title: Does concrete composition affect photoneutron production inside radiation therapy bunkers?
abstract: OBJECTIVE
  Different types of concretes are used for bunker construction for radiation therapy. As  neutron production occurs in high-energy photon beams, the purpose of this study was to investigate the effect of different concretes on photoneutron doses at an isocenter and maze entrance door.
  
  
  METHODS
  The 18-MV photon beam of a Varian 2100 C/D linear accelerator and a radiation therapy bunker were simulated using the MCNPX Monte Carlo code. Different commercially available concretes were used in photoneutron calculations for the simulated bunker.
  
  
  RESULTS
  Higher neutron doses of the water phantom were seen for barytes and galena concretes, while there was no significant (less than 1%) difference between the neutron dose of the phantom for all other concretes. Also, the neutron fluence at the inner and outer maze entrance varied up to 36% depending on the concretes' atomic compositions.
  
  
  CONCLUSIONS
  It can be concluded that application of high-density concretes in order to use limited space or for other purposes may cause higher neutron doses in the maze entrance door and consequently may impose stricter requirements for neutron shielding of maze entrance doors.
authors.affiliation: Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran. mesbahiiran@yahoo.com
authors.forename: Asghar
authors.initials: A
authors.lastname: Mesbahi
authors.forename: Ali-Asghar
authors.initials: AA
authors.lastname: Azarpeyvand
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Khosravi
mesh_terms: D003198:Computer Simulation; D003252:Construction Materials; D006268:Health Facilities; D009010:Monte Carlo Method; D009502:Neutrons; D010315:Particle Accelerators; D017785:Photons; D011829:Radiation Dosage; D011882:Radiotherapy, High-Energy