Why was introduction of station blackout regulation late? Failure to apply knowledge of possible major tsunamis to protect the Fukushima Daiichi Nuclear Power Plant

The severe accidents that occurred at the Fukushima Daiichi Nuclear Power Plant, which is operated by the Tokyo Electric Power Company (TEPCO), warrant a thorough examination and validation of factors such as the response and applicable regulations. To begin with, what were the reasons behind the belated regulation of station blackouts (SBOs) at nuclear power plants? Why did seismic regulations not reflect the possibility of earthquakes and tsunamis adequately despite the earlier warnings from experts? In Japan, seismic measures for safeguarding nuclear facilities were introduced in earnest a few years after the Great Hanshin Earthquake of 1995. A major revision of the Regulatory Guide for Reviewing the Seismic Design of Nuclear Power Reactor Facilities was announced in September 2006 in the wake of another major earthquake in Niigata. Regrettably, this revision took too long. It is high time Japan restructured its regulatory system giving due consideration to the importance of safety-related research. An independent agency is postulated as a part of this restructuring. However, the first step must be to examine the earthquake responses taken to date. This commentary has been written with reference to the flood-induced loss of external power supplies, the tsunami-induced loss of cooling pump functionality, and other events that offer important lessons. It also presents the state of severe accident regulations in the United States and France before providing recommendations for the regulatory measures to be taken in Japan. (author)