On the uncertainty in activity measurements for samples containing "hot particles"

The uncertainty in activity measurements for samples containing hot particles is considered under three assumptions: (1) all activity in the samples is due to hot particles; (2) hot particle dimensions are log-normally distributed with the logarithm of the median radius m and the standard deviation of the logarithm of the particle radius s; and (3) the number of particles in the sample is a random quantity. It is shown that the measurement uncertainty grows when both s and m increase. Also, that for s < 0.25-0.3 the primary source of uncertainty is the randomness of the number of particles in the sample, and, if s exceeds 0.3, the "log-normality" effect becomes more dominant. The values of the variance/uncertainty estimated by the measurement of replicate aliquots from a single sample can be used for the estimation of the m and s relationship and boundary values of these parameters.