Physical and chemical forms of radionuclides of 38S, 38Cl, 39Cl, and 82Br, produced at a high-energy proton accelerator facility

High-energy protons and neutrons produce various radionuclides in the air, mainly through the nuclear spallation of atmospheric elements. Air samples were collected from the EP-2 tunnel of the KEK 12 GeV proton synchrotron facility with a filter pack, which consisted of a membrane filter for aerosols, a Na2CO3-impregnated filter for acidic gases, and an activated carbon fiber filter for non-acidic gases. Sulfur-38 was found on the membrane and Na2CO3-impregnated filters, 38Cl and 39Cl were on the membrane, Na2CO3-impregnated, and ACF filters, and 82Br was only on the ACF filter. The results on the relative abundances of aerosol and gaseous acidic components have indicated that 38Cl produced by thermal neutron capture, which is the main reaction for 38Cl production in the EP-2 tunnel air, are likely not to be present as aerosol or acidic gas. This was similar to the case of 82Br produced by thermal neutron capture.