Analysis for progression of accident at Fukushima Dai-ichi Nuclear Power Station with THALES2 code

Matsumoto, Toshinori ; Ishikawa, Jun ; Maruyama, Yu 

The analysis of the progressions of the accidents at the Fukushima Dai-ichi Nuclear Power Station units 1 and 2 were performed with the THALES2/KICHE code. The analytical conditions were set on the basis of the information provided in the OECD/NEA BSAF project. The CV failures were assumed in the both units. The DW and S/C failure case was set as the CV failure of unit 2. The results of the analyses have indicated that the oxidation of the zirconium of the fuel cladding tube generated approximately 1,200 kg of hydrogen in both units. It is indicated that 80% of cesium and iodine distributed in the water phase of S/C due to the scrubbing. Cesium was released into the environment mainly as the form of CsOH or CsI. The release fraction has been predicted as 10E-3 for unit 1 and 10E-1 for unit 2. I2 and organic iodine were formed as the result of the chemical reaction in the water phase of S/C, and their released fractions were at the order of 10E-3 for unit 1 and 2.