The rupture of a container filled with nuclear waste from Department of Energy (DOE) sites that resulted in the radiological contamination of 21 workers appears to have resulted from a heat-producing reaction, possibly between the nuclear waste and the kitty litter used to stabilize the waste.
Yes, you read that correctly. The same stuff you use for Fluffy’s “business” is also used to stabilize nuclear waste. However, the kitty litter typically used is clay. One of the sites that provides waste to the Waste Isolation Pilot Plant, where the release occurred, changed from clay kitty litter to organic kitty litter, which is made of plant material. Although the reaction that resulted in the container’s rupture has not yet been determined, it is possible that it was due to the change in litter.
We can look at this incident in a Cause Map, or visual root cause analysis, to lay out both the effects and causes. In this case, the effects were significant. Twenty-one workers were found to have internal radiological contamination, impacting the safety goal. A radiological release off-site impacted the environmental goal. The waste repository has been shut down and is not accepting shipments, impacting both the customer service and production goals. The release requires the investigation of a formal Accident Investigation Board, impacting the regulatory and labor goal. Lastly, the damage to the container is an impact to the property goal.
The release was caused by the rupture of a container that stored radiological waste, including americium and plutonium. The release was able to leave the underground storage facility due to a leak path in the ventilation system, which was by design because the ventilation system was not designed for containment because the safety analysis assumed that a release within the storage facility would result from a roof panel fall and was adequately prevented.
The rupture appears to have resulted from a heat-producing reaction. The constituents of that reaction have not yet been determined, but the change from clay to organic kitty litter has been identified as a possible cause. (A possible cause indicates a cause for which evidence is not yet available.) More research is being done to determine the actual reaction. This will also allow a determination of which other waste containers may be at risk for rupture.
A solution that has already been implemented is to seal the leaks in the ventilation system with foam to reduce the risk of leak-by. Other solutions that have been suggested are to add an additional heavy-duty containment around the affected casks, reclassify the ventilation system as containment, and perform an independent review of the safety analysis of the site. Once appropriate solutions are determined and implemented, it’s hope the site will be able to reopen.
To view the Outline and Cause Map, please click “Download PDF” above.