@awesome
We know, this happened Saturday.

There was 4th explosion in japan today

TMC1995
We know, I heard that it was the extreme temperatures disassociating hydrogen and oxygen particles. This mix is highly explosive. I initially though it was exposed wiring or something similar causing electrolysis of the water.

@jarrodwhitty9090
I've got one! But I'm not allowed to use it for online stuff.

There are plenty way of producing hydrogen from water. Heat is one. For example, in oil wells, when the drilling bit is drilling some metal (casing or whatsoever that fell inside), some hydrogen is generated.
In the case of the nuclear power plant in Japan, it is steam on very hot pipe that produced H2.
These explosions are spectacular, they release some radioactivity but I am far more concerned by the cooling of the reactors 1,2 and 3.
They are using sea water and then, they want to pump boric acid (H3BO3). Boric acid absorbs neutrons, more specially thermal neutrons. On an engineering point of view, I am very concerned with reactor 2 situation and reactor 3 content (MOX = Uranium+Plutonium oxyde, very very toxic not only because of radiations)

@Mackrock
The "pool" they put the "spare" fuel rods in has reached double its normal temperature (or something like that anyway...).

Apparently the radiation is very bad. 1 hour after the disaster, radiation levels around the plant were 1000 times the acceptable/ normal dose per year. An American aircraft carrier ( or another military ship) passed through a radioactive cloud and the crew received a months worth of radiation in a few minuets.