Simulation Shows Meltdown Worse at Fukushima Japan Nuclear Reactor Than Previously Thought

Radioactive debris from melted fuel rods may have seeped deeper into the floor of a Japan’s tsunami-hit nuclear reactor than previously thought, to within a foot from breaching the crucial steel barrier, a new simulation showed Wednesday.

The findings will not change the ongoing efforts to stabilize the reactors more than eight months after the Fukushima Dai-ichi plant was disabled, but they harshly depict the meltdowns that occurred and conditions within the reactors, which will be off-limits for years.

The plant operator Tokyo Electric Power Co. said its latest simulation showed fuel at the No. 1 reactor may have eroded part of the primary containment vessel’s thick concrete floor. The vessel is a beaker-shaped steel container, set into the floor. A concrete foundation below that is the last manmade barrier before earth.

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Report reveals Japan feared aftershocks would cause nuclear meltdown at Fukushima plant

Japan feared three months after the Fukushima nuclear power plant was hit by a tsunami that aftershocks could further damage one of its fuel storage pools, causing rods inside to melt and spew radiation within hours, according to a newly released document.

The Japan Nuclear Energy Safety Organization said it carried out a simulation that showed some 1,500 mostly used fuel rods at the plant’s No. 4 reactor building could start breaking in two hours if aftershocks further damaged the pool and caused cooling water to escape. The fuel rods could start melting within eight hours, the organization said in a report dated June 30 and published Friday.

The report shows that the pool remained vulnerable for nearly four months until its operator completed reinforcement work in July. Tokyo Electric Power Co. had said before then that the building could withstand major aftershocks without reinforcement, but made repairs after acknowledging structural damage and water leaks from the pool area.

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Tepco confirms meltdowns at 2 more Fukushima reactors

Tokyo Electric Power Co, the operator of the Fukushima Daiichi nuclear power plant disabled by the March 11 earthquake and tsunami, confirmed on Tuesday that there had been meltdowns of fuel rods at three of the plant’s reactors early in the crisis.

The government and experts said previously that fuel rods at three of Daiichi’s six reactors had likely melted early in the crisis, but the utility, also known as Tepco, had only confirmed a meltdown of fuel rods at the No. 1 reactor.

On Tuesday, Tepco officials announced that fuel rods had also melted at the plant’s No. 2 and No. 3 reactors.

Explaining the timing of the announcement, a Tepco official told a news conference that the utility had been gradually retrieving data from the plant since early May, and had analyzed it before reaching a conclusion.

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