FLUKA CALCULATIONS OF RADIONUCLIDES, STAR, AND NEUTRON FLUENCE IN SOIL AROUND HIGH-ENERGY ELECTRON AND PROTON LINEAR ACCELERATORS

Information of radionuclide production and the attenuation of high-energy neutrons in the soil shielding around accelerators is important for environmental impact assessment. The radionuclide concentration of {sup 3}H, {sup 7}Be, {sup 22}Na, {sup 24}Na, {sup 45}Ca, {sup 54}Mn, and {sup 55}Fe in the soil outside the cylindrical concrete tunnel from a uniform beam loss along a copper Linac was calculated using FLUKA. The atom concentration and the number of atom per star for radionuclides were given as a function of soil depth. Attenuation length of star density, as well as the neutron fluence spectra, was calculated. Studies for electron and proton beams at 500 GeV were made and their results were compared to examine the common understanding that the radiation and radioactivity patterns outside a certain thickness of shielding are the same between high-energy electron and proton beams. The effects of star-scoring threshold (20 or 50 MeV) by neutrons or by all particles on the results were also investigated.