Abstract: Fast reactor with flexible breeding ratio can achieve variable breeding ratios without significant changes of core design. This concept enables fast reactor to effectively respond to the industrial needs. In order to obtain larger breeding ratio, the metal fuel with better performance was selected. Assemblies were heterogeneously arranged. Blankets of PWR spent nuclear fuels were axially and radially arranged. Various sodium cooled fast reactor core schemes with different breeding ratios were proposed. SRAC/COREBN package was used for neutronic calculation and perl scripts was used for shuffling and data exchange. Different breeding ratios were achieved by changing the number of assemblies and their loading pattern. The achieved breeding ratios varied from 1.0 to 1.4. Numerical results show that concerning parameters, such as void worth and maximum linear power, of all schemes satisfy the criteria of fast reactor designs.