{EOP}Japan: Damaged Nuclear Reactors being prepared for a cold shutdown

The manager of the crippled Fukushima Daiichi nuclear power plant on Friday began boosting the quantity of coolant being poured into the site's No. 1 reactor, Kyodo News reported (see GSN, May 5). The increased insertion of water is part of an ongoing effort to prevent additional radiation releases from four reactors at the six-reactor plant, which was severely damaged in the March 11 earthquake and tsunami that left more than 20,000 people dead or missing in Japan. Radiation releases on a level not seen since the 1986 Chernobyl disaster have already forced the evacuation of about 80,000 residents from a 12-mile ring around the facility. Tokyo Electric Power is now dumping 8 tons of water per hour into the No. 1 reactor's pressure vessel, up from a prior 6 tons per hour. Officials hope to inject enough liquid in the reactor's containment vessel to keep its nuclear fuel underwater for about 20 days, as they install and turn on a coolant system. The company intends over a three-month period to take a similar approach in reactors No. 1 to 4, Kyodo reported (Kyodo News/Japan Times, May 6).

Workers this week began readying ventilators to clear out radiation in the No. 1 reactor in advance of installation of the cooling system. Personnel had not been allowed inside the reactor since a hydrogen explosion that followed the natural disasters. "Things are moving forward steadily, one by one. Our final goal is to bring them (the reactors) to a cold shutdown. As a first step towards that, we were able to go inside the building and this is a major point", Tokyo Electric Power official Junichi Matsumoto said to reporters. In cold shutdown, nuclear fuel rods within reactors are submerged in water that is kept under 100 degrees Celsius, curbing additional overheating and releases of radiation. The company has ruled out further hydrogen explosions at the No. 1 reactor as more water is poured into the containment vessel, according to a report delivered to the Japanese Nuclear and Industrial Safety Agency. The agency is keeping watch on increasing temperatures in reactor No. 3, which have hit 240 degrees Celsius, said NISA Deputy Director General Hidehiko Nishiyama.

"We do not need to be suddenly worried, but we need to be careful if it continues to rise," he said, noting that Tokyo Electric Power has also boosted its rate of water insertion into that reactor. Radiation levels in some ocean material outside the plant have been identified at 10,000 times above standard amounts, Nishiyama added. "The possibility of a new leak (into the sea) is not zero, but we do not have firm data", he said. Achieving cold shutdown is expected to require three to six months beyond the three-month cooling period in the reactors, Reuters reported. Obstacles such as additional earthquakes and loss of power could extend the period needed to stabilize the reactor fuel, according to some observers. The site would be permanently shuttered, but would probably remain unsafe for humans.
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