U.S. Warns of a Large Radiation Release

The top U.S. nuclear regulator, Gregory Jaczko, gave a dire assessment of Japan's nuclear crisis yesterday, saying that lethal radiation from uncovered spent fuel above one of the reactors could force emergency workers to abandon their fight to prevent meltdowns of damaged reactor cores at the Fukushima Daiichi plant.

Jaczko, chairman of the Nuclear Regulatory Commission, said his staff in Tokyo had been told by Japanese utility officials that cooling water that normally covers spent fuel was nearly or totally gone from an uncovered concrete pool above reactor Unit 4. Based upon that assessment, the U.S. Embassy in Tokyo advised Americans living within about 50 miles of the plant on Japan's northeast coast to evacuate farther away. Japan has called for an evacuation within about 12 miles of the plant.

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