Sorption of palladium(II) on biotite, quartz and feldspar in brackish groundwater by batch experiment, sorption model and DFT calculation

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Internationally, agencies such as the NWMO (Nuclear Waste Management Organization) are considering underground deep geological repositories in either crystalline or sedimentary rock formations as a safe and long-term solution to the disposal of used nuclear fuel. These agencies will have to prepare a safety assessment to demonstrate that used nuclear fuel will be safely managed over hundreds of thousands of years. The reliability of the safety assessment will be improved if the sorption behaviours of radionuclides in the engineered and natural barriers of the repository are well characterized. In Canada, the NWMO is engaging with two potential siting areas, one in granitic rock and one in sedimentary rock. In this project, the sorption of Pd(II) on biotite, quartz and feldspar will be studied. (Pd-107 is a long-lived fission product present in used nuclear fuel in appreciable amounts. Quartz and feldspar are main mineral components of granite. Biotite is a common but minor mineral component of granite and is considered to dominate the sorption of some radionuclides such as Cs on granite.) The sorption reactions will be identified by integrating the experiments with a sorption model and with quantum chemistry calculations, and the optimized equilibrium constants of reactions will be evaluated. Qualified sorption data will be compiled in the sorption database of the NWMO. This study will lead to long-term benefits to Canadian society, as it will allow for increased confidence that a safe site has been selected (ensuring future health and wellbeing of Canadians and the environment). This project will use the unique research capability and expertise at McMaster University for working with trace radionuclides and extend our scientific understanding of sorption processes of one of the nuclides in safety assessment. Importantly, this will also contribute to the development of highly qualified personnel in the fields of used nuclear fuel management.