Validation tests and measuring trials for actual uranium bearing waste drums by the fast neutron direct interrogation method

Zaima, Naoki; Nakatsuka, Yoshiaki; Nakashima, Shinichi ; Ozu, Akira  ; Komeda, Masao   ; Kureta, Masatoshi   

JAEA developed NDA systems which applied to the actual scrapped nuclear materials and uranium bearing waste drums heavily generated from URCP and NEP in Ningyo-site. In order to improve the methodology of determination uranium mass the active assay neutron NDA measurement system (JAEA Waste Assay System-Ningyo=JAWAS-N) used by the Fast Neutron Direct Interrogation (FNDI) method have been configurated. The validation tests have been achieved successfully, also the trials for measuring the actual nuclear materials or waste drums just started and accumulated over 550 data with quick and high accuracy measuring. The die-away time, which means neutron decay time in phenomenon, may be used for analyzing uranium mass, at the same time, the neutron behavior simulations over time spectrum have been carried out and verified our measurement system.