A novel method for gamma spectrum analysis of low-level and intermediate-level radioactive waste

摘要: The uncertainty of nuclide libraries in the analysis of the gamma spectra of low- and intermediate-level radioactive waste (LILW) using existing methods produces unstable results. To address this problem, a novel spectral analysis method is proposed in this study. In this method, overlapping peaks are located using a continuous wavelet transform. An improved quadratic convolution method is proposed to calculate the widths of the peaks and establish a fourth-order filter model to estimate the Compton edge baseline with the overlapping peaks. Combined with the adaptive sensitive nonlinear iterative peak, this method can effectively subtracts the background. Finally, a function describing the peak shape as a filter is used to deconvolve the energy spectrum to achieve accurate qualitative and quantitative analyses of the nuclide without the aid of a nuclide library. Gamma spectrum acquisition experiments for standard point sources of Cs-137 and Eu-152, a segmented gamma scanning experiment for a 200 L standard drum, and a Monte Carlo simulation experiment for triple overlapping peaks using the closest energy of three typical LILW nuclides (Sb-125, Sb-124, and Cs-134) are conducted. The results of the experiments indicate that (1) the novel method and gamma vision (GV) with an accurate nuclide library have the same spectral analysis capability, and the peak area calculation error is less than 4%; (2) compared with the GV, the analysis results of the novel method are more stable; (3) the novel method can be applied to the activity measurement of LILW, and the error of the activity reconstruction at the equivalent radius is 2.4%; and (4) The proposed novel method can quantitatively analyze all nuclides in LILW without a nuclide library. This novel method can improve the accuracy and precision of LILW measurements, provide key technical support for the reasonable disposal of LILW, and ensure the safety of humans and the environment.