title: Safe bunker designing for the 18 MV Varian 2100 Clinac: a comparison between Monte Carlo simulation based upon data and new protocol recommendations.
abstract: OBJECTIVE
  The aim of this study was to compare two bunkers designed by only protocols recommendations and Monte Carlo (MC) based upon data derived for an 18 MV Varian 2100Clinac accelerator.
  
  
  BACKGROUND
  High energy radiation therapy is associated with fast and thermal photoneutrons. Adequate shielding against the contaminant neutron has been recommended by IAEA and NCRP new protocols.
  
  
  METHODS
  The latest protocols released by the IAEA (safety report No. 47) and NCRP report No. 151 were used for the bunker designing calculations. MC method based upon data was also derived. Two bunkers using protocols and MC upon data were designed and discussed.
  
  
  RESULTS
  From designed door's thickness, the door designed by the MC simulation and Wu-McGinley analytical method was closer in both BPE and lead thickness. In the case of the primary and secondary barriers, MC simulation resulted in 440.11 mm for the ordinary concrete, total concrete thickness of 1709 mm was required. Calculating the same parameters value with the recommended analytical methods resulted in 1762 mm for the required thickness using 445 mm as recommended by TVL for the concrete. Additionally, for the secondary barrier the thickness of 752.05 mm was obtained.
  
  
  CONCLUSIONS
  Our results showed MC simulation and the followed protocols recommendations in dose calculation are in good agreement in the radiation contamination dose calculation. Difference between the two analytical and MC simulation methods revealed that the application of only one method for the bunker design may lead to underestimation or overestimation in dose and shielding calculations.
authors.affiliation: Tehran University of Medical Sciences, Medical Physics Department, Tehran, Iran.
authors.forename: Manije
authors.initials: M
authors.lastname: Beigi
authors.affiliation: Radiobiology and Radiation Protection Radiological Technology Department, Faculty of Paramedicine, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Afarande
authors.affiliation: Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Hosein
authors.initials: H
authors.lastname: Ghiasi
keywords: Monte Carlo; Protocols; Radiation protection; Shielding