核燃料包壳FeCrAl基合金制备及抗辐照性能研究

Nuclear energy is one of the most effective methods to solve the energy problems. Nuclear power has been proven to be a reliable, environmentally sustainable, and cost-effective source of large-scale electricity. However, the Fukushima nuclear accident in 2011 shows that the existing Zr alloy fuel cladding is not enough to facing the precipitate serious accidents, for example the LOCA(Lost of coolant accident). It is necessary for scientists to design one of the most advanced fuel cladding, which could replace existing Zr alloy clad in light water reactors. FeCrAl alloys has been considered to serve as a substitute for Zr alloys with enhanced accident tolerance for light water reactor (LWR) fuel cladding, because of its strong steam oxidation resistance, corrosion resistance and radiation resistance. By the means of the combination of ion irradiation and electron microscopy theory, FeCrAl alloys could be intensively investigated in the mechanism with plastic deformation, high temperature creep behavior and radiation resistance. In the progress of preparation of FeCrAl alloys the mechanism with plastic deformation and grain boundary designing and controlling could be obtained. Meanwhile, the preparation technology contained composition screening could be decided. Then, ions irradiation with different conditions could be carried to FeCrAl alloys. After the nanoindentation and TEM analysis, the mechanism of high temperature creep behavior and radiation resistance could be obtained. And the embrittlement behavior of FeCrAl alloys could be investigated. Finally, all of the endeavor could promise accident tolerant fuel cladding enhancement.

核能是目前解决能源问题的最有效方法之一。但是，2011年福岛核事故说明目前的轻水堆包壳材料——锆合金在面对严重事故时抵抗能力不足。所以，为进一步提高核燃料包壳的事故容错能力，需要研发一种新型的核燃料包壳材料。高性能的FeCrAl基合金具有优异的抗水蒸气氧化能力、耐腐蚀能力等，可以满足事故容错要求，而且兼顾优异的抗辐照能力，是最有可能替代目前的锆合金包壳的新型材料之一。本项目以高性能FeCrAl基合金为研究对象，离子辐照与电子显微学分析结合，将对FeCrAl基合金的塑性加工变形机制、高温蠕变行为及抗辐照机理进行深入研究。在制备FeCrAl基合金过程，掌握其塑性变形机制、晶界设计及强化机理，筛选合金成分定型制备工艺；对FeCrAl基合金进行不同条件的离子辐照，结合纳米压痕与微观表征分析，掌握其抗辐照以及高温蠕变机理，研究离子辐照对其的合金脆化效应的影响。为新型包壳材料提供研究基础和科学依据。

随着核能发电在世界范围内快速发展，研究热点集中在事故容错压水堆、第四代先进核动力堆以及其关键结构材料。FeCrAl铁素体合金因其优异的抗氧化性能成为潜在的事故容错燃料(ATF)包壳材料之一。与商业包壳材料Zr合金不同，FeCrAl合金在中高温下可在表面产生保护性氧化层，防止核燃料包壳在典型核事故中进一步失效。通过在FeCrAl合金中添加Nb、Mo等元素能有效促进细小的Laves颗粒的析出，提高合金高温强度。此外，由于Laves相在晶界或亚晶界析出的钉扎效应，回复和再结晶的微观结构得到了有效的稳定。设计并制备了具有梯度Nb含量的FeCrAl合金，系统研究了重离子辐照下Laves相的辐照响应。研究结果证明了在辐照条件下Laves相中存在元素偏聚，但未改变其尺寸与钉扎效果。即使处于辐照非晶态，这种非共格相界面依然能有效吸收辐照缺陷。