The worst case in Japan would be a containment vessel blowing up from the pressure. That could kill the remaining workes on site and pose quite a messy cleanup

The worst case in Japan would be a containment vessel blowing up from the pressure. That could kill the remaining workes on site and pose quite a messy cleanup problem, but already the 20 km evacuation zone could be seen as a bit of an overreaction. However, that is not going to happen, because the containment is rather vented than letting it burst. Anyway, the carnage and tragedy _actually having struck_ in form of the earthquake and tsunami _dwarf_ even the most horrible scenario at the nuclear plants.