> Actually it is NOT cheap to operate a nuclear power plant after it is built
I would argue that the innovations in rival energy sources have made it comparatively expensive, but the cost was largely established when the plant was built (likely in the 1960s - 1970s). In other words, it was cheap, but the fact that nuclear requires such a massive outlay to build the facility means that nuclear is a very long term financial gamble and assumes that a variety of other energy sources don't fundamentally change their cost curve (like oil and natural gas did in recent decades).
I would argue that the innovations in rival energy sources have made it comparatively expensive, but the cost was largely established when the plant was built (likely in the 1960s - 1970s). In other words, it was cheap, but the fact that nuclear requires such a massive outlay to build the facility means that nuclear is a very long term financial gamble and assumes that a variety of other energy sources don't fundamentally change their cost curve (like oil and natural gas did in recent decades).