Description
The effects of radiation emitted from the repository on the host rock immediately surrounding repository, and the overall radiogenic evolution of the geosphere.
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.
Certain radionuclides that migrate from the repository, should there be transport pathways through the EBS, may exchange with other isotopes of the same element occurring naturally in the geosphere. Such exchange may impact upon radiological risk. For example, should U-235 that is transported in water from the repository will exchange with U-238 in the rocks, causing the overall radioactivity of mobile uranium to decrease along the transport pathway.
Radionuclide decay and ingrowth of radioactive daughter isotopes within the rock may impact upon long-term safety. Radionuclides that are transported from the repository in a mobile fluid phase (such as liquid water, non-aqueous liquids or gases) may be transported into the rock matrix by diffusion and there trapped within immobile porewater or be immobilised on / in solid phases by processes such as sorption and co-precipitation. Thereafter, radioactive decay of radionuclides in the rock could lead to the ingrowth of radioactive daughter isotopes. Later, parent and daughter isotopes may be transported to the biosphere, for example if conditions change causing the isotopes to partition into a mobile fluid phase, or by uplift and erosion.
The possibility that processes in the geosphere might lead to concentration of radionuclides sufficient to produce criticality may need to be considered.
Consideration may also need to be given to natural background radiation, including the component due to natural radon gas, as a basis for comparison with the effects of radionuclides that may leave the repository.
The direct effects of radiation emitted from the repository on the host rock immediately surrounding repository, such as radiolysis of porewater, are expected to be limited to the rock immediately surrounding the repository, if they occur at all.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.