Delayed Gamma-ray Spectroscopy for Nuclear Material Analysis (2): Design of a practical system with dd neutron generator

摘要

To safeguard nuclear material at facilities like reprocessing plants and MOX fuel fabrication facilities, new active-interrogation nondestructive assay techniques are needed. We are developing a new delayed gamma-ray spectroscopy (DGS) system to quantify the fissile composition in nuclear material samples. DGs quantifies the composition by comparing the ratios of gamma-ray peaks with energy above 3 MeV from short-lived fission products produced during irradiation of the sample by a high-rate external neutron source. Utilizing thermal neutrons allows more fission events to be produced by fissile nuclides (U-235, Pu-239 and Pu-241) to overcome the shielding required to reduce the low energy passive background from the long-lived fission products. While the dominant external sources proposed for this application are DT neutron generators, we are investigating the possibility to use a DD neutron generator that produces neutrons with starting energies that are easier to moderate and pose less safety issue for the operator. The main differences between the two systems will be presented here along with the description of the current design of our system.