Melting of key parts blamed for Fukushima meltdown — NHK World

” The operator of the Fukushima Daiichi power plant says excessive heat from nuclear fuel at one of its damaged reactors may have caused some key parts to melt.

Officials at Tokyo Electric Power Company believe the loss of those components made it difficult to stop the Number 2 reactor from melting down and spewing out large amounts of radioactive substances following the March 2011 accident.

Four days after the onset of the accident, the emergency cooling system at the reactor stopped working.

In an attempt to cool fuel inside the reactor, the workers had no choice but to pour in water from a fire engine.

But they were unable to inject water as planned because of the high pressure that had built up inside the reactor.

The officials also could not use safety relief valves to release pressure. Those valves were designed to open when hit by high-pressure gas from a tank.

The TEPCO analysis determined that key parts of the gas feeding system may have melted, leading to a gas leak. The analysis says the temperature inside the reactor exceeded 200 degrees Celsius, far beyond the limit of the parts’ durability.

Those parts are present in all other reactors in the model line used at the Fukushima Daiichi plant. The utility plans to replace the parts at its other nuclear power plant in central Japan with heat-resistant ones. ”



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