分类： 物理学 >> 核物理学 提交时间： 2024-12-31
摘要： With the rapid development of the nuclear power industry on a global scale, the discharge of radioactive effluents from nuclear power plants and their impact on the environment have become important issues in radioactive waste management, radiation protection, and environmental impact assessments. β-detection of nuclides requires tedious processes, such as waiting for the radioactive balance of the sample and pretreatment separation, and there is an urgent need for a method specifically designed for mixing β rapid energy spectrum measurement method for nuclide samples. The analysis of hybrid β-energy spectrum is proposed in this study as a new algorithm, which takes advantage of the spectral analysis of β-logarithmic energy spectrum and fitting ability of Fourier series. The logarithmic energy spectrum is obtained by logarithmic conversion of the hybrid linear energy spectrum. The Fourier fitting interpolation method is used to fit the logarithmic energy spectrum numerically. Next, the interpolation points for the ‘effective high-energy window’ and ‘effective low-energy window’ corresponding to the highest Em nuclide in the hybrid logarithmic fitted energy spectrum are set, and spline interpolation is performed three times to obtain the logarithmic fitted energy spectrum of the highest Em nuclide. Finally, the logarithmic-fitted spectrum of the highest Em nuclide is subtracted from the hybrid logarithmic-fitted spectrum to obtain a logarithmic-fitted spectrum comprised of the remaining lower Em nuclides. The aforementioned process is iterated in a loop to resolve the logarithmic spectra of each nuclide in the original hybrid logarithmic spectra. Then, the radioactivity of Em nuclides to be measured is calculated. In the experimental tests, 14C, 90Sr, and 90Y spectra, which are obtained using the Fourier fitting interpolation method are compared with the original simulated 14C, 90Sr, and 90Y spectra of GEANT4. The measured liquid scintillator data of 90Sr/90Y sample source and simulated data from GEANT4 are then analyzed. Analysis of the experimental results indicates that the Fourier fitting interpolation method accurately solves 14C, 90Sr, and 90Y energy spectra, which is in good agreement with the original GEANT4 simulation. The error in 90Y activity, calculated using the actual detection efficiency, is less than 10% and less than 5% when using the simulated full-spectrum detection efficiency, satisfying the experimental expectations.
分类： 核科学技术 >> 核科学技术其他学科 提交时间： 2023-05-31
摘要： Laminar -scanning (TGS), an advanced -ray nondestructive analysis technique, is capable of locating and analyzing the nuclides in radioactive nuclear waste, and the scanning of TGS falls into two parts (e.g., transmission measurement and emission measurement). To be specific, transmission measurement lays the basis for the accurate measurement of non-uniform radionuclide content in TGS scanning. The scan data were obtained using the Monte Carlo tool Geant4 simulation, and a total of 25 voxels were divided into 5 in length and 5 in width in a square barrel. In this study, the encoding cropping algorithm based on the draped foot vector judgment was adopted to rapidly calculate the voxel trace matrix within the square bucket of nuclear waste, and the transmission images were reconstructed using the Ordered Subsets Expectation-Maximization(OSEM). The results indicated that the cropping speed of the improved coding algorithm was significantly increased compared with the original algorithm, and the relative mean deviation (RMD) and root mean square error(RMSE) between the reconstructed attenuation coefficient and the reference standard value tended to decrease with the increase of the cropped line segments in the voxel, and the Pearson correlation coefficient(PCC) tended to converge to be 1.0. The image quality evaluation parameters of high media density materials were better than those of low media density materials in the above three indexes. The reconstruction effect was relatively poor under the more complex filling material. When there were more than 10 cropped line segments in the voxel, the reconstruction data generally tended to be stable. The graphical trimming algorithm is capable of rapidly calculating the trace matrix of the scanned voxels, it shows the advantages of speed and efficiency, and it can serve as a novel method to solve the trace matrix of TGS nuclear waste transmission scans.
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