Application of the Method of Repeated Mixing to Non-Uniformly Contaminated Bulky Samples

The method of repeated mixing was applied to soil samples containing hot particles. The results were interpreted using a developed mathematical formulation, which describes the frequency distribution of results in the presence of one or more hot particles in a sample, the statistical characteristics such as mathematical expectancy and dispersion, and includes an approach to estimate the activity of a hot particle without its separation from the sample. It was shown that by application of the method to a limited number of repeated mixings/measurements, the estimated activity of hot particles can be referred as a value determining the uncertainty of the results at a given level of confidence. For instance: for 5 mixings/measurements in a 103 cm3 vessel, the difference between the actual activity of a sample and the averaged result with a probability of about 64% does not exceed the estimated value of the hot particle activity. The probability is increasing with increasing number of mixings (to about 84% for the same uncertainty range at 10 mixings). For a fixed number of mixings the probability is increasing with increasing uncertainty range. The probability is increasing with decreasing size of the measuring vessel, but in many situations small samples can not be a representative subject of study.