Measurements of the Total and Unattached Radon Daughters in a House

Abstract

Abstract Continual and simultaneous measurement of unattached radon daughters (RaA, RaB and RaC) and the total radon daughters was performed in a house under normal living conditions which include ordinary living habits, the style of house construction and the normal natural ventilation rate in Japan. The hourly concentrations of three radon daughters were obtained separately and simultaneously with a radon daughter monitor, which has air filtration and gross alpha counting systems. The instrument was automatically operated (and maintenance free) over a period of two months. The unattached atoms of radon daughters were measured with another radon daughter monitor with wire screens substituting for the filter. From the measurements for seven months from Nov. 1986 to May 1987, it can be stated that: (1) the concentration of unattached RaA is the most predominant of these daughters, and the unattached RaB is always detectable; (2) the median value of the unattached fraction, fp indicated by potential alpha energy, is around 0.04, the RaB makes a contribution of more than 30% to the overall fp; (3) the data for the unattached fraction show a typical diurnal variation, having a low level in intervals of 7 to 9 and 20 to 22 local hours. It corresponds to aerosol generation from the use of gas ranges in the house.