Expert Group on Repositories in Rock Salt Formations (Salt Club)
Geological salt beds deep underground in New Mexico. Photo: US Nuclear Regulatory Commission.


Experience and expertise are available in technical organisations (academia, national research centres, industry, research organisations, etc.) of countries that have investigated the use of rock salt. Consequently, the main objective of the Expert Group on Repositories in Rock Salt Formations (Salt Club) is to make the current knowledge base on rock salt more readily available to member countries participating in the IGSC, particularly those countries with adequate rock salt deposits to host a repository.

Rock salt is a candidate rock to host a repository for high-level radioactive waste (HLW) because of its favourable characteristics. Specifically, rock salt provides isolation of waste from groundwater due to its low hydraulic conductivity.

The most important positive attributes of rock salt for use as a repository host rock are:

  • extremely low permeability/hydraulic conductivity that isolates the waste from any near-surface groundwater
  • dry environment
  • thermal conductivity
  • viscoplastic behaviour that increases with temperature and pressure, which closes all void spaces
  • predictable geology.

To further develop a repository in rock salt, a working group composed of scientists and experts was formed in 2011 to develop disposal methods using geological rock salt formations.


Among nations currently considering rock salt as a candidate medium, the mission of the Salt Club is to effectively develop and exchange scientific information on rock salt as a host rock formation for deep geological repositories for HLW, long-lived radioactive waste and underground research laboratories. By promoting information and knowledge exchange, the Salt Club also intends to stimulate the interest of other nations with substantial rock salt deposits to consider rock salt as a viable repository medium. In addition to the technical aspects, the working group’s goal is to transfer knowledge acquired to programmes in different phases of development, foster education and training to future subject matter experts in the field of rock salt and co-operate with other NEA working groups (e.g. the Forum on Stakeholder Confidence [FSC]) to engender public acceptance and build stakeholder confidence.

Publications and reports
Areas of interest

Mode of operation and co-operation

The work of the Salt Club will be co-ordinated by a steering group consisting of eight subject matter experts. Project topics are driven by common interest among members. The mode of co-operation is by organising working group meetings, periodic general workshops and the use of electronic media.

Table of membership


The Netherlands

  • Centrale Organisatie Voor Radioactief Afval (COVRA)
  • Nuclear Services for Energy, Environment & Health (NRG)



  • Institute for Nuclear Research Pitesti (RATEN ICN)

United Kingdom

  • UK: Nuclear Decommissioning Agency (NDA)

United States

  • United States Department of Energy (USDOE)
  • Sandia National Laboratories (SNL)
  • Los Alamos National Laboratory (LANL)

Research areas

The Salt Club has the following areas of interest:

  • geomechanical issues (coupled processes, excavation damaged zone (EDZ) behaviour, rock mechanic issues, backfilling, sealing and plugging of rooms, drifts, shafts);
  • brine and gas migration
  • actinide and brine chemistry
  • microbial activities in rock salt
  • geochemical issues (radionuclide chemistry, modelling, natural analogues)
  • technical/technological and engineering issues (construction, operation, closure)
  • performance of geotechnical barriers
  • contributions to the safety case (e.g. features, events, processes (FEP) catalogue, scenarios, performance assessment issues, uncertainties, use of natural analogues)
  • lessons learned from failure events/processes of conventional salt mines

Salt Club FEP Database

The Salt Club FEP Database is a comprehensive catalogue of generic features, events, and processes (FEPs) that are potentially important for the post-closure performance of a repository for high-level radioactive waste (HLW) and spent nuclear fuel (SNF) in salt (halite) host rock. The generic salt repository FEPs include consideration of relevant FEPs from a number of United States, Dutch, German, and international FEP lists and should be a suitable starting point for any repository program in salt host rock.

The salt FEP catalogue and database employ a FEP classification matrix approach that is based on the concept that a FEP is typically a process or event acting upon or within a feature. The FEP matrix provides a two-dimensional structure consisting of a Features/Components axis that defines the “rows” and a Processes/Events axis that defines the “columns” of the matrix. The design of the FEP classification matrix is consistent with repository performance assessment – the Features/Components axis is organized vertically to generally correspond to the direction of potential radionuclide migration (from the waste to the biosphere) and the Processes/Events axis is designed to represent the common two-way couplings between thermal processes and other processes (such as thermal-mechanical or thermal-hydrologic processes). Related FEPs can be easily identified – related FEPs will typically be grouped in a single matrix cell or aligned along a common row (Feature/Component) or column (Process/Event).

The online Salt FEP Database can be downloaded from It contains the FEP matrix, the FEPs, and the associated processes for each FEP. It provides a starting point to create and document site-specific individual FEPs. Furthermore, the FEP matrix is connected to the Salt Knowledge Archive (SKA), a database of about 20,000 references and documents representing the historical knowledge on radioactive disposal in salt.

This work is the result of an ongoing collaboration between researchers in the United States, the Netherlands, and Germany, and supports the NEA Salt Club Mandate.

Password-protected pages


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