抄録
The beyond design basis accident (BDBA) initiated by two low probability but linked phenomena - a large magnitude earthquake, followed (45 minutes) by a large tsunami, resulted in unprecedented damage to the 6-unit Fukushima Daiichi (FD1) NPS. Some 4 years later (in 2015) recovery, remediation and restoration (R3) is underway on- and off-site; however, onsite decommission and decontamination (D&D) of three melted reactor cores and 3 damages units are early in a multiple decade challenge. The accident spurred US nuclear utility and the US Nuclear Regulatory Commission (USNRC) review of the accident and emergency preparedness; outcomes of the latter Near-Term Task Force (NTTF) are emerging and may provide guidance for Japanese utilities planning to restart their units. In fact, the NRC intends to carry-out 'rulemaking' different from existing requirements for a station blackout (SBO) that addresses a 'prolonged' SBO, so that 'diversity' in establishing a path to cold shutdown can be accommodated and regulated. This work aims to integrate various aspects of a complex time of adjustment and transition for the US and Japanese nuclear operators and owners. The work proposes consistent use of LENDIT (length, energy, number, distribution, information, time) metrics across both soft and hard domains/issues as follows: lessons learned from the FD1 accident; classical and dynamic PRA for SBO events; the NRC NTTF, existing SBO versus emerging requirements for US plants, system analyses (RELAP or similar) in support of the restart of Japanese plants and emergency preparedness in the post-Fukushima era.
