Monte Carlo neutron doses estimations inside a PET cyclotron vault room.

Neutron organ equivalent doses, effective doses and dose equivalents received inside a positron emission tomography vault room in a maximum credible accident have been estimated with the Monte Carlo code MCNPX. While an operator was inside the vault room of a Cyclone 18/9 IBA cyclotron, this was producing (18)F with 30 muA proton current in the target and the operator had to activate a stopped emergency device placed on the wall. MC simulation of the cyclotron vault were carried out to estimate the organ and tissue equivalent doses in a mathematical male mannequin simulating the operator facing the wall on which the emergency device is placed. Doses were calculated at two emergency devices for each one of the two targets of the cyclotron, which were able to produce (18)F. The maximum effective dose in the mannequin was 6.70 Sv/h and the maximum organ equivalent dose was 18.47 Sv/h in spleen.