Why is a pressure cooker safe enough to be used by anyone at home (not radioactive anyway), and why can I claim nuclear pressure vessels are not safe?
Well, easy: radioactivity aside - by now it is public knowledge that for the boiling water reactors (BWR) in Fukushima, venting failed. Every pressure cooker legally sold today has a safety feature, that the nuclear pressure container has not. By design.
Let's investigate that further. This is first not about the radiation hazard, it is about risks related to mechanical engineering.