Safety Assessment for Decommissioning of Nuclear Facilities - From Methodology to the Use of Results in Decision Making

The safety assessment of operational facilities in the nuclear industry is well understood and methodologies have been developed and refined over several decades. Similarly safety assessment methodologies for near surface disposal facilities have been harmonized internationally during the last few years. There is however relatively less widespread and documented experience of safety assessment for decommissioning among Member States of the International Atomic Energy Agency (IAEA) and consequently there is less commonalty of approaches internationally. The importance of safety during decommissioning was further emphasized at the first review meeting of the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management, and the Berlin Conference 'Safe Decommissioning for Nuclear Activities' (14-18 October 2002). As a consequence during its June 2004 meeting the IAEA Board of Governors approved an Action Plan on Decommissioning of nuclear Facilities that requested the Secretariat to 'establish a forum for the sharing and exchange of national information and experience on the application of safety assessment in the context of decommissioning and provide a means to convey this information to other interested parties, also drawing on the work of other international organizations in this area'. In response the IAEA launched the International Project Evaluation and Demonstration of Safety during Decommissioning of Nuclear Facilities (DeSa) in November 2004 with the following objectives: - To develop a harmonized approach to safety assessment and define the elements of safety assessment for decommissioning; - To investigate the practical applicability of the methodology and performance of safety assessments for the decommissioning of various types of facilities through a selected number of test cases; - To investigate approaches for review of safety assessments for decommissioning activities and the development of a regulatory approach for reviewing safety assessments for decommissioning activities and as a basis for the regulatory decision making; - To provide a forum for exchange of experience in evaluation and demonstration of safety during decommissioning of various types of nuclear facilities. The project has involved over one hundred interested experts, of which fifty were actively involved throughout, from thirty plus countries working in eight working groups over the period 2004-2007. The experts presented and analyzed their experiences and on this basis developed recommendations on good practice in the development and review of safety assessments for decommissioning. According to the objectives, the project initially focused on the development of a harmonized methodology to undertake safety assessment. Later on the project entailed working groups testing out the methodology by applying it to a number of test cases representative of the typical facilities presently undergoing decommissioning. These included a nuclear power plant, a research reactor and a plutonium laboratory. The outcomes from the project and the key lessons learned are presented below. (authors)