SURVEYS OF CONCENTRATION OF RADON ISOTOPES IN INDOOR AND OUTDOOR AIR IN JAPAN

摘要

A series of radon and ~(220)Rn surveys using passive radon ~(220)Rn discriminative dosimeters were conducted in the Masutomi radium spa region, Yamanashi Prefecture, and at several subway stations in Metropolitan Tokyo. In Masutomi, the highest outdoor radon concentration was 569.8 ± 59.5 (SE) Bq m~(-3) and the lowest, 7.4 ± 0.1 (SE) Bq m~(-3), while the highest outdoor ~(220)Rn concentration was 142.8 ± 52.7 (SE) Bq m~(-3) at 0.04 m above the ground. The outdoor ~(220)Rn concentrations at some survey sites increased as the ground surface approached. The highest radon and ~(220)Rn concentrations in the public bathhouse were 530.2 ± 74.4 (SD) Bq m~(-3) and 592.0 ± 226.8 (SD) Bq m~(-3), respectively. Average indoor radon concentrations in the two houses in Masutomi, were 35.9 ± 2.9 (SE) Bq m~(-3) and 14.2 ± 1.4 (SE) Bq m~(-3), respectively. Indoor and outdoor radon and ~(220)Rn concentrations within a square kilometer region in Masutomi showed the irregular distributions, which might be easily influenced by the local geology and meteorology at each survey site. Average radon concentrations at several subway stations in Metropolitan Tokyo were 10.9 ±1.1 (SE) Bq m~(-3), which was unexpected. Significant ~(220)Rn concentrations were not observed at all survey sites (except some platforms, where values ranged from 11-12 Bq m~(-3)) since the ventilation system of all subway stations exchanged the stale air with the fresh air above ground entirely.