ASTM C1493-19

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1493 − 19
Standard Test Method for
Non-Destructive Assay of Nuclear Material in Waste by
Passive and Active Neutron Counting Using a Differential
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Die-Away System
This standard is issued under the fixed designation C1493; 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 1.2.1 For uranium-only bearing items, the DDT can mea-
235
sure the U content in the range from about 0.02 to over 100
1.1 This test method covers a system that performs nonde-
g. Small mass uranium-bearing items are typically measured
structiveassay(NDA)ofuraniumorplutonium,orboth,using
using the active mode and only large mass items are measured
the active, differential die-away technique (DDT), and passive
in passive mode.
neutron coincidence counting. Results from the active and
1.2.2 For plutonium-only bearing items, the DDT method
passive measurements are combined to determine the total
239
measures the Pu content in the range between about 0.01
amount of fissile and spontaneously-fissioning material in
and 20 g.
drums of scrap or waste. Corrections are made to the measure-
ments for the effects of neutron moderation and absorption,
1.3 Thepassivemodeiscapableofassayingspontaneously-
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assuming that the effects are averaged over the volume of the
fissioningnuclei,overanominalrangefrom0.05to15g Pu
drum and that no significant lumps of nuclear material are
equivalent.
present.Thesesystemsaremostwidelyusedtoassaylow-level
1.4 This test method requires knowledge of the relative
and transuranic waste, but may also be used for the measure-
abundances of the plutonium or uranium isotopes to determine
ment of scrap materials. The examples given within this test
the total plutonium or uranium mass.
method are specific to the second-generation Los Alamos
National Laboratory (LANL) passive-active neutron assay
1.5 Thistestmethodwillgivebiasedresultswhenthewaste
system.
form does not meet the calibration specifications and the
1.1.1 In the active mode, the system measures fissile iso-
measurementassumptionspresentedinthistestmethodregard-
235 239
topes such as U and Pu. The neutrons from a pulsed,
ing the requirements for a homogeneous matrix, uniform
14-MeVneutron generator are thermalized to induce fission in
source distribution, and the absence of nuclear material lumps,
the assay item. Between generator pulses, the system detects
to the extent that they effect the measurement.
prompt-fission neutrons emitted from the fissile material. The
1.6 The complete active and passive assay of a 208 Ldrum
number of detected neutrons between pulses is proportional to
isnominally10minorlessbuteithermodecanbeextendedto
the mass of fissile material. This method is called the differ-
meet data quality objectives.
ential die-away technique.
1.1.2 In the passive mode, the system detects time-
1.7 Some improvements to this test method have been
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coincident neutrons emitted from spontaneously fissioning
reported (1, 2, 3, 4). Discussions of these improvements are
238 240
isotopes. The primary isotopes measured are Pu, Pu,
not included in this test method although improvements
242
and Pu; however, the system may be adapted for use on
continue to occur.
other spontaneously-fissioning isotopes as well, such as kilo-
238 1.8 The values stated in SI units are to be regarded as
gram quantities of U. The number of coincident neutrons
standard. No other units of measurement are included in this
detected is proportional to the mass of spontaneously-
standard.
fissioning material.
1.9 This standard may involve hazardous materials,
1.2 The active mode is used to assay fissile material in the
operations, and equipment. This standard does not purport to
following ranges.
address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to
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ThistestmethodisunderthejurisdictionofASTMCommitteeC26onNuclear
Fuel Cycle and is the direct responsibility of Subcommittee C26.10 on Non
Destructive Assay.
Current edition approved March 15, 2019. Published April 2019. Originally
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approvedin2001.Lastpreviouseditionapprovedin2009asC1493–09,whichwas The boldface numbers given in parentheses refer to a list of references at the
withdrawn January 2018 and reinstated in March 2019. DOI: 10.1520/C1493-19. end of the text.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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