You could say so. The fact is, the level if radiation in most areas is such that it is a certain risk for humans which is considered unacceptable although not necessarily deadly. So even humans might live there, accepting mainly a higher risk of cancer. However, the factor limitating the lifespan of wildlife is not cancerogenesis but rather prey-predator relations or human actions like hunting, fishing, monoculture farming etc.

There are numerous studies showing human disturbance is also a major factor in animal distribution. Large carnivores for example become increasingly nocturnal when human presence increases (Griffiths and Carel P. van Schaik, Conservation Biology, Vol. 7, No. 3 (Sep., 1993), pp. 623-626)

The wildlife may be thriving, but that does not necessarily mean in the same condition as before the accident.  For instance, some animals near the the power plant look the same as always, but if you investigate some tissues histologically, differences can be found.  This means that the developmental biology of some animals is perturbed.  These pertubations seem to be below a selection threshold, but I have not seen any careful research on this.  

Cherry:

Serious studies on animals, plants, humans and microbial life has not been attempted so far after the Chernobyl disaster. Severity of radiation damage could be expected at microscopic level of generations. Have a look at this link for insights:

Best

Syed

The amount of radiation was only lethal in the initial stages, at the moment may have happened  mutagenic and teratogenic effects they can produce  polyploids , which increase the mass of individuals.

What it means "wildlife has been thriving"? increased species  richness? increased of biomass? increased the biodiversity?

Individual fitness can be lowered (by radiation or anything else) without reducing population fitness or population size, which may be limited by resources or predation (both potentially very different in the absence of humans).

I agree with most of what has been said by colleagues (above).  The real question is the long-term functionality of these populations.  Animals rarely die of diseases like cancer in the wild, so the impacts of radiation may not been seen over a 5-10 year period.  The bigger issue is whether these populations are sources or sinks, i.e. are they apparently doing well but replenished more by immigration than by successful reproduction?  On the other hand populations at Savannah River Ecology Lab have been doing OK despite multiple generations of radiation exposure.  Ultimately wildlife operate by different standards of lifespan and health than do human populations where longevity is very important.

also see this project on RG and a podcast interview with G. Orizaola

https://www.researchgate.net/project/Effects-of-long-term-exposure-to-ionizing-radiation-on-Chernobyls-treefrogs

https://soundcloud.com/slightlyevolvedpod/episode-8

If you are interested, check the site of Chernobyl Research Initiative.

There is a nice collection of papers, dealing with consequences of Chernobyl and Fukushima disaster on local wildlife.

http://cricket.biol.sc.edu/chernobyl/Chernobyl_Research_Initiative/Publications.html

Dear Cherry. 

Low and high dose radiation is different, but we don't have knowledge about his differences. Medics and governments use very small threshold for dose of radiation, because they must garants individuals life without cancer and other diseases.