Radiation Shielding Design and Residual Radioactivity Assessment for the Beam Dump at XiPAF

[Background] The Xi'an 200MeV proton application facility (XiPAF) was constructed as an accelerator facility for the study of single-event effects on aerospace devices. Recently, XiPAF has been planned for upgrade and transformation into a versatile experimental facility for both proton and heavy-ion applications. [Purpose] This study aims to develop a radiation-safe beam dump design ensuring compliance with operational dose limits during operation and minimizing post-irradiation residual doses. [Methods]Based on Monte Carlo simulations using FLUKA, a composite structure beam dump was designed with polyethylene as the target core material, which leaded a low neutron yield. Shielding performance was quantified via ambient dose equivalent rate (H*(10)) mapping at critical locations. Residual dose decay kinetics were modeled for three operational scenarios: 1-hour, 1-day, and 1-week continuous irradiation. [Results] The computational results show that the ambient dose equivalent rate at the rear and transverse sides of the beam dump is 4.2 mSv/h and 3.2 mSv/h (below the 5.5mSv/h limit), respectively. Compared to traditional graphite core, polyethylene demonstrated about 75% lower upstream dose while maintaining equivalent shielding performance. Analysis of residual dose under the three operational scenarios  showed consistent decay patterns reaching the dose constraint of 2.5μSv/h after 2-3 hours cooling time. [Conclusions]The results provide practical reference for radiation protection design of beam dumps at similar intermediate-energy proton accelerator facilities.