A study on double-layer neutron reflector for tritium breeding unit in test facility

The long-term performance verification of the Breeding Blanket (BB) considering continuous plasma operation is essential to develop fusion power reactor. The Korea Institute of Fusion Energy (KFE) has been planning the construction of the Integrated Breeding Test Facility (IBTF). One of the key components of this system is the Tritium Breeding Unit (TBU). In this study, an optimal reflector design was developed to improve the Tritium Production Rate (TPR). For this, candidate reflector materials were analyzed. This analysis indicated that some nuclides offer high neutron reflection efficiency, while certain nuclides are particularly effective for reflecting high energy neutrons. Based on these findings, a double-layer reflector design was proposed to combine the strengths of each material. A systematic evaluation procedure was established and applied to estimate the TPR. The configuration using beryllide/PbO configuration exhibited the highest performance, showing an 8 % improvement in TPR compared to a single-layer beryllide reflector. This approach not only improves TPR but also reduces the required amount of beryllide, which contains toxic beryllium. Additional evaluations using carbon as the first-layer material also demonstrated TPR enhancement. These results indicate that double-layer reflector configurations are an effective and practical approach for tritium breeding applications in accelerator-based fusion test facilities.