SMR CADOR: A Small SFR with Inherent Safety Features

Competitiveness and safety of future reactors has to improve in order to be acceptable by the population and decision-makers. Unfortunately, the nuclear industry faces a major issue: for now, safety means costs and the safer the reactor is, the more expensive it is. Research in advanced reactors needs to tackle this dilemma by promoting inherent safety and simplified design. In this context, Small Modular Reactors (SMR) show promise for addressing the energy challenges in terms of flexibility, cost, safety, manufacturability, ease of operation, integration in electricity networks, and coexistence with renewable energies. Besides, SFR allows also to close the fuel cycle by using the plutonium coming from LWR and to minimize final wastes. Specificities of SFR are also favourable for include inherent safety features : no pressure of the coolant in normal operation, good natural behaviour of the core during unprotected transients, a more effective decay heat removal in natural convection, air as a heat sink. The paper develops the idea to combine SMR and SFR advantages in terms of safety to simplify the design in order to make these reactors affordable from the technical and economical point of view. The reactor called "SMR CADOR", with a core concept featuring a reinforced Doppler reactivity feedback (CADOR stands for Core with Amplified DOppleR effect), providing inherent resistance to all accidents including unprotected reactivity insertions, which are a typical weakness in the SFR safety demonstration. The design includes also the possibility to achieve the decay heat removal function by a system through the reactor vault and in natural circulation, which is a key feature to reach a high level of safety, only achievable with SMR but not for higher nominal power SFR. The guiding principle is to develop intrinsic safety of the reactor and to simplify the system design at the same time. Besides the core and decay heat removal systems, the design includes innovative features regarding maintenance and fuel handling, energy conversion system, cogeneration possibilities. An enhanced safety level can be achieved with such a reactor type thanks to the integration of these innovative design options on the one hand, and the simplification of the reactor general design, on the other hand. (author)