在某1 000 MW核电机组的多台同型号设备冷却水泵检修过程中发现其叶轮普遍存在裂纹。从裂纹形貌、材料性能、铸造工艺、热处理工艺等多方面对叶轮出现裂纹的原因进行了分析。结果表明：材料铸造过程中出现的气孔和疏松等冶金缺陷是叶轮叶片出现裂纹的主要原因。对叶轮的铸造工艺及热处理工艺提出了改进措施，采用新生产工艺可以消除叶轮中的裂纹、穿孔等铸造缺陷，提高了叶轮的质量及服役性能。

Cracks were found in the impellers of several cooling water pumps of the same type in a 1 000 MW nuclear power unit during maintenance. The reasons of impeller cracking were analyzed from the crack morphology, material properties, casting process and heat treatment process. The results show that the metallurgical defects such as pores and porosity in the casting process were the main reasons for the impeller blade cracks. The casting process and heat treatment process of the impeller were improved. The casting defects such as crack and perforation were eliminated in the impeller produced by the new process, and the quality and service performance of the impeller were improved.