Radiation Protection Dosimetry Advance Access originally published online on April 16, 2008
Radiation Protection Dosimetry 2008 130(4):427-433; doi:10.1093/rpd/ncn099
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Analysis and improvement of cyclotron thallium target room shield
1 Agricultural, Medical and Industrial Research School, Nuclear Science and Technology Research Institute, Markaz Tahghighat Street, Moazzen Blvd, Rajaee shahr, PO Box 31485-498, Karaj, Iran
2 Radiation Applications Research School, Nuclear Science and Technology Research Institute, Atomic Energy Organization of Iran, End of Kargare Shomali, Tehran, Iran
3 Agriculture, Medicine and Industry Research School, Nuclear Science and Technology Research Institute, Markaze Tahghighat Street, Moazzen Blvd, Rajaee shahr, PO Box 31485-498, Karaj, Iran
* Corresponding author. nhajiloo{at}nrcam.org
Received January 9, 2007, amended March 9, 2008, accepted March 10, 2008
Because of high neutron and gamma-ray intensities generated during bombardment of a thallium-203 target, a thallium target-room shield and different ways of improving it have been investigated. Leakage of neutron and gamma ray dose rates at various points behind the shield are calculated by simulating the transport of neutrons and photons using the Monte Carlo N Particle transport computer code. By considering target-room geometry, its associated shield and neutron and gamma ray source strengths and spectra, three designs for enhancing shield performance have been analysed: a shielding door at the maze entrance, covering maze walls with layers of some effective materials and adding a shadow-shield in the target room in front of the radiation source. Dose calculations were carried out separately for different materials and dimensions for all the shielding scenarios considered. The shadow-shield has been demonstrated to be one suitable for neutron and gamma dose equivalent reduction. A 7.5-cm thick polyethylene shadow-shield reduces both dose equivalent rate at maze entrance door and leakage from the shield by a factor of 3.