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Tohoku Electric to scrap aging Onagawa nuke plant reactor over maintenance costs

The Onagawa Nuclear Power Plant is pictured in Onagawa, Miyagi Prefecture, in February 2017. (Mainichi)

Tohoku Electric Power Co. has decided to decommission the idled No. 1 reactor at its Onagawa Nuclear Power Station in the northeastern Japan prefecture of Miyagi, the utility's president Hiroya Harada announced on Oct. 25.

The company decided to scrap the reactor after determining that it would be burdensome to bring it up to new safety standards implemented in the wake of the Fukushima nuclear disaster triggered by the March 2011 Great East Japan Earthquake and tsunami.

To bring the plant back online, Tohoku Electric would need to greatly strengthen the reactors against earthquakes and tsunamis, and provide measures against terrorism to pass strict screening by the Nuclear Regulation Authority (NRA). Though the company has not provided details of the required work, it is believed it would cost a huge amount.

Furthermore, a rule implemented in the wake of the Fukushima disaster limits the operational life of nuclear reactors to 40 years in principle, and 34 years have passed since the Onagawa plant's No. 1 reactor went into service in June 1984. This means the reactor could only operate for a few years even if it were reactivated.

Additionally, the No. 1 reactor has an output of just 524,000 kilowatts, smaller than the 825,000 kilowatts of the plant's No. 2 and 3 reactors. All three reactors at the plant -- the oldest of four nuclear stations operated by Tohoku Electric -- remain idled in the wake of the 2011 tsunami, which flooded the No. 2 reactor building.

In its basic energy plan, the government has designated nuclear power as an important baseload source of energy, and it aims to increase the rate of nuclear power generation in the country to 20-22 percent of total electricity production by fiscal 2030. This is premised on having around 30 nuclear power reactors in operation, but since the Fukushima nuclear disaster, just nine reactors have passed NRA screening and been reactivated.

The decision to dismantle the No. 1 reactor at the Onagawa plant means that 10 reactors at seven plants -- not including the reactors at the disaster-stricken Fukushima Daiichi Nuclear Power Station in northeastern Japan -- have now been slated for decommissioning.

"Even if other nuclear power plants are reactivated in the future, unless exemptions are permitted to allow the reactors to operate for up to 60 years, then reactors will start being decommissioned one after another. Reaching the target nuclear power ratio in (Japan's) energy is quite a high hurdle," an official at one major power company commented.

(Japanese original by Atsuko Motohashi, Sendai Bureau; Takayuki Hakamada, Business News Department; and Riki Iwama, Science & Environment News Department)

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