Description

The internal and external mechanical processes that affect the waste packages. This includes mechanical loads imposed on the waste package by adjacent waste packages, other repository components and the surrounding geosphere.

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.

  • Event
  • Process

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.

Mechanical processes (this FEP, 2.3.3) concerns the effects of mechanical loads other than those due to Thermal processes (e.g. expansion, FEP 2.3.1).

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.

Thermal, hydraulic and mechanical loads imposed on the waste package, whether generated internally or imposed by external processes, may cause deformation of a waste package and/or waste form. If these loads are of sufficient magnitude and applied for sufficiently long times, then the integrity of the package could be affected. A package that initially contains openings (e.g. a vented container) may have larger openings produced within it. A package that initially offers complete containment may lose its integrity. If the loads affect a package that lacks integrity, then they could promote the migration of radionuclides and other contaminants from the package, by reducing the volume of any voids present within the package and producing a pressure gradient. Mechanical processes operating within and upon a waste package may also influence the performance of engineered and natural barriers that surround the package. For example, a reduction in the volume of a package, due to mechanical processes within it, could potentially lead to cracking or displacement of any surrounding backfill that might be present. Mechanical processes may operate over time periods that are very short compared to the assessment period (e.g. loading caused by seismic shearing) or over time periods that are very long compared with the assessment period (e.g. loading by creep of the surrounding geosphere).

2000 List

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

2.1.07, 2.1.12

Related References