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Setback in Japan: Plant is still too hot for workers

Radiation may delay latest shutdown plan

By Hiroko Tabuchi
New York Times / April 19, 2011

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TOKYO — Robots deployed inside two reactors at the Japanese nuclear plant overrun by last month’s devastating tsunami have detected radiation levels too high for workers to enter, posing immediate challenges for a new plan to bring the ravaged complex under control by year’s end.

Workers have not been able to enter four of the reactors at the Fukushima Daiichi Nuclear Power Plant since the days immediately after the earthquake and tsunami struck on March 11. Vital cooling systems at the plant were knocked out, setting off hydrogen explosions at four of the plant’s six reactors that blew off their roofs and littered the site with radioactive debris.

On Sunday, two robots made their way into two of those reactor units, opening doors and navigating radioactive debris and puddles of water to return with temperature, pressure, and radioactivity readings. The readings, released yesterday, showed continued high radiation levels inside the reactors.

The remote-controlled PackBots, built by the iRobot company of Bedford, Mass., are 60-pound contraptions with steel arms and caterpillar tracks. They can operate in austere environmental conditions, lift about 30 pounds, go up and down steps, carry cameras that send images back to an operator, and use a kit that senses radiation.

At Unit 1, the robots detected radiation of up to 49 millisieverts per hour, while at Unit 3, the reading was 57 millisieverts per hour. But in recent weeks far higher readings have come from areas where contaminated water has accumulated, like the turbine building at Unit 2, where engineers say the reactor pressure vessel may be cracked and leaking nuclear material.

Those levels must come down before workers can be allowed back inside, said Hidehiko Nishiyama, deputy director general at the Nuclear and Industrial Safety Agency.

Radiation exposure for emergency workers in Japan is currently capped at 250 millisieverts of radiation annually. That means workers would be able to work for about four hours at Unit 1 under current conditions. “It is a harsh environment for humans to work in,’’ Nishiyama said.

He said the high radiation would require the plant’s operator, the Tokyo Electric Power Co., to be creative in bringing the plant to a stable state known as a cold shutdown within six to nine months, as the company laid out in a timetable on Sunday.

The Japanese government continues to face severe challenges, both technical and political, in the aftermath of a multifaceted disaster that has left 13,800 people dead and 14,000 missing.

At least 137,000 people remain in evacuation centers, some driven from their homes by radiation leaks from the Fukushima Daiichi plant.

Japan’s Finance Ministry has said the cost of damage from the earthquake and tsunami alone could reach $300 billion, making it the world’s most costly natural disaster.

Prime Minister Naoto Kan came under fire yesterday from opposition lawmakers who accused him of bungling the initial response to the crisis at Fukushima.

“Many Japanese feel that Prime Minister Kan has no leadership,’’ Masashi Seki, a lawmaker of the main opposition, the Liberal Democratic Party, said at an unusually heated parliamentary session, as other opposition members heckled Kan.

Sadakazu Tanigaki, the leader of the Liberal Democratic Party, last month called on Kan to resign.

“I do not think that my response has been inadequate, as many say,’’ a flustered-looking Kan said. “Nonsense!’’

In a poll released yesterday by the Nikkei, Japan’s largest business daily, 69 percent of respondents said Kan should be replaced, and 70 percent said the government’s response to the nuclear crisis was unacceptable.

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