As part of the latest upgrade of the Laboratory for Radioactivity Measurements, a new method for determining detector efficiency has been introduced. Detector efficiency is one of the key parameters when performing measurements and analyses of samples, as it must be well understood in order to accurately calculate the specific activity of samples. The Efftran method is based on Monte-Carlo integration and requires an accurate detector model, but it is faster and comparatively cheaper than the older empirical method. My goal was to validate the new method using the results obtained with the old approach. Since the Efftran method relies on transferring the detector efficiency from a confirmational sample to the analyzed sample, I chose three samples for measurements that differ in their key parameters: a water sample, which is similar to the confirmational sample, an aerosol filter which has a different geometry, and a steel sample which has a a different matrix. Using the detector efficiencies obtained with both methods, I calculated the specific activities of radionuclides in the samples and compared them with the reference values. The results obtained with the Efftran method mostly agree within the limits of reported uncertainties with the reference values. However, I discovered, that Efftran incorrectly calculates true coincidence summing corrections that occur between emitted X-rays and γ-rays of a radionuclide in the sample. This finding is very relevant for further development of the method.
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