a hydrogen gas bomb is a chemical bomb oxidation with the oxygen in the air.
and please watch this video: http://videos.arte.tv/de/videos/fuku...u-6439122.html in this video many international experts also a American expert (Arnold Gundersen nuclear Engineer http://en.wikipedia.org/wiki/Arnold_Gundersen)-point out that the explosion in the reactor 4 was not a hydrogen chemical one. also Japanese nuclear experts point out that the explosion in reactor 4 was not a hydrogen chemical one.
the explosion in reactor 1-3 are hydrogen explosions "Clean" no black smoke and no "Mushroom"
please watch the videos the first 3 explosions are hydrogen really different to the last one.
also the reactor 4 never run! the reactor 4 was OFFLINE! but the earthquake breaks the cooling ponds of the MOX Plutonium fuel rods
the reactor 4 was the most dangerous of all reactors.