If I was going to a frat party, I'd want detachable items to throw at people too.
How about getting a cute bright yellow t-shirt and painting on the radioactive symbol? That'd be easy to do with a stencil and fabric paint or spray paint.
As for the detachable particles: cover a belt with velcro. Get some ping-pong or other small light balls, paint bright colors, attach piece of velcro so it sticks to belt. Them you could be ringed with them and thrown them at people. Bring extras with you since you won't get them all back after throwing them. You could go for bracelets as well with pompoms all over them; that wouldn't be unflattering.