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KEPCO’s Oi plant may be approved based on minimum seismic moment

  • June 8, 2016
  • , Asahi , p. 3
  • Translation

As a part of the appeal hearing concerning suspension of Oi nuclear plants number 3 and 4 reactors (Fukui Prefecture), a former deputy secretary-general of the Nuclear Regulation Authority (NRA) submitted to the Kanazawa Branch of the Nagoya High Court a statement warning that the method used by Kansai Electric Power Co. (KEPCO) to evaluate the scale of an earthquake “could lead to an underestimation.”


Kunihiko Shimazaki (70,) the former number two at Japan’s nuclear watchdog, is a seismologist and a professor emeritus of Tokyo University. During his service at the NRA, he was the key person for inspection of the two Oi reactors under the new regulatory standards. He says in his statement that the method KEPCO employed to evaluate the scale of earthquakes may lead to underestimates. The statement was requested by lawyers of the plaintiff.


An NRA official responded that they approved the seismic moment evaluation results only after a careful examination, allowing a wide safety margin. He said they considered uncertain factors such as length, width, and angle of the fault and the possibility Shimazaki raised. KEPCO agreed by saying that they calculated the seismic moment conservatively, using a method adopted by the government’s Headquarters of Earthquake Research Promotion. (Abridged)

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