原位合成法制备UO2-石墨烯复合燃料机理与性能研究  

Mechanism and Properties of UO2-Graphene Composite FuelPrepared by in Situ Synthesis

作　　者：吴学志[1] 尹邦跃[1] WU Xuezhi;YIN Bangyue(Reactor Engineering Technology Research Division,China Institute of Atomic Energy,Beijing 102413,China)

机构地区：[1]中国原子能科学研究院反应堆工程技术研究部,北京102413

出　　处：《材料导报》2020年第S02期6-10,共5页Materials Reports

摘　　要：二氧化铀(UO2)是目前核电站主要应用的核燃料,具有熔点高、抗辐照性能强、与包壳和冷却剂相容性好等优点。但UO2燃料热导率低,当反应堆燃耗较深时,极易发生燃料肿胀,使燃料与包壳发生机械与化学相互作用(PCMI),增大反应堆安全风险,故提高UO2燃料热导率是未来高性能核燃料改性研究的重点方向。石墨烯具有高熔点、高导热率以及高温稳定性等优势,是UO2燃料芯块中一种非常值得探索的第二相添加物。但目前石墨烯掺杂的普遍工艺为物理混合法,很难解决石墨烯与大比重陶瓷材料的混合均匀性问题,限制了其掺杂性能的发挥。本工作采用一种以石墨烯为形核,硝酸铀酰溶液与氨水在形核上反应沉积的原位合成法,通过控制反应参数,制备了掺杂2%(体积分数,下同)、4%、6%和8%石墨烯的UO2-石墨烯复合燃料粉末,通过放电等离子烧结工艺(SPS)制备得到复合燃料芯块,探讨了工艺机理,测试了燃料性能。结果表明:原位合成法制备UO2-石墨烯混合粉末的均匀度可达96.39%;相结构分析显示,1450℃烧结芯块中只存在UO2和石墨烯两种相结构,石墨烯与UO2未发生反应而破坏;掺杂2%、4%、6%和8%石墨烯的原位合成法芯块密度分别为95.56%TD、95.32%TD、95.08%TD和94.76%TD,芯块密度未因石墨烯掺杂量增加而大幅度下降;芯块在20℃热导率分别提高12.27%、20.13%、27.47%和34.13%,芯块在1000℃热导率分别提高18.36%、35.00%、47.07%和58.93%,石墨烯在燃料高温服役阶段性能表现更为优异,弥补了UO2在高温时热导率更低的缺点;由SEM可见,原位合成法制备的芯块晶粒尺寸在10~30μm,晶粒间结合致密,晶界处无明显气孔存在,石墨烯被UO2均匀包覆,通过形成桥联导热网,提高了芯块热导率。Uranium dioxide is the main nuclear fuel used in nuclear power plants.It has the advantages of high melting point,high radiation resistance and good compatibility with cladding and coolant.However,the thermal conductivity of UO2 fuel is low,and when the reactor burnup is deep,the fuel is prone to swell,which leads to the mechanical and chemical interaction(PCMI)between fuel and cladding,which increases the safety risk of the reactor,improving the thermal conductivity of UO2 fuel is the key direction of the future research on the modification of high performance nuclear fuel.Graphene has the advantages of high melting point,high thermal conductivity and high temperature stability.It is a valuable second-phase additive in UO2 fuel pellets.However,at present,the general process of graphene doping is physical mixing,so it is difficult to solve the problem of mixing uniformity between graphene and high density ceramic materials,which limits its doping performance.In this paper,a kind of nucleation method based on graphene and in situ synthesis of uranyl nitrate solution and ammonia water on nucleation was used,by controlling the reaction parameters,UO2-graphene composite fuel powders doped with 2vol%,4vol%,6vol%and 8vol%graphene were prepared,composite fuel pellets were prepared by spark plasma sintering(SPS).The process mechanism and fuel properties were investigated.The results show that the uniformity of UO2-graphene powder prepared by in situ synthesis method is up to 96.39%;The analysis of phase structure show that only UO2 and graphene exist in the sintered pellets at 1450℃,the graphene is not destroyed by reacting with UO2;the density of in situ synthesis pellets doped with 2vol%,4vol%,6vol%and 8vol%graphene are 95.56%TD,95.32%TD,95.08%TD and 94.76%TD respectively;the thermal conductivity of pellet at 20℃increase by 12.27%,20.13%,27.47%and 34.13%respectively,the thermal conductivity of pellet at 1000℃increase by 18.36%,35.00%,47.07%and 58.93%respectively,graphene has better performance in the high tempera

关 键 词：石墨烯 原位合成 制备 燃料 热导率 

分 类 号：TL352.21[核科学技术—核技术及应用]