Practical interpretative method for indicating values of the potential alpha energy concentration (PAEC) continuous monitor, especially a gross-alpha-counting type, is discussed. Radon WL Meter developed by Thomson & Nielsen Electronics Ltd. in Canada is adopted for the numerical analysis as a typical example of this kind of monitor. There is a time-lag of response to time-variation of PAEC due to the half life of radon decay products. As regards Radon WL Meter, the measuring interval being 60 min, the output counts are es-timated to be in proportion to the mean PAEC about 80 min before the actual output time. Indicating values of the Radon WL Meter are infected with thoron decay products in the air. Thus the ratio between alpha counts due to thoron decay products and the total output counts increases over 10% as the sampling period exceeds 10h. A proposed method for the correction of this influence from thoron decay products, assuming that the concentration of these products is in proportion to the output counts, is discussed.
For application of dual energy gamma-ray transmission techniques to practical mineral grade analysis, some problems including selection of gamma-ray energies, influence of sample thickness and main causes of errors in measurement have been examined. The relationships between the R-values (the ratio of mass attenuation coefficients for low and high energy gamma-rays) and the effective atomic numbers for various samples (e.g., iron ore, coal and coke, limestone, minerals and gem stones) were determined using different energy combina-tions of gamma-rays from 152Eu. On the basis of the experimental results, the optimum conditions for analysis of minerals were discussed.