Actually some lands were returned back to commercial usage. The land is extremely beautiful and rich. They have even created new resorts on the former land of the Exclusion Zone. [1]
I have been a part of the working group researching possible commercial usage of contaminated land, which should not be returned into agriculture or cannot be made livable BUT is perfectly suitable for things like prison, recycling plant or launch pad for space.
"cannot be made livable BUT is perfectly suitable for things like prison"
That sounds a bit dark.