Numerical simulation on thermal-hydraulic-mechanical coupling of core corium migration during severe accidents

IF 1.9 3区工程技术 Q1 NUCLEAR SCIENCE & TECHNOLOGY

Nuclear Engineering and Design Pub Date : 2025-04-25 DOI:10.1016/j.nucengdes.2025.114083

Yujian Huang, Zhengyang Dong, Mingjun Wang, Kui Zhang, Suizheng Qiu, G.H. Su, Wenxi Tian

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引用次数: 0

Abstract

Core corium migration is one of the critical challenges of severe core accidents. The lower support plate is a critical load-bearing component within the pressure vessel among core corium migration. Investigating the thermal exchange and mechanical failure of the lower support plate during the core migration process holds significant practical value. The heat transfer between the corium and the support plate is complex, involving multiple phenomena such as fluid dynamics, thermal exchange, melting, and mechanical effects, making a comprehensive analysis of the failure process challenging. In this study, a migration heat transfer model has been established, incorporating radiation heat transfer, impact heat transfer, and direct contact heat transfer. The interaction between the corium and the support plate is modeled using a mechanical analysis approach, while the mechanical effects are analyzed through the formulation of a constitutive equation. A Thermal-Hydraulic-Mechanical (THM) coupling calculation method is also developed to address these interactions. The results show that the corium migration heat transfer is consistent with findings in the relevant literature. The majority of corium migrates close to the wall of the RPV lower head, causing the temperature at the edges of the lower support plate to exceed that at the center, leading to creep failure under thermal stress. As the corium continues to migrate, the cumulative mass of molten material and the convective heat transfer coefficient increase. At 60 s, the maximum total deformation of the support plate reaches 0.89025 mm, with a maximum total strain of 0.01636 mm/mm. The equivalent stress is concentrated at the upper surface edges, exceeding the yield limit, indicating fracture failure. Ultimately, the support plate fails within 1 min due to sustained radiation heat. These simulation results offer insights for the safe design of the lower head.

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重大事故堆芯迁移热-水-力耦合数值模拟

堆芯堆芯迁移是严重堆芯事故的关键挑战之一。下支撑板是堆芯堆芯迁移过程中压力容器内的关键承重部件。研究岩心迁移过程中下支撑板的热交换和力学破坏具有重要的实用价值。堆芯与支撑板之间的传热过程复杂，涉及流体力学、热交换、熔融、力学效应等多种现象，对其失效过程进行综合分析具有挑战性。本研究建立了一个迁移换热模型，包括辐射换热、冲击换热和直接接触换热。采用力学分析方法模拟了堆芯与支撑板的相互作用，并通过本构方程的建立分析了堆芯与支撑板的力学效应。为了解决这些相互作用，提出了一种热-液压-机械（THM）耦合计算方法。结果表明，堆芯迁移换热与相关文献的研究结果一致。大部分堆芯向RPV下封头壁面附近迁移，导致下支板边缘温度超过中心温度，在热应力作用下发生蠕变破坏。随着堆芯继续迁移，熔融物质的累积质量和对流换热系数增大。60 s时，支撑板最大总变形为0.89025 mm，最大总应变为0.01636 mm/mm。等效应力集中在上表面边缘，超过屈服极限，表明断裂破坏。最终，由于持续的辐射热，支撑板在1分钟内失效。这些仿真结果为下机头的安全设计提供了参考。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Nuclear Engineering and Design 工程技术-核科学技术

CiteScore

3.40

自引率

11.80%

发文量

377

审稿时长

5 months

期刊介绍： Nuclear Engineering and Design covers the wide range of disciplines involved in the engineering, design, safety and construction of nuclear fission reactors. The Editors welcome papers both on applied and innovative aspects and developments in nuclear science and technology. Fundamentals of Reactor Design include: • Thermal-Hydraulics and Core Physics • Safety Analysis, Risk Assessment (PSA) • Structural and Mechanical Engineering • Materials Science • Fuel Behavior and Design • Structural Plant Design • Engineering of Reactor Components • Experiments Aspects beyond fundamentals of Reactor Design covered: • Accident Mitigation Measures • Reactor Control Systems • Licensing Issues • Safeguard Engineering • Economy of Plants • Reprocessing / Waste Disposal • Applications of Nuclear Energy • Maintenance • Decommissioning Papers on new reactor ideas and developments (Generation IV reactors) such as inherently safe modular HTRs, High Performance LWRs/HWRs and LMFBs/GFR will be considered; Actinide Burners, Accelerator Driven Systems, Energy Amplifiers and other special designs of power and research reactors and their applications are also encouraged.