FZK-INE together with the Chemistry Department of Lomonosov Moscow State University, was awarded funding for a Helmholtz – Russia Joint Research Group (HRJRG) entitled “Actinide Nano-Particles: Formation, Stability and Properties Relevant to the Safety of Nuclear Waste Disposal” (HRJRG-011) for the years 2008 through 2010. The project goal is to develop a molecular-level understanding of the formation, stability, and properties of nano-sized actinide containing colloids relevant to safe spent nuclear fuel (SNF) and high level radioactive waste (HLW) disposal, thereby filling conceptual gaps in the source term and transport models used in long-term assessment for deep geological repositories.

Contact person: Melissa A. Denecke

Co-workers

Publications

Since March 1, 2008, the Helmholtz virtual institute „advanced solid –aqueous radiogeochemistry“ is studying the interaction of radionuclides with minerals using a multidisciplinary approach in order to improve our understanding of the long-term safety of the disposal of high-level radioactive waste. It involves five international partners - Forschungszentrum Karlsruhe, University Karlsruhe, University Frankfurt, University Oviedo (Spain) and Paul Scherrer Institute (Switzerland). It is funded by the Impulse- and Networking Fund of the Helmholtz Association.

Contact person: Thorsten Stumpf

Group members: 

	Thorsten Stumpf, Nicolas Finck, Frank Heberling	(Campus Nord)
	Thomas Neumann, Alexander Diener	(Campus Sud)
	Björn Winkler, Victor Vinograd
	Enzo Curti, Dimitrii Kulik
	Manolo Prieto

Research programme of the virtual institute …

The disposal of high-level nuclear waste in deep geological formations poses major scientific and social challenges to be met in the next decades. One of the key issues is related to the long term safety of a waste repository system over extended periods of time (up to 106 years). Demonstrating the safety over such geologic time scales requires a sound understanding of the migration and retention of radionuclides in the geosphere. In principle, sorption reactions between radionuclides and minerals control the retention. In recent years, various molecular-level sorption mechanisms have been identified: outer-sphere adsorption, inner-sphere adsorption, ion exchange, and structural incorporation (solid solution formation). The structural incorporation of trace elements in host minerals via coprecipitation or recrystallization in aqueous systems is usually not yet considered in the safety analysis for repository systems, although these phenomena are quite common and extensively studied in natural systems. The main reason of this discrepance is the lack of thermodynamic and kinetic data needed for the quantitative description of such processes.

The virtual institute is focusing on structural incorporation of key-radionuclides into relevant host minerals as baseline information for improving long-term safety aspects of nuclear waste disposal.

Structural incorporation of radionuclides leading to solid solution formation in low-temperature (0 < T < 100°C) aquatic environments may involve complex substitution mechanisms that proceed at slow kinetic rates (thus requiring long-term experiments). Also, it implies trace concentration levels as an additional experimental and analytical challenge. The virtual institute brings together several expert groups in order to combine novel synthesis procedures (for actinide and fission product doped minerals) with state-of-the-art spectroscopic methods, advanced thermodynamic approaches, and cutting-edge molecular modeling techniques. A main strength of the virtual institute is the coordinated experimental, analytical and theoretical work. Ultimately, a coherent model of aqueous – solid solution thermodynamics for actinide and fission product containing host minerals will be developed (for selected systems). It will allow refined predictions of radionuclide solubility in repository near and far-field. Geochemical model calculations on radionuclide migration in the geosphere and, ultimately, dose calculations rely on the availability of such data. Eventually, decisions regarding the long term safety of a nuclear waste repository will be based on the results of such calculations.

Highlights

April 2008: 1st joint publication – Publication of „Subsolidus phase relations in Ca2Mo2O8 - NaEuMo2O8 - powellite solid solution predicted from static lattice energy calculations and Monte Carlo simulations“ by V.Vinograd, D.Bosbach, B.Winkler, & J.Gale in Physical Chemistry Chemical Physics

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