Fukushima pressure vessel leak 'may have been worse'

01 December 2011

Posted by Michelle Devonshire

A new report on the pressure vessels breach at the Fukushima Daiichi nuclear power plant in March this year has indicated the level of damage may have been worse than initially thought.

Operator Tokyo Electric Power (TEPCO) has revealed that molten fuel leaking out of the reactors may have melted through a concrete containment base, in addition to the inner casing, in at least one case.

The plant's cooling systems were damaged by the earthquake and subsequent tsunami that struck the north-east of Japan on March 11th 2011, leading to a nuclear meltdown at the facility.

It was the worst nuclear disaster since Chernobyl and information is still being released about the impact of the breach as it is not currently possible to get inside the pressure vessels to assess the situation.

TEPCO has conducted a new simulation exercise and found that the No. 1 reactor may have been damaged so badly that leaking fuel came close to the outer steel casing, having eaten through the inner pressure vessel.

It suggests that the damage caused by the disaster and melting nuclear fuel rods may have been more acute than initially believed.

"Using (realistically assumed) conditions for the evaluation, the concrete could have been penetrated, but (the fuel) stayed inside the casing," the report stated, according to news agency AFP.

An examination of the reactors themselves has not yet been possible because of the high levels of radioactive material in the area and modelling has been used instead to reach conclusions about the impact of the disaster.

The reactors of units one to four at the Fukushima plant are in cold shutdown and efforts continue to stabilize the site, as thousands of people remain displaced and some areas in the vicinity of the facility are expected to be uninhabitable for many years.

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