Need for engineered barriers at the Waste Isolation Pilot Plant

To dispose of defense transuranic waste in the Waste Isolation Pilot Plant (WIPP) in southeast New Mexico, federal law specifies that the U.S. Department of Energy (DOE) must receive certification from the U.S. Environmental Protection Agency (EPA) that the facility is in compliance with the EPA disposal regulations. This includes compliance with the containment requirements and the assurance requirements of the EPA standards for the disposal of transuranic waste, 40 CFR 191. The containment requirements rely largely on the predicted performance of the repository over the next 10,000 years. The EPA recognized the inherent uncertainties in forecasting repository performance over such a long period of time and mandated the use of both engineered and natural barriers as an assurance requirement to compensate for those uncertainties. Thus, the potential contribution of engineered barriers is not to be measured simply by improvements in compliance with the containment requirement of the standards; they are required to provide additional assurance in the integrity of the disposal system