Shielding study at the Fukui Prefectural Hospital Proton Therapy Center

At the Fukui Prefectural Hospital Proton Therapy Center, neutron doses behind the concrete shields and at the maze were measured with three types of radiation monitors (DARWIN, Wendi-2, and a rem meter) along with solid-state nuclear track detectors. The measured data were compared with estimations of analytical models and the Monte Carlo code, Particle and Heavy-Ion Transport code System (PHITS). The analytical model, using the parameters employed in the shielding design of the facility, gave considerably larger values than the measured data. This means that the facility was designed with a sufficient margin of safety. The results calculated by PHITS were less than those of the analytical model and were about three times larger than the measured data. From a perspective that seeks conservative estimation with less margin, the Monte Carlo simulation is a good tool for shielding design of accelerator-based proton treatment facilities.