Year
1992
Abstract
An in-plant thermal-neutron multiplicity counter was designed and built to assay plutonium samples for which the relative (cc,n) neutron yield and the neutron multiplication are not known. Such samples are difficult to assay with conventional neutron coincidence counting techniques. We have characterized this counter with various ^^Cf sources and plutonium samples to study the neutron detection efficiency, electronic deadtime, and neutron die-away properties of the detector and associated electronics. We used a new shift-register electronics module that features 256 channels for multiplicity counting. Preliminary reference parameters have been obtained for performing assays with the multiplicity counting system. We measured a variety of plutonium materials with the in-plant counter in the Los Alamos Plutonium Facility. The materials included samples with high neutron multiplication and samples with high (a,n) neutron yields. Preliminary assay results are presented.