Development of a modified sum-peak method for activity determination of some gamma emitters

A novel sum-peak method was developed to measure samples containing multiple radionuclides. The conventional sum-peak method is one of the absolute radioactivity measurement methods for radionuclides emitting more than one photon in coincidence. The method requires the knowledge of the total count rate as well as the peak count rates and the sum peak count rate. If there are other radionuclides in a sample, it is fraught with difficulty to estimate the total count rate of the nuclide of interest. To solve the problem, a novel calculation method solely using the peak count rates and the sum peak count rate was developed by modifying the conventional sum-peak method. The new method was theoretically verified and experimentally investigated using 60Co and 22Na, and was successfully confirmed. It was proved that the modified sum-peak method is effective to measure samples with multiple radionuclides and is quite simple and practical.