Yao Tiankai, Xin Guoqing, Scott Spencer Michael, Gong Bowen, Lian Jie
Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
Sci Rep. 2018 Feb 14;8(1):2987. doi: 10.1038/s41598-018-21034-4.
Low thermal transport behavior along the radial direction of nuclear fuel pellets and pellet-cladding mechanical interaction significantly impact fuel performance and the safety of current nuclear energy systems. Here we report a new strategy of advanced fuel design in which highly thermally-conductive and mechanically-robust graphene nanoplatelets are incorporated into UO fuel matrix to improve fuel thermal-mechanical properties. The 2D geometry of the graphene nanoplatelets enables a unique lamellar structure upon fuel consolidation by spark plasma sintering. The thermal conductivity along the radial direction of the sintered fuel pellets at room temperature reaches 12.7 and 19.1 wmK at 1 wt.% and 5 wt.% loadings of the graphene nanoplatelets, respectively, representing at least 74% and 162% enhancements as compared to pure UO fuel pellets. Indentation testing suggests great capability of the 2D graphene nanoplatelets to deflect and pin crack propagation, drastically improving the crack propagation resistance of fuel matrix. The estimated indentation fracture toughness reaches 3.5 MPa·m by 1 wt.% loading of graphene nano-platelets, representing a 150% improvement over 1.4 MPa·m for pure UO fuel pellets. Isothermal annealing of the composite fuel indicates that the graphene nano-platelet is able to retain its structure and properties against reaction with UO matrix up to 1150 °C.
核燃料芯块径向的低热传输行为以及芯块与包壳之间的机械相互作用，对燃料性能和当前核能系统的安全性有显著影响。在此，我们报告一种先进燃料设计的新策略，即将高导热且机械性能强劲的石墨烯纳米片掺入UO燃料基体中，以改善燃料的热机械性能。石墨烯纳米片的二维几何结构使得通过放电等离子烧结进行燃料固结时能形成独特的层状结构。在室温下，烧结燃料芯块径向的热导率在石墨烯纳米片负载量为1 wt.%和5 wt.%时分别达到12.7和19.1 W/(m·K)，与纯UO燃料芯块相比，分别提高了至少74%和162%。压痕测试表明二维石墨烯纳米片具有很强的使裂纹偏转和阻止裂纹扩展的能力，极大地提高了燃料基体的抗裂纹扩展能力。通过1 wt.%的石墨烯纳米片负载量，估计的压痕断裂韧性达到3.5 MPa·m，相较于纯UO燃料芯块的1.4 MPa·m提高了150%。复合燃料的等温退火表明，石墨烯纳米片在高达1150 °C的温度下能够保持其结构和性能，不与UO基体发生反应。
