The Department of Energy has released a report into its investigation into the minor radiation accident at the WIPP site near Carlsbad, NM last year. As had been suspected, the cause of the accident was the use of an improper packing/absorbing material in a waste container. While the people preparing the waste were supposed to use some sort of clay material (basically inorganic cat litter), they instead used an organic cat litter. While these two things might seem functionally similar for most uses, that was not the case. Material reacted with the organic cat litter, eventually causing a breach in the container that led to the accident.