Estimates of Parameter and Scenario Uncertainties in Shallow-Land Disposal of Uranium Wastes Using Deterministic and Probabilistic Safety Assessment Models

Abstract

Safety and uncertainty analyses for the shallow-land disposal of uranium wastes were performed using the deterministic and probabilistic safety assessment models. The analyses for uranium accumulated with 4.5% enrichment show that the doses in residence scenario are of great importance in the safety assessment owing to the influence of daughters built up by uranium decay chain. The dose in residence scenario is sensitive to the release condition of radionuclides from the facilities over long-term period. The parameter uncertainties for the important pathways in residence scenario are estimated from the probabilistic analyses using the statistical methodology. The uncertainty analysis indicates that the influence of parameter uncertainty is the most remarkable in the estimation for the inhalation of radon gas with residence. The parameter importance in each exposure pathway is estimated from using the partial rank correlation coefficients (PRCCs) between variable parameters and the evaluated doses. The important parameters identified by the PRCCs are depth of intrusion, infiltration rate, thickness of covered soil, diffusion coefficient of radon in soil etc. for the inhalation exposure of radon.