Role of the bio- and geosphere interface on migration pathways for Cs-135 and ecological effects

An approach is described for hydrological, geochemical, and ecological process modeling in assessing the migration pathways of radionuclides from a repository for radioactive waste in crystalline bedrock back to the surface environment where dose to individual humans can occur. The approach is based on the characterization residence times in geologic media of a unit pulse of Cs-135 released from the repository. Performance assessment modeling of geosphere transport processes generally focuses on the properties of the host rock (crystalline bedrock in this case). Our approach includes a detailed representation of the quaternary deposits that overlie the bedrock. Although water residence times in quaternary deposits can be short, geochemical reactions, predominantly sorption, can increase solute residence times significantly. Moreover, the quaternary deposits govern the pathways to terrestrial and aquatic ecosystems and are of utmost importance for the assessment of doses to individual humans.
QC 20100525