Description

The dissolution, precipitation and crystallisation of contaminants in the waste package under repository conditions. Dissolution is the process by which constituents of a solid or gas dissolve into solution. Dissolution is controlled by changes in pressure, temperature and gas partial pressures. Precipitation is a process by which solids are formed out of liquids and are controlled by changes in pressure, temperature and concentrations of chemical species. Precipitation occurs when chemical species in solution react to produce a solid. Crystallisation is the process of producing crystals of an element, molecule or mineral from a fluid or solution, often during a cooling process.

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.

Dissolution, precipitation and crystallisation influence the partitioning of radionuclides and other contaminants between solid and fluid phases within a waste package. These processes therefore influence the potential mobility of the radionuclides and other contaminants. These processes may also influence the form of a contaminant within any phase. For example, a radionuclide may exist within more than one crystal form of a solid phase with a particular chemistry. The form of a radionuclide or other contaminant within a solid phase will influence the likelihood that the contaminant could be re-mobilised by a fluid phase should conditions change.

2000 List

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

3.2.01

Related References