The demand for non-destructive assay (NDA) techniques for nuclear materials has increased worldwide in the field of nuclear security and safeguards. In addition to conventional nuclear materials such as U and Pu, it is expected that the needs for detection of and accounting for minor actinides (MAs) such as 237Np would increase as its utilization demands increases in the future closed fuel cycle. In next-generation nuclear reactors and fuel cycles, there is a strong demand to recycle MAs with U and Pu for sustainability and nuclear waste minimization. According to the United States Department of Energy, the nuclear security treatment of separated 237Np is graded at the same level as that of 235U in highly enriched uranium (HEU). In the nuclear safeguards of the International Atomic Energy Agency, it is treated as “alternative nuclear materials”, and information on separated Np is collected under voluntary arrangements with relevant states. Additionally, because of the low spontaneous radioactivity of 237Np, it would be difficult to measure it using passive NDA methods, similar to HEU. Therefore, for the appropriate and efficient management of MAs in the future, the development of an NDA method for MAs is important for nuclear security and safeguards. In this study, we propose a novel detection method for 237Np, which is called the photon-induced multiple neutron generation reaction ratio (PMNRR) method. In this method, 237Np was identified using the PMNRR with multiple high-energy gamma rays. The feasibility of the discrimination between the separated 237Np and uranium (235U, 238U) and the detection of the 237Np above a certain composition ratio in UO2 was examined by numerical analysis simulations.
Year
2022
Abstract