Description
The biological processes affecting the repository such as degradation of organics, nitrate ions and sulphate ions, biofilm growth and volatilisation.
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.
Microbially / biologically mediated processes may influence the physical and chemical properties of the EBS and the surrounding geosphere. These processes may possibly affect the performance of the engineered and natural barriers.
Potential pathways for flowing fluids (such as liquid water, non-aqueous phase liquids and gases) could form or be enhanced by biological processes that cause dissolution of solid EBS and geosphere constituents. Existing potential fluid flow pathways may partially or completely seal due to different microbially / biologically mediated processes causing solids to precipitate, or else due to micro-organisms themselves occluding porosity (e.g. by forming biofilms).
Microbially / biologically mediated processes may also affect forces that could potentially drive fluid flow through the repository, by consuming or generating fluids (such as water, non-aqueous liquids and gases). Microbially / biologically mediated processes may also result in chemical gradients developing within the repository materials, which could possibly affect the diffusion of dissolved species.
By possibly influencing the characteristics of fluid flow pathways and/or forces driving fluid advection and/or diffusion of solutes and gases, microbially / biologically mediated processes could impact upon the migration of radionuclides and other contaminants originating in the wastes, should these be released by a waste package.
The influence of microbially / biologically mediated processes upon the chemical conditions in the repository (e.g. Eh, pH, dissolved inorganic carbon content) could in turn affect partitioning of radionuclides and other contaminants between different immobile solid phases and potentially mobile fluid phases. This influence could in turn affect the retardation of migrating radionuclides and other contaminants, by processes such as sorption and precipitation/coprecipitation of solids.
Micro-organisms could concentrate certain radionuclides and other contaminants within their structures. Potentially, micro-organisms may behave as “living colloids”, which, if they are mobile in flowing fluids, could enhance the mobility of any radionuclides and other contaminants that they might contain.
2000 List
A reference to the related FEP(s) within the 2000 NEA IFEP List.