Intensive soil decontamination will be necessary for evacuees from the areas surrounding the Fukushima nuclear plant can return to their homes, according to an expert said Wednesday the Atomic Energy Commission of Japan. Tomio Kawata, a researcher at the Organization for Nuclear Waste Management Japan, submitted to the commission an estimate of the contamination in the soil of the area based on radiation levels in air collected by the Ministry of Science Japan.
As assessed by Kawata, soil in an area of 600 square kilometers northwest of the plant could have absorbed more than 1.48 million becquerel radiocaesium per square meter, which was the limit for mandatory evacuation in the vicinity of rugged Chernobyl plant. Kawata also noted that the full extent of the contaminated areas are only one-fifth to one tenth of the area affected by radiation from the Ukrainian plant, which in 1986 suffered the worst nuclear accident in history.
It is estimated that radiation exposure to 1.48 million becquerel per square meter is around five mSv per year, well below the limit of 20 mSv per year set by the Government of Japan for evacuation. However, the study says Kawata will need to decontaminate the land intensively before the return of the evacuees as cesium adheres strongly to it and makes it difficult to reduce radiation levels in the long term.
The earthquake and tsunami of March 11 severely damaged the plant facilities, operated by Tokyo Electric Power (TEPCO), who on Wednesday indicated that the primary containment vessel of the reactor 1 was almost certainly damaged. The electric noted that the molten fuel unit caused the vessel temperature reached 300 degrees Celsius for 18 hours after the quake, twice what it can stand, so it is very likely to be drilled and poured radioactive water the building that houses the unit.
On Tuesday, TEPCO announced that the reactor fuel 2 and 3 also partially melted, but remains, as in unit 1, a stable cooling. Will require further analysis to determine whether they were perforated containment vessels of the two reactors and whether any leakage of contaminated water. Because of the problem to possible perforation of the vessels, TEPCO announced May 17 that would change his plan to flood with water for cooling reactors, although it maintained its plan to take a "cooling down" at the latest by January 2012. 
As assessed by Kawata, soil in an area of 600 square kilometers northwest of the plant could have absorbed more than 1.48 million becquerel radiocaesium per square meter, which was the limit for mandatory evacuation in the vicinity of rugged Chernobyl plant. Kawata also noted that the full extent of the contaminated areas are only one-fifth to one tenth of the area affected by radiation from the Ukrainian plant, which in 1986 suffered the worst nuclear accident in history.
It is estimated that radiation exposure to 1.48 million becquerel per square meter is around five mSv per year, well below the limit of 20 mSv per year set by the Government of Japan for evacuation. However, the study says Kawata will need to decontaminate the land intensively before the return of the evacuees as cesium adheres strongly to it and makes it difficult to reduce radiation levels in the long term.
The earthquake and tsunami of March 11 severely damaged the plant facilities, operated by Tokyo Electric Power (TEPCO), who on Wednesday indicated that the primary containment vessel of the reactor 1 was almost certainly damaged. The electric noted that the molten fuel unit caused the vessel temperature reached 300 degrees Celsius for 18 hours after the quake, twice what it can stand, so it is very likely to be drilled and poured radioactive water the building that houses the unit.
On Tuesday, TEPCO announced that the reactor fuel 2 and 3 also partially melted, but remains, as in unit 1, a stable cooling. Will require further analysis to determine whether they were perforated containment vessels of the two reactors and whether any leakage of contaminated water. Because of the problem to possible perforation of the vessels, TEPCO announced May 17 that would change his plan to flood with water for cooling reactors, although it maintained its plan to take a "cooling down" at the latest by January 2012.
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