Description

The migration of dissolved contaminants by the bulk flow of water through the geosphere. The rate of advection will vary depending on hydraulic, thermal and density conditions in the geosphere and repository. Fluid flow driven by temperature, chemical or electrical gradients, rather than due to hydraulic head gradients is called thermal, chemical or electrical osmosis.

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.

Bulk flow of water through the geosphere may transport radionuclides and other contaminants from the repository (if there are pathways through the engineered EBS). Advection will be accompanied by dispersion, which will act to diminish the concentrations of radionuclides and other contaminants dissolved in the water. Related to this, water that has transported through the repository with radionuclides and other contaminants may mix with other bodies of water having different origins. As well as dilution, a range of chemical processes (e.g. mineral precipitation, dissolution or alteration) may accompany such mixing, and affect the mobility of the radionuclides and other contaminants (FEP 4.2.4). The direction and rate of advection will influence whether radionuclides and other contaminants are transported from the repository to the biosphere within the assessment period. Should this occur, the rate of advection and the magnitude of accompanying dispersion will influence the temporal variation in doses received by biological receptors.

2000 List

A reference to the related FEP(s) within the 2000 NEA IFEP List.

3.2.07