease the sensitivity of the test method.
D 1193 Specification for Reagent Water
6. Apparatus
3. Summary of Test Method
6.1 Counting disks of polished platinum, tantalum, or stain-
3.1 This determination method involves the measurement of
238 239 240
less steel, sized to fit the detection chamber. A disk 25 mm in
the alpha-activity ratio of Pu and Pu + Pu. The isotopic
238
diameter and 0.5 mm thick has been found to be acceptable.
analysis of plutonium for the Pu isotope requires the prior
6.2 Alpha spectrometer. This instrument should typically
separation of interferences. After dissolution of the sample (see
consist of the following components:
Practice C 1168), the plutonium is separated from interferences
6.2.1 Silicon surface barrier detector, with an active area of
by an anion-exchange purification technique. Nitric acid
2
at least 100 mm , a depletion depth of greater than 100 μm, and
(HNO ) is used to adsorb the plutonium fraction on the resin.
3
a resolution of 30 keV or less full width at half maximum
Interfering ions, principally uranium and americium, are not
241
(FWHM) (for Am 5.486 MeV alpha).
adsorbed. The plutonium is then eluted with dilute HNO (0.1
3
6.2.2 Evacuable, light-tight chamber in which the detector
M). Because an alpha-activity ratio is used, quantitative recov-
and the counting plate on its support can be mounted.
ery of the plutonium is not required. The alpha spectrum in the
238
6.2.3 Preamplifier (charge-sensitive field-effect transistor)
5 to 6-MeV region is obtained. The total counts in the Pu and
239 240 with noise less than 4.6 keV when used with above detector
the Pu + Pu peaks are obtained and corrected for back-
238
(100 pF capacitance).
ground. The Pu abundance is calculated from the ratio of the
6.2.4 Detector bias supply, 0 to 150 V, continuously vari-
able, well-regulated and stable, with noise and ripple less than
1
This test method is under the jurisdiction of ASTM Committee C26 on Nuclear 0.0002 %.
Fuel Cycle and is the direct responsibility of Subcommittee C26.05 on Methods of
6.2.5 Main spectroscopy amplifier, low noise, with variable
Test.
shaping constants and baseline restoration.
Current edition approved Feb. 10, 2001. Published April 2001. Originally
6.2.6 Biased amplifier and pulse stretcher, with continu-
published as C 1415 – 99. Last previous edition C 1415 – 99.
2
Annual Book of ASTM Standards, Vol 12.01.
ously adjustable post-gain and automatic pile-up rejection.
3
Annual Book of ASTM Standards, Vol 11.01.
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