When I was there in the early 90s, I had some friends that went biking somewhere west of campus. They came across a big sign from the U.S. Dept of Energy (I think) warning people to stay at least 20 feet away. Being idiots, they kept going and ended up seeing a bunch of dudes in hazmat suits carrying trays around. Later on, one of them had a professor who said that after the Manhattan Project, they dumped a bunch of plutonium or something out there and were finally cleaning it up some 45 years later.
The only other story I have about exploring on campus was when the plumbing went out in my fraternity & we had to crap on campus. After a few days, we all agreed that Alumni Hall had the finest crappers on campus. The basement of the Union was nice too, but not as secluded.