Worst possible case right now is a meltdown in the core (which is not explosive, just hot thermally and radioactively). A meltdown is not a problem because cont

Worst possible case right now is a meltdown in the core (which is not explosive, just hot thermally and radioactively). A meltdown is not a problem because containment vessel is still intact and it's designed to handle a meltdown. It's just expensive and a bit dangerous to clean up radioactive sludge off the bottom of the containment vessel. (The building that blew off just protected the containment vessel from weather.) The article linked by anonymous246 explains in detail.