A Novel In-Beam Delayed Neutron Counting Technique for Characterization of Special Nuclear Materials

作者：Bentoumi G^*; Rogge R B; Andrews M T; Corcoran E C; Dimayuga I; Kelly D G; Li L; Sur B

来源：IEEE Transactions on Nuclear Science, 2016, 63(6): 2807-2814.

DOI：10.1109/TNS.2016.2624146

• Delayed neutron counting
• fissile material
• non-destructive assay
• neutron beam
• nuclear forensics
• nuclear non-proliferation

A delayed neutron counting (DNC) system, where the sample to be analyzed remains stationary in a thermal neutron beam outside of the reactor, has been developed at the National Research Universal (NRU) reactor of the Canadian Nuclear Laboratories (CNL) at Chalk River. The new in-beam DNC is a novel approach for non-destructive characterization of special nuclear materials (SNM) that could enable identification and quantification of fissile isotopes within a large and shielded sample. Despite the orders of magnitude reduction in neutron flux, the in-beam DNC method can be as informative as the conventional in-core DNC for most cases while offering practical advantages and mitigated risk when dealing with large radioactive samples of unknown origin. This paper addresses (1) the qualification of in-beam DNC using a monochromatic thermal neutron beam in conjunction with a proven counting apparatus designed originally for in-core DNC, and (2) application of in-beam DNC to an examination of large sealed capsules containing unknown radioactive materials. Initial results showed that the in-beam DNC setup permits non-destructive analysis of bulky and gamma shielded samples. The method does not lend itself to trace analysis, and at best could only reveal the presence of a few milligrams of U-235 via the assay of in-beam DNC total counts. Through analysis of DNC count rates, the technique could be used in combination with other neutron or gamma techniques to quantify isotopes present within samples.

• 出版日期2016-12
• 单位Los Alamos