Description

The physical, chemical and biological characteristics and properties of any site investigation/ monitoring boreholes at the time of sealing.

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.

  • Feature

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.

If radionuclides and other contaminants are able to leave the repository via the EBS, their potential to migrate through the surrounding geosphere will be impacted by the characteristics of seals in any boreholes there. The borehole seals may influence the rate at which fluids (such as liquid water, non-aqueous liquids or gases) may enter or leave the repository in the post-closure period. This in turn may affect the chemical and biological conditions within the repository.

Boreholes may connect the surface to the deeper geosphere, and potentially the repository itself. The effectiveness of its seals will determine whether a borehole may form a pathway to the biosphere for radionuclides or other contaminants that can leave the repository via the EBS.

Boreholes that do not penetrate from the surface to the repository may connect different permeable rock formations or structures (e.g. transmissive faults) that are naturally separated by impermeable rock formations or structures.

Impairment of borehole seals may, depending upon the natural hydraulic gradients, result in cross-flow of groundwater or other fluids (e.g. hydrocarbon liquids or gases) between different rock formations or structures in the rock sequence above the repository.

2000 List

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

2.1.05

Related References