Abstract: Shielding calculations were performed for the room of a linear accelerator of model DZ-12/5500, with NCRP Report No. 151, GBZ/T 220.2—2009 and etc as references, to illustrate how to select a suitable calculation method to determine the optimal shielding thickness of room for industrial flaw detecting linear accelerator of energy above 10 MV. It shows that a 278 cm thick concrete shielding wallis needed in the useful beam direction, while the concrete thickness in other 3sides should be 182, 195 and 204 cm respectively. With a roof of 110 cm thick concrete, sky inverse scattering results in an extremely small dose equivalent rate in any location 20 m away from the nose of the accelerator. The ambient dose equivalent is 115.69 μSv in the Z-shaped labyrinth entrance, in which X-ray scattering and leakage, neutron irradiation, and neutron capture of X-ray give rise to 2.43, 102.96 and 10.30 μSv/week respectively. Analysis of test results upon operation indicates that calculated and tested values agree well, our calculation method and parameters selected are viable.

Key words: Industrial flaw detection, 12 MV linear accelerator, Shielding calculation, Neutron