Protection characteristic of shielding materials towards radiation of an 11 MeV positron emission tomography cyclotron

An 11 MeV cyclotron used for production of positron emission radionuclide aiming at positron emission tomography (PET) imaging produces a huge quantity of instant neutron and gamma ray radiation. For shielding this kind of accelerator, a self-shielding bunker-like structure is employed, which can be designed with Monte Carlo method. The discrete dual-differential section data are calculated first to obtain the input data for Monte Carlo code, with which the protection characteristics with a single layer and composite structure of various materials are simulated next. The results show that with a single layer, the heavy concrete which has 73.8% iron content brings greatest protection characteristic among all of the materials included in this paper and attenuates the total dose rate about 100 kilo times at the position of 1 m far away from the radiation source with 0 emission angle with thickness of 90 cm. With materials of iron and boracic acid liquor, a particular composite structure can bring the same characteristic with the same thickness and reduce the total density about 20% at least.