Preliminary survey on radon and thoron concentrations in Korea

A preliminary survey was conducted to determine atmospheric radon and thoron concentrations, and soil gas radon concentrations in South Korea. The atmospheric radon and thoron measurements were made with a radon-thoron discriminative monitor and soil eas radon measurements with a hand-made radon monitor over a year. Six cities were chosen as the measurement sites in South Korea. A polycarbonate film and a CR-39 detector were used as detectors for the radon-thoron discriminative monitor and the soil gas radon monitor, respectively. The detectors were replaced every 2-3 months during the survey period so as to observe seasonal variations of the concentration. From the limited data, the outdoor radon concentration has appeared to be somewhat higher than the typical value in the UNSCEAR report. The mean outdoor to indoor concentration ratio was estimated to be 0.6. Since high thoron concentrations were found in some areas, attention must be paid to thoron for accurate dose assessment. The soil gas radon concentration was observed in the range of 3.9-23.1 kBq.m(-3).