Whose Afraid of the Nuclear Bogeyman? Fukushima Meltdown and Safety

Whose Afraid of the Nuclear Bogeyman? Fukushima Meltdown and Safety 

Now that the crisis with Fukushima Dai-ichi Unit 1 seems at least momentarily averted, media attention has been averted to Fukushima Dai-ichi Unit 3 and other reactors with coolant problems which are reportedly is near partial or complete meltdown. But what is a reactor meltdown, and does it represent the sort of end of the world horror stories that anti-nuclear "experts" who appear on television to tell us about?