The critical heat flux of fuel assembly was of great interest for pressurized water reactors, which was related to the safety and economic efficiency. Recently, many studies showed that the nano- and micro-structures on the heat surface could improve the CHF greatly by changing the wettability, onset of nucleate boiling, bubble behaviors (grow, slip, departure etc.) on the modifying surfaces. In present study, the square column microstructures was manufactured on the zirconium alloy surface with ultraviolet laser, whose column microstructure images acquired by SEM (scanning electron microscope) showed many smaller microstructures in the bottom region than the size of square column. And the modified surface showed anisotropic hydrophily, which was smaller than that on the original surface. And the CHF of zirconium alloy microstructure surface was improved about 25%, which was a considerable value for the fuel assembly. And more studies are recommended to focus on the stability and flow boiling behaviors of the zirconium alloy microstructure surface in the future study.

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