Neutron transport in a clinical linear accelerator bunker: comparison of materials for reducing the photo-neutron dose at the maze entrance

Megavoltage photons above 10 MeV used in external beam radiotherapy lead to a significant photo-neutron fluence, which must be taken into account in b unker design (IPEM, 1997. Report 75, The design of radiotherapy treatment r oom facilities). This work describes Monte-Carlo simulations of such neutro ns for a proposed bunker, which is to house a IS MV accelerator. Neutron fl uence spectra and absorbed dose due to neutrons and neutron-capture photons were scored at the accelerator isocentre and at the maze entrance for mono -energetic neutron sources of 0.5, 3 and 6 MeV. The reduction in neutron an d photon dose at the maze entrance, achieved by cladding concrete maze wall s with either wood, polyethylene or a commercially available plastic, was d etermined. (C) 2001 Elsevier Science Ltd. All rights reserved.