| Summary: | In this study, we used the integral method of the probability density function to evaluate the detection efficiency of an inhomogeneous iodine cartridge source by fitting the function relationship between the efficiency of the 131I γ-ray and the height of the disk source from the detector. We constructed a mathematical model by combining the efficiency ratio of the positive and negative placement, K, and the distribution parameter, α, to determine the activity of 131I in the iodine cartridge. To verify this method, we analyzed the inhomogeneous iodine cartridge samples obtained from a gaseous iodine collection experiment. The average deviation of the total activity of 131I, calculated by using 131I γ-ray (364.48 keV), in the iodine cartridge between our method and the homogeneous iodine cartridge source obtained by employing disassembly-stirring-backfilling was 5.71%, and the maximum deviation was 8.54%. The results showed that the disk source calibration method of the probability density function can be used to determine the detection efficiency of inhomogeneous iodine cartridges, thereby providing a feasible method for monitoring gaseous iodine.
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