Japan raised the alert level from 5 to 7, the highest rating, at the earthquake-damaged Fukushima Daiichi nuclear-power plant. That makes the disaster equal to the explosion at Ukraine's Chernobyl power plant in 1986. The amount of nuclear material released from the Japanese facility is about 10% of the total that escaped from Chernobyl, said Hidehiko Nishiyama, deputy director general of Japan's nuclear regulator.

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