Study on induced radioactivity in proton therapy accelerators

Abstract

The study focuses on the investigation of induced radioactivity resulting from the operation of a proton therapy accelerator which poses an enduring risk to both staff and the public. Therefore, it is imperative to conduct research on this topic. The Monte Carlo code FLUKA is utilized to study the residual dose rate of a 250 MeV proton therapy accelerator under various operational and cooling durations, as well as the types and specific activities of radionuclides produced in the structural components, concrete walls, cooling water, cooling water pipe, soil, and underground water. The findings indicate that after continuous operation for 100 days followed by a 1-h cooling, the residual dose rate at the distance of 30 cm from the surface of the structural components is 0.98 mSv/h. At this point, maintenance personnel can safely enter the hall. During emergency equipment maintenance after shutdown, it's advised to keep maintenance personnel at least 1 m away. After 30 years, cooling water, soil, and underground water meet exemption requirements. Air and concrete walls necessitate cooling for 30 min and 3 days, respectively. Directly exemption cannot be granted for metal components due to long-lived nuclides present in these materials, such as 60Co which takes over several years to decay to safe levels. Consequently, highly activated metal components require remote disassembly and storage.