Neutron field analysis for a proton therapy installation

Full text: A proton therapy centre is planned to be sited in Rome, Italy. It will be based on a medium energy proton accelerator and should be associated to a National Health Institute. At least two treatment station should be realized: a 140 MeV area for shallow tumors therapy and the 200-250 MeV full energy station for deep tumors treatment. Additional experimental areas are foresee for studying the interactions of low energy, high LET, protons with tissues and the effectiveness of proton therapy on specific pathologies. The project is now in a preliminary design phase. The accelerator is under study, the building layout has to be defined and the preliminary safety solutions are considered as well in this phase. The radiation protection approach requires that all the radiation fields are well known, even those that are not useful for the treatment itself. In this frame the neutron field due to proton interactions in solid, liquid and gaseous materials has to be analyzed during the design phase in order to reduce this component to its minimum extent and to address the radiation protection program. The injector of the proton accelerator has been installed at the ENEA Research Center in Frascati, Rome and will be used to perform the preliminary low proton energy testing and the benchmarks for the simulations needed to assess the neutron field. In the paper the simulation models and the calculation performed with MCNPX Monte Carlo code [mcnpx.lanl.gov] are described. The related results are presented together with the comparison with the low energy benchmarks and the data found in the literature for similar projects. Considerations about workers and patients protection are issued taking into account different technical options and related advantages and disadvantages. (author)