Shuffler instruments for the nondestructive assay of fissile materials

Technical Report · Wed May 01 00:00:00 EDT 1991

DOI:https://doi.org/10.2172/5585772· OSTI ID:5585772

Rinard, P M

A shuffler is a nondestructive assay instrument used to determine the fissile content of materials. It places an isotopic source of neutrons near the material to induce fissions, withdraws the source, and counts the delayed neutrons. The source is shuffled until a sufficient number of delayed neutrons have been counted. The shuffler technique is generally applied to difficult assay cases. The amount of material present may be very small (a few milligrams), and thus it does not spontaneously emit neutrons of consequence; the amount of material is also below an active well counter's level of sensitivity. On the other hand, the fissile amount may be fairly large, but the rate of spontaneously emitted neutrons may still be low (so a passive neutron count will not work) or the highest assay precision may be desired (favoring a shuffler over an active well counter) even if the material is inhomogeneous (making it difficult to interrogate with thermal neutrons). In all these cases, gamma-ray backgrounds, self- shielding, or matrix effects can make gamma-ray assays impractical. Materials ranging from highly radioactive spent-fuel assemblies to low-level waste drums have been assayed with shufflers, as have leached hulls, various process materials, scrap, and waste. This report presents a theoretical background for shufflers and describes techniques for practical applications. Procedures for assaying mixtures of fissile isotopes, inhomogeneous materials, and flowing liquids are discussed. It is shown how the precision and limits of detection of a shuffler can be calculated for a given neutron background rate. A section on data analysis gives a stepwise procedure for converting the measured counts into an assay value, including random, systematic, and total uncertainties. 31 refs.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5585772
• Report Number(s): LA-12105; ON: DE91014281
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
FISSILE MATERIALS
DELAYED NEUTRON ANALYSIS
CALIFORNIUM 252
FISSION
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NONDESTRUCTIVE TESTING
SPENT FUELS
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
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FUELS
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NUCLEAR FUELS
NUCLEAR REACTION ANALYSIS
NUCLEAR REACTIONS
NUCLEI
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050800* - Nuclear Fuels- Spent Fuels Reprocessing
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