Decision limit, detection limit, and confidence interval for counting nuclear radiation measurements involving flowing media

The theoretical foundation for the envisaged German Standard DIN 25482-7 has been elaborated. This standard will serve to establish the decision limit, the detection limit, and a confidence interval for counting nuclear radiation measurements involving flowing media, applying enrichment of radionuclides to be controlled on filters. A single radionuclide and a mixture of long-lived radionuclides are considered. A simpler case of counting measurements involving flowing media is also investigated: a sequence of measurements on a fixed volume traversed by the medium. The measurand is the activity concentration carried by the medium. The decision limit, the detection limit, and also a confidence interval are determined for the measurand and for its variation to be detected. The activity concentration and its measurement uncertainty are calculated from the counts of nuclear radiation events registered during successive time intervals of different durations, assuming a constant count rate or a linear time dependence of the count rate and requiring an unbiased estimation of the measurand. (orig.)