Laminated primary ceiling barriers for medical accelerator rooms

In this work the performance of a number of laminated shields used as the primary ceiling barrier for high-energy accelerator rooms was investigated. The neutron and photon dose equivalent rates were measured outside each shield. Based on the measured photon level and the calculated x-ray leakage level the dose equivalent rate due to photons produced by neutron interactions with the shield materials was estimated. Shielding parameters for polyethylene were established for photons and neutrons. It was found that the barriers designed using the techniques given in an NCRP report suffered from excessive radiation leakage. (author)