My friend Makar studied how radiation affected populations of mice. I mean, he actually caught great numbers of mice somewhere on Urals in a disaster zone.
The conclusion was: mice adapted, there are no statistically distinguishable differences compared to a normal population.
I spent part of 2 summers (in '98 & '00) in some of the cities/villages near the exclusion zone (as close as 30-40 miles from the plant). Seen the road barriers and warning signs. Met kids and adults with cancer from the radiation.
Ukraine has a wonderful culture and beautiful people. It's a shame that this happened to them.