Description

The physical, chemical and biological characteristics and properties of the engineered features (other than waste packages, buffer/backfill, and seals) at the time of repository closure. Such features can include rock bolts, shotcrete, tunnel and shaft liners, silo walls, any service components and equipment not removed before closure.

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.

Other engineered features have the potential to influence the physical, chemical and biological conditions in and around the repository. These influences may impact upon the stability of EBS components and upon the chemical forms and mobility of radionuclides and other contaminants that are can leave the repository by the EBS. They may also contribute to gas generation.

Engineered features such as rock bolts and tunnel lining that affect the mechanical responses of the geosphere, could influence the potential for migration pathways to develop through the geosphere for radionuclides and other contaminants.

Engineered features that affect chemical conditions could impact upon the stability of EBS components and the chemical forms and mobility of radionuclides and other contaminants. For example, an alkaline plume could develop from shotcrete and might dissolve mineral phases in nearby bentonite barriers. Cement might react with bicarbonate in the groundwater, thereby reducing its concentration and the ability of certain radionuclides to complex with carbonate. Certain engineered features, such as shotcrete or rock bolts, could provide surfaces for sorption of radionuclides or other contaminants that might be able to leave the repository via the EBS.

Emplacement of engineered features might introduce micro-organisms to the sub-surface, thereby influencing microbially-mediated reactions that might occur. These reactions might in turn impact upon the stability of engineered materials and the mobility and chemical forms of radionuclides and other contaminants that leave the repository.

2000 List

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

2.1.06

Related References