Exposure risk for the workers of a hadrontherapy center and collective and individual protection measures

SUMMARY In the last few years a wide dissemination of hadrontherapy facilities is taking place. In these facilities, proton or heavy ion (mainly carbon) accelerators are used to treat cancers in peculiar positions (i.e. close to critical organs), or with peculiar biological features that make them not eligible for conventional radiation therapy with photons. During the design, the commissioning and the use of these facilities many radiation safety issues are to be addressed, that are different from the ones that the professionals in the field are used to facing. Many problems need to be solved, among which the characterization of the radiations fields produced by the accelerators, the shielding design, the design of the interlock systems, and the management of the activated materials (PE11). Both the personal and environmental dosimetry systems need to be set up and implemented, taking into consideration the peculiarities of the involved radiation fields, that are often made of many different high energy particles. So, the approach to this kind of problems is usually much more complex than the one that is required for lower energy machines, and the adopted techniques are much more similar to the ones used for the high energy research accelerators. Due to the complexity of the physics involved in the radiation/matter interaction at these energies, the radiation safety calculations are often based on Monte Carlo simulations (that take into account all the physical processes for all the particles involved), and the data should be cross-checked with the experimental data available in literature (e.g. Na06). Moreover, all the radiation measurements must be carried out with instruments conceived for this kind of radiation fields, or anyway with instruments whose behavior can be foreseen also when measuring in high energy mixed fields (Na04). The shielding design and the activation evaluations obviously depend on the different accelerator technologies (e.g. if synchrotrons, or cyclotrons, are used) and on the energy and nature of the accelerated beam. On the other hand, while the technologies used for the interlock safety systems are well known, a big research and development effort is still ongoing about the technologies adopted for personal or environmental dosimetry. Anyway, while the state-of-the-art of instrumentation is still far from being completely satisfactory, many detectors are available, that can be a good option to solve some of the measurement problems found in such environments.