Description

The biological characteristics and properties of the geosphere prior to repository construction. Included are biological characteristics and properties such as the extent and composition of microbe populations. Potentially, more complex organisms could occur in the deep sub-surface. For example, nematode worms have been found in deep (>1 km) South African gold mines.

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.

Biological characteristics and properties of the geosphere, prior to repository construction, will influence the subsequent biological evolution of the geosphere, during repository construction, during repository operation, and later, post-closure. The biological characteristics and properties of the geosphere, including those of rocks and the fluid phase (such as water, non-aqueous liquids or gases), may influence the effectiveness of the EBS and the geosphere barrier. Chemical conditions in the geosphere may be influenced by microbially mediated chemical reactions. Examples include SO₄ reduction and methanogenesis. Potentially, certain of these reactions may impact upon the performance of some engineered barriers. For example, consideration may need to be given to the possibility that microbially mediated corrosion may occur. By influencing chemical conditions, biological characteristics and properties of the geosphere may impact upon partitioning between the solid and fluid phases of radionuclides and other contaminants that originate within the repository.

2000 List

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

2.2.09