Nuclear power plants produce many many orders of magnitude more radioactivity than coal power plants for a given amount of energy produced. You are probably misinterpreting the famous 1978 study [1] where the radioactive emissions of nuclear and coal power plants were estimated to be roughly the same. This does not include the solid and liquid nuclear waste, only the radioactive gases that are inadvertently leaked from nuclear reactors. Coal ash is barely radioactive at all, and the radioactivity is completely negligible compared to the chemical toxicity.

[1] https://doi.org/10.1126/science.202.4372.1045