Description
The processes related to the migration of contaminants through the waste package in the aqueous phase (including dissolved gases).
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.
Radionuclides and other contaminants that are present within the waste package in a liquid phase will have the potential to migrate throughout the waste package. The nature of this migration will determine the degree to which the concentrations of radionuclides and other contaminants in the liquid phase are homogenised at any given time. For example, bulk movement of liquid due to temperature gradients (convection) may result in the concentrations of radionuclides and other contaminants becoming homogenised more rapidly than if liquid movement occurs only by diffusion. If liquid-mediated migration does not homogenise concentrations of radionuclides or other contaminants within the waste package, then potentially rates at which these contaminants are released from a vented or breached waste package will depend upon the location of the vent or breach. If there is more than one immiscible liquid phase within the waste package, liquid-mediated migration could cause spatial separation of different contaminants / radionuclides. Such a situation might arise if an aqueous phase and an immiscible non-aqueous phase liquid (NAPL) of different density coexist and different radionuclides or other contaminants partition differently between the two phases. The nature of the liquid phase(s) will also influence the partitioning of radionuclides and other contaminants between the liquid phase(s), coexisting solid phases and any coexisting gases present.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
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Ahn J and Apted M (Eds) (2010). (), Geological Repository Systems for Safe Disposal of Spent Nuclear Fuels and Radioactive Waste, Woodhead Publishing, ISBN 9781845695422, http://store.elsevier.com/product.jsp?isbn=9781845699789
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Benbow SJ, Rivett MO, Chittenden N, Herbert AW, Watson S, Williams SJ and Norris S (), Potential migration of buoyant LNAPL from Intermediate Level Waste (ILW) emplaced in a geological disposal facility (GDF) for UK radioactive waste, Journal of Contaminant Hydrology, Elsevier, 167, 1-22, http://www.sciencedirect.com/science/article/pii/S0169772214001223