Study Of Discrete Ordinates-point Kernel Integration Coupling Method Based On Build-up Factor Optimization

The study of shielding materials is a very important topic in the field of radiation protection.The accuracy of the calculation depends largely on the accuracy of the accumulation factor.the ANSI/ANS-6.4.3-1991 database contains the attenuation coefficients and build-up factors of common shielding materials for γ-rays,but it is no longer suitable for the present-day applications.In practice,in addition to using the build-up factors in the database directly,point kernel integration programs also use fitting formulas such as G-P and Taylor to calculate single-layer build-up factors and empirical formulas such as Kalos and Broder to iterate over multi-layer build-up factors.The former is derived from the regular summary of the build-up factors in the ANSI/ANS-6.4.3-1991 database and has the characteristic of inaccurate fitting parameters;the latter is based on experimental data and empirical formulas summarized by Monte Carlo simulation,but fewer experimental elements lead to the inability to achieve uniform accuracy for different shielding materials.Based on the new version of photon cross-section data and new algorithm,this study calculates the accumulation factor under different conditions based on Monte Carlo program,and analyzes the influence of various factors on the accumulation factor of shielding materials;recalculates the single-layer and multi-layer accumulation factor of some materials proposed by ANSI/ANS-6.4.3-1991 standard through neural network and equivalent atomic number;uses Monte Carlo program The Monte Carlo program is used as a benchmark test tool to verify the feasibility and accuracy of the above methods to calculate the build-up factors.At the same time,to address the obvious shortcomings of most existing point kernel integration programs in shielding calculations,i.e.,errors of order of magnitude may occur during the calculation of large source and multi-layer shielding combinations,this study introduces the discrete longitudinal scale method in point kernel integration calculations and initially designs a coupled calculation method combining the two,which solves the problems of poor source discrete calculation accuracy and lack of diagonal decomposition in traditional point kernel integration programs.A simple geometric model is designed for the feasibility study of this method.The results show that the accumulation factors calculated in this study are better than those calculated by previous fitting formulas and empirical formulas,and the computational accuracy of the coupled discrete longitudinal scale-point kernel integral method improves by 20% compared with that of the single method in the calculation of deep penetration problems,and even reaches an order of magnitude improvement in some problems,which can provide more accurate results in the practice of radiation shielding calculation.