Description
The spread in the spatial distribution of contaminants with time in the geosphere because of differential rates of advective transport through the geosphere. Variations in water velocity and pathways cause dispersion, i.e. the spatial spreading of solutes from advective transport. Dispersion can occur in the direction of flow (longitudinal dispersion) and perpendicular to the direction of flow (transverse dispersion).
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.
- Event
- 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.
Should the EBS of a repository has pathways through it through which radionuclides and other contaminants can leave the repository, dispersion will tend to decrease aqueous concentrations of released radionuclides and other contaminants along groundwater flow paths through the geosphere. Thus, dispersion in the geosphere has the potential to diminish the dose rates to biological receptors, should the flowing groundwater transport radionuclides and other contaminants from the repository to the biosphere. On the other hand, dispersion will tend to increase the volume of water that contains radionuclides and other contaminants originating in the repository.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.