Year
2016
Abstract
Improving the ability to characterize unknown as- semblies of SNM is an important component of non-proliferation and arms control research. We are investigating a new means of assessing the neutron multiplication of an assembly of SNM by measuring the angular distribution of coincident prompt fission neutrons. It has been well established that, for non-multiplying sources, there is a strong anisotropy in coincident prompt fission neutrons. For multiplying sources, previous work showed an isotropic distribution for coincident prompt fission neutrons from different generations of a fission chain reaction. Therefore, there is a correlation between the anisotropy in the prompt fission neutron coincidence angular distribution and the neutron multiplication of the assembly. Here, novel results regarding the impact of shielding on the prompt neutron coincidence anisotropy will be presented. Specifically, the anisotropy resulting from SNM inside low-Z shielding (high-density polyethylene) or high- Z shielding (lead) will be demonstrated using MCNPX-PoliMi simulations. The impact of these shielding scenarios on the possibility of using the prompt neutron coincidence anisotropy to assay the neutron multiplication of SNM will be shown.