a. The bottom line is that nuclear power technology is very complex -- it's not as simple as putting some coal in a furnace and running a turbine. Everything is expensive.
b. Nuclear plants require highly-trained, specialized personnel and lots of oversight. We don't even have decent staff as it is; training more is a long-term cost borne by the public, and the demand is inelastic, so the marginal cost of getting more nuclear engineers actually increases over time. The higher premium you place on safety, the worse this problem becomes.
c. There are significant ongoing repair and maintenance costs -- nuclear power generation involves a lot of delicate equipment that's often operating in extreme conditions and with enormously restrictive failsafe requirements.
d. The fuel ain't free. Nuclear fuel is relatively cheaper and more accessible than coal or oil, but the cost to obtain it is non-trivial no matter what, and it's not even a single order of magnitude better than hydrocarbons in terms of cost-per-watt, even if you don't include all the secondary costs; see "wind" link in previous post.
e. There are many, many ancillary costs associated with nuclear fuel even aside from supply. Even if it were possible to simply "bury" nuclear waste without worrying about leakage polluting the groundwater -- which it's not -- you can't avoid the costs of security and transportation, neither of which is trivial.