Characterization study of candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station, 3; Active neutron technique (interim report)

Komeda, Masao   ; Maeda, Makoto  ; Furutaka, Kazuyoshi  ; Tobita, Hiroshi; Hattori, Kentaro; Shimofusa, Taichi; Ozu, Akira  ; Kureta, Masatoshi   

This report describes applicability evaluation results of active neutron technique (AN) for characterization study of candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station. In this characterization study, we used the Fast Neutron Direct Interrogation (FNDI) method which is one of the active neutron methods. We had performed simulation studies of the FNDI measurement system for measuring the debris using the Three Mile Island (TMI) canister model. Since then, we have modified the design of the FNDI measurement system in order to apply the new canister model, and carried out simulations of a common set of debris models. As the result of the simulations, it has been found that the fissile mass can be measured with an error of less than 20% under the condition in which B-10 density is less than 0.04 wt%.