Description
The effect on regional groundwater flow and pressures arising from large-scale geological changes. These effects could include changes in groundwater flow and pressures caused by the effects of uplift/erosion on topography, and changes to hydraulic properties of geological units caused by changes in geological conditions.
Category
Categorisation as a Feature, Event and/or Process.
Features
are physical components of the disposal system and environment being assessed. Examples include waste packaging, backfill, surface soils. Features typically interact with one another via processes and in some cases events.Events
are dynamic interactions among features that occur over time periods that are short compared to the safety assessment timeframe such as a gas explosion or meteorite impact.- "Processes" are issues or dynamic interactions among features that generally occur over a significant proportion of the safety assessment timeframe and may occur over the whole of this timeframe. Events and processes may be coupled to one another (i.e. may influence one another).
The classification of a FEP as an event or process depends upon the assessment context, because the classification is undertaken with reference to an assessment timeframe. In this generic IFEP List, many IFEPs are classified as both Events and Processes; users will need to decide which of these classifications is relevant to their context and its timeframes.
- Process
Relevance to Performance and Safety
The “Relevance to Performance and Safety” field contains an explanation of how the IFEP might influence the performance and safety of the disposal system under consideration through its impact on the evolution of the repository system and on the release, migration and/or uptake of repository-derived contaminants.
The hydrogeological responses to geological changes will influence the flux and directions of groundwater flow through and around a repository. These processes may be coupled to changes in groundwater chemistry along flow paths through and around a repository, for example by influencing mixing patterns between chemically distinct groundwater bodies. These responses could therefore impact upon the transport of radionuclides and/or other contaminants from the repository to the biosphere. The hydrological / hydrogeological regime around a repository at the start of repository development will reflect to some degree past hydrological / hydrogeological responses to geological changes. These responses will have occurred more slowly in lower permeability rocks than in higher permeability rocks. Groundwater head gradients in lower permeability rocks in and/or around a repository may be out of equilibrium with present hydraulic heads at the boundaries of the groundwater system within which the repository resides. In higher permeability rocks within and around a repository, groundwater head gradients may be at equilibrium with present heads at the boundary of the groundwater system. However, irrespective of whether head gradients are presently in a state of equilibrium, the chemistry of groundwater may still record past groundwater movements in response to past geological changes. Geological change in the post-closure period, such as uplift/erosion and subsidence/sedimentation, and their influences on topography, could cause future hydrological and hydrogeological changes. The rates of these changes would be more rapid in higher permeability rocks than in lower permeability rocks.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
-
IAEA (), Hydrogeological Investigation of Sites for the Geological Disposal of Radioactive Waste, IAEA TRS-391, International Atomic Energy Agency, Vienna