Fundamental studies to improve analysis of accident progression at Fukushima Daiichi NPP

Nagase, Fumihisa ; Yoshida, Hiroyuki  ; Nemoto, Yoshiyuki  ; Amaya, Masaki  ; Yamashita, Shinichiro   

In order to conduct decommissioning of the Fukushima-Daiichi NPP properly and reliably, increase of accuracy is required in estimation of the accident progress and status inside the reactors. It is also required to improve analytical methods to estimate severe accident progression in the existing light water reactors. Therefore, JAEA conducts fundamental studies in terms of thermal hydraulic behaviour in reactor, fuel damage and degradation process, behaviour of structural materials and pressure vessel, release and migration of fission products, and so on under severe accident conditions. The present paper reports overview of the fundamental studies and recent results.