Measurement of gaseous radioactivity concentration of short-lived nuclides produced by air activation in the spallation neutron source facility of J-PARC

Sakashita, Koichi; Arakawa, Yuto; Masuyama, Koichi; Sato, Koichi ; Seki, Kazunari; Kasugai, Yoshimi  ; Ishii, Tetsuro  

Radioactivity concentrations of short-lived nuclides of C, N, O and Ar with half-lives of about 2 to 110 min, produced by air activation under the spallation neutron environment at the Materials and Life Science Experimental Facility in J-PARC, were measured using a scintillation gas monitor. Since these radionuclides decay with without emitting -rays except for Ar, the contribution of each radionuclide was separated by fitting a multi-component function depending on the half-lives of the products to the time variation of measured counting rates. Concentration conversion factors to convert count rates to radioactivity concentrations were determined by taking account of the result of Monte Carlo calculations. Using this method, the radioactivity concentrations of these nuclides were obtained with an accuracy of about 10-25%.