Understanding the behaviour of gas in a geological disposal facility: modelling coupled processes and key features at different scales

Abstract

Understanding the behaviour of gas in a geological disposal facility (GDF) is an essential component of analysing the facility evolution and long-term (post-closure) safety performance. This includes the impacts of gas on the physico-chemical evolution of the GDF, and the release and migration of radionuclides in water and gas.The Nuclear Decommissioning Authority Radioactive Waste Management Directorate is participating in the EC FORGE (fate of repository gases) project (www.forgeproject.org) and conducting independent research. Key research themes are modelling the impacts of different host rocks on facility evolution including coupled processes, and upscaling the effects of small scale features that can significantly influence the evolution of the whole facility.Recent code developments have enabled coupled processes to be represented more realistically in models. This has significantly advanced understanding of facility evolution, as discussed in this paper, and will improve future assessment models. There is potential to further improve approaches to upscaling the effects of small scale features on strongly coupled processes, within the context of the EC FORGE project.

Temperature and tortuosity effect on gas migration in a high-level waste disposal tunnel

“…The key data allowing evaluation of gas migration regularities in the geological repository are: gas saturation in porous materials, peak pressure in the analysed system and gas release (in gaseous and dissolved state) from the repository (Towler et al, 2012).…”

Geological disposal of radioactive waste: underpinning science and technology

“…Discussion of gas begins with an overview of gas research in support of the UK geological disposal programme by Steve Williams of the NDA (Williams, 2012). There follow contributions which describe: gas migration experiments in bentonite and their implications for numerical modelling by Caroline Graham (BGS) and coworkers (Graham et al, 2012); the rate and speciation of volatile carbon-14 and tritium releases from irradiated graphite by Graham Baston (AMEC) and co-workers (Baston et al, 2012d); gas flow in Callovo-Oxfordian clay including results from laboratory and field-scale measurements by Jon Harrington (BGS) and coworkers (Harrington et al, 2012a); the comparison of alternative approaches to modelling gas migration through a higher strength rock by Andrew Hoch and Martin James (AMEC) (Hoch and James, 2012); evidence for gas-induced pathways in clay using a nanoparticle injection technique by Jon Harrington (BGS) and coworkers (Harrington et al, 2012b); multicomponent gas flow through compacted clay buffer in a higher activity radioactive waste geological disposal facility by Shakil Masum (Cardiff University) and co-workers (Masum et al, 2012); the migration and fate of 14 CH 4 in subsoil: tracer experiments to inform model development by George Shaw (The University of Nottingham) and co-workers (Atkinson et al, 2012); a data analysis toolkit for long-term, largesc ale experiments by Daniel Benn ett (Geoenvironmental Research Centre) and coworkers (Bennett et al, 2012); and understanding the behaviour of gas in a geological disposal facility by George Towler (Quintessa Ltd) and coworkers (Towler et al, 2012).…”

Extremophilic microbial metabolism and radioactive waste disposal

“…Resaturation with deep groundwater will lead to the formation of redox gradients and alter geochemical parameters such as pH (Beattie and Williams 2012 ). Gas generation from corrosion, radiolysis and microbial degradation or organics in the wastes will also impact on physiochemical evolution (Towler et al 2012 ). Not all barrier evolutions are negative as some are proposed to enhance GDF safety requirements, such as reduction in hydraulic permeability through swelling of materials (Sellin and Leupin 2014 ).…”