Description
The geochemical characteristics and properties of the geosphere prior to repository construction. These characteristics and properties include rock mineral composition, ground- and porewater composition (in particular pH and redox conditions), salinity and chemical gradients.
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.
Geochemical characteristics and properties of the geosphere prior to repository construction will influence the subsequent geochemical evolution of the geosphere, during repository construction, during operation, and later, post-closure. Geochemical characteristics and properties, including both of the fluid phase (such as liquid water, non-aqueous liquids or gases) and of rocks, may influence the effectiveness of both the EBS and the geosphere barrier. These characteristics and properties will influence the rates and nature of reactions in the EBS and in the geosphere. The chemical characteristics of groundwater also determine the solubility and speciation of dissolved contaminants. pH, Eh and concentrations of Cl- and S₂₋ in groundwater may affect the rate of steel corrosion. The concentrations of SO²⁻ and Cl- in groundwater may influence the degradation pathway of cementitious barriers, and the cation concentrations in groundwater may influence cation exchange reactions involving clay barriers and affect the swelling pressure of bentonite. The chemical characteristics and properties of rocks will influence the chemical evolution of the fluid phase present within them. For example, the redox buffering capacity of the rocks will influence the depth to which infiltrating oxidising water can penetrate. The chemistry of the rocks, minerals they contain and fluid phase within the pore space will influence the partitioning of solutes between the solid and fluid phases. These solutes may include radionuclides and other contaminants originating in the repository.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.