Abstract The heat generated by high-level waste or spent fuel will create disturbances around a deep geological repository (DGR) containing these wastes. Since the 1990s, SCK CEN, EIG EURIDICE and ONDRAF/NIRAS have been characterizing the thermo-hydromechanical (THM) behaviour of Boom Clay and assessing the impact of the thermal disturbances. This research has included laboratory tests as well as in situ experiments in the HADES Underground Research Laboratory. The two types of tests have been complementary. Laboratory tests have allowed understanding of the THM behaviour and determination of associated values of the THM parameters of the clay under well-controlled boundary conditions and loading paths. This knowledge and the parameters were then validated and even improved by in situ tests which allowed investigation of the effects of temperature on the Boom Clay behaviour at large scales. This paper gives an overview of this research and presents the main findings. It also explains how the knowledge gained supports the design of a possible future DGR and contributes to assessing the extent and impact of the THM disturbances in the Boom Clay around a DGR.

Abstract To examine the impact of the heat generated by high-level radioactive waste on Boom Clay, two heater tests have been launched in the HADES underground research facility: the small-scale ATLAS Heater Test and the large-scale PRACLAY Heater Test. The major objective of these tests is to confirm and refine the thermo-hydro-mechanical (THM) constitutive models and associated parameter values obtained from a laboratory characterization programme. This paper presents the observations from the ATLAS and PRACLAY heater tests and the combined numerical modelling of these tests. To characterize the excavation damaged zone in the clay around these tests, a mechanical model with a strain-dependent elastic modulus is introduced for the Boom Clay. The consistency between the observations from laboratory tests and in-situ tests and the outcomes from the numerical models strengthen the confidence in our understanding of the THM behaviour of Boom Clay. They also enabled us to validate the mechanical model and produce a set of anisotropic THM property values for both intact and damaged Boom Clay.

Abstract A wide range of metals have been studied as a candidate container material to be considered in the geological disposal concept of high-level radioactive waste and spent fuel in Belgium. More than 40 years ago, SCK CEN started studies on the corrosion of these metals. The HADES underground research laboratory (URL) played an important role in the corrosion research as it enabled in situ corrosion experiments to be carried out that simulate realistic disposal conditions as closely as possible. These experiments consisted of placing metallic coupons on a steel support tube, heated from the inside, that was installed in Boom Clay, thereby exposing the coupons to various conditions representative of the disposal concept that was considered at that time. Test durations lasted from 6 months to approximately 7.5 years. This paper summarizes the results from the various corrosion studies and discusses their implications in the choice of disposal concept. One of the main outcomes of these experiments was a change of rationale regarding the choice of the container material from carbon steel (corrosion-allowance) to stainless steel (corrosion-resistant). The main arguments for this change were the need to avoid severe pitting corrosion during the aerobic period and to minimize the generation of hydrogen gas during the subsequent anaerobic period.

Abstract In the 1980s, HADES (High-Activity Disposal Experimental Site) was the first underground research laboratory (URL) dedicated to the study of the geological disposal of radioactive waste in a deep clay formation, the Boom Clay. It was not until the early 2000s, after a siting process, that ANDRA implemented the Meuse/Haute-Marne URL, in the Callovo-Oxfordian formation at a depth of about 500 m in order to develop the Cigéo project (French industrial centre for geological disposal). ANDRA therefore relied heavily on the work carried out in HADES, through numerous co-operation projects (participation in in situ experiments) both between ANDRA and ONDRAF/NIRAS and SCK CEN (EURIDICE) and/or with Mont Terri consortium, and within European projects (CLIPEX, RESEAL, etc.). This was driven by a dual objective: (1) to prepare its own experimental programmes in the Meuse/Haute-Marne underground laboratory (methodology, experimental devices and protocols, etc.); and (2) to acquire general knowledge on the behaviour of argillaceous rocks, in particular in terms of similarity and differences between the various argillaceous rocks. This paper illustrates the contribution of HADES to the ANDRA programme. This concerns the characterization of the claystone behaviour, host rock and swelling clay-based seals (hydromechanical, thermo-hydromechanical, excavation damaged zone, etc.), and the design and the behaviour of underground structures and seals in deep clay formation (constructability, lining/support, etc.).

Abstract After decades of research, development and demonstration (RD&D), mature concepts for the geological disposal of long-lived and high-level radioactive waste exist and some are close to being implemented. Underground research laboratories (URLs) have made an essential contribution to this progress. They enable in situ characterization and testing of host rocks and the demonstration of technologies and component performances at representative scales and under realistic geological conditions. They also offer a tool for training personnel and show aspects of the geological disposal concepts to stakeholders, including the public. In this paper we will present the different types and roles of URLs and we will discuss how the RD&D role of URLs has evolved and how it is likely to evolve in the near future.

Abstract The timeframes involved in nuclear waste management often speak to the imagination, and even transcend it: what does it mean to isolate and contain human-made materials for periods up to hundreds of thousands or even a million years? In this article, we reflect on the role played by the HADES Underground Research Laboratory in making the distant future comprehensible today. Our argument starts by focusing on the pioneering role HADES played and plays in knowledge production on geological disposal. It highlights the heterogeneous nature of scientific experiments and experiences, and the performative role these play in defining matters of concern for research and development. Second, attention is directed to how HADES contributes to the defining of what is considered possible and imaginable, and how it therefore not only renders the future more predictable, but also contributes to the making of that future. We end the paper with a reflection on the implications of what ‘making the future’ could entail from an ethical perspective, discussing how the intergenerational responsibilities that come with these future-making capacities could be handled.