Chips of uranium metal sparked at Y-12 on Feb. 22, 2023, causing the emergency response, said Y-12 Communications manager Taz Painter in an email to 10News.
"The event involved rapid exothermic oxidation, a known hazard for which we have established plans," Painter said in the email.
A Tennessee Emergency Management Agency situation report, obtained through an open records request, said crews tried to put out the fire using petroleum coke, but "the fire continued," the report said. "The time to extinguish the reaction was longer than expected, so an emergency was declared as a precaution," Painter said.
Painter said Building 9212, where the fire happened, was evacuated and firefighters "applied additional coke and allowed the oxidation to complete under the coke container."