As September drew to a close, residents of southwest Michigan found themselves taking in a little extra tritium, thanks to their daily habit of breathing. The tritium was courtesy of the 40-year-old Palisades Nuclear Generating Station in Covert Township, which suffered its third “event” (as they are politely called) in less than two months, and was forced to vent an indeterminate amount of radioactive steam.

The reactor at Palisades was forced to scram after an accident caused an electrical arc in a transformer in the DC system that powers “indications and controls“–also known as monitoring devices, meters and safety valves.

While it is nice to see rectors shut themselves down when a vital system goes offline, remember that “turning off” a fission reactor is not like flicking a light switch. Shutting down a reactor is a process, and the faster it is done, the more strain it puts on the reactor and its safety and cooling systems. And even after fission is mitigated, a reactor core generates heat that requires a fully functional cooling system.