Understanding the mechanisms of interaction between radionuclides (I, Se and Tc) and geocolloids

Understanding the mechanisms of interaction between anionic radionuclides (129I, 79Se and 99Tc) and geocolloids

Heather Sanders

Project Aim: To develop predictive models for the fate of 129I, 79Se and 99Tc in soils and aquatic systems by resolving underlying mechanisms and reaction rates.

There is a substantial gap in our understanding of the immediate and longer-term reactions of selected radionuclides in terrestrial and aquatic systems.  This project will address these reaction mechanisms for selected radionuclides and soil components. A range of techniques including size exclusion chromatography (SEC) linked to ICP-MS and X-ray absorption spectroscopy (XAS) will be applied to investigate the interactions of 129I, 79Se and 99Tc with geocolloids including Fe, Al and Mn-oxides and humic substances. Time-dependent changes in speciation (chemical form and redox state) will be monitored as the isotopes are progressively incorporated into native organic pools to elucidate reaction mechanisms and rates. Results will be quantified using geochemical speciation models and by direct measurement of mass/charge balance.  A model will be developed predicting the fate of I, Se and Tc released from underground sources (e.g. radioactive waste repositories) and aerially deposited loads.