Japan's Oi reactor resumes operations

FUKUI - The No. 3 reactor at Kansai Electric Power Co.'s Oi nuclear power plant reached criticality at 6 a.m. Monday after its operations resumed Sunday, ending the nation's 57-day nuclear power hiatus.

A nuclear reactor reaches criticality when a sustained nuclear chain reaction occurs inside the reactor, and this is considered to be the first hurdle to clear in the process of generating electricity.

Confirmation of criticality verifies a nuclear reactor can operate properly, and if the process goes smoothly, the No. 3 reactor will start supplying electricity Wednesday and resume full operations Sunday.

Operations of the No. 3 reactor at the power plant in Oi, Fukui Prefecture, which had been suspended for regular inspection since March 18 last year, were restarted at 9 p.m. Sunday, and in nine hours reached criticality as initially scheduled.

This is the nation's first reactor to resume operations after a regular inspection, which was conducted following the crisis at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant in March last year.

With the No. 3 reactor at Hokkaido Electric Power Co.'s Tomari power station in Tomari, Hokkaido, going offline May 5, the number of active reactors in the nation was brought to zero. But with Sunday's resumption at the Oi power plant, Japan has made the first step in its return to the use of nuclear power.

At 9 p.m. Sunday, a worker in the central control room gave the command to withdraw control rods inside the pressurized-water reactor and declared its operation had resumed.

Seishu Makino, senior vice minister of the Economy, Trade and Industry Ministry, was present in the room as the rods were withdrawn, while an inspector from the Nuclear and Industrial Safety Agency oversaw the worker's operations procedures.

Makino is responsible for the government's special monitoring system, which was set up to ensure safety at the power plant until a new nuclear regulatory agency is formed.

The No. 3 reactor, which has a maximum power output of 1.18 million kilowatts, will be tested on the operation of its turbine to generate electricity at a 5 per cent level.

If it runs without any problem, it will enter a control operation, which generates power by connecting to the transmission system, raising its output to 100 per cent.

Assuming the power plant passes a final inspection by the government, it will be approved for commercial operations in early August.

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