Biopreparat (Russian: Биопрепарат, "Biological substance preparation") was the Soviet Union's major biological warfare agency from the 1970s on. It was a vast network of secret laboratories, each focused on a different deadly agent. Its 30,000 employees researched and produced pathogenic weapons for use in a major war. (from Wikipedia)
So what if the Soviets had set up one of these secret labs in the Chernobyl area? What if the nuclear disaster happens, and some nasty biological agents get out? Possible?