UChicago Twitter link to this 2012 New Yorker article:
"...In 1999, for five hundred points, a pair of physics students built a working nuclear breeder reactor in a Burton-Judson dorm room in one day, converting thorium powder collected from the inside of vacuum tubes into weapons-grade uranium, using a device made from scrap aluminum and carbon sheets. A concerned nuclear physicist attested to the machine’s efficacy."
That was pre 9/11 days. I am not sure they can pull it off today without Homeland Security asking a lot of questions before and after. Nonetheless, that was an amazing feat.