A Neutron Multiplicity Counter for Plutonium Assay

A new neutron multiplicity counter has been developed that can provide International Atomic Energy Agency inspectors a means of verifying plutonium samples by a full neutron multiplicity analysis where conventional neutron coincidence counters yield outliers. This prototype detector comprises an array of ³He and liquid scintillator neutron detectors and is one of a new generation of multiplicity counters under development for nuclear safeguards. A moments analysis solution to the plutonium mass, (α,n) rate, and multiplication is calculated using the measured neutron multiplicity distributions, and an expression for the uncertainty in the multiplication-corrected mass has been derived.