Operating costs aren't so bad.
Capital costs for building nuclear reactors have gone up over time. That's partially to pay for necessary improvements to safety. But mostly down to double standards that require much higher standards in nuclear than other sources of power.
For example, coal plants release orders of magnitude more radiation than nuclear plants.
Well yeah, nuclear plants don't release much radiation when there are no accidents and the waste is safely contained. But very often the waste isn't contained properly, and sometimes there are accidents. These events release a lot more radiation than coal plants.
Unless you have data that supports this statement, I'd state the opposite. It's easy to think nuclear accidents release a lot of radiation, but the actual accumulated dose from nuclear power (including accidents) for the average individual over time is very low. Coal, on the other hand, continuously spews out radioactive ash in large quantities.
Granted, other sources of radiation (radon, cosmic rays, medical x-rays, etc.) are a lot larger, but if comparing the two I'd guess coal is the larger culprit even when including nuclear accidents.
This is only because nobody's living in nuclear disaster zones. If people were carrying on their daily lives in the Chernobyl or Fukushima then their accumulated dose would be much much higher.
As you say, the levels from coal are small enough that other naturally occurring sources are more significant, and thus it has little practical effect on people's lives. On the other hand, nuclear accidents take large areas of land out of use for time scales long enough that they effect several generations.
See for example:
* https://www.scientificamerican.com/article/coal-ash-is-more-...
(It might very well be economically the best for them. But making that judgement requires more context.)
We create these problems for ourselves. Legal challenges are the number one cause of construction delays.