Japan reviews radiation exposure levels

April 6, 2011 at 12:20 PM
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TOKYO, April 6 (UPI) -- Japan is reviewing radiation exposure levels used to designate the evacuation zone around the earthquake-damaged Fukushima nuclear power plant, officials said.

Currently, the government said outside radiation levels greater than 50 millisieverts require evacuation and levels exceeding 10 millisieverts mean residents should remain indoors, Kyodo News reported.

"The current standards represent safety in the event of absorbing a huge amount of radiation in a short period," Chief Cabinet Secretary Yukio Edano said during a news conference.

Residents within 12 miles of the Fukushima Daiichi nuclear facility damaged by the March 11 9-magnitude earthquake and tsunami are ordered to evacuate, and those living within a 12-to-18-mile radius must stay indoors.

In emergencies, the International Commission on Radiological Protection recommends the highest planned residual dose over a year's time range from 20 millisieverts to 100 millisieverts.

Seiji Shiroya, a member of the Japan's safety commission, said the international organization's recommendation would be used as a reference point to possibly strengthen Japan's radiation exposure limits.

Edano said residents who left their homes near the crippled plant should be eligible for compensation paid by plant operator Tokyo Electric Power Co., Kyodo said.

The government also decided to allow residents of areas within the zone to return home for short, supervised visits, possibly starting Monday, one month after the catastrophic quake killed thousands of people, left hundreds of thousands homeless and cut a path of destruction across northeastern Japan.

Tokyo Electric Power, operator of the Fukushima nuclear plant, said Wednesday its workers stopped the heavy leakage of highly contaminated water into the Pacific Ocean by injecting huge quantities of what is called "water glass" or sodium silicate and other chemical agents around a pit near the No. 2 reactor, believed to be the source of the leak. Water from the reactor's core, where fuel rods have partially melted, may have ended up in the pit.

Despite government assurances to the contrary, the escape of the water may have contaminated the marine environment near the plant, Kyodo News reported.

Adding to the concerns of food contamination is Tokyo Electric's program to release low-level radioactive water into the Pacific, which Tokyo Electric hoped would provide additional storage for the more contaminated water in the basement of the reactor buildings.

Japanese Industry Minister Banri Kaieda Tuesday apologized to the public, especially fishermen, for causing concern about the process but assured the discharge of the low-level radioactive water posed no major health risk. The government nuclear safety agency is part of his ministry.

Kaieda said the flooded basement of the buildings and their underground trenches at Nos. 1, 2 and 3 reactors are believed to hold about 60,000 tons of the more highly radioactive water. This water, which is also preventing workers from doing other emergency work, eventually will be removed by the company, the minister said.

As current plans stand, Tokyo Electric was to dispose of about 11,500 tons of the less contaminated water into the sea by the weekend. The more highly radioactive water is to be stored in tanks at the reactors' nuclear waste disposal sites, the nuclear safety agency said. Those tanks will be shipped by the end of the month.

But before that happens, the utility must ensure there is no more higher radioactive water leaking from the facility. Only after that can workers perform such critical tasks as restoring the cooling systems.

Agriculture, Forestry and Fisheries Minister Michihiko Kano said his ministry will tighten inspections of marine products caught off Ibaraki prefecture, down-current from the nuclear plant. He said halibut, flounder and sardines would be inspected daily for radioactive material at Nakaminato fishery port in Hitachinaka in Ibaraki prefecture, Yomiuri Shimbun reported.

The human death toll from the March 11 catastrophe, as confirmed by Japan's National Police Agency, was 12,468 as of Wednesday morning. The agency put the number of missing at 15,091.

In Fukushima Prefecture, authorities, at the request of the parents of children who are starting a new academic year, have begun taking radiation measurements in school areas. The effort will cover about 1,400 schools outside the 12.5-mile evacuation zone of the plant.

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