One further thought about the radiation. Since these students all worked in graduate studies at a polytechnic institute in the Urals, maybe they were all involved (or most) in secret government work with nuclear materials. Crappy safety measures would certainly been no surprise with Soviet SOP as far as I know. Radiation at what level? What kind of radiation? From what kind of materials? All unanswered and fitting with information suppression then and now.
Just my $0.02.
One of them was. And I have read that he was the only one with radioactivity on his clothes.