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Japan: Ohi-3 Restarted After 4.5-Year Outage

Saturday 17 March 2018

Japan: Ohi-3 Restarted After 4.5-Year Outage

WNISR, 17 March 2018

On 16 March 2018, Japanese utility Kansai Electric Power Company (KEPCO) reconnected its reactor Ohi-3 to the grid, four and a half years after it was shut down on 2 September 2013. KEPCO plans to restart Ohi-4 in mid May 2018. The Ohi nuclear plant has been the subject of multiple lawsuits since its shutdown. KEPCO submitted its applications to the Nuclear Regulation Authority (NRA) for safety examinations of Ohi-3 and -4 on 8 July 2013. On 24 May 2017, the NRA approved safety examinations for the two reactors. KEPCO estimated costs of ¥122 billion (US$1 billion) for retrofits of Ohi-3 and -4.

A major issue at the Ohi site is the status of geologic faults within the site and the area around it. The seismic issue was a central element that led on 22 May 2014 to the Fukui District Court issuing a landmark ruling against the operation of the Ohi reactors, the case was not an injunction as there was no immediate risk of restart. The Fukui Court ruled in favor of the 200 plaintiffs, who contended that the plant was not sufficiently robust against active seismic faults and that the acceleration at the site could exceed the very high level of 1,260 gal.

Kunihiko Shimazaki, the former NRA deputy chair and a professor emeritus of seismology at the University of Tokyo, in July 2016, voiced strong concerns related to the Ohi reactors and his “sense of crisis” over the approach to earthquake risk analysis by the NRA. Shimazaki had led the team of experts when the NRA examined the fitness of the Ohi reactors at the plant under the new regulations created in the aftermath of the 2011 Fukushima nuclear disaster. He was the only seismologist among the NRA’s five members and in charge of checking utilities’ preparedness for earthquakes and tsunami before he resigned in 2014. In evidence to the NRA, he called for a re-examination of the Ohi site, stating that he had realized that there were problems with the calculating equation adopted by KEPCO and accepted by the NRA, after analyzing the data on the seismic movement during the series of Kumamoto earthquakes that occurred from mid-April 2016.

The NRA on 27 July 2016 announced that it would not be revising its seismic methodology, dismissing Shimazaki’s assessment as “not up to a level that should be recommended by the NRA on the basis of scientific and technical sophistication.” In summer 2016, Shimazaki submitted his analysis to the Kanazawa court, which is considering the KEPCO court appeal. On 23 April 2017, Shimazaki testified to the court that the formulas used by the NRA in computing the scale of earthquakes underestimates potential seismic impact by a factor of 3.5. The case is ongoing.

KEPCO formally announced on 22 December 2017 that it would not invest in the retrofit of its Ohi units 1&2, but had decided to opt for decommissioning.

The restart of Ohi-3 brings to six the number of reactors that have resumed operation since applying for NRA safety review in July 2013. Four reactors are currently operating, three of which are owned by KEPCO, while Sendai-1 is in extended outage for maintenance. Ikata 3, which was in maintenance outage at the time, was ordered shutdown in December 2017 by the Hiroshima High Court due to inadequate defense against volcanic eruption. This means that 30 reactors remain in Long Term Outage (LTO) since none of these have generated electricity during 2014 or 2015. WNISR considers that all 10 Fukushima units are closed and will never restart.

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