Description

The chemical/geochemical processes that affect the waste packages. Included are the effects of chemical/geochemical influences 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

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.

Chemical processes acting within and / or upon a waste package may alter the chemical and/or physical forms of the waste package components. There may be consequent influences on the integrity of the waste package and the potential for radionuclides or other contaminants to be released from it. Chemical processes may cause a package that offers containment initially to lose its integrity. Alternatively, where a package does not offer complete containment initially (e.g. because the package is vented), the ability of the package to resist migration of radionuclides or other contaminants may be affected. Where a waste package does not provide containment, the forms in which radionuclides and other contaminants are released and migrate from it will be influenced by chemical processes within the waste package. In such a case, the ability of the waste package components to retard the migration of radionuclides and other contaminants (e.g. by sorption) will also be affected by chemical processes. Chemical processes within the waste package may be coupled to chemical processes outside the waste package, where the package lacks integrity. Chemical processes at the outer surface of a waste package will be coupled to chemical processes in the surrounding natural and / or engineered barriers. These couplings may cause the chemical processes that affect the waste package to also influence the functions of the surrounding barriers.

2000 List

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

2.1.09, 2.1.12

Related References