Alpha counting methods for continuous measurements of radon and thoron emanation rates

Two instruments for determining radon/thoron surface emanation rates were investigated. One relies on electrostatic precipitation of ions onto a solid state detector. The performance of this monitor is discussed in terms of the results of a continuous emanation study at a tailings dam in South Australia. The second monitor, which is a fast response emanation detector, uses the two-filter concept with gross alpha counting. An evaluation of this instrument is given by a comparative study of the prototype model operated in the manual mode, with charcoal canister measurements of radon emanation rates on the ore stockpiles and ore benches at the Ranger uranium mine