Simulations of hydrogeological evolution at Olkiluoto

• Main Authors: Löfman, Jari, Karvonen, T.
• Format: Book
• Language: English
• Published: Posiva 2012
• Subjects: Hydrology; postglacial crustal uplift; groundwater flow; salt transport; permafrost; glaciation; numerical modelling; spent nuclear fuel; Olkiluoto; /dk/atira/pure/sustainabledevelopmentgoals/climate_action; SDG 13 - Climate Action; Onkalo; Ice; Ice Sheet
• Online Access: https://cris.vtt.fi/en/publications/b17a699a-b17b-48f3-8df0-3b8ca13f1f82; https://www.posiva.fi/en/index/media/reports.html

On assignment by its owners, Fortum and TVO, Posiva will take care of the disposal of spent fuel from the nuclear power plants at Loviisa and Olkiluoto. The site (Olkiluoto) for the repository has been chosen on the basis of site investigation programme, which currently is focused on the construction of an underground rock characterisation and research facility (the ONKALO). The hydrogeological conditions at the site may constitute a significant factor with regard to the performance of the disposal facility. Of particular importance are the changes within the glacial cycles, during which major climatic changes are expected to occur. The glacial cycles consists of several periods ranging from temperate to glacial climate conditions, which affect the groundwater flow not only in the soil but also deep in the bedrock. This study comprises of the numerical modelling of the hydrogeological evolution at Olkiluoto over the next glacial cycle. Because of the high uncertainties relating to the prediction of the long-term climate changes (e.g., the future evolution of the atmospheric CO2 concentration is highly uncertain) and the associated climate-driven boundary conditions, the modelling was not striving for a detailed continuous simulation of the whole glacial cycle, but it was focused on assessing the impact of a range of the expected most relevant climatic conditions (temperate, permafrost, ice sheet retreat). The hydrogeological evolution for the three time windows were modelled using climate-related boundary conditions on the top surface, which for the temperate and permafrost time windows were derived from the separately conducted surface hydrological model, while the glacial simulations were based on an ice sheet model. Both the hydrogeological and the surface hydrological models used permafrost data from a separate permafrost evolution model. The Olkiluoto surface hydrological model was used to compute water fluxes in the overburden soils and in the shallow bedrock to provide proper treatment of the hydraulic ...