Analysis of induced radionuclides in low-activation concrete (limestone concrete) using the 12 GeV proton synchrotron accelerator facility at KEK

22Na is one of the long-lived radionuclides induced in shielding concrete of a beam-line tunnel of a high-energy particle accelerator facility and poses a problem of radiation wastes at the decommissioning of the facility. In order to estimate the 22Na concentration induced in shielding concrete, chemical reagents such as NaHCO3, MgO, Al203, SiO2 and CaCO3 were irradiated at several locations in the beam-line tunnel of the 12 GeV proton synchrotron accelerator at KEK, and the 22Na concentrations induced in those chemical reagents were measured. Low-activation concrete made up of limestone aggregates was also irradiated by secondary particles in the beam-line tunnel and the long-lived radionuclide, such as 22Na, concentrations induced in the concrete were measured. It was confirmed that 22Na concentrations induced in Mg, Al, Si and Ca were lower than that in Na, and that 22Na concentrations induced in the low-activation concrete was lower than those induced in ordinary concrete made up of sandstone aggregates.