Soaring radioactivity deals blow to Japan's plant (Shinichi Saoshiro)

Mar. 27, 2011 -- 11:21 p.m. JST (10:21 EST) -- TOKYO (Reuters) -- Workers were withdrawn from a reactor building at Japan's earthquake-wrecked nuclear plant Sunday after potentially lethal levels of radiation were detected in water there, a major setback for the effort to avert a catastrophic meltdown.

The operator of the facility said radiation in the water of the No. 2 reactor was measured at more than 1,000 millisieverts an hour, the highest reading so far in a crisis triggered by a massive earthquake and tsunami on March 11.

That compares with a national safety standard of 250 millisieverts over a year. The U.S. Environmental Protection Agency says a single dose of 1,000 millisieverts is enough to cause hemorrhaging.

Plant operator Tokyo Electric Power Co. later said the extremely high radioactivity readings might have been wrong, adding the levels were being re-checked.

READ MORE: Reuters