TSURUGA, Fukui Pref. – Kansai Electric Power Co. on Friday shut down a reactor at the Mihama nuclear plant in Fukui Prefecture after failing to halt a leak that had been spewing radioactive cooling water for almost three days, company officials said.
The leakage from the container vessel at the plant’s No. 3 reactor was detected shortly after 1:40 a.m. Tuesday, Fukui prefectural officials said.
By the early hours of Friday morning, 5.6 tons of radioactive water had leaked out.
While the authorities of the town of Mihama, the Fukui Prefectural Government and the national government were informed by Kansai Electric of the leak Tuesday morning, the public was kept in the dark until the early hours of Friday, when Kansai Electric was forced to shut down the reactor to carry out repairs.
The leaked water contains low levels of radioactivity, the officials claimed, and poses no threat to the local community. The water has accumulated inside the reactor, they said.
Company officials said the leak, located in a welded part of a reactor container valve that regulates the flow of coolant water, was detected by employees carrying out an inspection of the reactor system.
The leak came from the primary cooling system of the 826,000-kw pressurized-water reactor. After the leakage rate had accelerated nearly sevenfold, engineers decided to shut down the reactor.
When the leakage was first detected, radioactive water was flowing out of the container vessel at a rate of about 60 liters per hour. By late Thursday, it was gushing out at about 400 liters per hour, according to Kansai Electric officials.
Fukui officials said they determined it was unnecessary to inform the public of the leak as there were no changes in power output and no apparent influence on the reactor’s operation.
Local residents opposing nuclear power complained about the situation. Such incidents should be made public regardless of scale, they said.
A government agency on nuclear safety said it provisionally rated the incident as being of the lowest level in accordance with an international evaluation system.
The radioactive level of the coolant water was “quite low,” an official of the Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade and Industry said, pointing out it had been filtered.
Also Friday, Kansai Electric Power said in a midterm report of its review of close to 100 occasions of voluntary inspections of nuclear reactors conducted over the past decade that the inspections were carried out appropriately.
The report was presented to the national government and the Fukui Prefectural Government in the wake of a series of scandals involving Tokyo Electric Power Co., which concealed safety problems at its nuclear plants.
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