Workers at Los Alamos National Laboratory used organic cat litter to clean up nuclear waste. The litter triggered chemical reactions that later caused a drum to burst.
Department of Energy/Flickr
As NPR reported shortly after the accident, cat litter was the chief suspect. The highly absorbent material is great at soaking up liquid nuclear waste, and it has been used for years in cleanup activities at the nation's nuclear laboratories.
Unfortunately, workers at Los Alamos National Laboratory, also in New Mexico, apparently switched from inorganic clay litter to organic litter. According to the report, workers put the brand "Swheat Scoop" inside drum 68660.
"Experiments showed that various combinations of nitrate salt, Swheat Scoop®, nitric acid, and oxalate self-heat at temperatures below 100°C. Computer modeling of thermal runaway was consistent with the observed 70-day birth-to-breach of Drum 68660," the summary of the report concluded.
In other words, the litter caused the drum to burst after it arrived at the dump, releasing radioactive uranium, plutonium and americium throughout the underground facility.
WIPP has come under intense scrutiny since the accident for what critics say was a lax culture of safety and oversight. But the Energy Department wants the dump to get back to work. It hopes to reopen it early next year.