Abstract
Up till now, from a radiation safety management point of view, it has been discussed to construct guidelines on estimation of neutron fluxes produced via operating various medical small accelerators and to establish uniformly the clearance system related to having neutron activation effects into each accelerator facility.That is, it was the aim of this investigation to accumulate the data on estimation basis of neutron flux measurements at those medical small accelerators by an activation foil method.In this work, the neutron fluxes at the self-shielded PET cyclotron and the electron liniac apparatus of Tokushima University Hospital have been measured as the medical small accelerator.As a result, for the self-shielded PET cyclotron, it was found that the thermal neutron flux is (1.04±0.05) x107 cm-2s-1 and the fast neutron fluxes are distributed over the range 1x104 (the neutron energy En=9MeV) to 1x107 (En=1.5 MeV) cm-2s-1 into the radiation shelter, and while the thermal neutron fluxes would be distributed over the range 5.0x101 to 9.9x101 cm-2s-1 and then the fast neutron dose leakages were not detected outside there. For the 6/10 MV electron liniac apparatus, it was also found that nearly the same thermal neutron fluxes would be distributed all around the liniac room and those measured values are over the range (1.01±0.18) x103 to (1.32±0.10) x103cm-2s-1.
