The movement was so severe that the country moved a few metres east, the local coastline dropped, and it triggered a tsunami which killed thousands of people.
But what many people outside Japan remember is the nuclear meltdown at the Fukushima Daiichi power plant (hereafter just ‘Fukushima’), which released a plume of radiation into the surrounding area and ocean.
The disaster took place just as some nations were considering the idea of a “nuclear renaissance”. The impact of Fukushima on the nuclear industry was severe, in Japan and beyond.
Nuclear heat
When the earthquake hit, there were 11 reactors operating at four nuclear power plants in the affected Miyagi region.
These were the four reactors at Fukushima Daini, three reactors at Onagawa, one reactor at Tokai, and three reactors at Fukushima Daiichi. Daiichi’s three other units were not in operation at the time, with the fourth reactor down for refuelling.
All the units shut down automatically when the quake hit — but this is not enough to stop a plant from generating heat. Even after a plant has shut down it continues to produce “decay heat”, which amounts to 6-7% of the heat power produced by a fully operating plant.
This heat quickly diminishes. But to avoid nuclear meltdown, it is imperative that the reactor is kept cool in the first day or so after the reaction has stopped taking place.
This was what happened at the eight reactors sited at the Daini, Onagawa and Tokai plants, which were able to access the back-up power needed to run the cooling process.
At Fukushima Daiichi, however, the process failed. The result was the largest nuclear disaster since the Chernobyl accident in 1986 in what is now Ukraine.
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