Analysis of Initial In-plant Active Neutron Multiplicity Measurements

This paper analyzes initial in-plant measurements made by active neutron multiplicity counting, a new technique currently under development for the assay of bulk uranium containing kilograms of 235U. The measurements were made at Savannah River and Y-12 using active well coincidence counters and prototype multiplicity electronics and software from Los Alamos. For one of the sets of highly enriched uranium samples measured to date, we improved the assay accuracy by an order-of-magnitude by adding the multiplicity analysis to the conventional coincidence analysis. This paper summarizes our results and describes areas where further work is needed.