This disposal concept is based on the Tumulus design developed by the French at the La Manche facility. Waste units are stacked above-grade on a concrete pad. The facility currently under development at the Oak Ridge National Laboratory (ORNL) involves sealing waste in concrete vaults, placing the vaults on a grade level concrete pad, and covering the pad and vaults with a soil cover after vault emplacement is complete. Emplacement is expected to continue until the facility exhausts its approximate 800 m/sup 3/ (28,000 ft/sup 3/) capacity. The facility incorporates engineered barriers to radionuclide migration; a monitoring system to ensure barrier performance; and a newly developed set of Demonstration Waste Acceptance Criteria to reduce the likelihood of groundwater contamination.