When looking if it was feasible to convert coal power plants to nuclear, we found out that most of the coal sites have more radioactivity than is allowed for a future nuclear site

And Mercury

This is an often misquoted fact. The study that compared coal and nuclear was only studying air pollutants, and obviously the steam stacks from nuclear reactors don’t have as much radionuclide pollutants as coal. However, the study did not look at other sources like wastewater - which is where most radionuclide pollution from nuclear reactors comes from (along with other sources like spent fuel, casings, and moderator rods).