Research Lines
  • Engineered barrier system of deep geological repositories
  • Gas transport in sealing materials
  • Natural barriers (argillaceous rocks, marls)
  • Physical and hydraulic characterisation of concrete
  • Physical and hydraulic characterisation of soils and liners

In this field the group works among others in these topics:

  • Effect of salinity and temperature on the properties and behaviour of sealing materials.
  • Hydro-mechanical behaviour of unsaturated geological materials (soils).
  • Bentonite microstructural changes driven by hydration.

The boost to this core line was the ENRESA’s project FEBEX, financed also by the European Commission and with a large international participation. This project included a large-scale demonstration test of the near field of a deep geological repository (DGR) under natural conditions. The FEBEX in situ test was completely dismantled in 2015, after 18 years of operation, in the framework of the FEBEX-DP project. The group led the sampling and postmortem characterisation works (http://www.ciemat.es/portal.do?IDM=61&NM=2&identificador=1313). So far, this is the longest such in situ test ever dismantled, hence it is of outstanding interest for the scientific community working in the DGR field.

As part of the FEBEX project a large-scale mock-up test was installed at CIEMAT facilities to simulate the bentonite engineered barrier of a DGR. It is in operation since 1997 

Related projects:

 

Currently we are paying particular attention to the following aspects inside this research area:

  • Long-term behaviour of sealing materials

In the DGR context “long-term” means “close-to-saturation conditions”, that is, following the first transient stage during which the saturation of the barrier takes place under a significant thermal gradient. In the course of the barrier saturation its properties are affected by the changes in water content and dry density that take place as a result of heating and hydration. Until now neither the large-scale nor the laboratory tests have provided conclusive evidence about the reversibility of these changes occurred in the barrier. This is why the European project BEACON (2017-2021) analyses the long-term mechanical evolution of the bentonite barrier.

  • Effect of temperature >100°C in bentonite-based barriers

The effect of temperatures higher than 100°C on barrier materials has been addressed in the last years because, if higher temperatures could be tolerated in a repository, it would be more effective on economic terms. This is one of the topics dealt with by the European Union inside Horizon2020, and the group is currently participating in the project EURAD-HITEC (Influence of temperature on clay-based material behaviour, 2019-2023).

  • Mineralogical alteration of bentonites

The project MINALBEN (Experimental and modelling study of  MINeralogical ALteration of BENtonites, 2016-2024) studies the geochemical behaviour and the mineralogical alteration of bentonite tested in thermo-hydraulic cells and their modelling. It is therefore an experimental and theoretical research carried out through a contract between CIEMAT and AMPHOS-21, whose end user is POSIVA, the Finnish nuclear waste management agency.