Evaluation of temperature-induced effects on safety-relevant properties of clay host rocks with regard to HLW/SF disposal

Abstract

DBE TECHNOLOGY, BGR and GRS are developing a methodology to demonstrate the safety of a repository for high-level waste and spent fuel (HLW/SF) in clays according to the requirements of the German regulating body. In particular, these requirements prescribe that the barrier effect of host rocks must not be compromised by a thermal impact resulting from HLW/SF emplacement. To substantiate and quantify this requirement, we carried out a literature survey of research on thermally-induced changes on clay properties. Effects thus compiled can be divided into thermo-hydro-mechanical and chemical-biologicalmineralogical effects and were analysed with regard to their relevance to the integrity of clay host rocks. This analysis identified one effect of major influence within each group: thermal expansion and compaction as well as results of microbial activities. Importantly, it further revealed that a moderate temperature increase above 100°C cannot be expected to compromise the integrity of the geological barrier according to the current knowledge state. Evidence is presented in this paper that temperature increases up to 150°C can actually contribute to an improved performance of a radioactive waste repository by increasing the consolidation of the clay and sterilizing the repository's near-field to depress the deteriorative microbial effects. A quantitative temperature criterion for thermal impact of HLW/SF on clay host rocks is accordingly proposed.

The IGD-TP Geodisposal 2014: Introduction to the Conference Proceedings

“…Section 2: Natural Systems Including Biogeochemistry, Biosphere and Geosphere The discussion of natural systems includes a diverse range of papers covering: iodine behaviour in model sediment systems (Guido-Garcia et al, 2015); characterization of the mineralogy and redox reactivity of potential GDF host rocks in the UK (Quirke et al, 2015); modelling studies applying pore network models to Opalinus clay (Xiong and Jivkov et al, 2015); the behaviour of pertechnetate in hyperalkaline conditions in the context of recrystallization of kaolinite (Littlewood et al, 2015); the impact of GDFrelevant temperatures on clay systems in the context of high-level waste disposal (Jobmann and Meleshyn, 2015); the impact of humic substances on metal ion behaviour (Bryan et al, 2015); an evaluation of the Herberts Quarry site in the UK as an analogue for intermediate level waste disposal (Moyce et al, 2015); a study examining the inhibition of colloidal formation in intermediate level waste systems (Felipe-Sotelo et al, 2015); microbial degradation of cellulosic materials under conditions relevant to intermediate level waste disposal (Bassil et al, 2015); microbial degradation of isosaccharinic acid under far-field conditions (Kuippers et al 2015); radiation damage studies in natural sheet silicate minerals (Bower et al, 2015); and a representation of biosphere systems in the UK relevant to higher activity waste disposal (Walke et al, 2015).…”