Publications Details

Radioactive disequilibria in the saturated zone transport model and the biosphere model for the Yucca mountain repository - The case of Radon-222

Olszewska-Wasiolek, Maryla A.; Arnold, Bill W.

In the saturated zone transport model for the Yucca Mountain repository, the transport of the long lived radionuclides is explicitly modeled, while the concentrations of the short-lived decay products are inferred from the concentrations of their respective parent radionuclides. When assessing dose from 226Ra and its decay products, it is important to consider radioactive disequilibrium between the concentrations of 226Ra in the groundwater and the concentrations of its short-lived decay product, 222Rn caused by the preferential sorption of 226Ra on mineral grains in the aquifer. This paper discusses behavior of radon in the groundwater, 222Rn transfer to indoor and outdoor air, and the resulting transport and exposure pathways for the groundwater enriched in 222Rn. The processes considered include the buildup of radon decay products in the soil, the transfer of radon from groundwater to outdoor and indoor air, and the consequent radionuclide transfer to other environmental media, such as plants and animal products. The increased concentrations of radon and its decay products in the environmental media (water, soil, air, crops, animal products, and fish) result in additional exposure pathways that should be taken into account when evaluating the dose to the receptor. It is concluded that the unsupported 222Rn can have a significant effect on the dose from 226Ra and its decay products.