Talk given by Dr. Robert Polly Institut für Nukleare Entsorgung KIT Abstract: The reliable long-term prediction of actinide migration in geological formations requires understanding of the adsorption/desorption and incorporation mechanism at the molecular level. The sorption and incorporation of metal ions at mineral surfaces is a very important process which leads to the retention/retardation of radionuclides such as actinide ions and fission products.We present two different investigations in this talk: (1) interaction of selenite with the hydrated calcite surface and (2) the incorporation of trivalent lanthanides and actinides in calcite. This calculation are carried out with plane-wave DFT, as implemented in the Vienna Ab initio Simulation Package (VASP). Se-79 is a fission product of U-235 with a long radioactive half life of 1.1x10^6 years. Selenite (SeO32-) and selenate (SeO4 2-) interact only weakly with common mineral surfaces. Therefore they have been identified as crucial radio nuclides for long term safety assessments of nuclear waste disposal. We determined the structure of the water/calcit interface and identified surface sorbed and incorporated selenite species at the calcite/solution interface. The second point tackles the incorporation of trivalent lanthanides and actinides into calcite. Earlier spectroscopic investigations suggest incorporation of lanthanide/actinide ions occupying Ca-sites in the calcite lattice. Charge compensation is achieved by the substiution of two Ca atoms by one trivalent lanthanide/actinide and one Na ion. Here, we studied modifications of the calcite structure induced by the substitution.

This event is part of the eventgroup INT Talks

Homepage
https://www.int.kit.edu/events.php

Speaker
Dr. Robert Polly

KIT
http://www.ine.kit.edu/

Organizer
PD Dr. Karin Fink
Institute of Nanotechnology (INT)
Karlsruhe Institute of Technology (KIT)
Eggenstein-Leopoldshafen
Mail: karin fink ∂does-not-exist.kit edu

Targetgroup
Interested / Everyone