Description
The effects of volume changes in materials used in the waste package.
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
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.
Material volume changes (this FEP, 2.3.3.2) covers the actual volume change, rather than its cause. Thermal processes (FEP 2.3.1), Hydraulic processes (FEP 2.3.2) and Chemical processes (FEP 2.3.4) may all cause changes in material volume.
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.
Material volume changes within a waste package, if of sufficient magnitude, could affect the integrity of the package. Existing openings in a vented container may be enlarged, or new openings may form. A package that initially offers complete containment may lose its integrity. If the material volume changes occur within a package that does not offer complete containment, then the potential for radionuclides and other contaminants to migrate from the package could be affected. Material volume reduction within a package could produce pathways for such migration, such as fractures or inter-connected matrix pores. Material volume increase may lead to such pathways sealing, which may tend to diminish the potential for such migration. However, at the same time pressures within the package may be increased, thereby tending to enhance the potential for migration. Material volume changes within a waste package may also influence the performance of engineered and natural barriers that surround the package. For example, an increase in the volume of a package due to corrosion could lead to cracking of any surrounding cementitious backfill that might be present. Material volume changes may occur over time periods that are very short compared to the assessment period (e.g. due to microbially-mediated gas generation within certain organic LLW or over time periods that are very long compared with the assessment period (e.g. corrosion of copper canisters for spent fuel).
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
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Towler G, Watson S, Hicks T, Hunter J, Shaw R, Paulley A, Penfold J, Bond A, Wilson J and Jones C (), Implications of Voidage for Post-Closure Safety of a GDF. Final Report, QRS-1698A-1, V2.3, https://rwm.nda.gov.uk/publication/implications-of-voidage-for-post-closure-safety-of-a-gdf/