I wonder how it is that the Cherynobyl area will be uninhabitable for hundreds of years, but those Japanese cities we nuke bombed back in WW2 have been rebuilt and are lived in today.
Primarily, the vastly different amounts of radioactive material released.
Hiroshima was one bomb, with a few kg of plutonium, some percentage of which was converted into energy. The bomb was detonated at some distance above ground level, allowing much of the fallout to be dispersed by the winds.
Chernobyl involved the release of hundreds if not thousands of kg of radioactive material at ground level. Much of the radioactive material fell in the surrounding area, contaminating the ground, the water table, and the crops growing near the site.