核石墨氧化后微观结构观测与分析

摘要

针对高温气冷堆中石墨材料在可能出现的事故中的氧化问题,开展了不同氧化程度下IG-11石墨的表面二维电镜扫描观测和三维CT扫描观测实验,分析了石墨氧化后的表面形态特征和内部微结构分布特点.通过试样氧化前后表面灰度概率分布图可知,石墨氧化后由于内部大孔隙的出现,灰度概率分布图由单峰变为双峰.通过分析灰度平均值以及试样分层密度随深度的变化可知,氧化主要发生在距离石墨试样表面1 mm的区域内;当氧化失重率较小时,在浅层区域损失的质量所占比重相对更大,而氧化程度较高后反应形成的开孔孔隙网络才逐步深入材料内部.%In the possible accidents ,the nuclear graphite used in high-temperature gas-cooled reactor may be oxidized .2-D scanning electron microscope observation and 3-DCT scanning analysis on the oxidized graphite were conducted to study the surface and inner micro-structure of the graphite .After the oxidation ,there appear big voids inside the graphite ,which makes the probability distribution of grayscale change from single-peak to double-peak .By analyzing the mean grayscale and the mean density of layered graphite versus the depth of the graphite ,it is found that the oxidized zone of the graph-ite is mainly within 1 mm under the surface .When the total mass loss is small ,the superficial zone suffers more oxidizing mass loss , and the crack network caused by oxidation grows into the graphite when oxidizing process continues .