So, nuclear reactors are very safe except of dangerous-tech-xA45b which we only know is deadly after one or two incidents?
1) Don't use crappy Soviet reactors like Chernobyl; this should be a no-brainer.
2) Don't locate a nuclear power plant in a place where it can be flooded easily.
Other than the crappy Chernobyl reactor, I don't know of any inherently dangerous reactor designs, especially in Western nations.