ASTM D3084-05

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Designation: D3084 − 05
StandardPractice for
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Alpha-Particle Spectrometry of Water
This standard is issued under the fixed designation D3084; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope carried out by several methods involving magnetic
spectrometers, gas counters, scintillation spectrometers,
1.1 This practice covers the processes that are required to
nuclear emulsion plates, cloud chambers, absorption
obtain well-resolved alpha-particle spectra from water samples
techniques, and solid-state counters. Gas counters, operating
and discusses associated problems. This practice is generally
either as an ionization chamber or in the proportional region,
combined with specific chemical separations, mounting
have been widely used to identify and measure the relative
techniques, and counting instrumentation, as referenced.
amounts of differenta -emitters. However, more recently, the
1.2 This standard does not purport to address all of the
solid-state counter has become the predominant system be-
safety concerns, if any, associated with its use. It is the
cause of its excellent resolution and compactness. Knoll (3)
responsibility of the user of this standard to establish appro-
extensively discusses the characteristics of both detector types.
priate safety and health practices and determine the applica-
4.2 Of the two gas-counting techniques, the pulsed ioniza-
bility of regulatory limitations prior to use.
tion chamber is more widely used as it gives much better
2. Referenced Documents
resolution than does the other. This is because there is no
2 spread arising from multiplication or from imperfection of the
2.1 ASTM Standards:
wire such as occurs with the proportional counter.
C859 Terminology Relating to Nuclear Materials
C1163 Practice for MountingActinides forAlpha Spectrom-
4.3 The semiconductor detectors used for alpha-particle
etry Using Neodymium Fluoride
spectrometry are similar in principle to ionization chambers.
D1129 Terminology Relating to Water
The ionization of the gas by a-particles gives rise to electron-
D3648 Practices for the Measurement of Radioactivity
ion pairs, while in a semiconductor detector, electron-hole
D3865 Test Method for Plutonium in Water
pairs are produced. Subsequently, the liberated changes are
D3972 Test Method for Isotopic Uranium in Water by
collected by an electric field. In general, silicon detectors are
Radiochemistry
usedforalpha-particlespectrometry.Thesedetectorsaren-type
base material upon which gold is evaporated or ions such as
3. Terminology
boron are implanted, making an electrical contact. A reversed
3.1 For definitions of terms used in this practice, refer to bias is applied to the detector to reduce the leakage current and
Terminologies D1129 and C859. For terms not found in these to create a depletion layer of free-charge carriers. This layer is
thin and the leakage current is very low. Therefore, the slight
terminologies, reference may be made to other published
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glossaries (1, 2). interactions of photons with the detector produce no signal.
Theeffectofanyinteractionsofbetaparticleswiththedetector
4. Summary of Practice
can be eliminated by appropriate electronic discrimination
(gating) of signals entering the multichannel analyzer. A
4.1 Alpha-particle spectrometry of radionuclides in water
semiconductor detector detects all alpha particles emitted by
(also called alpha-particle pulse-height analysis) has been
radionuclides (approximately 2 to 10 MeV) with essentially
equal efficiency, which simplifies its calibration.
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This practice is under the jurisdiction ofASTM Committee D19 on Water and
4.4 Semiconductor detectors have better resolution than gas
is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemical
Analysis.
detectors because the average energy required to produce an
Current edition approved Jan. 1, 2005. Published January 2005. Originally
electron-hole pair in silicon is 3.5 6 0.1 eV (0.56 6 0.02 aJ)
approved in 1972. Last previous edition approved in 1996 as D3084 – 96. DOI:
compared with from 25 to 30 eV (4.0 to 4.8 aJ) to produce an
10.1520/D3084-05.
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ion pair in a gas ionization chamber. Detector resolution,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
defined as peak full-width at half-maximum height (FWHM),
Standards volume information, refer to the standard’s Document Summary page on
is customarily expressed in kiloelectron-volts. The FWHM
the ASTM website.
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increases with increasing detector area
...