Description
The diffusion of contaminants through the waste package. Diffusive migration is driven by chemical potential gradients, and can be affected by thermal gradients, and can thus be in any direction.
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.
Diffusion within the waste package will influence the degree to which concentrations of radionuclides and other contaminants are homogenised within the fluid phases present at any time. Diffusion will influence the rate at which homogenisation occurs and will depend upon the concentration gradients that exist at any time. Any spatial heterogeneity in the concentrations or radionuclides or other contaminants will mean that releases of these contaminants from a vented or breached waste package at any time will depend upon the location of the vent or breach.
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