They studied the population in Hiroshima and Nagasaki for generations and found that in the first generations after the bombs there were elevated levels of hard-tissue cancers and in later generations elevated levels of soft-tissue/blood cancers. They're still dealing with the population effects of radiation 75-years later.
No one will be able to live in Chernobyl or Fukushima for hundreds of years. Or, well, they could but it would be stupid.
Around 98% of Fukushima is inhabited again, unless of course you meant the NPP itself, but people were not living in a power plant to begin with.
Much of the Fukushima area is inhabited again (the exclusion zone has shrunk from an original 1250km2 down to 371) and there is ample evidence that the overreaction evacuation did a lot more harm than good.