RAPID ESTIMATION OF RADON DAUGHTER WORKING LEVELS WHEN DAUGHTER EQUILIBRIUM IS UNKNOWN

A technique is described based on a method of Kusnetz which allows radon daughter working levels to be determined after a single alpha count on a filtered air sample. The value of alpha dis/min/l. determined from this count is divided by a universal factor which covers any daughter equilibrium situation, to obtain the value for working levels. The error associated with the working level value for this universal factor is less than ±25%. Factors are also derived for specific ranges of daughter equilibrium to be used when the ranges are known. Whenever information is available concerning the range of equilibrium, the error associated with this calculation is reduced. For example, when the range of RaA/RaB/RaC' is known to be between 1/1/1 and 1/0.1/0.01, the error associated with the working level is no more than ± 13%. The technique requires one alpha count at 30 or 40 min after the end of sampling and for this reason is a highly practical technique for use in uranium mine monitoring. A table of values is included which allows the calculation of these factors for any desired concentration or range of concentrations. © 1969 Health Physics Society.