Citation:
D.C. Strohmeyer W.S. Charlton, “Feasibility Study of a Portable Coupled 3He Neutron Detector with LaBr3 Gamma Scintillator for the Purpose of Plutonium Identification and Quantification”, Proceedings of 31st Annual Meeting of ESARDA, May 26-28, 2009, Vilnius, Lithuania.
Abstract:
In recent years there has been several research endeavors to increase the ability to identify and quantify special nuclear material in field measurements. Many have included both gamma spectroscopy and neutron coincidence systems that are portable and work in a variety of environments. In this work a MCNPX1 model was designed that includes four gamma detection slabs placed within four neutron detection slabs. Four Plutonium (Pu) samples of known quantity were modeled and tested to determine what data was available from each individual signature. Each model included a separate MCNPX deck for each individual isotope that contributes to the gamma signature in photon mode and a spontaneous fission and (α,n) deck for the neutron signature. The first three samples were used to create spectrums and efficiency curves for each odd isotope as well as for a Pu effective mass for the neutron signature. The data from these simulations were then used to identify the isotopics in the fourth sample to within acceptable accuracy. From this data a total Pu mass was obtained as well as an ability to determine the ratio of (α,n) to spontaneous fission neutrons without additional simulations. This provides a new method to detected and identify the Pu content within a sample without producing additional information since isotopics can be determined with the use of the gamma and neutron system.