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Annual Report 2010 KIT SCiEntiFiC REPOrts 7600 Annual Report 2010 Institute for Nuclear Waste Disposal Institut für Nukleare Entsorgung H. Geckeis, T. Stumpf (eds.) KArLsrUHEr InstitUt FÜr TECHnOLOGiE (KIT) ISSN 1869-9669 H. Geckeis, T. Stumpf (eds.) Annual Report 2010 Institute for Nuclear Waste Disposal Institut für Nukleare Entsorgung Karlsruhe Institute of Technology KIT SCIENTIFIC REPORTS 7600 Cover illustration (from left to right): SEM image of a polished UO2 surface with studtite crystals, uranyl peroxide hydrate, grown as secondary phase in water under γ-irradtiation (acquired energy dose 1.5 MGy). Artificial view with pseudocolors. SEM image of a spherical crystalline molybdate particle formed on the surface of a simulated nuclear waste glass containing 5.5 wt% MoO3. Eu(III) fluorescence of calcite and clay containing sample after excitation at 394 nm. Annual Report 2010 Institute for Nuclear Waste Disposal Institut für Nukleare Entsorgung H. Geckeis T. Stumpf (eds.) Report-Nr. KIT-SR 7600 Impressum Karlsruher Institut für Technologie (KIT) KIT Scientific Publishing Straße am Forum 2 D-76131 Karlsruhe www.ksp.kit.edu KIT – Universität des Landes Baden-Württemberg und nationales Forschungszentrum in der Helmholtz-Gemeinschaft Diese Veröffentlichung ist im Internet unter folgender Creative Commons-Lizenz publiziert: http://creativecommons.org/licenses/by-nc-nd/3.0/de/ KIT Scientific Publishing 2011 Print on Demand ISSN 1869-9669 Table of contents 1 Introduction to the Institut für Nukleare Entsorgung ............................................... 6 2 Highlights ..................................................................................................................... 8 3 Education and training .............................................................................................. 11 4 National and international cooperation ................................................................... 13 5 Fundamental studies: process understanding on a molecular scale ................... 16 5.1 Chemistry and thermodynamic of actinides in aqueous solution ........................ 16 5.2 Sorption on mineral surfaces .............................................................................. 22 5.3 Retention of radionuclides by secondary phase formation.................................. 28 6 Applied studies: radionuclide retention in the multi-barrier system .................... 33 6.1 Key processes influencing corrosion of highly active waste forms ..................... 33 6.2 Actinide retention in cemented nuclear waste forms .......................................... 39 6.3 Colloid impact on radionuclide migration ............................................................ 42 6.4 Numerical simulation studies .............................................................................. 47 7 Separation of long-lived minor actinides ................................................................ 53 8 Vitrification of high-level radioactive liquid waste.................................................. 58 9 Development of actinide speciation methods ......................................................... 66 9.1 R&D projects conducted at the INE-Beamline for Actinide Research at ANKA and at external SR sources .................................................................. 66 9.2 Laser spectroscopy ............................................................................................. 71 9.3 Mass spectrometry methods ............................................................................... 74 + 9.4 XPS and TEM study of neptunyl (NpO2 ) - green rust interaction ....................... 78 9.5 NMR spectroscopy as a new tool for structural investigations on radioactive materials in solution ........................................................................................... 80 9.6 Computational Chemistry ................................................................................... 83 10 Publications ............................................................................................................ 88 - 5 - 1 Introduction to the Institut für Nukleare Entsorgung R&D at the Institut für Nukleare Entsorgung, availability of thermodynamic data and a INE, (Institute for Nuclear Waste Disposal) comprehensive understanding of these deals with the long-term safety assessment for processes at a molecular scale. final disposal of nuclear waste, the separation of Relevant radionuclide concentrations in natural minor actinides from high-level waste groundwater lie in the nano-molar range, which (partitioning) and the immobilization of high-level is infinitesimally small in relation to the main liquid waste by vitrification. All activities are groundwater components. Quantification of integrated into the programme Nuclear Safety chemical reactions occurring in these systems Research within the Energy Center of the calls for the application and development of new Karlsruhe Institute of Technology, KIT. INE sophisticated methods and experimental contributes to the German provident research for approaches, which provide insight into the the safety of nuclear waste disposal, which is in chemical speciation of radionuclides at very low the responsibility of the federal government. concentrations. Innovative laser and X-ray Based on the scheduled operation times for spectroscopic techniques are continuously nuclear power plants in Germany, about 17.000 developed and applied. A theoretical group tons of spent nuclear fuel will be generated. performs quantum chemical calculations on About 6200 tons have been shipped to France actinide complexes as an additional tool to and UK before 2005 for reprocessing to recover support experimental results. plutonium and uranium. Therefore two types of The long term safety assessment of a repository high level, heat producing radioactive waste for nuclear waste has to be demonstrated by have to be disposed of safely, namely spent fuel application of modelling tools on real natural and vitrified high level waste from reprocessing. systems over geological time scales. The There is an international consensus that storage experimental research programme at INE aims in deep geological formations is the safest way to acquire fundamental knowledge on model to dispose of high level heat producing subsystems and to derive model parameters. radioactive waste. It ensures the effective Geochemical models and thermodynamic protection of the population and the biosphere databases are developed as a basis for the against radiation exposure over very long description of radionuclide geochemical periods of time. The isolation and immobilization behaviour in complex natural aquatic systems. of nuclear waste in a repository is accomplished The prediction of radionuclide migration in the by the appropriate combination of redundant geosphere necessitates a coupled modelling of barriers (multi-barrier system). geochemistry and transport. Transferability and INE research focuses on the geochemical applicability of model predictions are examined aspects of nuclear waste disposal. Special by designing dedicated laboratory experiments, emphasis is given to actinides and long-lived field studies in underground laboratories and by fission products because of their significant studying natural analogue systems. This contribution to the radiotoxicity for long periods strategy allows to identify and to analyse key of time. uncertainties related to the accuracy and the relevance of the developed models. Relevant scenarios for the geological long-term behaviour of nuclear waste disposal have to The Partitioning & Transmutation (P&T) strategy take into account possible radionuclide transport is pursued in many international research via the groundwater pathway. programmes. The objective is to reduce the time Thermomechanical studies are performed at INE horizon for safe disposal of high level waste in order to describe the evolution of the from some hundred thousand to less than repository after closure. The possible thousand years by significant reduction of the groundwater access to emplacement caverns is radiotoxicity and heat inventory. The aim of R&D assumed to cause waste form corrosion. at INE in P&T is to develop efficient processes Radionuclide mobility is then determined by the for long-lived minor actinide separation from various geochemical reactions in the complex high active nuclear waste for subsequent aquatic systems: i.e. dissolution of the nuclear transmutation into short-lived or stable fission waste form (high-level waste glass, spent fuel), products. INE develops highly selective radiolysis phenomena, redox reactions, extracting agents and performs experiments to complexation with inorganic and organic ligands, derive kinetic and thermodynamic data for the colloid formation, surface sorption reactions at extraction reaction. R&D spans theoretical and mineral surfaces, precipitation of pure solid experimental work dedicated to a mechanistic phases and solid solutions. Prediction and understanding of extraction ligand selectivity on quantification of all these processes require a molecular scale, to development of extraction processes. - 6 - Within the third R&D topic at INE, the vitrification techniques are developed and applied for of high level waste, INE contributes to the sensitive actinide and fission product speciation decommissioning of nuclear facilities. The core such as time-resolved laser fluorescence process technology for the Vitrification Plant spectroscopy (TRLFS), laser
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