The Active Fault Problem in Relation to Nuclear Power Plants: Current Issues

Abstract

The explosion of the Fukushima Daiichi Nuclear Power Plant in 2011 due to the Great East Japan Earthquake led to the initiation of a comprehensive inspection of the earthquake resistance of every nuclear power plant in Japan. In addition to protection against tsunamis induced by interplate earthquakes, the inspections covered resistance against extremely strong vibrations and surface deformations caused by earthquakes. Reconsideration of the safety regulations for Japan’s nuclear power plants actually began with the 1995 Kobe earthquake, and in 2006 the safety review guidelines were strengthened. However, in a reexamination (“back-check”) after 2006, strict examination based on the new guidelines was not performed. The sensitive location of the reactor (the reactor is located directly above the active fault) was also overlooked. The situation has been described as a “regulatory capture” by the Fukushima Nuclear Accident Independent Investigation Commission of the National Diet. In addressing the reasons behind the lack of strict screening, the ambiguity and arbitrariness of the definition of active faults seem to be the fundamental problems.