Research and Development of the Engineered Barrier System for the DGR at the Bukov URF

As part of the programme for the development of a deep geological repository (DGR) for the disposal of radioactive waste in the Czech Republic, SÚRAO has provided support for research, development and demonstration activities at various underground research facilities for many years. SÚRAO’s research facility, the Bukov Underground Research Facility (URF), is located in the crystalline rock of the Bohemian Massif. This generic underground laboratory, which is used for the conducting of in-situ experiments and the testing of a range of methodological approaches, is situated on level 12 of the former Rožná I uranium mine, approximately 500 metres below the earth’s surface. The URF consists of two sections – Bukov URF I and URF II, both sections provide the critical infrastructure required for the testing of host rock, material testing and modelling methods and allow for the conducting of the research projects included in SÚRAO’s extensive experimental plan. The Bukov URF is critical in advancing the DGR project, supporting related scientific research, conducting experiments and, in the future, the performance of full-scale tests.The Bukov URF research programme is based on seven defined key areas covering long-term monitoring, description of the rock environment, groundwater flow, engineered barriers for the DGR, effects of underground structures on the rock mass, construction technologies, and demonstration experiments. Currently, two major experiments are in operation at the URF I site will provide information that will enhance the understanding of the DGR engineered barriers and provide data for the long-term monitoring programme and the description of the rock environment. Completed projects considered groundwater flow and construction technologies, as well as some of the aforementioned research areas.Experiments that focus on the development of the DGR engineered barrier system involve the use of bentonites from Czech deposits, e.g. BCV quarried at the Černý Vrch deposit, which comprises a calcium-magnesium material which is currently considered to be the Czech DGR reference material. Besides bentonite, the experiments are concerned with estimating the corrosion rates of the materials considered for the waste disposal package (e.g. carbon steel, which is being considered for the outer casing of the WDP, and copper as an alternative construction material).The experiments that involve the research of BCV bentonite include subjecting the material to various conditions, such as artificial saturation and elevated temperatures (varying from 70°C up to 170°C), and the research of the influence of this bentonite on cement-based materials (to be used for the plugs of the DGR) and carbon steel. These experiments provide valuable information on the interactions that might occur within the bentonite itself and on how the bentonite will potentially influence other materials.Future experiments will focus on the behaviour and characterisation of bentonite in the context of both small-scale and (near) full-scale projects. The experiments will focus on defining the behaviour of bentonite in solutions containing selected cations, the provision of information on the transfer of heat from the bentonite buffer into the host rock, and the study of the erosion of bentonite.