Palaeohydrogeology and geoforecasting for performance assessment in geosphere repositories for radioactive waste disposal (Pagepa)
Document Date: 2001-01-01
Document Type: Publication
A palaeohydrogeological methodology has been created to test the capacity of groundwater models to simulate the long-term performance of the geosphere. Known palaeo-climates are used to drive groundwater flow and geochemistry through the Gorleben and Delta-sp-fi sites. Their predictions have been tested against actual geochemistry.
Delta-sp-fi lay beneath an ice sheet during the last glacial cycle. A theory is presented which shoes how the sub glacial cycle. A theory is presented which shows how the subglacial hydraulic system operates, and how it controls the pattern and rate of groundwater flow. This is used to simulate the history of groundwater flow through the whole of the last glacial cycle and to set initial conditions for the coupled evolution of groundwater flow and chemistry from the time of de-glaciations until the present day.
At Gorleben, the dominant influence on changing patterns of groundwater flow during the last glacial cycle has been the development of permafrost, which inhibits both recharge to and discharge from the system. Modeling suggests that if glacial melt waters were injected directly into subsurface aquifers, they would have energized groundwater flow beneath the Elbe valley and flushed out saline waters from the aquifers. Absence of such flushing would have left higher residual salinities.
Programme(s): NFS 2