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JAPAN鈥橲 Nuclear Safety Commission has upgraded the incident at the Fukushima Daiichi nuclear power station to level 7, the most severe category on the used to rate nuclear accidents. Only the Chernobyl disaster of 1986 has previously been rated level 7.
Fukushima, previously assessed at level 5, was recategorised on the basis of the amount of radioactive material released so far. Japan鈥檚 Nuclear and Industrial Safety Agency into the environment, substantially exceeding the level 7 threshold of 鈥�.
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Nevertheless, , a nuclear engineer at Imperial College London, says he is surprised by the decision. 鈥淎ll the evidence so far is that the amount and form of material released is nothing like Chernobyl,鈥� he says, pointing out that the Chernobyl plant exploded while the reactor was running, while the reactors at Fukushima shut down immediately after last month鈥檚 earthquake struck. Chernobyl released a total of 5,200,000 TBq.
The decision came shortly after the Japanese government announced plans to widen the evacuation zone around the plant 鈥� two weeks after the recommended such a move. Everyone within 20 kilometres has already been evacuated, but the wind carried radioactive material further in some directions. As a result, five towns and villages outside the zone will also be cleared.
The plant鈥檚 operator, Tokyo Electric Power Company, has into the Pacific Ocean to make room in a storage pond for more highly radioactive water from the reactors. Circulation models created by the at the University of Toulouse in France suggest that most of the material is still .
Oceanographer of the University of Southampton, UK, says that fishing in this area could be banned for decades. Any material escaping further into the ocean will rapidly become harmlessly dilute.