Description
The properties and characteristics of discontinuities in and between the host rock and other geological units, including faults, ductile shear zones, intrusive dykes and interfaces between different rock types. “Large-scale” is not precisely defined but implies a length-scale comparable to the scale of the repository or larger. Depending upon the processes by which they formed, large-scale discontinuities could have any orientation. Furthermore, the orientation of a single large-scale discontinuity may change spatially. At the scale of a repository a large-scale discontinuity may be modelled as a planar feature, but in reality may be 3-dimensional, with one dimension orders of magnitude smaller than its other two dimensions. There could be considerable heterogeneity (e.g. variations in porosity and permeability) within the volume of such a large-scale discontinuity.
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
Comments
The “Comments” field, when present, contains any additional explanation of the IFEP, beyond that implicit in the FEP's description and provided in the “Relevance to Performance and Safety” field. This additional explanation may include, where appropriate, the IFEPs characteristics, the circumstances under which it might be relevant and its relationship to other (especially similar) IFEPs.
Large-scale discontinuities (this FEP, 4.1.2) grade into small-scale discontinuities such as faults and joints, which are covered by FEP 4.1.6 (Hydraulic characteristics) and FEP 4.1.7 (Mechanical characteristics).
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.
Large-scale discontinuities such as unconformities, faults, ductile shear zones, and contacts at the margins of intrusive igneous bodies like dykes or larger intrusions, may influence the layout of the repository and / or the locations within it where wastes are emplaced. These discontinuities may also influence the effectiveness of the geosphere barrier in the post-closure period. Individual discontinuities may affect patterns of fluid flow (such as water, non-aqueous liquids or gases) through the geosphere. Potentially, in the post-closure period, the discontinuities may act either as pathways for the flow of these fluids, and hence for the transport of radionuclides and other contaminants that originate in the repository. Alternatively, discontinuities may act as barriers to the flow of these fluids. Certain properties of these discontinuities, such as the porosity distribution and the mineralogy of the rocks along them, will influence the retardation of radionuclides and other contaminants that might be transported along them. Some of these features might focus contaminant releases into the biosphere at discharge locations.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.