Seawater radiation level soars near nuclear plant

Previous measurements have shown that water from the No. 2 reactor is highly radioactive and is believed to have come from partly melted fuel in the reactor's core.

March 31, 2011 12:38 IST | India Infoline News Service

Evels of radiation in the ocean next to the Fukushima Daiichi nuclear power plant have surged to record highs, the government said Wednesday, as operators try to deal with large amounts of radioactive water-the unwanted byproduct of operations to cool the reactors. The Nuclear and Industrial Safety Agency said water taken Tuesday afternoon from the monitoring location for the troubled reactors Nos. 1 to 4 had 3,355 times the permitted concentration of iodine-131. That is the highest yet recorded at the sampling location, which is 330m south of the reactors' discharge outlet. "The levels are rising and we would like to find the reasons as soon as possible so we can put countermeasures in place," agency spokesman Hidehiko Nishiyama said at a press conference. Previous measurements have shown that water from the No. 2 reactor is highly radioactive and is believed to have come from partly melted fuel in the reactor's core.

The source of the leak is not yet known, authorities said. To reduce the amount of water leaking from unit No. 2, as well as from unit No. 3, plant operator Tokyo Electric Power Co. has been injecting less fresh water into the vessels. This, however, has led to some increase in temperature, requiring a careful balancing to keep the reactors from overheating while reducing the discharge of highly radioactive water. As Tepco struggled with the enormous task of trying to bring the three most seriously damaged reactors to a safe condition, company president Masakata Shimizu was admitted to hospital on Tuesday due to elevated blood pressure and dizziness. The company said that Mr. Shimizu had previously been away from the company's crisis headquarters due to illness. Tepco chairman Tsunehisa Katsumata held an unscheduled news conference Wednesday to announce the news on Shimizu.

He said that "some stability" has been achieved at the Daiichi plant but acknowledged that the reactors Nos. 1 to 4 were expected to be retired from service. The nuclear agency's Nishiyama, meanwhile, said that low pressure levels recorded for the No. 2 and 3 reactors could be a sign that the areas around valves and other inlets of the pressure and containment vessels may have weakened and may be leaking. The scope of the water problem became clear earlier in the week when authorities announced that three trenches holding pipes had filled with radioactive water. The situation at reactor No. 2 was especially problematic: The water's radioactivity was measured at 1,000 millisieverts per hour, four times the allowable annual dose for a nuclear worker, even in an emergency situation. There is no place to transfer the water, since other appropriate locations were already filled.

Nishiyama said that the lessdangerous water would be moved to other tanks on the site to allow for pumping of the most- radioactive water into what are known as the condenser units, which are normally used to allow steam to cool down. Removing the water is the key prerequisite to the critical task of bringing the in-house cooling units back on line, which would provide a stable source of cooling over the longterm. But progress is expected to be slow. Tepco officials said that it would take three days to transfer the water so that the pumping out of the basements could begin. Nishiyama said that the contamination of the seawater was not a risk because of the government's 20km evacuation zone and because iodine-131 degrades quickly and does not pose a long-term health threat.

Earlier, chief government spokesman Yukio Edano said that special covers may be put over the now-open roofs of reactors 1, 3 and 4-the roofs were destroyed in a series of hydrogen explosions-to help reduce the amount of radiation escaping into the air. He added that officials are also studying the use of emulsions at the plant to reduce dust, which can carry radioactive material. Small amounts of highly dangerous plutonium were detected in soil around the plant Monday. The international focus on the crisis also remained at a high level. US President Barack Obama spoke Tuesday with Japanese Prime Minister Naoto Kan, and French President Nicolas Sarkozy is to visit Japan on Thursday in his role as head of the G-20 group of nations. A team of experts from the French nuclear-fuel company Areva SA are also on their way to Japan to offer advice on removing radioactive contaminants.

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