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Takahama-4 Reactor Fails Grid Connection in Japan

Wednesday 2 March 2016

Takahama-4 Fails Grid Connection in Japan

2 March 2016

After a nearly five-year-long outage, Takahama-4 reactor failed to connect to the grid as planned on 29 February 2016. Only three other units have been restarted in Japan after all nuclear plants had progressively been shut down following the 2011 Fukushima disaster. Located in Fukui prefecture in the Chubu region of Japan, the 32-year-old Takahama-4 reactor, owned by Kansai Electric Power Company, was restarted on 26 February 2016, having been shutdown since 21 July 2011. When grid connection was attempted, the main transformer/generator internal failure alarm went off, which triggered an automatic generator trip, according to Kansai Electric. The exact cause has yet to be determined, while the utility announced that an investigation, including root cause analysis, would be conducted into the grid connection failure. Kansai Electric submitted an application for review of the reactor by the Nuclear Regulation Authority (NRA) in July 2013. The reactor is being moved to cold shutdown status with restart now not expected before April 2016.

Takahama-4 had already experienced restart problems, when on 20 February 2016, radiation alarms went off in an auxiliary building following a leak of primary cooling water. Kansai Electric proceeded to check other cooling water valves and identified the problem as being loose bolts dating from 2008. Preparation tests for restart were temporarily suspended.

Both Takahama reactors were subject to an injunction preventing restart, issued by the Fukui District Court in April 2015. The court ruled in favor of local citizens, who charged that the safety regulations of the NRA were inadequate and that, amongst other safety issues, the Takahama reactors remained vulnerable to seismic risks. On 24 December 2015, the injunction was overturned on an appeal filed by Kansai Electric, which opened the way for restart. The case has now been addressed to the Kanazawa High Court, where an appeal on the decision filed by citizens will hear evidence on the multiple safety issues that have raised concerns within the wider Kansai region, including prefectural governments in Shiga and Kyoto.

Takahama-3 and -4 are the first reactors to be restarted in Japan with a percentage of plutonium bearing MOX fuel in the core. The MOX fuel was supplied by French company AREVA, with four assemblies loaded in unit 4.

The failure to restart Takahama-4, leaves 37 reactors (including Monju) in Japan in Long Term Outage (LTO), since none of these have generated electricity during 2014 or 2015. WNISR considers that the 10 Fukushima units are shut down and will never restart.

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