Kyushu Electric Restarts Genkai No. 4 Nuclear Reactor

June 18, 2018

Genkai, Saga Pref.- Kyushu Electric Power Co. said Sunday that the No. 4 reactor at its Genkai nuclear plant in southwestern Japan reached criticality, a self-sustained nuclear fission chain reaction, Saturday night following its restart earlier in the day.

The reactor in Saga Prefecture was reactivated for the first time since December 2011, when it went offline for a routine inspection.

The No. 4 unit became the ninth nuclear reactor that has been restarted under the country's stricter safety standards introduced after the March 2011 triple meltdown at Tokyo Electric Power Company Holdings Inc.'s Fukushima No. 1 plant.

Kyushu Electric brought the Genkai plant's No. 3 reactor back online in March this year following the restart in 2015 of the No. 1 and No. 2 reactors at its Sendai nuclear plant in Kagoshima Prefecture, also in southwestern Japan.

All of the four reactors on which Kyushu Electric applied for the Nuclear Regulation Authority's safety checks have now been reactivated.

At the Genkai No. 4 reactor, the company started work to pull out control rods, which stop nuclear fission reactions when fully inserted, at 11 a.m. Saturday (2 a.m. GMT).

The reactor reached criticality at 11:45 p.m. It is expected to begin electricity generation and transmission as early as Wednesday. Commercial operations are seen starting in mid-July.

The Genkai No. 3 and No. 4 reactors passed safety screenings by the NRA in January last year. Kyushu Electric obtained approval for restarting the reactors from the town of Genkai in March last year and from Saga Prefecture in the following month.

The company initially planned to restart the two reactors in January and March this year, respectively.

But the schedule was delayed as it took time to check whether the reactors use products affected by quality data manipulation at Kobe Steel Ltd. <5406> and Mitsubishi Materials Corp. group companies.

The restart of the No. 4 reactor was further delayed by the discovery of a defective cooling water pump in May. Jiji Press