Estimation of radiation source term and concrete shield thickness for low energy particle accelerators

摘要

Electron beams with varying energy (0.5-15 MeV) have been extensively used for processing of various materials. Main source of radiation is bremsstrahlung radiations (X-rays) generated when electron beam strikes high Z materials. The emergent spectra have angular distribution and with increasing electron energy X-ray emission rate peaks in the forward direction. Photo neutron generation in such electron accelerator is less significant as it generates after certain threshold energy. The accelerated protons interact with matter and lead to the primary radiological hazards, which consist of prompt radiation (neutrons and gamma). Another source is delayed radiation which is due to induced radioactivity in accelerator component. Thus, in electron accelerator bremsstrahlung radiation and in proton accelerator, neutrons are the main sources of radiation that decide the shield thickness. The emergent radiation has angular distribution and accordingly shield thickness also varies. Radiation source terms are evaluated for 3, 7, 10 and 15 MeV electron beam and 10/20 MeV proton beam accelerator. Required concrete shield thickness for housing these accelerators is also evaluated and presented in this paper. Emergent radiation yield values are verified by Monte Carlo stimulations and are found to be in good agreements.