I suppose one part of the problem is inertia. Once a government bureaucracy has gone down a certain road for a certain amount of time, it’s very difficult for them to change course. Honing in on reasons for this being the case requires some reflection.
The Telegraph reports a number of interesting things in diplomatic cables revealed by Wikileaks, including disclosing
how Taro Kono, a high-profile member of Japan’s lower house, told US diplomats in October 2008 that the government was “covering up” nuclear accidents.
as well as concerns over earthquake designs:
the Japanese government opposed a court order to shut down another nuclear power plant in western Japan because of concerns it could not withstand powerful earthquakes.
Not that this information was necessarily actionable. Still, such observations and events surely add to the arguments against expanding nuclear power.