Sourceless Efficiency Calibration Technique Application Research on Heterogeneous Uranium-bearing Material Measurement Equipment

This paper firstly introduces the measurement system of heterogeneous uranium-bearing materials based on Segmented Gamma-Ray Scanning (SGS) method, and establishes the corresponding Monte-Carlo simulated model of this equipment with sourceless efficiency calibration method, which is verified by experiments with standard point source and body source, in the verification experiments of high purity Germanium detector characterization and the whole equipment with point source, the deviation between the calculated value of absolute detection efficiency and the experimental value is less than 2%, then the experimental verification based on the sourceless efficiency calibration method is carried out with uranium nitrate solution of known concentration, and the specific experimental analysis steps and conclusions are given, the deviation between the measured value and the nominal value of the sample is also within 2%. Finally, under the laboratory conditions, the trial evaluation experiment of blind sample measurement and analysis is carried out by using the principle of added method. The equivalent position of point source is determined by using the unequal calibration method. Based on the blind sample value of the first measurement and analysis, the mixture of working standard samples with known ²³⁵U content was measured one by one, the difference between the mixture value and base value is the added working sample value, the deviations between analysis value and the nominal working standard sample are all less than 8.5%. The linear fitting of the above four measurement results is carried out, fitting coefficient R² is 0.995 4. By extrapolation the fitting curve it can get ²³⁵U content in the blind sample, the deviation between this value and the measured base value is -1.87%. The accuracy of the passive efficiency calibration technology of the heterogeneous uranium bearing material measurement system is acceptable. The added method can be used to evaluate the measurement results of unknown heterogeneous samples. This method can also be applied to other nuclear safeguard heterogeneous material measuring devices.