Irradiation conditions such as fission power, fission rates, and temperature are important parameters for nuclear fuels because they influence the microstructural behavior and ultimate irradiation performance. Two U-7Mo/Al-3.5 wt.% Si dispersion fuel plates were irradiated in the Advanced Test Reactor edge-on to the core in the RERTR-9B experiment at different powers to study the effects of power on fuel phase swelling behavior. The results of non-destructive measurements have been reported in a previous paper [1], and the destructive examination results are being reported here. In particular, the microstructural evolution of the U-Mo fuel phase in irradiated fuel plates has been investigated by cutting transverse cross-sections, using generated scanning electron microscopy micrographs, and image processing methods to assess the changes in microstructural features, such as fission gas pore growth and non-recrystallized grain fraction. In this study, the focus was to examine the evolution of fission gas pores from both the constrained and unconstrained regions of U-Mo fuels irradiated at different powers. Based on an estimated linear gradient, the rate of change of fission gas pore size with locally calculated fission densities is more prominent in the higher power specimen. As such, the average porosity and pore area is approximately 11% and 2 × larger in the fuel irradiated at higher power than that of the lower power specimen. The growth of fission gas pores can accelerate the pore interconnectivity and thus fission gas outside the fuel kernel (FGO), which are two precursors for swelling in U-Mo fuels. The influence of increased power, internal plate stresses, and fission-induced creep on fuel kernel deformation and lateral mass transfer is also highlighted.

诸如裂变功率，裂变速率和温度等辐照条件是核燃料的重要参数，因为它们会影响微观结构行为和最终辐照性能。在RERTR-9B实验的高级测试反应堆中，以不同功率将两块U-7Mo / Al-3.5 wt。％Si分散燃料板沿边缘辐射到堆芯，以研究功率对燃料相溶胀行为的影响。非破坏性测量的结果已在先前的论文中报道[1]，破坏性检查结果也已在此报告。特别是，通过使用生成的扫描电子显微镜显微照片切割横截面，研究了辐照燃料板中U-Mo燃料相的微观结构演变，和图像处理方法来评估微观结构特征的变化，例如裂变气孔生长和未重结晶晶粒分数。在这项研究中，重点是检查以不同功率辐照的U-Mo燃料的受约束和不受约束区域的裂变气孔的演变。根据估计的线性梯度，裂变气体孔径随局部计算的裂变密度的变化率在高倍率样品中更为突出。因此，以较高功率照射的燃料比以较低功率样品照射的燃料的平均孔隙率和孔面积大约为11％和大2倍。裂变气孔的生长可以加速孔的互连性，从而加速裂变气在燃料核（FGO）外部，而燃料核是U-Mo燃料膨胀的两个前体。