Description
The diffusion of contaminants through the geosphere. Diffusive migration is driven by chemical potential gradients, can be affected by thermal gradients, and can be in any direction. Diffusion can be the most important migration mechanism in situations where groundwater flow in the geosphere is very slow.
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.
Given sufficient time, diffusion could transport radionuclides and other contaminants through all or part of the distance between the repository and the biosphere. Possibly, diffusion could transport radionuclides and other contaminants through a low-permeability host rock, into a higher permeability overlying or adjacent rock formation, through which water is able to flow and result in radionuclide and contaminant by advection.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.