[2H07-09] 1F Accident

11:40 AM - 11:55 AM JST(2:40 AM - 2:55 AM UTC)

[2H09] Modeling radio-nuclide behavior for estimating their amount in radioactive waste of Fukushima Daiichi NPS(2) Effects of fuel deposits on initial core inventories of 60Co

*Shunsuke Uchida, Chiaki Kino¹, Yoshikazu Koma², Youko Takahatake², Hidetoshi Karasawa ³, Kenichi Tezuka¹ (1. Institute of Applied Energy, 2. Japan Atomic Energy Agency, 3. Hachinohe Institute of Technology)

Keywords:

Fukushima Daiichi NPP,reactor water,Fuel claddings,Co-60,radio-nuclide behavior

In order to determine radioactive nuclide composition of radwaste in Fukushima Daiichi NPP, evaluation of the amounts of long lives, non-gamma ray emitted nuclide, e.g., ⁹⁰Sr, ⁶³Ni, ¹²⁹I, was strongly required. The evaluation was often carried out based on transport factors applying ¹³⁷Cs as the index nuclide. However, its application was not always adequate for low-volatile nuclide, ⁹⁰Sr, or non-volatile one, ⁶³Ni. ⁶⁰Co was another candidate as the index nuclide for low- and non-volatile species and its accurate inventory in the core was required. The amounts of cobalt and ⁶⁰Co depositing on the fuel surface was evaluated based on the micro layer evaporation and drying out model. Then, it was evaluated that their depositing amounts were about 300 times larger than ones calculated with ORIGEN2 and it was suggested that transport factor procedure based on ⁶⁰Co as the index could be applicable for evaluation of low- and non-volatile species.