Neutron spectra due 13N production in a PET cyclotron

• MCNPX code was used to estimate the neutron spectra in a PET cyclotron.
• Neutrons were estimated when 13N is produced.
• Neutron spectra show evaporation and room-return neutrons.
• Calculated H*(10) were compared with measured H*(10).

Monte Carlo and experimental methods have been used to characterize the neutron radiation field around PET (Positron Emission Tomography) cyclotrons. In this work, the Monte Carlo code MCNPX was used to estimate the neutron spectra, the neutron fluence rates and the ambient dose equivalent (H*(10)) in seven locations around a PET cyclotron during 13N production. In order to validate these calculations, H*(10) was measured in three sites and were compared with the calculated doses. All the spectra have two peaks, one above 0.1 MeV due to the evaporation neutrons and another in the thermal region due to the room-return effects. Despite the relatively large difference between the measured and calculated H*(10) for one point, the agreement was considered good, compared with that obtained for 18F production in a previous work.