The Solution Method for Ultra-Fine Group Slowing-Down Equations Applicable to Stochastic Media

Song Li (), Lei Liu (), Yongfa Zhang, Qian Zhang and Qi Cai
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Song Li: College of Nuclear Science and Technology, Naval University of Engineering, Wuhan 430033, China
Lei Liu: College of Electrical Engineering, Naval University of Engineering, Wuhan 430033, China
Yongfa Zhang: College of Nuclear Science and Technology, Naval University of Engineering, Wuhan 430033, China
Qian Zhang: Laboratory for Advanced Nuclear Energy Theory and Applications, Zhejiang Institute of Modern Physics, Department of Physics, Zhejiang University, Hangzhou 310027, China
Qi Cai: College of Nuclear Science and Technology, Naval University of Engineering, Wuhan 430033, China

Mathematics, 2025, vol. 13, issue 11, 1-20

Abstract: This study presents an innovative solution method for ultra-fine group slowing-down equations tailored to stochastic media with double heterogeneity (DH), focusing on advanced nuclear fuels such as fully ceramic microencapsulated (FCM) fuel and Mixed Oxide (MOX) fuel. Addressing the limitations of conventional resonance calculation methods in handling DH effects, the proposed UFGSP method (the ultra-fine group slowing-down method with the Sanchez–Pomraning method) integrates the Sanchez–Pomraning technique with the ultra-fine group transport theory to resolve spatially dependent resonance cross-sections in both matrix and particle phases. The method employs high-fidelity geometric modeling, iterative cross-section homogenization, and flux reconstruction to capture neutron self-shielding effects in stochastically distributed media. Validation across seven FCM fuel cases, four poison particle configurations (BISO/QUADRISO, Bi/Tri-structural Isotropic), and four plutonium spot problems demonstrated exceptional accuracy, with maximum deviations in effective multiplication factor k ef f and resonance cross-sections remaining within ±138 pcm and ±2.4%, respectively. Key innovations include the ability to resolve radial flux distributions within TRISO particles and address resonance interference in MOX fuel matrices. The results confirm that the UFGSP method significantly enhances computational precision for DH problems, offering a robust tool for next-generation reactor design and safety analysis.

Keywords: ultra-fine group slowing-down equation; reactor physics numerical computation; stochastic media; double heterogeneity (search for similar items in EconPapers)
JEL-codes: C (search for similar items in EconPapers)
Date: 2025
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