Core neutronics design and analysis for the Pb-cooled traveling wave reactor

The traveling wave reactor is an advanced nuclear energy system. By optimizing the layout of fissile nuclides and fertile nuclides, the total amount of fissile nuclides can be kept constant in the lifetime and the effective multiplication factors (k_eff) fluctuates within a very small range. Due to the superiority characteristics of lead-based material, Pb-cooled traveling wave reactor gradually revealed for its good neutronics and thermal-hydraulic properties and inherent safety. Compared with LBE and the natural lead, ²⁰⁸Pb has low capture cross-section and low inelastic capture section which can give harder spectrum. At first, this paper presented a design of ²⁰⁸Pb-cooled axial traveling wave reactor, and used SuperMC program for calculation and analysis of the core. The change of k_eff during the lifetime was small and it was about 1.02 at steady state. The power distribution curve moved axially along with time and the moving rate was about 2.0 cm/a. Secondly, based on the core design scheme, the influence of the ignition zone and the reflector on the core performance of the axial traveling wave reactor was studied. The results showed that the length and enrichment of the ignition zone almost had no effect on k_eff, but had effect on power distribution. Different reflector materials and thickness had a great impact on the performance of the axial traveling wave reactor. While ²⁰⁸Pb as the reflector, k_eff of steady state was the largest, so it had best core performance. (authors)