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Japan reactor shutdown to take months

The Financial Times: Jonathan Soble - April 17, 2011

http://www.ft.com/cms/s/0/6a9af5f8-68f3-11e0-9040-00144feab49a.html#axzz1JsQlOzZ0

Japan’s nuclear crisis may take nine months to resolve, according to the first timetable released by Tokyo Electric Power, the operator of the crippled Fukushima atomic plant.

Tepco on Sunday unveiled a plan – its first since the earthquake and tsunami critically damaged the nuclear plant on March 11 – aimed at stopping the leakage of radiation.

The company, which has come under harsh criticism for its handling of the nuclear crisis, said it would take three months to stabilise the cooling system for overheated reactors and spent fuel pools at the plant. Another three to six months would be needed to achieve a “cold shutdown”, it added.

A “cold shutdown” means the water inside a reactor is below 100 degrees centigrade at normal atmospheric pressure – conditions that indicate the reactor’s radioactive uranium fuel is safe from heating up again.

Tepco has been under intense pressure to explain how, and when, it would end the crisis. More than 100,000 people living near the plant have been evacuated, while contamination continues to leak into the air and the sea, albeit in shrinking amounts.

On Sunday, Tsunehisa Katsumata, Tepco’s chairman, suggested that senior executives would resign over the accident. The Japanese government last week upgraded the Fukushima incident to level 7 on the International Atomic Energy Agency scale, putting it on a par with the 1986 Chernobyl accident.

“I feel responsibility ... and so does our president,” said Mr Katsumata, referring to Masataka Shimizu, the executive nominally in control of Tepco’s day-to-day operations but who has been ill during much of the crisis.

Government officials said evacuees would have to wait at least until the “cold shutdown” to return to their homes, though experts say it could be years before residents of the worst contaminated areas can do so.

To meet the timetable, Tepco engineers must cool down radioactive uranium fuel and deal with thousands of tonnes of contaminated coolant water that has collected under the site.

The two tasks are to some extent in conflict. Cooling requires large injections of water, but damage caused by hydrogen explosions means that the more water engineers pump in, the more will leak down into service tunnels and other low-lying areas – from where it could escape into the sea.

One possible new approach is to flood the reactors’ containment chambers with enough water to immerse the steel pressure vessels that hold the fuel. So far, Tepco has been pumping water directly into the pressure vessels – the usual procedure for cooling a reactor – but adding coolant to the normally dry area around them could help bring their temperatures down faster.

Before it can do so, however, engineers must find and seal leaks. The plan also calls for the blown-out reactor buildings to be covered to keep in air.

Once a “cold shutdown” has been achieved, the long decommissioning effort can begin. The whole process is expected to take at least a decade.