Active Faults and Nuclear Regulation by Yasuhiro Suzuki

Author:Yasuhiro Suzuki
Language: eng
Format: epub
ISBN: 9789811507656
Publisher: Springer Singapore

4.1 Problem Presentation by the Former Nuclear and Industrial Safety Agency

The earthquake that occurred on April 11, 2011, in Hamadori, Fukushima Prefecture, revealed a considerable problem with active fault assessments during nuclear power plant reviews. This earthquake occurred because of recurring movement in active faults, which caused obvious seismic faults to appear on the surface [1]. However, some of these had been deemed inactive in the assessment undertaken during the license application process for TEPCO’s Fukushima Daiichi Nuclear Power Plant. The fact that this fault was a normal fault with low probability of activity given today’s stress field was given considerable weight in the construction review of the former Nuclear Safety Commission in June 2010. However, since this normal fault did move, it became clear that considering normal faults as not active is inappropriate. This lesson was observed with gravity, and on April 29, 2011, the former Safety Agency required operators across the nation to reassess faults and the geology around nuclear power plants and to report the outcomes as soon as possible.

After September 2011, to hear professional opinions regarding earthquakes and tsunamis, the former Nuclear and Industrial Safety Agency (MISA) hosted a meeting at which they began discussion both on coupled movement in active faults and on assessment problems of tsunamis. In addition, after April 2012, they opened discussion on faults within nuclear power plant sites. They visited the Tsuruga Nuclear Power Plant on April 24 and they ordered the Japan Atomic Power Company to conduct a full reexamination, because there was a possibility that a fault near the nuclear reactor building might have moved in the new geologic era. Examination targets included faults that passed underneath the nuclear reactor. They explained that the nuclear power plant site would be deemed inappropriate unless the possibility of this fault moving in association with active faults in the area could be eliminated. This was the first of a series of onsite fault surveys (Fig. 4.1).

Fig. 4.1Newspaper article of The Japan Times on April 26, 2012, reporting assessment result of the fault in the Tsuruga Nuclear Power Plant premise by the Nuclear and Industrial Safety Agency (MISA). Reprinted by permission from The Japan Times

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