Description
The operation of the repository including the placing of wastes (usually in containers) in their final position within the repository, placing of any buffer and backfill materials (including any sealing of emplacement rooms/tunnels), and the management of any water and gas in the repository prior to closure.
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.
There are some similarities between Construction (FEP 1.1.5), Operations (this FEP, 1.1.6) and Closure (FEP 1.1.7). FEP 1.1.5 is intended to cover activities concerned with construction (notably excavation), whereas FEP 1.1.6 covers activities other than excavation (e.g. emplacement of wastes in a disposal hole), except for activities concerned with the emplacement of final closure engineering. Emplacement of buffer and backfill materials, or seals in part of a repository, while waste emplacement is ongoing elsewhere, is covered by FEP 1.1.6. However, emplacement of backfill and seals after waste emplacement has stopped is covered by FEP 1.1.7. The sequencing of operations, as opposed to the activities themselves, is covered by FEP 1.1.4 (Schedule and planning).
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.
Operations impact upon performance and safety by governing the effectiveness with which wastes are contained within the system of engineered and natural barriers. Potential operational issues that might impact post-closure performance and safety include container damage during handling, errors in backfill or buffer emplacement and poor sealing of emplacement rooms/tunnels. Waste packages must be emplaced in their final positions without damaging them to the extent that their performance is compromised. Any buffer and / or backfill required by the design must also be emplaced to achieve its required function. Generally, operations will need to ensure that buffer emplacement and / or backfilling and closure of emplacement rooms achieves the required degree of sealing against gas and water movement, and contaminant migration, including radionuclide migration. However, in certain concepts, where the potential for gas generation from wastes or packaging to result in high gas pressures and associated damage to the barrier system is a concern, operations may need to ensure that there are gas migration pathways through the barriers to mitigate gas pressurisation.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.
Related References
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IAEA (), Disposal of Radioactive Waste, Specific Safety Requirements No. SSR-5, International Atomic Energy Agency, Vienna, ISBN 978–92–0–103010–8, http://www-pub.iaea.org/MTCD/publications/PDF/Pub1449_web.pdf