... because we don't do these kinds of things:
http://en.wikipedia.org/wiki/Chernobyl_disasterChernobyl disaster
... the reactor had been constructed without any secure containment. This allowed the radioactive contaminants to freely escape into the atmosphere after the steam explosion burst the primary pressure vessel.
... the plant's management was largely composed of non-RBMK-qualified personnel: the director, V.P. Bryukhanov, had experience and training in a coal-fired power plant. His chief engineer, Nikolai Fomin, also came from a conventional power plant