RD and D steering of a geological disposal programme in poorly indurated clays - ONDRAF/NIRAS example

Document available in extended abstract form only. For more than thirty years, Belgium has been investigating clay formations for its potential suitability to host a geological disposal. The R and D programme initiated as early as 1974 by the Belgian Nuclear Research Centre (SCK.CEN) at Mol was pursued from the early 1980's under ONDRAF/NIRAS' responsibility. These studies quickly focused on the Boom Clay formation at Mol-Dessel, in northeastern Belgium, as a potential host formation for a geological repository. The state of scientific and technical research on the possible disposal of high-and intermediate level radioactive waste (B and C waste) in clay layers was presented in decanal safety assessment reports and internationally reviewed. Over time, geological disposal in Boom Clay has progressively become the reference solution of ONDRAF/NIRAS for the long-term management of category B and C wastes, geological disposal in Ypresian Clays being considered as an alternative solution. The national and international peer review of the second Safety and Feasibility interim report (SAFIR 2) acknowledged in 2001 the maturity of the Belgian scientific program and endorsed ONDRAF/NIRAS conclusion to pursue the RD and D program on poorly indurated clays. Consequently, the NEA International Review Team urged ONDRAF/NIRAS to move on to the implementation phase while pursuing RD and D necessary to reduce the remaining uncertainties. This major step required ONDRAF/NIRAS to develop the frame and tools to embed its national program in a societal dialogue and in a stepwise decision-making plan with key milestones stretching over the next decades towards the licensing process. To serve these ends, ONDRAF/NIRAS has reassessed the organization of its geological disposal program. A strategy had to be set out to frame and formalize the stepwise and iterative development of a geological disposal in a coherent and integrating manner. Indeed, firstly, the maturity of the program had led ONDRAF/NIRAS to depart from a decade of studies focused on host rock and to consider the disposal program development in its whole globality by bringing together next to long-term safety, the aspects of operational safety, feasibility, cost and environmental impacts and their complex dependences among each other. Secondly, the interplay with the stakeholders expressing different concerns required a strategic tool to translate their demands into technical requirements, to identify possible conflicts between these or with fundamental safety and feasibility principles and to introduce flexibility in the program to account for possible socio-economic changes and technical innovations. In recent years ONDRAF/NIRAS has worked out a safety and feasibility strategy (ONDRAF/NIRAS, The Long-Term Safety Strategy for the Geological Disposal of Radioactive Waste, ONDRAF/NIRAS report NIROND-TR 2009-12E, 2009) fulfilling these management requirements. The strategy sets out in broad terms how it is envisaged that safe disposal will be achieved. It is mainly based on safety principles established by IAEA and are, among others, passive safety, defence-in-depth, robustness, best-available technology and optimisation. The safety and feasibility strategy also includes the boundary conditions to be met and the requirements to be satisfied. Boundary conditions include, for example, the relevant international and national regulatory frameworks, institutional policy and conditions required by other stakeholders. The central tool of the ONDRAF/NIRAS strategy is the safety and feasibility statements. Most of these statements are derived from the safety concept and are organised in a hierarchical tree structure. The top level statements define the a priori objectives pursued by the program stage in agreement with the boundary conditions. Lower-level statements setting out more detailed requirements of these objectives are then derived from these top-level statements in a top-down approach. The substantiation of the safety and feasibility statements, with the multiple lines of eviden ce and their associated uncertainties generated from the RD and D program, is performed bottom-up. The assessment of the level of support given to the statements and the impact of the associated uncertainties to the higher-level statements provide an efficient and synoptic tool to steer the research and development activities and set the priorities between the issues to handle for a given decision. Further than methodology, this paper will discuss an example of key statements and their substantiation. The idea of a safety case which was stimulated by the NEA Cordoba Workshop in 1997, has led to a series of publications that reflects similar in-depth thinking in other national programs to develop coherent strategies to guide system optimization towards its implementation. These are grounded on a compact set of fundamental safety and design principles which form the safety concept that steers RD and D in a formal iterative way and identify priorities for the safety case at hand. As national programs are approaching implementation phase, refinement of these strategic approaches might be necessary to connect more closely again feasibility and operational high level requirements but also societal aspects to the existing and well-defined long-term safety concepts in order to capture a global and integrated view of the RD and D programs. (authors)