Ron Smith: Fukushima: the consequences

The earthquake and subsequent tsunami that struck Japan on 11 March of this year, caused enormous damage over a wide area of the east coast of Honshu. It also inflicted major damage on key nuclear assets, near the provincial city of Fukushima. Specifically, the coastal site of Fukushima-Daiichi, which housed six reactors, was so badly affected as to raise questions, not only about the future of the Fukushima-Daiichi site but also about the future of nuclear power in Japan and, indeed, around the world.

At the moment of the earthquake, only three of the Fukushima reactors were in operation. All three immediately went in to automatic shutdown, as they were programmed to do. However, the cores of shutdown reactors (reactors where fission is not longer taking place) still contain fission products, which continue to decay and produce heat. They thus need continuous cooling. The genesis of the problem at Fukushima was, because of damage caused by the earthquake and tsunami, that this cooling could not be maintained. Electrical power was lost and back-up arrangements were damaged. There is also evidence that essential pipe-work, serving the reactor cores, was also damaged. The net effect of this was a meltdown of the overheated fuels rods, which damaged the reactor containment structures. This made maintaining cooling even more difficult, since water that was inside was able to escape.