Perturbation Theory-Based Whole-Core Eigenvalue Sensitivity and Uncertainty (SU) Analysis via a 2D/1D Transport Code

Ji Ma,Chen Hao,Yuekai Zhou,Lixun Liu

doi:10.1155/2020/9428580

Ji Ma, Chen Hao + Show 2 more

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https://doi.org/10.1155/2020/9428580

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Abstract

For nuclear reactor physics, uncertainties in the multigroup cross sections inevitably exist, and these uncertainties are considered as the most significant uncertainty source. Based on the home-developed 3D high-fidelity neutron transport code HNET, the perturbation theory was used to directly calculate the sensitivity coefficient of keff to the multigroup cross sections, and a reasonable relative covariance matrix with a specific energy group structure was generated directly from the evaluated covariance data by using the transforming method. Then, the “Sandwich Rule” was applied to quantify the uncertainty of keff. Based on these methods, a new SU module in HNET was developed to directly quantify the keff uncertainty with one-step deterministic transport methods. To verify the accuracy of the sensitivity and uncertainty analysis of HNET, an infinite-medium problem and the 2D pin-cell problem were used to perform SU analysis, and the numerical results demonstrate that acceptable accuracy of sensitivity and uncertainty analysis of the HNET are achievable. Finally, keff SU analysis of a 3D minicore was analyzed by using the HNET, and some important conclusions were also drawn from the numerical results.

Highlights

Due to the fact that the nuclear reactor is a complex nonlinear multiphysics, multiscale coupling system, the high-fidelity simulations and modelling with full consideration of the coupling among neutronics, thermal hydraulics, fuel performance, and so on have become the powerful numerical tool for the detailed analysis of both the current and advanced reactor design
Nuclear reactor physics is the branch of science that deals with the study and application of the chain reaction to induce a controlled rate of fission in the nuclear reactor for the production of energy, so understanding the nuclear reactor physics is very important for each nuclear reactor design, operation, and safety analysis
Multiplication factor is one of the most important integral parameters that need to quantify its uncertainty propagated from the multigroup cross sections

Summary

Introduction

Due to the fact that the nuclear reactor is a complex nonlinear multiphysics, multiscale coupling system, the high-fidelity simulations and modelling with full consideration of the coupling among neutronics, thermal hydraulics, fuel performance, and so on have become the powerful numerical tool for the detailed analysis of both the current and advanced reactor design. The uncertainties in the basic data, such as the multigroup cross sections, manufacturing tolerance of fuel and materials, naturally exist, and these uncertainties inevitably propagate in the progress of nuclear reactor simulations. Understanding these uncertainties and quantifying the total uncertainty of the nuclear reactor key parameters is important for improving the reliability of the best estimated results, identifying the importance of uncertainty sources and ensuring appropriate design margins, and to establish best-estimate calculations for nuclear reactor design and safety analysis. There are three basic uncertainty sources in nuclear physics calculations, including modelling error, numerical solution error, and input parameter uncertainties [1]

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