IWAKI (Japan): An explosion at a nuclear power station yesterday destroyed a building housing the reactor amid fears that it was close to a disastrous meltdown after being hit by a powerful earthquake and tsunami.
Tokyo Power Electric Co, the utility that runs the Fukushima Dai-ichi plant, said four workers had suffered fractures and bruises and were being treated at a hospital.
A nuclear expert said a meltdown may not pose widespread danger.
Footage on Japanese TV showed that the walls of the reactor's building had crumbled, leaving only a skeletal metal frame standing. Puffs of smoke were spewing out of the plant in Fukushima, 30km from here.
"We are now trying to analyse what is behind the explosion," said government spokesman Yukio Edano, stressing that people should quickly evacuate a 10km radius.
The trouble began at the plant's Unit 1 after the massive earthquake and the tsunami it spawned knocked out power there.
Japan has declared states of emergency for five nuclear reactors at two power plants after the units lost cooling ability.
The most troubled one, Fukushima Dai-ichi, is facing meltdown, officials have said.
A "meltdown" is not a technical term. Rather, it is an informal way of referring to a very serious collapse of a power plant's systems and its ability to manage temperatures.
It was not immediately clear if a meltdown would cause serious radiation risk, and if it did how far the risk would extend.
Pressure has been building up in Fukushima reactor -- it's now twice the normal level -- and Japan's Nuclear and Industrial Safety Agency told reporters yesterday that the plant was venting "radioactive vapours."
The reactor in trouble has already leaked some radiation: Operators have detected eight times the normal radiation levels outside the facility and 1,000 times normal inside Unit 1's control room.
Ryohei Shiomi, a nuclear official, said that each hour the plant was releasing the amount of radiation a person normal absorbs in a year.
He said that even if there were a meltdown, it wouldn't affect people outside a 10km radius -- an assertion that might need revising if the situation deteriorates.
Most of the 51,000 residents living within the danger area had been evacuated, he said.
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