Analysis of radon and thoron daughter concentrations in air by continuous alpha spectroscopy

A procedure is presented here for continuous sampling using alpha spectrometry. The method allows determination of low concentrations of 218Po, 214Pb, 214Po and 212Pb typically found in dwellings as a function of time. Achievable time resolutions range from 10 min for 218Po up to 24 h for 212Pb. The practicability of the method was tested in inhabited dwellings. Measurements were carried out at air sampling rates of 80 to 100 1.h-1 through a filter. Alpha radiation from the filters was registered continuously by a silicon detector and the spectra were stored twice per hour. Evaluation of data in the laboratory shows that even at these low flow rates reasonable results are obtained. Knowledge of the time dependency of air activity concentrations will help to reduce possible errors in exposure measurements with charcoal canisters or nuclear track detectors. (author)