Clay Club

A wide spectrum of argillaceous media are being considered in NEA member countries as potential host rocks for the final, safe, near-surface or at-depth disposal of radioactive waste, and/or as major constituents of repository systems in which waste will be emplaced. These media have a number of favourable generic properties, such as homogeneity, low groundwater flow, chemical buffering, a propensity for plastic deformation and self-healing of fractures by swelling, and a marked capacity to chemically and physically retard the migration of radionuclides.

In this context, the NEA established in 1990 a Working Group on Argillaceous Media, known informally as the "Clay Club".

The Clay Club examines those various argillaceous rocks that are being considered for the deep disposal of radioactive waste, ranging from soft clays to indurated shales. These rocks exhibit a wide spectrum of characteristics which make them useful as barriers to the movement of water and solutes and as repository construction materials. Studies include clay media characterisation and modelling.

Three key initiatives have now been completed:

1. The Feature, Events, Processes catalogue: Agillaceous media (the FEPCAT report) is now available. The Clay Club acknowledges the limitation of the database in time: and in particular that the recently published reports are not formally included.
2. A catalogue of characteristics. The catalogue consists of a brochure and a CD-ROM containing all data tables in Excel format.
3. The self-healing study that aims to establish a state-of-the art document on the self-healing of clay media, is currently being finalised.

Initially, the Clay Club launched a compilation and review of the relevant literature on the basic concepts and mechanisms which control the movement of water, solute and gas through the whole spectrum of argillaceous media being considered for radioactive waste disposal. Subsequent work has included an examination of fluid flows through faults and fractures in argillaceous formations and the complex question of extracting solutions from them. The fluid flow research has also included an evaluation of the advantages and limitations of current approaches.

The Clay Club's current work focuses on the ongoing FEPCAT project to provide a detailed catalogue of "features, events and processes" specific to the disposal of long-lived waste in argillaceous formations and a catalogue of their characteristics. A topical session on self-healing was held during the 11th Clay Club plenary meeting in May 2001. The proceedings of this session are available online (pdf format, 4.0mb).

In 2005 the Clay Club published a Catalogue of Characteristics that provides an overview of key geoscientific characteristics of clay formations studied with regard to deep geological disposal.

The Clay Club initiative on long-term natural tracers profiles (CLAYTRAC), completed the data collection stage of the project in late 2006. The project aims to provide an overview of available data sets regarding long term natural tracers' profiles. The added value of that work compared to studies dealing with individual sites in isolation lies in the comparison and integration of data, results and conclusions from a variety of sites and formations.

Clay Club Catalogue of Characteristics of Argillaceous Rocks (2005)
This catalogue gathers in a structured way the key geoscientific characteristics of the various argillaceous formations that are - or were - studied in NEA member countries with regard to radioactive waste disposal.

Stability and Buffering Capacity of the Geosphere for Long-term Isolation of Radioactive Waste (2003)
Application to Argillaceous Media - "Clay Club" Workshop Proceedings, Braunschweig, Germany, 9-11 December 2003
An NEA workshop was organised on 9-11 December 2003 in Braunschweig, Germany, devoted specifically to argillaceous settings for deep geological repositories. The workshop brought together scientists from academic institutions, engineers from various research institutions or companies, consultants, regulatory authorities and national waste management organisations to establish the scientific basis for stability and buffering capacity of deep geological waste management systems. The present report synthesises the main outcomes of that workshop and presents a compilation of the related abstracts.

Features, Events and Processes Evaluation Catalogue for Argillaceous Media (2003)
This report provides the results of work performed by an expert group to develop a FEPs database related to argillaceous formations, whether soft or indurated. It describes the methodology used for the work performed, provides a list of relevant FEPs and summarises the knowledge on each of them. It also provides general conclusions and identifies priorities for future work.

Porewater Extraction from Argillaceous Rocks for Geochemical Characterisation (2000)
A synthesis of available extraction methods, assessing their respective advantages and limitations, identifying key processes that may influence the composition of the extracted water, describing modelling approaches that are used to determine in situ porewater composition, and highlighting, wherever possible, some of the unresolved issues and recommendations on ways to address them.

Fluid Flow through Faults and Fractures in Argillaceous Formations (1998)
An evaluation of the occurrence of fluid flow through faults and fractures is of primary importance for the performance assessment of radioactive waste repositories located in argillaceous settings. The NEA and the EC jointly organised a workshop on this topic (Berne, Switzerland, 10-12 June 1996). This publication includes the papers presented orally or as posters at the workshop, and is introduced by a synthesis of the topics addressed and the conclusions reached.

Proceedings of the Clay Club Topical Session on Self-healing
11th Clay Club Plenary Meeting, May 2001 (pdf format, 4.0 mb)

Water, Gas and Solute Movement Through Argillaceous Media - A "Clay Club" Report (1996)
A review of the relevant literature on the basic concepts and mechanisms which control the movement of water, solute and gas through the whole spectrum of argillaceous media being considered for radioactive waste disposal (pdf format, 17.5 mb).

Related links

NEA Integration Group for the Safety Case (IGSC)

Clay Club Working Area (requires password)

E-mail contact: IGSC Secretariat (igsc@oecd.org)

Last updated: 30 July 2008