Robot enters Fukushima Daiichi unit 1 containment vessel

[FBaggins]

31. Actually... it's entirely relevant.

In this case, getting it right would mean that you wouldn't make the mistake of thinking that the explosion occured within the reactor vessel.

With your earlier theory, the burning zirconium is creating both hydrogen and oxygen... which could create an explosive mix within the reactor vessel.

In reality, ziroconium (or in this case zircalloy) does not burn in water without the prexistence of oxygen. The hydrogen is created by the oxydation of the zircalloy in water. The chemical reaction strips oxygen from the water (but that oxygen is now bound to the new "rust" molecule) and frees the hydrogen. The key difference being that there still isn't any free oxygen in the reactor vessel to form an explosive mix. The hydrogen has to escape the RPV and mix with the oxygen outside of the reactor (in this case... within the reactor building).

Note (as mentioned to RE in the prior post) that if the explosion was from within the reactor, it would have to blow the lid off of the RPV and the concrete cap. The cap is clearly still in place, so we would now know for certain that this didn't happen (if we didn't already agree that BWR cores can't explode).