Simi Valley meltdown
We had no idea that Simi Valley was the site of America's first nuclear accident (obviously we should watch more History Channel). At the Santa Susana Field Laboratory, a liquid sodium reactor had a partial meltdown in 1959; the facts weren't made public until UCLA investigated 20 years later. Researchers speculate that the radiation released was as much as 240 times that of the Three Mile Island accident. Exactly what was contaminated in the area, and by how much, was never accurately measured. Yikes, just 30 miles from downtown LA.