Description
The dissociation of molecules by ionising radiation in the repository surrounding the waste package. The actual composition and amount of the radiolysis products that will be formed is controlled by the radiation dose rate and by the compositions and amounts of the solid and fluid phases contained in the repository surrounding 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
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.
Radiolysis has the potential to change the physical, chemical and biological properties of the EBS and the adjacent geosphere. Radiolysis may change the chemical environment within the repository, for example by producing locally oxidising conditions. There may be a consequent impact upon the stability of solid components of the EBS and the adjacent geosphere, and the natures and quantities of fluid phases present. Any changes in the identities and quantities of immobile solid phases and potentially mobile fluid phases (such as water, non-aqueous liquids and gases) produced by radiolysis might affect forces driving advection. Any changes in the chemical environment caused by radiolysis may produce chemical potential gradients that could influence diffusion.
There may be implications of radiolytic processes for the partitioning between immobile solid phases and potentially mobile fluid phases (such as water, liquid hydrocarbons and gases) of radionuclides and other contaminants originating in the wastes, if they are released by a waste package. As a result, radiolysis may impact upon transport rates through the repository of radionuclides and other contaminants.
Radiolysis may affect the viability of microbial populations within the repository. This could then result in implications for the biological processes that might impact upon performance of the EBS and natural barriers, forces driving fluid flow and solute transport, and the mobility of radionuclides and other contaminants.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.