Neighborhood-corrected interface discontinuity factors for multi-group pin-by-pin diffusion calculations for LWR

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• 作者：José ; J. Herrero ; ^{josejavier.herrero@upm.es} ; Nuria Garcí ; a-Herranz ; Diana Cuervo ; Carol Ahnert
• 关键词：Interface discontinuity factor ; Pin-by-pin computations ; Environment effect ; ACMFD
• 刊名：Annals of Nuclear Energy
• 出版年：2012
• 期刊代码：1_03064549
• 类别：pw
• 出版时间：August, 2012
• 卷：46
• 期：Complete
• 页码：106-115
• 文件大小：1695 K

摘要

Performing three-dimensional pin-by-pin full core calculations based on an improved solution of the multi-group diffusion equation is an affordable option nowadays to compute accurate local safety parameters for light water reactors. Since a transport approximation is solved, appropriate correction factors, such as interface discontinuity factors, are required to nearly reproduce the fully heterogeneous transport solution.

Calculating exact pin-by-pin discontinuity factors requires the knowledge of the heterogeneous neutron flux distribution, which depends on the boundary conditions of the pin-cell as well as the local variables along the nuclear reactor operation. As a consequence, it is impractical to compute them for each possible configuration; however, inaccurate correction factors are one major source of error in core analysis when using multi-group diffusion theory.

An alternative to generate accurate pin-by-pin interface discontinuity factors is to build a functional-fitting that allows incorporating the environment dependence in the computed values. This paper suggests a methodology to consider the neighborhood effect based on the Analytic Coarse-Mesh Finite Difference method for the multi-group diffusion equation. It has been applied to both definitions of interface discontinuity factors, the one based on the Generalized Equivalence Theory and the one based on Black-Box Homogenization, and for different few energy groups structures.

Conclusions are drawn over the optimal functional-fitting and demonstrative results are obtained with the multi-group pin-by-pin diffusion code COBAYA3 for representative PWR configurations.