Japan's No. 4 N-reactor at Oi plant resumes power supply

The No. 4 reactor at the Oi nuclear power plant in Oi, Fukui Prefecture, resumed electricity generation and transmission at 7 a.m. Saturday.

The reactor of Kansai Electric Power Co. has an output capacity of 1.18 million kilowatts and is scheduled to reach full capacity on Wednesday.

Once at full capacity, the operation will resolve most power shortages in KEPCO's service area.

After the reactor reaches full capacity, the government will lower its electricity-saving target in Shikoku Electric Power Co.'s service area, which was expected to transfer power to KEPCO to make up for a possible shortfall.

The target in Shikoku's service area will now drop from 7 per cent less than power levels consumed in summer 2010 to 5 per cent.

Electricity saving targets in the service areas of Chubu Electric Power Co., Hokuriku Electric Power Co. and Chugoku Electric Power Co. will be canceled.

The government will soon officially decide whether the target in KEPCO's service area should be maintained.

Because two of the Oi plant's reactors, which can operate 24 hours a day, have gone online, output from pumped storage power generators, which use surplus power from nuclear plants at night and produce electricity in peak demand hours, will also increase.

KEPCO had estimated if all its nuclear reactors remained idle, power supply would be 4.45 million kilowatts, or 14.9 per cent, short of the peak demand seen in summer 2010, when temperatures were extremely high.

With the resumption of operations at the Nos. 3 and 4 reactors at the Oi plant, KEPCO's supply capacity rose by a total of 2.36 million kilowatts from the two nuclear reactors plus 2.1 million kilowatts from water storage power generation.

Thus power supply and demand in the utility's service area will mostly be in balance.

However, should trouble arise, such as a breakdown at the plant, the supply-demand conditions will quickly become tight. In that case, rolling blackouts may occur.

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