Pore structure evolution of A3–3 matrix graphite during heat treatment

IF 2.8 2区工程技术 Q3 MATERIALS SCIENCE, MULTIDISCIPLINARY

Journal of Nuclear Materials Pub Date : 2024-10-22 DOI:10.1016/j.jnucmat.2024.155474

Xi Tong, Xiangwen Zhou, Kaihong Zhang, Huixun Gao, Shouchi Zhang, Bing Liu, Yaping Tang

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引用次数: 0

Abstract

Matrix graphite (MG), a key component of fuel elements for high-temperature gas-cooled reactors (HTRs), has a profound effect on the comprehensive performance and service safety of fuel elements. A3–3 MG was selected as the matrix material for the pebble fuel elements of the 10 MW experimental high-temperature gas-cooled reactor (HTR-10) and the high-temperature gas-cooled reactor pebble-bed module (HTR-PM) in China. During the preparation process of A3–3 MG, the green MG pebble must undergo two-stage heat treatment, namely carbonization and purification, to obtain excellent comprehensive properties for safe service. However, the porosity of A3–3 MG and its change during heat treatment remains unclear. Herein, the pore structure evolution through three different stages of A3–3 MG - the green, carbonized and purified samples- were tested using the gas adsorption method, mercury intrusion porosimetry and X-ray computed tomography (X-CT). The green sample had the smallest pore diameter and a uniform pore size distribution. The pore structure of the carbonized sample was the most developed, with the most micropores, mesopores and macropores. The molecular-sized micropores were produced due to the pyrogenic decomposition of the resin binder. Purification led to a decrease in pore diameter, together with a slight increase in closed pores and a decrease in pore connectivity due to pore merging and conversion. Two- and three-dimensional (2D and 3D) pore structure models were established by X-CT scan. The variation in pore size and shape, different types of pores as well as the pore conversion during the heat treatment process of A3–3 MG were observed. In this work, the porosity evolution of A3–3 MG was studied in detail, and references and strategies were provided for optimizing the preparation process and performance of pebble fuel elements.

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A3-3 基质石墨在热处理过程中的孔隙结构演变

基质石墨（MG）是高温气冷堆（HTR）燃料元件的关键成分，对燃料元件的综合性能和服役安全性有着深远的影响。A3-3 MG 被选为中国 10 兆瓦实验高温气冷堆（HTR-10）和高温气冷堆鹅卵石床模块（HTR-PM）鹅卵石燃料元件的基体材料。在 A3-3 MG 的制备过程中，绿色 MG 卵石必须经过碳化和净化两个阶段的热处理，以获得优异的综合性能，保证安全服役。然而，A3-3 MG 的孔隙率及其在热处理过程中的变化仍不清楚。在此，使用气体吸附法、汞侵入孔隙度测定法和 X 射线计算机断层扫描（X-CT）对 A3-3 MG 的三个不同阶段（绿色样品、碳化样品和净化样品）的孔隙结构演变进行了测试。绿色样品的孔径最小，孔径分布均匀。碳化样品的孔隙结构最为发达，具有最多的微孔、中孔和大孔。分子大小的微孔是由于树脂粘合剂的热解作用产生的。由于孔隙合并和转换，纯化导致孔隙直径减小，闭合孔隙略有增加，孔隙连通性降低。通过 X-CT 扫描建立了二维和三维（2D 和 3D ）孔结构模型。观察了 A3-3 MG 热处理过程中孔隙大小和形状的变化、不同类型的孔隙以及孔隙转换。这项工作详细研究了 A3-3 MG 的孔隙率演变，为优化卵石燃料元件的制备过程和性能提供了参考和策略。

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.