1994 Volume 29 Issue 1 Pages 33-39
Experimental methods for determining the counting efficiency of instruments that measure radon progeny concentration are proposed and described in this paper. For determining the counting efficiencies of 218Po and 214Po, alpha particles from radon progeny were first sampled from a radon-tank and deposited on the surface of a filter. These alpha particles were then alternately counted by two instruments; a standard instrument, S, with known counting efficiency, and an instrument, G, with unknown counting efficiency. Using the proporsed methods, the relative counting efficiency of 218Po and 214Po using instrument G was determined by comparing the indicated counting efficiency with the known counting efficiency of instrument S. In addition, measured radon progeny concentration data are shown that were calculated from the counting efficiencies obtained with this calibration procedure. These results show that it is important to accurately determine counting efficiencies because a small difference between the counting efficiencies of 218Po and 214Po may give relatively large differences between indicated concentrations of 218Po, 214Pb and 214Bi.
