部門設立30周年記念出版: Vol.4沸騰型原子炉

（福島第一原子力発電所の事故の教訓を生かしたパッシブ冷却系）

抄録

Many lessons can be learned from the Fukushima Daiichi NPS accident in Chapter 4. First, if an isolation condenser (IC) had continued to operate, the accident would have terminated soon. Reactor core isolation cooling (RCIC) steam turbines also stopped because loss of battery power in Units 2 and 3, and temperature and pressure in each primary containment vessel (PCV) were so high that the accident management and water injection took too long. After the loss of emergency core cooling system (ECCS) and IC core cooling, fuels in the core melted. Leak of fission product and hydrogen began because of the damage to the O-ring seals between PCV upper flanges due to high temperature. Hydrogen explosion occurred in the upper floor in the reactor building at Units 1, 3, and 4. The New Regulatory Requirements, based on the concept of “defense in depth,” for Commercial Nuclear Power Reactors came into force on July 8, 2013. It is hoped that the lessons learned from this accident will improve the safety of nuclear power plants worldwide.