Description

The biological/biochemical processes that affect the seals and other engineered repository features, and the overall biological/biochemical evolution of the repository. This includes the effects of biological/biochemical influences on repository components by the waste packages and surrounding geosphere. In addition to the microbes that might be present prior to repository construction, a range of microbes can be expected to be introduced into the repository during its construction and operational phases. Some could be present in the waste packages, whereas others could be introduced as the emplacement rooms are excavated and infrastructure erected. Only some of the microbes present at repository closure will find the subsequent conditions suitable for their growth. Besides requiring certain types of nutrients, individual microbial populations will only operate under particular conditions of temperature, pH, Eh and salinity.

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.

Biological processes may influence the physical and chemical properties of the EBS and the surrounding geosphere. For example, gas might be produced or consumed. The performance of the engineered and natural barriers may possibly be affected. Growth or loss of biomass may impact upon the permeability of EBS materials and the surrounding geosphere. For example, growth or loss of biofilms may affect the degree to which fracture porosity is interconnected.

Biological processes may influence the migration rates through the engineered and natural barriers of radionuclides and other contaminants that originate in the wastes, should these be released by the waste packages. The physical and chemical forms of the radionuclides and other contaminants may be affected by biological processes. For example, whether a radionuclide is in gaseous form or dissolved within water may be influenced by biological activity. Should a radionuclide or other contaminant be dissolved in water, its chemical complexation may depend to some extent on biological processes. Organisms may directly concentrate radionuclides or other contaminants within their structures. Depending upon whether the organisms are immobile or mobile there might be a consequent influence on the migration rate through the engineered and natural barriers of the radionuclides and other contaminants.

2000 List

A reference to the related FEP(s) within the 2000 NEA IFEP List.

2.1.10, 2.1.12

Related References

  • Wolfram J H, Rogers R D and Gazsó L G (Eds) (), Microbial Degradation Processes in Radioactive Waste Repository and in Nuclear Fuel Storage Areas, Volume 11, Microbial Degradation Processes in Radioactive Waste Repository and in Nuclear Fuel Storage Areas, Springer, ISBN 978-0-7923-4488-9, http://www.springer.com/gb/book/9780792344889