Comment by teamonkey

Coal plants spread radioactivity because it concentrates all the radioactive elements naturally found in the coal into ash, much of which then gets released into the air, deposited on surfaces and breathed in, which is extremely harmful.

But if decommissioned properly, most of the ash inside the building can be collected and mixed into soil and bricks at a safe concentration not far above background radiation level.

In a nuclear power plant, there is no release of radioactive materials, but it’s possible for parts of the structure to absorb radiation and become radioactive itself, and that’s much harder to deal with.