The worst case scenario of a nuclear reactor going wrong is much worse than any other alternative, however slim the chances of that happening may be. This fact is enough to be concerned about the safety of nuclear reactors.
Put another way, on average driving 100 million miles is safer than flying 100 million miles (contrary to popular belief that flying is safer than driving).
http://www.pbs.org/wgbh/nova/planecrash/risk-01.html
You can see the fallacy of "cars are dangerous" when you compare cars to motorcycles on that chart, because most people don't ride motorcycles so the probability of death for most people is lower than for a car.
Fukushima is extraordinarily safe for everyone living in Iceland. It is far less safe for everyone living in Japan.
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.