Certain aspects of it were exaggerated, such as the helicopter crash, which actually did happen, but several weeks later. However, it wasn't the direct result of radiation poisoning, rather because it struck a tower. Also, not nearly as many people were killed as a direct result of the initial explosion, which was implied, but many others eventually succumbed to the effects of radioactive poisoning, in the forthcoming weeks, months, and years later (largely due to increased cancer rates.)

On the other hand, the Chernobyl disaster did actually heavily contaminate large areas of the surrounding area, and also in a much larger area, to some extent, to the point where some parts have been left permanently uninhabitable. In terms of the effects of extreme radioactive poisoning, what it showed, some people looking like that, with their bodies degenerating, as unconformable as that might seem, it is what actually happens in extreme cases of radioactive poisoning.