12 april 2011

Fukushima crisis ‘on par with Chernobyl’

By Jonathan Soble and Michiyo Nakamoto in Tokyo and Clive Cookson in London, Financial Times, April 12 2011

Japan has raised its assessment of the continuing crisis at Fukushima Daiichi nuclear power station, putting it on a par with the 1986 Chernobyl disaster in the former Soviet Union.

Japanese authorities said on Tuesday that the two-notch increase from five to seven – the highest level on the International Atomic Energy Agency scale – did not signal new dangers or setbacks at the plant. Rather, they said, it reflected the first comprehensive contamination estimate since the crisis was triggered by an earthquake and tsunami on March 11.

The country’s nuclear regulator said the volume of radioactive material released at Fukushima was only about a 10th of that at Chernobyl.

Most of the radiation escaped in the first few days of the emergency, when hydrogen explosions damaged the facility. Readings at the plant and surrounding areas have fallen steadily since. The reassessment marks only the second time in the six-decade history of commercial nuclear power that an accident received the worst rating on the IAEA scale. It will, however, be weeks or months before engineers can cool the station’s overheated uranium fuel to safe levels – a precondition for stopping radiation leaks altogether.

The decision to raise the level by two steps surprised some experts, given that the radiological consequences of Chernobyl were far more serious. The fire and explosion at Chernobyl propelled more nuclear material into the atmosphere, causing significant radioactive fallout far from the stricken reactor.

Japanese authorities – unlike their Soviet counterparts in what is now Ukraine – took steps to protect the health of emergency workers and the local population immediately after the Fukushima accident.

“By evacuating and sheltering the population, implementing food bans and distributing potassium iodide tablets, the Japanese authorities will have prevented the most serious health effects,” said Jim Smith, an environmental physicist at the University of Portsmouth in the UK.

Twenty-one workers at Fukushima have been exposed to radiation doses of more than 100 millisieverts, normally the maximum annual amount for nuclear workers in emergency situations but below the level at which acute radiation sickness occurs.

Two more workers died in the tsunami but none have been killed battling the radiation leaks – compared with about 30 deaths from radiation poisoning among emergency workers at Chernobyl.

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