NEA Mandates and Structures


Working Group on the Characterisation, the Understanding and the Performance of Argillaceous Rocks as Repository Host Formations (CLAY CLUB)

Chair(s): Bastian GRAUPNER, Switzerland
Secretary:  Hideki YAGIHASHI
(hideki.yagihashi@oecd-nea.org)
Member(s):All NEA member countries*
Russia (Suspended*)
*Russian Federation suspended pursuant to a decision of the OECD Council.
Full participant(s): European Commission
Under the NEA Statute
Observer(s)(International Organisation): International Atomic Energy Agency (IAEA)
By agreement
Date of creation:01 January 1991
End of mandate:31 December 2022

Mandate (Document reference):

  • CLAY CLUB Mandate [NEA/RWM/CLAYCLUB(2002)1]
  • CLAY CLUB Mandate [NEA/RWM/CLAYCLUB(2006)3]
  • Summary Record of the 8th Meeting of the IGSC [NEA/RWM/IGSC(2006)5]
  • Summary Record of the 11th Meeting of the IGSC [NEA/RWM/IGSC(2009)7]
  • Summary Record of the 12th meeting of the IGSC [NEA/RWM/IGSC(2010)8]
  • CLAY CLUB Mandate [NEA/RWM/CLAYCLUB(2009)1/PROV]
  • CLAY CLUB Mandate [NEA/RWM/CLAYCLUB(2010)3/PROV]
  • CLAY CLUB Mandate [NEA/RWM/CLAYCLUB(2014)3/PROV]
  • Extension of the CLAY CLUB Mandate [NEA/RWM/IGSC(2014)5/PROV]
  • Extension of the CLAY CLUB Mandate [NEA/RWM/IGSC(2016)5/PROV]
  • CLAY CLUB Mandate [NEA/RWM/CLAYCLUB(2016)3]
  • Extension of the CLAY CLUB Mandate [NEA/RWM/CLAYCLUB(2019)1/FINAL]
  • Mandate of the CLAY CLUB approved by the IGSC under the written procedure on 30 December 2021 [NEA/RWM/CLAYCLUB(2021)1]

Mandate (Document extract):

Extract from document NEA/RWM/CLAYCLUB(2021)1

Background

Repository development for long-lived radioactive waste is a strategic area in the Progamme of work of the NEA Radioactive Waste Management Committee (RWMC) and an area of traditional strength of this committee.

In the context of geological repositories, argillaceous (clay-rich) media are being considered in numerous NEA member countries as potential host rocks for subsurface disposal of radioactive waste. These media have a number of favourable attributes, e.g. significant lateral continuity, very low rock mass hydraulic conductivities, self-sealing of fractures, solute migration dominated by diffusive transport processes, a capacity to chemically retard radionuclide migration and amenability for self-analogues studies of hydrogeologic stability.

For evaluating these geological media and, notably, for quantitatively assessing the potential migration of radionuclides to the environment, an understanding of the physical and chemical processes that govern groundwater, gas and solute transport through host rocks is a key issue. In that context, the Nuclear Energy Agency (NEA) established in 1991 a Working Group on Measurement and Physical Understanding of Groundwater Flow through Argillaceous Media (Clay Club).

Despite the wide spectrum of argillaceous media and the various stages of repository programme development across countries, common issues related to the reliable characterisation and role of argillaceous media in a repository safety case have provided a basis for a directed and meaningful programme of work achieved through workshops, regular meetings, joint industry conferences and seminal state-of-the-art NEA reports.

Scope

The programme of work and modus operandi of the Clay Club emphasises the pooling of resources, the sharing and synthesis of understanding and experiences as well as the communication of findings to various audiences.

The Clay Club promotes the exchange of information, approaches and methods to develop and document an evolving understanding of clay media as a host rock for a repository.

Objectives

The Clay Club provides advice to the Integration Group for the Safety Case (IGSC) on major and emerging issues related to the understanding of the multi-scale characterisation, numerical model simulation and barrier performance of argillaceous media. In particular, the Clay Club addresses recommendations, trends and information gaps concerning issues such as:

  • current knowledge regarding the long-term barrier integrity of argillaceous rocks as relevant to establishing a deep geological repository safety case on time frames of one million years;
  • the development of best international practice with respect to multi-disciplinary laboratory, borehole and in situ characterisation of argillaceous sediments necessary to understand far-field phenomena governing repository evolution, behaviour and long-term performance;
  • a refinement of the understanding of repository-induced effects in argillaceous rocks during excavation, operation and post-closure phases;
  • the application of self-analogues, which at formation scale, provide direct up-scaled formation specific properties and evidence of past argillaceous groundwater system stability and resilience to external perturbations;
  • performance assessment, including development of integrated conceptual geosphere models, predictive numerical simulation and abstraction and, traceability of related data and information;
  • links and potential knowledge transfer between the understanding of clay as a host material and its use in engineered barrier systems for deep geological repositories;
  • relevant progress in research and development on argillaceous sediments in other fields or industries, such as oil and gas exploration (performance of cap rocks, unconventional shale oil, shale gas) and CO2 sequestration (performance of enclosing clay barriers).

Working methods

The mode of operation of the Clay Club is discussed and refined during its plenary meetings. In addition to discussions to evaluate the programme of work and to review progress on specific activities, the Clay Club may also periodically undertake more in-depth evaluations to assess the effectiveness of the Clay Club and to update the overall directions of the programme of work. The decision of the Clay Club is made in its plenary meetings or through written procedure by mutual agreement.

Membership

The Clay Club is a task-oriented expert group. It is composed of senior technical specialists with experience in assembling or reviewing the understanding of argillaceous media as host rocks for deep geological repository projects. Members represent waste management agencies, regulatory authorities, academic institutions and research and development institutions. Clay Club members have a level of seniority in their organisations such that they can mobilise resources as contributions to Clay Club initiatives.

Interactions

Through the IGSC, the Radioactive Waste Management Committee (RWMC) and the Secretariat, the Clay Club will co-operate with the NEA standing technical committees and their subsidiary bodies when relevant. It may also collaborate with the NEA Data Bank.

Deliverables

The Clay Club will produce appropriate reports, presentations or workshops with the support of the Secretariat.