They were the first western film crew allowed into the actual site - he has some pretty gnarly stories about it, and the shit he saw making the film has pretty much fucked him up for life.
They ran in to serious problems with the local authorities when out there, despite having government permission to go in, and several of the crew got radioactive poisoning.
If you can find it, watch the documentary, its incredibly hard going and very disturbing, but lifechanging shit.
http://www.veoh.com/search/videos/q/Chernobyl+Heart#watch%3Dv4737139aGst85t