Technical preparations for atmospheric radioactivity monitoring

To evaluate the suitability of a location for a radionuclide monitoring station of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) at Takasaki, Japan, the assessment was done in terms of the concentration of natural background radioactive nuclides in airborne dust and soil samples. The samples were taken four times at the proposed site and several points around the site, then their radioactivities were measured by gamma-ray spectrometry. For the airborne dust samples, only natural background radionuclides: 212 Pb, 7 Be and 214 Pb were detected. The radioactivity concentrations of these radionuclides varied in four sampling periods but were almost the same as the previous measurements. For the soil samples, the concentration of an anthropogenic radionuclide, 137 Cs, fluctuated among the different sampling points and periods, but the concentration of 40 K was constant. These concentrations were 2 to 3 times lower than those of the soil taken at JAERI Tokai. Based on these results, the proposed site was evaluated and has been accepted by the CTBT Organization as a CTBT radionuclide monitoring station.