Development of basic NDA technologies for nuclear material accountancy of debris of melted fuel formed in severe accidents

Seya, Michio; Harada, Hideo   ; Kitatani, Fumito  ; Koizumi, Mitsuo ; Tsuchiya, Harufumi ; Iimura, Hideki  ; Kureta, Masatoshi   ; Takamine, Jun ; Hajima, Ryoichi; Hayakawa, Takehito; Shizuma, Toshiyuki; Angell, C.; Bolind, A.

The forming of MF in a severe accident of a nuclear reactor may change the category of the nuclear reactor from item facility to non-item facility. Taking this removal process into account, the damaged reactor could be categorized as a bulk-handling facility. The NM accountancy is essential for the safeguards of a bulk-handling facility. This paper presents a categorization of debris of MF (into cut or small rock-like debris and particle (or grain)-like debris) and a selection of possible NDA technologies which could be applied to the NM accountancy of MF debris. The paper introduces two NDA technologies for NM accountancy of debris: NRD for particle-like (or grain-like) debris, and NRF NDA using LCS rays for cut or small rock-like debris. The paper also describes about the development of basic parts of these two technologies and near future plan.