Description

The impact of mechanical effects on hydraulic processes influencing the waste package.

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.

  • 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.

The evolution of the waste package’s mechanical condition over time (FEP 2.3.3) can influence the associated hydraulic conditions (for example material volume changes resulting in changes in hydraulic properties).

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.

Mechanical effects may influence the volume and connectivity of pore space within a waste package and the pressures to which free water within the pore space is subjected. Pressures will affect the distribution of water between bound (to solid phases) and free forms and the form of free water (whether liquid or steam). Pressure gradients could cause free water to move. These mechanical effects can also influence the degree to which a waste package will saturate with free water sourced from outside the package, should the package lack integrity. Mechanical effects may therefore influence the degree to which materials within the waste package are water-saturated, the ability of water to mobilise radionuclides and other contaminants, and the ability of water to participate in reactions with any other materials present, including any immobilisation matrix and the waste container.

2000 List

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

2.1.07

Related References