Keywords:Nuclear Accident of Fukushima Daiich, High Pressure Coolant Injection System, Radioactive Material, Pressure Containment Vessel Venting
About cause of the Fukushima Daiich nuclear accident, investigation reports had been written by investigation committees of the Japanese National Diet, the Japanese National Government, the private sector and TEPCO. However, in the present state, some judgement are different between the investigation reports and between specialists. Our working group has advanced investigation of the accident event which occurred at Fukushima Daiich NPS from an academic point of view, through the four accident investigation reports were mainly compared and through newly published facts and hearing from the person concerned were examined. In this second report, three items of our working group opinion, about the situation of the unit 3 HPCI, accident progression of unit 2 and the problem of the PCV venting, were described.