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Japan – Ohi No.4 reactor working at full capacity

Wednesday, July 25, 2012

Laaska News  July 25,   2012

The second reactor to resume operation in Japan after the nuclear accident in Fukushima is now generating power at full capacity.

Officials raised the output of the No.4 reactor at the Ohi nuclear plant in Fukui Prefecture, central Japan, at midnight on Tuesday after final safety checks.

The reactor reached its full capacity about one hour later on Wednesday morning. Senior vice industry minister Seishu Makino was at the plant’s central control room to oversee the procedure.

The plant operator, Kansai Electric Power Company, restarted the No.4 reactor on July 18th.

Ohi’s No.3 reactor resumed operation earlier this month and is running at full capacity.
The 2 reactors have the biggest output of those run by Kansai Electric, whose service area covers the country’s second-largest city, Osaka.

Now that the 2 reactors are working at full swing, the government plans to lift the power-saving targets imposed on the service areas of 3 other utilities in central and western Japan.

These firms are supposed to supply electricity to Kansai Electric in the event of power shortages.

The government gave the go-ahead for Ohi’s restart last month, saying its safety has been confirmed.

But a panel of experts is calling for a fresh survey of the underground cracks at the plant to check if they are active faults.

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Causes of largest radioactive leaks may be found

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Experts say work to lower the core pressure at one of reactors may have led to the largest radioactive leaks from the Fukushima Daiichi nuclear plant in March last year.

Among the 4 reactors at the Fukushima plant, the No. 2 reactor leaked the largest amount of radioactivity according to nuclear disaster monitoring.

Researchers from the University of Tokyo, the Japan Atomic Energy Agency and other experts have examined the crisis response log at the reactor facility. They also checked radiation levels in surrounding areas.

They found radiation levels rose sharply 3 times at monitoring posts 10 kilometers south of the plant over a period of 5 hours during the night of March 14th.

These rises came 1 hour after each time workers at the No. 2 reactor released steam from the core to lower its pressure. The plant employees did so to protect the reactor.

But it is believed that by that time the nuclear fuel in the core had already melted down and its containment vessel was also full of radioactive substances.

The experts assume that the radioactive plume escaped from cracks in the containment vessel after steam was released from the core. It was carried south by the wind.

They say the amount of the radioactivity leaked from the No. 2 reactor was 10 to 20 times higher than other reactors, following their hydrogen explosions.

The Japan Atomic Energy Agency’s Masamichi Chino says the leaks were serious and need to be further studied even though they occurred as a result of work to protect the reactor.

Tokyo Electric Power Company, the operator of the Fukushima Daiichi nuclear power plant, says opening the valve was the only solution at the time.

It says there was a need to prevent radioactive substances from leaking massively due to damage to the reactor.

TEPCO also says it will examine how the radioactive leaks occurred.

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Jul. 24, 2012

 

NHK.