The Department of Energy says a nuclear lab used the wrong kind of kitty litter to dispose of hazardous waste that lead to the major radiation leak at the Waste Isolation Pilot Plant.

The report states that the Los Alamos National Laboratory took actions with the material that one chemist called the creation of a “potential bomb.”  The LANL works on nuclear technology and other high level national security projects.

The lab reportedly used a wheat-based kitty litter instead of clay-based.  The resulting mixture is similar to plastic explosives according to the Santa Fe New Mexican.

“This action may have led to an adverse chemical reaction within the drums resulting in serious safety implications,” the Department of Energy’s Office of Inspector General said in an October report.

At least 20 workers at the plant were injured by low levels of radiation as a result of the leak and the storage facility is still closed.  DOE estimates it could cost $500 million to reopen the storage facility.