Core design of ma-transmutation fast reactor with zirconium hydride target

•Zirconium hydride containing MA is stable in solid phase even at high temperature.•Fast reactor with Am-Zr hydride target can transmute Am more than 100 kg/EFPY.•All of Am generated from LWR spent fuel can be transmuted without FBR reprocessing.•Np can be transmuted in the core fuel due to Na void reactivity is small enough.•Spent target with high transmutation needs to cool in reactor vessel for 0.5 years. The use of zirconium hydride in fast reactors provides excellent MA transmutation performance by neutron moderation with hydrogen. This study has designed an MA transmutation fast reactor loading a ‘target” containing MA-zirconium hydride in the blanket fuel region to maximize the transmutation capability of the core. As the result, the three-region core of the small fast reactor has been designed to adopt the operation of removing the irradiated target from the reactor vessel after temporarily placing in the neutron shielding area during one cycle, and to adopt the method of setting the Pu enrichment of each core fuel to increase neutron leakage to the target. By only changing the target Am/(Zr + Am) ratio to 0.1 ~ 0.3, the three-region core can be used with 2 types; one is the high-amount type with the Am/(Zr + Am) ratio of about 0.25 to be used in the disposal phase in which the amount of stored Am is positively reduced, and the other is the high-ratio type with the Am/(Zr + Am) ratio of about 0.1 to be used in the equilibrium phase in which the amount of stored Am is kept constant. One unit of the high-amount type can transmute Am generated from the spent fuel up to about 10 GWe-LWR without Pu supply from the FBR reprocessing. The three-region core can be designed with excellent core safety characteristics that is the sodium void reactivity is $1.4 or less. In addition, the core can transmute Am and Np in parallel by using Pu, which is not separated Np, as the core fuel in the condition that the Am-Zr hydride target is loaded.