Conceptual radiation shielding design of the integrated breeding test facility at KFE

The Integrated Breeding Test Facility (IBTF) is being developed by Korea Institute of Fusion Energy to assess the long-term performance of breeding blankets under continuous irradiation environment. The facility is based on a 40 MeV deuteron linear accelerator incident on a beryllium target to generate high-intensity neutrons, thereby enabling quasi–steady-state blanket testing. Owing to the associated production of secondary neutrons, deuterons, and gamma rays, an optimized shielding design is essential to ensure radiation safety. In this study, a conceptual shielding design for the IBTF was performed through benchmarking of nuclear data libraries and Monte Carlo simulations using MCNP6. Comparisons with experimental neutron yields confirmed that the FENDL-3.2b reproduced measurements most accurately, with FENDL-3.2b selected for subsequent analyses. For the Test Cell containing the target, tritium breeding unit, and reflector, the results demonstrated that increasing concrete thickness was more effective than extending cooling time in reducing residual doses. A conservative shielding thickness of 1.5 m was determined to satisfy dose limits while accounting for radiation streaming through penetrations. Additional analyses showed that applying pipe bends substantially mitigated streaming effects. In the accelerator region, beam-loss for tubes made of SS 304, OFHC, and Al6063 were evaluated. Al6063 exhibited higher neutron yields and average energies, leading to larger dose contributions; nevertheless, a concrete thickness of at least 1.5 m was sufficient to meet controlled area requirements for all materials. These findings provide a technical basis for the IBTF shielding concept and are expected to support the subsequent detailed engineering design