Development of a radon daughters monitor for the continuous long-term measurement

We developed a radon daughters monitor for the continuous long-term measurement. Radon daughters and their unattached fraction in air are collected on a membrane filter (pore size: 0.8 μm) and a 200 mesh wire screen respectively. In either case, alpha energy spectra due to both radon and thoron daughters are measured by using a planar silicon detector. Concentrations of RaA, RaB, RaC and their unattached fractions are determined by analyzing the alpha energy spectra. Concentrations of thoron daughters are obtained assuming equilibrium among its daughters. This monitor is capable of measuring radon daughters down to 1 Bq/m3, and can be stably used in various temperature (0 ∼ 40 degrees). We examined the radon daughters deposited to a sampling pipe or tube, in order to evaluate radon daughters concentration exactly when we applied this monitor to measurement of outdoor air. (author)