An azimuthal contact and free-centerline boundary condition for cracked fuel pellets in 2D axisymmetric models

IF 3.2 2区工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY

Journal of Nuclear Materials Pub Date : 2025-08-07 DOI:10.1016/j.jnucmat.2025.156101

Andrew Prudil

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引用次数: 0

Abstract

A fuel pellet deformation model comprised of plane-stress, azimuthal contact, and free-centerline displacement boundary condition is proposed to improve the prediction of Pellet-Cladding Mechanical Interaction (PCMI) in two-dimensional (2D) axisymmetric fuel codes at low power. This modification is motivated by case 3 of the EGRFP-PCMI modelling benchmark, in which none of the participants consistently correctly predicted the linear power at which pellet-cladding contact starts, nor the relationship of this threshold power with pellet length. In the benchmark, the 2D fuel codes with discrete fuel pellets did not significantly outperform the one-dimensional codes in predicting PCMI and the effects of pellet length. In the present work, we analyze the predictions of the Canadian Fuel And Sheath modelling Tool (CFAST) in the benchmark study and argue that the zero radial displacement solid-mechanics boundary condition commonly used in 2D axisymmetric models limits pellet hourglassing and is inconsistent with the expected pellet cracking. This hypothesis is confirmed by a three-dimensional (3D) thermomechanical model with cracked fuel pellets compared against experimental measurements of clad elongation. Based on these findings, the modified 2D axisymmetric model is proposed and compared against the 3D model and the experimental measurements of cladding elongation at low power.

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二维轴对称模型中破碎燃料球团的方位接触和自由中心线边界条件

为了改进二维轴对称燃料码在低功率条件下对球团-包壳力学相互作用（PCMI）的预测，提出了包含平面应力、方位接触和自由中心线位移边界条件的燃料球团变形模型。这种修改的动机是EGRFP-PCMI建模基准的案例3，其中没有参与者始终正确地预测颗粒包层接触开始时的线性功率，也没有这个阈值功率与颗粒长度的关系。在基准测试中，具有离散燃料颗粒的二维燃料代码在预测PCMI和颗粒长度的影响方面没有显著优于一维代码。在本工作中，我们分析了加拿大燃料和鞘层建模工具（CFAST）在基准研究中的预测，并认为二维轴对称模型中常用的零径向位移固体力学边界条件限制了球团沙漏，并且与预期的球团开裂不一致。这一假设被一个三维（3D）热力学模型与裂纹燃料球团的包层伸长率的实验测量相比较证实。在此基础上，提出了改进的二维轴对称模型，并与三维模型和低功率下包层伸长率的实验测量结果进行了比较。

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

Journal of Nuclear Materials 工程技术-材料科学：综合

CiteScore

5.70

自引率

25.80%

发文量

601

审稿时长

63 days

期刊介绍： The Journal of Nuclear Materials publishes high quality papers in materials research for nuclear applications, primarily fission reactors, fusion reactors, and similar environments including radiation areas of charged particle accelerators. Both original research and critical review papers covering experimental, theoretical, and computational aspects of either fundamental or applied nature are welcome. The breadth of the field is such that a wide range of processes and properties in the field of materials science and engineering is of interest to the readership, spanning atom-scale processes, microstructures, thermodynamics, mechanical properties, physical properties, and corrosion, for example. Topics covered by JNM Fission reactor materials, including fuels, cladding, core structures, pressure vessels, coolant interactions with materials, moderator and control components, fission product behavior. Materials aspects of the entire fuel cycle. Materials aspects of the actinides and their compounds. Performance of nuclear waste materials; materials aspects of the immobilization of wastes. Fusion reactor materials, including first walls, blankets, insulators and magnets. Neutron and charged particle radiation effects in materials, including defects, transmutations, microstructures, phase changes and macroscopic properties. Interaction of plasmas, ion beams, electron beams and electromagnetic radiation with materials relevant to nuclear systems.