Assay Sensitivity for Isotopic Fissile in LSDS System

摘要

The quantitative isotopic fissile assay was performed in LSDS system. The experimental fissile fission measurement was done in RPI LSDS facility using U235 rod(4.8%) and Pu239 material(47g, 91g). In the spectrometer, the interrogation neutron induced individual fissile fission directly and prompt fast neutron is detected at the surrounding threshold detectors. The simulated detection signal was assessed in the slowing down channels. The self-shielding effect was dominant at an energy of large neutron absorption property of fissile materials. The fissile assay model has linear relationship between fissile mass and direct fission. From the measurement, the results show very good agreement with 1~2% uncertainty of Pu239 actual mass. For simulation, the assay results show 2~3% uncertainty when the content of Pu239 is changed from 3~13%. Therefore, from the results, LSDS is very promising technology to analyze the content of isotopic fissile mass in used fuel and recycled material. An accurate isotopic fissile mass assay will contribute to international transparency for fissile material utilization and spent fuel management.