Most nuclear accidents are caused by greed, laziness and shortsightedness. Japan seems to be one of the few societies (possibly the only wealthy one) that doesn't suffer too badly from these issues. When I worry about nuclear power here in the UK, I don't worry about earthquakes, I worry to PMs cousin will get a billion pounds to build a containment unit and not do it. Or the reactor will need to be shut down but the CEO will decide to keep it running because safety and maintenance are just "cost centres"...