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.
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Operators knew an explosion was a possibility as they struggled to reduce pressure inside the reactor containment vessel, but apparently felt they had no choice if they wanted to avoid a complete meltdown. In the end, the hydrogen in the released steam mixed with oxygen in the atmosphere and set off the blast.
Tokyo Electric Power Co., which operates the plant, said radiation levels at Unit 3 were well under the levels where a nuclear operator must file a report to the government.
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International scientists say there are serious dangers but little risk of a Chernobyl-style catastrophe. Chernobyl, they note, had no outer containment shell.
"The likelihood there will be a huge fire like at Chernobyl or a major environmental release like at Chernobyl, I think that's basically impossible," said James F. Stubbins, a nuclear energy professor at the University of Illinois.