Description
The processes resulting in the release of contaminants in a liquid phase from the waste form. Included is the release of contaminants in the aqueous phase from liquid waste forms and release of contaminants in non-aqueous phase liquids.
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
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.
Liquid in contact with the waste form may release radionuclides or other contaminants from the waste form, by dissolving the waste form or causing the contaminants to desorb from the waste form’s solid surfaces. Some waste forms may undergo reactions that evolve a liquid phase, into which radionuclides or other contaminants may partition. Radionuclides and other contaminants that are released in/by a liquid phase will have the potential to be transported from the waste package with the liquid, should the waste package be vented or breach later in the post-closure period. The rate of liquid-mediated release depends upon the degree to which the liquid is unsaturated with respect to the radionuclide or other contaminant (a function of temperature, pressure and liquid composition) and the rate at which the liquid moves to / from the surface of the waste form. The nature of the liquid phase will also influence the partitioning of radionuclides and other contaminants between the liquid phase in which release occurs, other liquid or gaseous phases that might be present, and solid phases. Liquids that mediate release of contaminants may also undergo phase changes (to gas or solid), which will influence the behaviour of radionuclides and other contaminants. For example, if water transporting contaminants partially freezes in cold-climate periods, contaminants will partition between the solid water (ice) and residual (more saline) water.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
-
Bond AE, Egan MJ, Metcalfe R, Robinson PJ and Towler G (), Understanding Controls on the Performance of Engineered Barrier Systems in Repositories for High-level Radioactive Waste and Spent Fuel, Environment Agency Science Report SC060055, Environment Agency, Rio House, Waterside Drive, Aztec West, Almondsbury, Bristol, BS32 4UD, 200, http://www.gov.uk/government/uploads/system/uploads/attachment_data/file/291238/scho0910bsze-e-e.pdf