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Neutron coincidence counting

Photo related to the term with caption below

AWCC Detector at ORNL

A technique that detects prompt neutrons from spontaneous or induced fission in a sample and distinguishes them from neutrons from other sources (such as α,n) reactions) by separating detected events that occur closely together in time (correlated events) from those that are randomly distributed in time. The correlated events are counted to produce a measurement result indicative of the amount of fissionable isotopes in the sample.

The high level neutron coincidence counter (HLNCC) has been designed to handle high count rates and therefore large samples of Pu.

The active well coincidence counter (AWCC) incorporates an isotopic source (e.g. AmLi) that randomly produces neutrons used to interrogate a fissionable sample. The prompt neutrons from the induced fission are then detected to verify large samples of U. The sensitivity of this active non-destructive assay device is higher than that of the passive HLNCC.

Various instruments have been developed which incorporate this technology and are adapted for the verification of specific nuclear material items, such as light water reactor fuel assemblies or fast reactor fuel elements.