Considerations on GEN IV safety goals and how to implement them in future Sodium-cooled Fast Reactors

From a general perspective generation IV (GEN IV) reactors shall excel in safety and, as part of a continuous improvement process, provide safety enhancements. Safety objectives for GEN III reactors are already very ambitious and, therefore, relevant for GEN IV reactors. This notably concerns : - Severe accident prevention; - Severe accident mitigation which is considered in the frame of the fourth defense in depth level; - Response to external hazards, including natural hazards of extreme intensity. Concerning GEN IV sodium-cooled fast reactors (SFR), the achievement of these ambitious safety objectives and the reinforcement of the robustness of the safety demonstration, will be ensured : - Firstly, by mastering the sensitive points of the SFR such as neutron reactivity potential of the core, chemical reactivity of sodium, in-service inspection of structures under sodium. - Secondly, by taking full benefit in the design of the favorable characteristics of the SFR such as large thermal inertia, large margin to boiling, natural convection capabilities and by providing high diversification and independence between safety systems associated to different levels of defense in depth. The paper presents some of these possible ways of safety improvement for the future SFR. (author)