We report here on the generation of simulated defects on sintered uranium dioxide fuel pellets by taking advantage of the underwater laser ablation procedure and their subsequent characterization. This work, we believe, can play a role towards the validation of the performance of fuel pellet inspection machines. A repetitive fiber laser, capable of delivering pulses of nanosecond duration, in conjunction with a galvo-scanner served as the machining tool in the experiment. The study of the dependence of mass ablation rate on laser fluence, water column height, repetition rate, and beam scanning speed formed the bulk of this work. A water column of height ∼3 mm above the pellet surface in combination with a laser fluence of lying within 6–7 J/cm² yielded the maximum ablation rate. The generated defects were analyzed using optical and electron microscopy. Clean defects, e.g. longitudinal cracks, circumferential cracks, pits, and end caps of different sizes and depths were created on the pellet surface by varying the laser parameters, beam travel trajectory, and beam scanning parameters. The mechanical pressure arising out of shock wave generated as a result of the confinement of the laser-produced plasma and the collapse of cavitation bubbles together with the microfluid jet formed due to the implosion of the bubbles pushed the molten ablated products from the interaction zone thereby facilitating the generation of cleaned machined surfaces. An insight into the physical processes’ operative in the underwater laser machining process has been offered, albeit qualitatively.

我们在这里报告了利用水下激光烧蚀程序及其后续特征在烧结二氧化铀燃料颗粒上模拟缺陷的产生。我们认为，这项工作可以对验证燃料颗粒检查机的性能发挥作用。实验中，一种能够传送纳秒级脉冲的重复光纤激光器与振镜扫描仪一起用作加工工具。有关质量消融速率对激光能量密度，水柱高度，重复率和光束扫描速度的依赖性的研究构成了这项工作的大部分。丸粒表面上方约3 mm高的水柱，激光能量密度在6-7 J / cm ^2之内产生了最大的消融率。使用光学和电子显微镜分析产生的缺陷。通过改变激光参数，光束行进轨迹和光束扫描参数，在颗粒表面上产生干净的缺陷，例如纵向裂纹，圆周裂纹，凹坑和不同尺寸和深度的端盖。由于激光产生的等离子体的局限而产生的冲击波产生的机械压力以及空化气泡的破裂以及由于气泡的爆破而形成的微流体射流将熔融烧蚀的产品推离了相互作用区促进清洁表面的产生。尽管定性地提供了对水下激光加工过程中物理过程的操作的见解。