Research subjects for analytical estimation of core degradation at Fukushima-Daiichi Nuclear Power Plant

Nagase, Fumihisa ; Ishikawa, Jun ; Kurata, Masaki ; Yoshida, Hiroyuki  ; Kaji, Yoshiyuki  ; Shibamoto, Yasuteru ; Amaya, Masaki  ; Okumura, Keisuke ; Katsuyama, Jinya  

Estimation of the accident progress and status inside the reactor is required to properly and reliably conduct decommissioning of the Fukushima-Daiichi NPPs. For that, it is necessary to obtain additional experimental data and revised models for the estimation using computer codes with increased accuracies. JAEA has selected phenomena to be reviewed and developed in terms of thermo hydraulic behavior in the reactor, progression of fuel bundle degradation, failure of the lower head of the reactor pressure vessel, and analysis of the accident, considering previously obtained information, conditions specific to the Fukushima-Daiichi NPP accident, and recent progress of experimental and analytical technologies. This paper introduces the selected phenomena to be reviewed and developed and recent results from the JAEA's corresponding research programs.