[en] SCK-CEN participated in several PA projects supported by the European Commission. In the BENIPA project, the role of bentonite barriers in performance assessments of HLW disposal systems is evaluated. In particular, the main objective of the BENIPA project is to review the current treatment of bentonite barriers in integrated performance assessment, evaluating the consistency of methods and data available to justify the capacity of bentonite to perform its assigned safety functions. Conclusions and results derived from process level models as well as of integrated models are summarised

[en] The technique of microfocus X-Ray tomography is used for the non-destructive follow-up of the hydromechanical behaviour of clay materials. In particular, SCK-CEN has applied this technique as part of its research programme on the geological disposal of radioactive waste to investigate the complex hydromechanical behaviour of a mixture of bentonite pellets and powder to seal shafts and boreholes in plastic clay. In addition, this technique has been used to study the evolution of fractures that might be created during shaft and gallery construction in the Boom Clay

[en] The main objective of the metal corrosion programme is to evaluate candidate container materials for high-level radioactive waste. Electrochemical experiments and immersion tests were performed to complement earlier results from in situ tests in the HADES underground research facility. Values of the critical potentials for localised corrosion were determined by potentiodynamic polarisation experiments as well as to investigate the influence of critical anions

[en] This contribution to the annual report describes the results of the experimental programme for studying transport mechanisms of radionuclide species. The main objective of this research is to develop and demonstrate a conceptual model for the description of the migration of radionuclides in a reducing, natural organic matter rich clay environment in view of implementation performance assessment models. Principal results of the experimental programme are briefly discussed

[en] In the frame of its radwaste disposal research programme, SCK-CEN started the construction of the HADES underground research facility in 1980. Including several extensions and a comprehensive experimental programme, it has provided a lot of experience on monitoring. Monitoring is performed for many reasons: construction follow-up, field characterisation, investigation of phenomena, and model validations - in which the underground lab offers the opportunity for up-scaling conventional laboratory set-ups. Construction monitoring has allowed to develop and optimise the underground construction techniques in a previously poorly known environment, resulting in a well-mastered application of mechanised methods for gallery construction with minimal damage to the host formation. Access to this formation also allows its characterisation, both geotechnical, geological and geochemical, and the detailed investigation of phenomena such as fracturing and oxidation. Finally, instrumented set-ups allow to test various numerical models by comparing the observations with the predicted behaviour. The specific conditions of the underground laboratory put particular requirements to the sensors. These conditions include the long-term nature of many set-ups - typically several years to decades, the inaccessibility of many sensors after installation, high mechanical and water pressures, and corrosion. Combined with the fact that many sensors are custom made, obtaining and maintaining a fully functional instrumented set-up can be challenging. A lot of experience has therefore been gained which is very valuable when designing the monitoring of radwaste repositories - and it has allowed us to determine the critical success factors for monitoring. Engineers tend to look at this first from a technical viewpoint - and there are many technical aspects indeed that determine the reliability of monitoring. A first one is the combination of different observations ('redundancy') which can be implemented by the use of several sensors, different sensor principles, different (coupled) parameters, and the combination of point measurements with geophysical techniques. Cabling is also a critical issue as it is often considered as the primary enemy of barrier integrity. Minimal cabling techniques, such as distributed fibre optic monitoring and wireless signal transmission, therefore get increasing attention. Also the interpretation of the monitoring data - in particular those that are perceived as 'wrong' or 'unexpected', needs sufficient attention. The long-term experience has however also shown that the design of a monitoring programme must look beyond the technical part. In particular for long-term applications, issues such as data management and record keeping are vital to guarantee success in this. (authors)

[en] This contribution to the annual report describes the CLIPEX experiment, which is a R and D programme to characterise the hydro-mechanical behaviour of the Boom Clay formation and the excavation Disturbed Zone during the excavation phase of the connecting gallery. Instrumentation was installed in situ in order to monitor the hydro-mechanical parameters ahead of the excavation front, which was realised with a tunnel boring machine. This enabled comparison of the in situ measurements with the blind prediction performed earlier. This type of exercise is important to test capabilities to predict the behaviour of the host rock as part of confidence building

No abstract available

[en] This paper describes the aim of the IRMM activities in the HADES laboratory, the equipment and the measurement program and gives examples of radiopurity measurements carried out in order to develop better low-level measurements.

[en] In Belgium, Boom Clay is studied as a reference host formation for geological disposal of radioactive waste. The current reference design of the engineered barrier system (supercontainer design) plans to use a considerable amount of cementitious materials as construction material, buffer and backfill. Interactions between the alkaline pore fluids from the concrete engineered barriers with the Boom Clay may change the retention properties of the Boom Clay in the vicinity of the interface with the engineered barriers. The objective of this work is to assess the extent of an alkaline disturbed zone in the Boom Clay for a period up to 10⁵ years using reactive-diffusion model simulations. The sensitivity of different model parameters and of (major) model assumptions regarding the Boom Clay mineralogy and the choice of the secondary phases is assessed

[en] The EIG EURIDICE is responsible for performing large-scale tests, technical demonstrations and experiments so as to assess the feasibility of a final disposal of vitrified radioactive waste in deep clay layers. This programme is part of the Belgian Research and Development programme managed by ONDRAF/NIRAS. The research infrastructure includes the Underground Research Facilities HADES (URF HADES) in the Boom Clay geological formation and surface facilities. The achievements of the demonstration programme are the demonstration of the construction of shafts and galleries at industrial scale, the characterisation of the hydro-mechanical response of the host rock, and the 'OPHELIE mock-up' a large scale hydration test under thermal load of pre-fabricated bentonite blocks. The future works will consist mainly in the realisation of the 'PRACLAY experiments' including a large scale heater test. The results of this test will constitute an important input for the Safety and Feasibility Cases 1 (SFC-1, 2013) and 2 (SFC-2, 2020). (author)