Design to neutron shielding for medical LINAC therapy room

Abstract

Objective To study the source of neutron in the therapy room and the essence of neutron scattering,to analyze the change patten of neutron dose in the therapy room as well as in the maze so as to design the shielding.Methods Based on the measurement of the neutron flux for concerning points at the patient plane caused by a running 15 MeV accelerator and referred to NCRP report 79,this paper carried out the radiation protection design and calculation.Results When X-ray produced by medical accelerator reached certain energy,photonuclear reaction is the main source of neutron contamination in medical accelerator room.The main target of protection is the scattered neutron that comes to inside entrance of the maze and the γ-ray caused by them.As a result neutron contamination has nothing to do with the therapeutic effect,but only to increase the dose commitment for relevant person.Conclusions Neutron contamination has nothing to do with therapeutic effect,but only to increase the dose commitment for relevant person.Under certain conditions,it may also cause radiation insult to them.Therefore,certain attention should be paid the hazard caused by neutron external exposure,at the same time shielding design and evaluation should be implemented against the neutron contamination in medical accelerator room. Key words: Medical accelerator; Neutron contamination; Scattering in maze; Dose estimation