Second hydrogen explosion at Japan n-plant

Soma: A second hydrogen explosion in three days has rocked Japan's stricken Fukushima Daiichi nuclear plant. The explosion on Monday sent a massive column of smoke into the air and wounded six workers. There is no report on the extent, if any, of radiation released through the explosion.

The explosion took place at the plant's Unit 3, which authorities have been desperately trying to cool following a system failure in the wake of a massive earthquake and tsunami. Earlier, a similar hydrogen explosion at Unit 1 on Saturday had blown the roof of that building and injured four workers.

It also sparked fears of a nuclear meltdown.

There is an accumulation of hydrogen as seawater mixes with the fumes emanating from the damaged reactor core. With no outlet for escape it can cause an explosion. Experts say that such explosions, on their own, do not cause any lasting damage as, post-explosion, the hydrogen mixes with the atmosphere and dissipates.

The threat of a reactor meltdown, however, still exists as engineers and scientists battle damage to the plants and try and cool down reactor cores that have already been shut down after the double strike of an earthquake and a tsunami.

Even after a shutdown, a nuclear reactor core takes time to cool down from its super-heated status. For this, it needs the plants cooling systems to be operating. Unfortunately these systems were damaged by the earthquake and the follow-on tsunami knocked out the back-up diesel generators.