Description
The internal thermal processes that affect the waste packages.
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.
External thermal processes (i.e. from the repository and surrounding geosphere) are considered under separate FEPs 3.2.1 and 4.2.1.
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.
Heat production, consumption and transport within a waste package may influence the evolution of the waste package’s physical, chemical and biological properties. Relevant thermal processes are the production of heat by radioactive decay, the production and consumption of heat by chemical reactions and the transport of heat by conduction and convection of any fluid present through any gaps within the waste package. Thermal processes will influence the temperature evolution of the waste package and the rates of chemical and biological processes within it. Heat generated within the waste package may also influence the physical, chemical and biological properties of the barriers that surround the waste package (whether natural or engineered). The effects of temperature and associated gradients could include the thermal expansion and consequent generation of stresses in the waste packages (that could cause cracks to form) and changes in fluid densities and viscosities, which in turn could affect the movement of fluids through the waste packages.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
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Hodgkinson DP, Lever DA and Rae J (), Thermal Aspects of Radioactive Waste Burial in Hard Rock, Progress in Nuclear Energy, Elsevier, 11(2), 183-218
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NDA (), Geological Disposal: Generic specification for waste packages containing low heat generating waste, NDA Report, NDA, NDA/RWMD/068, https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/461322/Geological-Disposal-Generic-specification-for-waste-packages-containing-low-heat-generating-waste-August-2012.pdf
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Bond A and Watson S (), Understanding the Post-Closure Thermal Impact of HLW/SF Waste Packaged, An NDA RWMD Research Study, NDA RWMD, https://rwm.nda.gov.uk/publication/qrs-1384q-r2-v2-1/