Cooling Problem Shuts Nuclear Reactor in Japan

TOKYO — In a fresh blow to public confidence, a reactor in southern Japan went into automatic shutdown on Tuesday because of problems with its cooling system, clouding the outlook for an imminent restart of the country’s idled nuclear plants.

Kyushu Electric, the operator of the reactor at the Genkai nuclear power plant, characterized the incident as minor and said there was no risk of a radiation leak. A problem with the condenser unit that turns steam back into cooling water appeared to have caused the halt, but the reactor stopped safely and was undergoing checks, the utility said.

“At no point was the plant under any danger, and the reactor has been brought to a stable shutdown,” said Eiji Yamamoto, a spokesman for Kyushu Electric. “There has been no effect on radiation levels outside the plant.”

Still, the shutdown came as the government was renewing a push to restart reactors that were idled after the nuclear accident at Fukushima Daiichi in March. Kyushu Electric said that inspection work had been carried out on a valve of the condenser in question on Tuesday, raising the possibility that human error had triggered the shutdown.

“As we saw in Fukushima, cooling systems are central to the safety of nuclear reactors,” said Chihiro Kamisawa, a researcher at the Citizens’ Nuclear Information Center, an antinuclear organization.

“We cannot take lightly the fact that there was also trouble with the cooling system at Genkai,” he said. “It underscores the fact that safety problems riddle Japan’s reactors.”

After Tuesday’s shutdown, only 10 of 54 reactors remain on the grid, threatening to deprive the nation of the source of almost a third of its electricity. At least four of six reactors at the Fukushima plant, which suffered multiple meltdowns, are expected to be permanently decommissioned.

Many other reactors have passed maintenance checks, but have not received the go-ahead to restart. At Genkai, five of six reactors remain offline, and the last is scheduled to halt in December for a maintenance check, legally required every 13 months.

Prime Minister Yoshihiko Noda recently argued for a swift restart of reactors, albeit after extensive “stress tests” of their safety and ability to withstand earthquakes and tsunamis. A drastic loss of nuclear power would bring dire economic consequences, he has repeatedly argued, echoing warnings from Japan’s business lobby.

But he faces an uphill battle amid a collapse of public confidence in Japan’s nuclear program after the accident at Fukushima, where a tsunami knocked out the plant’s cooling systems, setting off meltdowns and a major radiation leak.

The government’s handling of the crisis and its aftermath, from the inadequate evacuation of local residents to scandals involving the restart of other reactors, have added to the public mistrust.

In fact, the governor of the southern prefecture of Saga had tentatively agreed to allow the restart of two idle reactors at Genkai in July. But he rescinded his permission when it was found that Kyushu Electric had tried to manipulate public opinion with fake e-mails to support a reopening of the reactors.

In an Associated Press-GfK poll of Japanese voters conducted this summer, 6 out of 10 respondents said they had little or no confidence in the safety of the country’s nuclear plants. Only 5 percent were very confident.