Pre-Design Of An Innovative Passive Decay Heat Removal System For Atrium Amr-Sfr

The Fukushima accident emphasized additional needs to improve the performance of the safety systems in the new generation of nuclear power plants. The design of the loop-type ATRIUM reactor proposes some breakthrough in the inherent safety of a Sodium Cooled Fast Reactor (SFR), including the neutronic behavior of the core and the Decay Heat Removal function. The first improvement is accomplished by a new type of core, characterized by a reinforced Doppler reactivity feedback that guarantees a margin with respect to the unprotected reactivity injection transients. The second aspect is improved by a design of a fully passive Decay Heat Removal System (DHRS), performing this function from the outside of the Primary Vessel. This system is coupled with a tank containing a Phase Change Material (PCM) inside, which confers a strong diversification with respect to the other classical systems accomplishing the same function. The design of the major reactor components, as well as the one of the new DHRS, is illustrated in this article. The purpose is to design a new type of passive safety system maintaining the integrity of the fuel cladding and the one of the primary vessel during a Station Blackout transient. The overall design presents some improved safety features by enhancing the natural convection of the inner NaK, improving the compactness of the innovative heat sink coupled with the DHRS. This last characteristic would allow the heat sink to ensure a further protection against external attacks.