Description

The dissolution and precipitation of any repository-derived contaminants in the biosphere under prevailing environmental conditions.

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.

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 concentrations in the biosphere. Precipitation occurs when chemical species in solution react to produce a solid that does not remain in solution.

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.

Any repository-derived contaminants moving through the biosphere could be subjected to precipitation or dissolution as a result of different local conditions, or by active microbial and plant processes. These processes can change in response to processes such as daily and seasonal changes in meteoric precipitation, temperature and land use change. Dissolution into the liquid phase will increase the mobility of the contaminants, whilst precipitation would lead to their retention in that part of the biosphere.

2000 List

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

3.2.01, 3.2.06

Related References