It is all explained here "in a calm rational scientific manner".
Refs
* Japan nuclear threat: The tsunami is the bigger tragedy By David Spiegelhalter, Professor of the Public Understanding of Risk, Cambridge University
* Pakistan miners feared dead - for anyone who thought that coal was safe.
* Why Fukushima made me stop worrying and love nuclear power - George Monbiot
* Jurrassic Park is a triumph for dino theme parks: Build more dinosaur theme parks now!
* JEB on some back-of-the-envelope calculations of radiation risk