燃料元件基体石墨Xe离子辐照缺陷的慢正电子束研究  

Slow positron beam study on defects induced by Xe ions irridiation in matrix graphite of fuel elements

作　　者：许红霞[1] 林俊[1] 朱智勇[1] 刘建党 谷冰川 叶邦角 XU Hongxia;LIN Jun;ZHU Zhiyong;LIU Jiandang;GU Bingchuan;YE Bangjiao(Shanghai Institute of Applied Physics,Chinese Academy of Sciences,Shanghai 201800,China;State Key Laboratory of Particle Detection and Electronics,University of Science and Technology of China,Hefei 230026,China)

机构地区：[1]中国科学院上海应用物理研究所,上海201800 [2]中国科学技术大学核探测与核电子学国家重点实验室,合肥230026

出　　处：《核技术》2022年第10期26-33,共8页Nuclear Techniques

基　　金：中国科学院院战略先导科技专项(No.XDA02030000);中国科学院前沿重点研究项目-钍铀燃料循环特性和若干关键问题研究(No.QYZDY SSW-JSC016);国家自然科学基金(No.12005289)资助。

摘　　要：室温下采用能量为1 MeV、剂量分别为5.8×10^(14) ions·cm^(−2)和2.9×10^(15) ions·cm^(−2)的Xe离子对核燃料元件基体石墨进行了辐照试验,用慢正电子束和纳米压痕研究了离子辐照对基体石墨微观缺陷和宏观力学性能产生的影响,根据正电子湮没S参数随正电子入射能量E的变化曲线,获得了辐照缺陷随深度和剂量的变化规律,并与SRIM(Stopping and Range of Ions in Matter)软件模拟的辐照损伤和注入离子随深度的分布进行了对比。慢正电子束测试结果表明:Xe离子辐照在燃料元件基体内引入一个深度约为600 nm的损伤层,且缺陷浓度峰值出现在离表面250-350 nm的深度范围内。S参数在辐照样品损伤层的显著增加表明,辐照引入了高浓度的空位型缺陷,且随着辐照剂量的增加,损伤层内空位型缺陷的浓度或尺寸明显增大。纳米压痕结果表明:在辐照后的样品内出现了明显的硬化现象,原因是辐照引起的高浓度空位型缺陷所致,与慢正电子束的分析结果一致。[Background]The solid fuel thorium element molten salt reactors(MSR)have attracted more attention recent years.A3-3 graphite is chosen as the fuel matrix for MSR,thus its irradiation behavior and mechanical property is very important before the application.[Purpose]The study aims to observe the irradiation defects and hardness of A3-3 matrix graphite after ion irradiation by slow positron beam and nano-indentation,respectively.[Methods]The matrix graphite of fuel elements was irradiated with 1 MeV Xe ions to fluence of 5.8×10^(14) ions·cm^(−2) and 2.9×10^(15) ions·cm^(−2) respectively at room temperature.The slow positron beam and nano-indentation were employed to investigate the effect of Xe ions irradiation on vacancy defects and hardness of matrix graphite.The changes in irradiation induced defects distribution with depth and fluence were analyzed according to the obtained positron annihilation S parameters versus positron incidence energy or depth curves,compared to SRIM(Stopping and Range of Ions in Matter)calculation.[Results]Results from slow positron beam measurement show that 1 MeV Xe ions irradiation in matrix graphite introduces a damage layer with depth of about 600 nm,and the damage peak locates at about 250-350 nm in depth,consisted with SRIM simulation.The S parameters in irradiation samples increase significantly compared to virgin sample,which suggests that a high concentration of vacancy-type defects appeared within irradiation damage layer.In addition,the S parameters increase with the irradiation fluence,which shows that the concentration or size of vacancy-type defects increases.The nano-indentation results show that the hardness of irradiated graphite matrix is enhanced.[Conclusions]The enhanced hardness of A3-3 matrix graphite after ion irradiation is ascribed to the pinning of basal plane dislocation by the high concentration of vacancy type defects introduced by irradiation,consisted with the slow positron beam analysis.Slow positron beam is a very sensitive tool to study the irra

关 键 词：慢正电子束 缺陷 辐照 燃料元件 石墨 

分 类 号：TL99[核科学技术—核技术及应用]