Breakeven core design studies for a sodium cooled fast reactor

The effect of the rated power on a nuclear core design has been examined for a SFR breakeven core. In order to develop the conceptual core design for a SFR, which enhances the economic potential and safety of KALIMER-600, three design core concepts were examined: I) a zoning of a fuel fraction in a core, 2) a reduced core height to decrease the sodium void reactivity, and 3) the number of fuel zonings. It was observed that the rated power needs to be increased to at least 1,200 MWe from 600 MWe of the KALIMER-600 in order to enhance the economic potential of the fuel cycle for a commercial SFR. Even though two proposed zoning concepts, an enrichment split and a single enrichment with varying clad thickness, have been designed to have a considerably reduced Pu fissile inventory per power and sodium void reactivity worth, the enrichment-split core concept is preferable to the single enrichment core concept from the view point of its neutron economy. For an alternative to reduce the sodium void reactivity, the concept of a reduced core height is preferable to the use of an axial moderator or absorber layer below the active core. And a zoning with two sub-regions in a core was also proposed as a core design concept. The detailed core neutronic, fuel behavior, thermal, and safety analyses will be performed for the proposed candidate core concepts to finalize the core design concept for a 1,200 MWe SFR. (authors)