Simulation of Neutron Streaming through Labyrinth of the Shield of Thallium Target Room of Cyclotron “Cyclone 30” using MCNP Computer Code

Thallium-201 is one of the medical radioisotopes produced in Nuclear Research Center for Agriculture and Medicine via 203Tl (p, 3n) 201Pb reaction, using protons from cyclotron Cyclone 30. Due to high intensity of the neutrons produced from the thallium target and its copper substrate, protection against this radiation is a necessity. The radiation shield is the concrete walls of the target room accessible from outside through a multi-bend maze. In this work, we have calculated the streaming of neutrons through the maze of the target room using MCNP Monte Carlo radiation transport code. The target has been bombarded with 145 µA of 28.5 MeV protons. Equivalent dose rate of neutrons in various positions in the maze has been calculated and compared with the measured values. The maximum deviation between the calculated and measured values is found to occur at the farthest position from the source, namely at the entrance door of the maze, for which the neutron equivalent dose has been calculated as 93 mSv/hr and the corrected measured value upon using the energy spectrum weighted correction factor is 136 mSv/hr. These values are in good agreement with each other according to the shielding point of view.