Measurements of regional distribution of 222Rn concentration and analysis on optimal allocation of monitoring stations

Outdoor 222Rn concentrations were measured with electrostatic integrating radon monitors (EIRM) at 40 points around Nagoya, in which fifteen sets of 2-month-exposure data over 2.5 years were obtained. Seasonal variation of 222Rn concentration showed a clear pattern which has a spring-to-summer minimum and an autumn-to-winter maximum. Annual mean 222Rn concentration ranged from 3.5 to 11.7 Bq m-3 depending on locations. From the obtained regional distribution of 222Rn concentration, optimal allocation of measuring instruments was analysed. As a result, it was expected that the same concentration distribution could be obtained with less instruments. (author)