The 7th EURATOM project PEBS (Long-term Performance of Engineered Barrier Systems) was initiated to evaluate the sealing and barrier performance of clay-based EBS over time, through development of a comprehensive approach involving experiments, model development and consideration of the potential impacts on long-term safety functions. The project aims are to
- deepen the knowledge and understanding of the THM and THM-C (thermo-hydro-mechanical and -chemical) evolution of the EBS system,
- provide a more quantitative basis for relating the evolutionary behaviour to the safety functions,
- clarify further the significance of residual uncertainties for long-term performance assessment.
The work performed within the project builds on existing knowledge and experience gained during past years and supported by ongoing national and EC research programmes. The experiments and models cover the full range of conditions from the early post-closure stage (high heat generation and EBS resaturation) through to later stages with the establishment of near steady-state conditions, i.e. full resaturation and thermal equilibrium with the host rock. A broad spectrum of laboratory and in-situ experiments is covered by the project, some of which have been in progress for many years (e.g. the FEBEX full-scale laboratory mock-up and the associated in-situ experiment at Grimsel, as well as the EB experiment at Mont Terri). In addition, new in situ experiments were developed specifically for the project (e.g. the half-scale heater experiment with clay-based barrier at Mont Terri).
Findings of the experimental studies are integrated into numerical codes for the simulation of coupled thermal, hydraulic, mechanical and chemical (THM(-C)) processes in the EBS and near-field rock. The importance of uncertainties arising from potential disagreement between models and experiments and their implications for extrapolation of results over the transient phase are being assessed. Particular emphasis is set on possible impacts of residual uncertainties on safety functions over the short and long term.
In addition to the scientific objectives, the dissemination of the essential results to the broad scientific community within the EC, China and Japan is an important aim of the project. The consortium uses its expertise for public information purposes and to promote knowledge and technology transfer through training.
The consortium involves 15 European organizations as well as the Beijing Research Institute for Uranium Geology.