Significantly less than digging up millions of tons of coal. Note also that coal is somewhat radioactive too, and there is a lot more of it, so the radiation difference is small and might even favor nuclear
Coal is terrible. That doesn't make nuclear power the best option compared to all the others.
The radiation difference isn't small if you include accidents. (Are we somehow supposed to pretend they never happened, and no nuclear accident - even if it's "just" a fuel spill, or a small fire - will ever happen again?)
Which current option is better than nuclear? Please take into account the lack of battery storage capacity and water pumped storage capacity that makes an all solar and wind grid completely impractical, and that adding extensive hydro power would cause further degradation of our rivers. Nuclear power is our best option among coal/oil/natural gas/nuclear, if you believe that reducing carbon/methane emissions to slow or halt global warming is important.
The radiation difference isn't small if you include accidents. (Are we somehow supposed to pretend they never happened, and no nuclear accident - even if it's "just" a fuel spill, or a small fire - will ever happen again?)