Enhancing minor actinide transmutation in ARR

This paper presents a optimized homogeneous core concept of Advanced Recycling Reactor (ARR) toward enhancing Minor Actinide (MA) transmutation satisfying safety requirements, especially the void reactivity requirements. In pursuit of these objectives, following items are optimized: blanket type (AmO2 or AmN), dimensions of axial and radial blanket, residual duration of radial blanket, and ratio of transuranics (TRU) to heavy metal. In this study, 'Optimization of MA transmutation' shall be defined as follows: 1) Enhanced TRU burning rate per unit power generation satisfying the design requirements. 2) Reduced recycling amount of the MA bearing fuel, while maintaining the large TRU burning capability and the enhanced MA transmutation capability. The main specifications of core and fuel are a sodium cooled fast reactor with 1180MW of thermal output, 70cm of core height, 150GWd/t of design based burn-up, 276 of subassembly in the active core, 331 of fuel pins per subassembly (including moderator pins), 82% of smear density in fuel, and three exchanging fuel batches for core fuel assembly. In this design study the current requirements for the Japan Sodium-cooled Fast Reactor (JSFR) are applied. TRU contained in fresh fuel are Pu, Americium (Am) and Neptunium (Np). Curium (Cm) is not contained in the fresh fuel. The group constants used are the fast reactor group constants JFS3-J3.3. For the calculation of the burning, the power distribution and the control rod reactivity, 3D-TRIZ diffusion code, TRISTAN developed and owned by Mitsubishi Heavy Industries, Limited (MHI), is used, while TRISTAN with 18-groups of cross sections has been used for the reactivity coefficients. Cases of calculations to optimize MA transmutation core is shown. It is clear from the nuclear calculation that the provided ARR has a significant Am transmutation capability, 81 kg/Tweh, satisfying the safety requirements, through the utilization of optimized Am blanket with long duration time