Development of three-dimensional neutronics calculation system for design studies on helical reactor FFHR

Construction of a three-dimensional neutronics calculation system has been started for design studies on the helical reactor FFHR2. In the calculation system, geometry data of the helical structures are generated according to numerical equations for quick feedback between neutronics evaluation and design modification. The tritium breeding abilities of the FFHR2 with the Flibe + Be/JLF-1 (Reduced Activation Ferritic/Martensitic Steel) and the Li/V-alloy blanket systems were investigated by using the calculation system. Since the original design could not achieve the tritium breeding ratios (TBRs) > 1.0 due to neutron leakage through opening between the blanket components, the dimensions have been modified to enhance the breeding ability. After the modification, the TBRs of 1.08 and 0.98 were obtained for the Flibe + Be/JLF-1 and Li/V-alloy blanket systems, respectively. The present results indicate that the blanket systems have potential to achieve adequate tritium breeding ability in the FFHR2 by further design optimization.