Several design challenges for the realization of a compact sodium-cooled B&BR for recycling PWRs spent nuclear fuel have been characterized from the neutronics perspective. One of the design challenges is a high excess reactivity particularly during the transition of the active core from the initial core to the blanket region. A concave zirconium zoning initial core has been found as a practical solution to address the high excess reactivity. By zoning the core, the radial power distribution can also be flattened. In this work, the zirconium zoning was first applied to the initial core and then applied further to the blanket region of B&BR. The reactivity evolution and power distribution were compared and analysed to achieve the design target and to understand the underlying physics. The neutronics analysis is performed using the Monte Carlo code McCARD with the ENDF/B-7.0 library.
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