1998 年 33 巻 1 号 p. 25-33
The ionization chamber is one of the fundamental devices for radon measurement. Therefore, calibrations of the ionization chamber must be carefully carried out. We have performed calibrations of devices for measuring radon and radon progeny at our laboratory and on the site for several organizations since the 1960's. During calibration in the laboratory, air with radon emanated from a standard 226Ra solution with activity proved by the US National Bureau of Standards was used as the sample gas. We also participated in the OECD/NEA Radon Intercomparison and Intercalibration Programme arranged by Australian Radiation Laboratory (ARL) during 1984-1987. In 1984, we performed another radon Intercomparison experiment at Ningyotoge Works, Power Reactor and Nuclear Fuel Development Corporation (PNC) in collaboration with the PNC. In 1990, mutual-comparison experiments for radon concentration were carried out by four organizations (Nagoya University, Kyoto University, Waseda University and PNC) using the radon calibration system of Nagoya University. In 1995, the radon and radon progeny intercomparison experiment was performed between Japanese organizations and the US Environmental Measurement Laboratory (EML) using the radon chamber system at the EML. From these activities, it was clear that our radon calibration coefficient agreed well with those of other Japanese organizations with the exception of the Intercomparison experiment at Ningyotoge Works. However, our calibration coefficient was smaller than those of ARL and EML (92% of ARL/EML).