Unsaturated Zone Model for Low-Level Radioactive Waste Disposal Facility
HydroAnalysis contributed to the performance assessment of a currently operating low-level radioactive waste disposal facility. Our task was to evaluate the sensitivity of unsaturated flow model predictions to uncertainty in the model parameters. To do so, we developed a one-dimensional HYDRUS model that captured the essential features of a previously developed two-dimensional model, but with much shorter computer simulation times that allowed for comprehensive sensitivity simulations. The approach used for the sensitivity analysis was a variation on the “one-at-a-time” method, which has the advantages of both computational and conceptual simplicity.
The sensitivity analysis revealed that the model of the unsaturated zone beneath the facility was robust and only sparingly sensitive. The analysis confirmed previous findings that the unsaturated zone is not a pathway for migration of water from the facility to the underlying groundwater over a broad range of parameter values.
The project was completed for Waste Control Specialists in cooperation with Risk Assessment Corporation.