Clay Club


Argillaceous (i.e. clay-rich) media are being considered in many NEA member countries as potential host rocks for the long-term, safe, near-surface or at-depth disposal of radioactive waste, as well as serving as major constituents in repository systems into which waste will be placed. Argillaceous rock formations have a number of favourable properties, such as homogeneity, low groundwater flow, chemical buffering capacity, a propensity for plastic deformation and self-healing of fractures by swelling, as well as a demonstrated capacity to chemically and physically retard the migration of radionuclides.

In this context, the NEA established an international working group on argillaceous media in 1990, informally known as the Clay Club. The role of the Clay Club is to examine those argillaceous rocks that are being considered for the deep disposal of radioactive waste, which range from soft clays to indurated shales. These rocks exhibit a wide array of characteristics that make them useful both as barriers to the movement of water and solutes and as repository construction materials. Studies include clay media characterisation (mineralogy, geochemistry, porosity, pore geometry, hydraulic properties, etc.) and complementary numerical modelling.


  • Federal Agentschap voor Nuclaire Controle (FANC)
  • Organisme National des Déchets RadioActifs et des matières Fissile enrichies/Nationale Instelling voor Radioactif Afval en verijkte Splijtstoffen (ONDRAF/NIRAS)
  • Studiecentrum voor Kernenergie•Centre d'Etude de l'Energie Nucléaire (SCK•CEN)
  • Nuclear Waste Management Organisation/Société de gestion des déchets nucléaires (NWMO/SGDN)
  • Agence Nationale pour la gestion des Déchets RadioActifs (ANDRA)
  • Institut de Radioprotection et de Sûreté Nucléaire (IRSN)
  • Gesellschaft für Reaktorsicherheit (GRS)
  • Bundesanstalt für Geowissenschaften und Rohstoffe (BGR)
  • Institute for Nuclear Waste Disposal, Karlsruhe Institute of Technology (INE-KIT)
  • PUblic Limited Company for RAdioactive Waste Management (PURAM)
  • Japan Atomic Energy Agency (JAEA)
  • Nuclear Waste Management Organization of Japan (NUMO)
  • Centrale Organisatie Voor Radioactief Afval (COVRA)
  • Empresa Nacional de Residuos Radioactivos S.A. (ENRESA)
  • Eidgenössische Nuklearsicherheits-inspektorat (ENSI)
  • Nationale Genossenschaft für die Lagerung Radioaktiver Abfälle (Nagra)
  • University of Bern (Universitate Bern)
United Kingdom
United States of America
  • Nuclear Decommissioning Agency (NDA)
  • Lawrence Berkeley National Laboratory (LBNL)


Mode of operation

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

The mode of operation of the Clay Club meeting is discussed and refined at the plenary meetings of the group. In addition to discussions at plenary meetings to evaluate the work programme 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.

Recent news

Release of the proceedings of the International Workshop on Microscopic Observations and Imaging Techniques for Clays

The Clay Club organised the International Workshop on Microscopic Observations and Imaging Techniques for Clays. The workshop took place on 6-8 September 2011 at the Karlsruhe Institute of Technology (KIT) in Germany. The objective of this workshop was to share state-of-the-art microscopic observation methods and modelling techniques to enhance understanding of properties of microstructure, water flow and mass transport processes in clay, which are key processes in the long-term safety assessment of geological disposal.

Proceedings of the workshop: Clay characterisation from nanoscopic to microscopic resolution

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Last reviewed: 6 February 2014