Nuclear waste disposal and redox phenomena
With this in mind, the EU-funded RECOSY project was initiated to enhance performance and conduct safety case analysis for all scenarios. RECOSY investigated the effects of redox phenomena controlling systems through the development of advanced methods, analytical tools and geochemical modelling of redox-related phenomena. Some key achievements in this regard are the development of redox determination methods taking into consideration factors such as host-rocks, redox speciation, thermodynamics and kinetics. For redox measurement, amperometric and potentiometric tools using optical fibre-based optode technology and ultra-micro-electrodes were successfully developed. For electrochemical characterisation of clays such as Boda claystone, Boda Albitic Claystone and Callovo-Oxfordian argillite, voltammetry was applied. Macroscopic models were developed representing distribution of the redox elements iron, sulphur, manganese and nitrogen as well as speciation–solubility calculations. Through field studies and simulations, factors affecting redox-sensitive nuclear waste radionuclides' (e.g. Uranium) transport through host-rocks (e.g. clay rocks and crystalline rocks) were determined. RECOSY activities will thus contribute to the optimisation of waste management through effective radionuclide immobilisation. RECOSY activities were highly successful, resulting in the publication of KIT Scientific Reports based on the four annual project workshop proceedings. Important scientific and technological achievements were included and communicated through 67 poster presentations and 129 oral contributions. A detailed comparison of established and newly developed redox measurement techniques was presented at the ReCosy Intercomparison Exercise (ICE), resulting in the consolidated report 'Intercomparison of Redox Determination Methods on Designed and Near-Natural Aqueous Systems'. Other dissemination activities included participation in 77 conferences, workshops and seminars. Besides this, over 46 papers have been published and several others have been submitted for publication. Training activities included the participation of 36 students and 19 post-doc researchers in RECOSY. Project activities will have important implications for European energy needs with regard to use of nuclear energy and safe radioactive waste disposal. The resultant tools and methods will increase the quality and reliability of redox processes, ensuring better acceptance of a proposed Safety Case.
Keywords
Safety case, redox phenomena, radionuclide, voltammetry, radioactive waste management, optode, biofilm, micro-electrode