Radon concentration in indoor occupational environments in Aomori Prefecture, Japan

The Rn-222 concentrations in indoor workplaces were measured in Aomori Prefecture, Japan, and the results are reported here. This survey was part of a program to measure background natural radiation dose rate in the prefecture where the first Japanese nuclear fuel cycling facilities are now under construction. The survey of the Rn-222 concentrations in indoor workplaces was carried out at 107 locations from 1996 to 1998. The Rn-222 concentrations were measured for approximately one year at each site with passive Rn detectors, which used a polycarbonate film for counting alpha-rays and could separate concentrations of Rn-222 from Rn-220. Weeklong measurements of Rn-222 concentration and working level were carried out with active detectors to get the ratio of Rn-222 concentration during working hours to non-working hours as well as equilibrium factors in selected locations. Diurnal variation of Rn-222 concentration depended on building structure, air-conditioning, time of day and day of the week (week days or weekend). The Rn-222 concentration during working hours was generally lower than that in non-working hours. Although the annual average Rn-222 concentration in indoor occupational environments was higher than that in dwellings, radiation dose for Aomori Prefecture residents from Rn in the former was 14% of the total indoor dose by Rn because of the lower concentration in working hours and lower occupancy factor. (C) 2003 Elsevier Science Ltd. All rights reserved.