ANALYSIS OF ACTIVITY OF RADON DAUGHTER SAMPLES BY WEIGHTED LEAST SQUARES

A new mathematical method employing weighted least-squares has been developed for the analysis of air samples for radon daughters. This method allows calculation of the concentrations in air of the daughter products of both 220Rn and 222Rn based upon the radioactive decay of a sample. It employs observations of the total counts of alpha particles from the sample during various periods of time, rather than estimates of the counting rate at any particular time. There is no upper limit to the number of observations that may be used in the computations. Errors are estimated based upon the statistical limitations of the data. The method has been tested on radon daughter samples taken in uranium mines under conditions both of equilibrium and extreme disequilibrium and compared to the commonly employed Tsivoglou method. Filters were counted in the mines using a combination of ZnS phosphor, photomultiplier tube, and scalar. The concentrations of radium A, B, and C were calculated with both methods. The results of this comparison indicate major advantages of the new technique in research applications, including greater accuracy and clearly defined estimates of errors. © 1969 Health Physics Society.