Design features of advanced sodium cooled fast reactors with emphasis on economics

Full text: New incentives have recently been given by French authorities to promote the development of advanced fast reactors and fuel re-cycle options. Priority is given to Sodium cooled fast reactors (SFR) on which a significant experience exists. The objective of current R and D program carried out in tight collaboration between CEA, AREVA and EDF is to propose SFR concept(s) including innovative technologies and assess the associated industrial viability by 2012. The objective is also to propose the specification of a prototype that would qualify whole or part of the most promising selected options. An overall specification was established by EDF for future Commercial SFR. The target for such SFR will be the same as contemporary LWR as regards availability factor, design life expectancy, maintenance, safety and electricity generation cost (investment + operation + fuel cycle). In addition, outstanding performances as regards energy resources sustainability are requested. The risk on investment must also be reduced, through adequate inspection and repair capabilities, and through a satisfactory public acceptance. Specific Proliferation Resistance and Plant Protection measures are also requested. The present paper will give an overview of R and D orientations and efforts made to increase the SFR attractiveness, in line with preceding objectives: - Enhanced safety is expected to be obtained by prevention and mitigation of severe accidents and a low vulnerability to external events and aggressions (use of a robust containment). The objectives are: - To prevent core damage by making an extensive use of the lines of defence approach, focusing on the design of a core with favourable reactivity coefficients, minimizing risks associated with sodium and diversifying and enhancing reliability of safety systems. - To mitigate consequences of core damage by making provisions against energetic criticality sequences resulting from core melt down and by ensuring a safe management of degraded configurations. These enhanced safety features will contribute to minimize licensing and financial risks and will also take part to the enhanced public acceptance objective. - To improve Sustainability, R and D efforts are put on closing the fuel cycle, optimizing the core for an optimal use of fertile and fissile materials while using highly performing U-Pu oxide fuel as a reference (dense fuel is evaluated as a longer term option). - Different tracks are investigated to increase SFR economic competitiveness: - Minimizing plant capital cost by: - simplifying the system and components design; - performing R and D on ferritic-martensitic steels to evaluate how promising is this option to simplify and reduce costs of IHX, secondary piping and SG; - improving the energy conversion system thermal efficiency; - looking for a reduction of the size of the secondary circuit; - looking for a mutualization, on the same site, of systems for fuel handling and component maintenance (when modularity is envisaged); -optimizing the power level. - Reducing generating costs, at the time of SFR deployment, with, for example, a closed Pu cycle with extended fuel burn up (development of high dose cladding materials), increased plant load factor, in particular through long cycle duration and reduced refuelling and component handling outage durations. - Lowering operational costs, with a target that should be as low as those for Generation III+ reactors, including staffing requirements, maintenance/inspection, spare parts, repair/replacement, waste management costs, general services costs, and support from off-site facilities: - Systems need to be simplified to facilitate maintenance operations, reduce O and M costs and limit risks associated to human factors. - The control rod lifetime needs to be increased - Reactor design needs to be optimized to minimize personnel exposure. - A trade-off has to be found between prevention of Na issues and ease of access for maintenance operation. - The ability to carry out maintenance and inspection 'on-line' has to be developed. - Securing investment by means of an assured licensing (including a robust safety demonstration) and planning process, reduced investment and operating costs, enhanced In-Service Inspection and Repair (ISIR) capabilities and by taking decommissioning into account at the design stage. (author)