The Development of non-destructive assay technology for the quantification of nuclear material in high active solid waste; Overview of the collaborative research using neutron measurement techniques by the Japan Atomic Energy Agency and the U.S. Department of Energy

Shirafuji, Masaya ; Sano, Kyohei; Horiuchi, Masakazu; Kato, Akane ; Watanabe, Kazuki ; Tanigawa, Masafumi ; Maruyama, Hajime ; Kitao, Takahiko ; Conner, J.*; LaFleur, A.*; Watson, M.*

The Japan Atomic Energy Agency, in collaboration with the U.S. Department of Energy and Los Alamos National Laboratory, initiated a joint research project to develop the Advanced Hulls Measurement and Monitoring System (A-HMMS) for quantifying trace amounts of nuclear material in hull drums. Monte Carlo simulations using the MCNP code confirmed that the presence of water significantly attenuates neutron count rates. However, sufficient sensitivity to plutonium mass variations was observed, indicating that measurements are feasible even with water present. Passive NDA methods based on the Cm/Pu ratio were found to be limited due to curium decay over long-term storage, necessitating the use of active interrogation techniques. Small-scale experiments validated the simulation results and demonstrated that waste type and source position significantly affect count rates, highlighting the need for waste-specific calibration curves. Full-scale testing is planned to evaluate system performance under realistic conditions and optimize the A-HMMS design.