Description
The spread in the spatial distribution of contaminants with time in the waste package because of differential rates of and pathways for advective transport through the waste package. Dispersion can occur in the direction of flow (longitudinal dispersion) and perpendicular to the direction of flow (transverse dispersion). It can occur under both saturated conditions and unsaturated 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.
- 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.
Dispersion 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. Dispersion will influence the rate at which homogenisation occurs. Any spatial heterogeneity in these concentrations 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