Description

The impact of repository-generated gas effects on hydraulic processes influencing 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.

  • 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.

The generation, consumption and migration of gases in the waste packages due to chemical (FEP 2.3.4), biological (FEP 2.3.5) and radiological (FEP 2.3.6) processes can affect the associated hydraulic conditions (for example the generation of gas can slow the saturation of waste packages).

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.

The generation, consumption and migration of gases in the waste packages, due to a combination of chemical, biological and radiological processes, can influence pressure gradients in the waste package. Pressures attained will affect the distribution of water between bound (to solid phases) and free forms and the form of free water (whether liquid or steam). Hence, gas effects can impact upon the generation and movement of free water. These gas effects can also influence the degree to which a waste package will saturate with free water sourced from outside the package, should the package lack integrity. Depending upon the gas pressures attained, gas effects may therefore influence the degree to which materials within the waste package are water-saturated, the ability of water to mobilise radionuclides and other contaminants, and the ability of water to participate in reactions with any other materials present, including any immobilisation matrix and the waste container.

2000 List

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

2.1.12

Related References

  • Hoch A, Swift B, Smart N and Smith P (), Gas Generation from HLW and Spent Fuel, NPO004726, RWM NDA, 005126/001 Issue 4, https://rwm.nda.gov.uk/publication/gas-generation-from-hlw-and-spent-fuel/
  • Watson S, Benbow S, Suckling P, Towler G, Metcalfe R, Penfold J, Hicks T and Pekala M (), Assessment of Issues Relating to Pre-closure to Post-closure Gas Generation in a geological disposal facility (GDF), A Quintessa Ltd report for NDA RWMD, QRS/1378ZP/R1
  • Levasseur S, Sillen X, Marschall P, Wendling J, Olin M, Grgic D, Svoboda J (), EURADWASTE’22 Paper – Host rocks and THMC processes in DGR EURAD GAS and HITEC: mechanistic understanding of gas and heat transport in clay-based materials for radioactive waste geological disposal, EPJ Nuclear Science and Technology, HAL, 8, 21, https://dx.doi.org/10.1051/epjn/2022021
  • Villar MV, Carbonell B, Martín PL, Gutiérrez-Álvarez C (), The role of interfaces in the bentonite barrier of a nuclear waste repository on gas transport, Engineering Geology, Elsevier, 286, 106087, https://doi.org/10.1016/j.enggeo.2021.106087
  • Zhang C-L, Talandier J (), Self-sealing of fractures in indurated claystones measured by water and gas flow, Journal of Rock Mechanics and Geotechnical Engineering, Elsevier, 15, 227-238, https://doi.org/10.1016/j.jrmge.2022.01.014