SOMA, Japan – The second hydrogen explosion in three days rocked Japan's stricken Fukushima Dai-ichi nuclear plant Monday, sending a massive column of smoke into the air and wounding 11 workers. Hours later, the U.S. said it had shifted its offshore forces away from the plant after detecting low-level radioactive contamination.
The aircraft carrier USS Ronald Reagan was about 100 miles (160 kilometers) offshore when it detected the radiation, which U.S. officials said was about the same as one month's normal exposure to natural background radiation in the environment.
It was not clear if the radiation had leaked during Monday's explosion. That blast was felt 25 miles (40 kilometers) away, but the plant's operator said radiation levels at the reactor were still within legal limits.
The explosion at the plant's Unit 3, which authorities have been frantically trying to cool after a system failure in the wake of Friday's massive earthquake and tsunami, triggered an order for hundreds of people to stay indoors, said Chief Cabinet Secretary Yukio Edano. The two disasters left at least 10,000 people dead.