Transcript

JIM AL-KHALILI

We can't get inside the Fukushima Daiichi plant, but in May this year, an international group of scientists went inside to investigate what went wrong. There's now a well-established story of what happened at the Fukushima Daiichi nuclear plant on March 11. First the earthquake hit, followed by the tsunami, wiping out the vital power supply needed to cool the reactors once they shut down. And they did shut down.

This is the moment the tsunami struck the power station. As the 14 metre wave hit, it overwhelmed the sea wall and swamped the diesel pumps. The resulting loss of power shut off cooling to the reactors. This was crucial, because even though the reactors were shut down, they were still generating heat.

Heat remained within the reactors, and they slowly started to cook. And this led ultimately to the buildup of pressure and explosions. Not nuclear explosions, but gas explosions. Accompanied by them was the release of radioactive particles out into the atmosphere. There was a release of steam and radioactive material, including isotopes of cesium and iodine.