NHK is presenting an official ‘explainer’ of why the nuclear safety and backup systems failed. I’ll try to put it simply.

1: Earthquake triggered automatic shut down procedures, which involves raising/exposing fuel rods. This still requires cooling of the rods.

2: Cooling of raised rods failed because main power supply cut. Back up generators came on, but failed when tsunami hit the plants. They could not be restarted.

3: A third backup cooling system failed. This is a steam reclamation system that collects steam off the hot rods, condenses it to water, then sprays the water on the rods. It failed because coolant levels dropped too much for steam to be created. Officials say coolant levels might have leaked due to structural damage caused by the quake and tsunami. They can not be sure what happened to the coolant, until they can inspect the structures.

The failed safety & back up systems are causing the raised fuel rods to partially melt down.  The report suggests that all the reactors along the coast line hit by the quake/tsunami are in partial melt down. An official now says they obviously didn’t expect such a powerful natural disaster when they planned the safety/back up systems. In Fukushima Prefecture alone, one of the hardest hit areas, there are 10 reactors.

There are a total of 55 plants, with anywhere between 2 and 6 reactors each, in Japan. There are 2 plants under construction, with another 11 planned.  In the United States there are at least 104 commercial nuclear plants.  Most of the plants are east of the Rocky Mountains, in highly populated areas.

The failure of all these systems, in Japan, will give anti-nuclear activists plenty of ammo for the demand to end the use of nuclear power plants.