[ars]

My guess is a criticality accident. They are very hard to avoid without [institutional] experience.

I've been expecting one for quite a while.

[baguasquirrel]

True... but even supposing that it were to happen, it may not have been a big deal, in the grand scheme of things. It happened twice to the US A-Bomb program and life went on. General Leslie was not forced down.

http://en.wikipedia.org/wiki/Louis_Slotin http://en.wikipedia.org/wiki/Harry_K._Daghlian,_Jr.