MARKII型低压转子末级叶片原位叶根的超声相控阵检查

摘要

In Daya Bay nuclear plant, the type of the last stage blade of turbine rotor is MARK II vertical tree root, which is designed by GEOA. In some plants, cracks were found on the rotor blades of old type, which were not improved before by GEC-A. For that reason, Daya Bay nuclear plant began feedback preventive inspection in a very early time. But there is a problem that it has to tear down all the rotor blades before inspection each time, so the inspection will cost about 8-9 days and become the critical path of the refueling outage, what,s more, it may cause the risk of mechanical damage. Therefore, to extend the cycle time of the low-pressure cylinder blades＇ disassembly can further improve the economy of the steam turbine and keep the nuclear power plant steam turbine maintaining a reliable. Through years of researches and experiments, in-situ phased array ultrasonic inspection techniques can meet the requirement, and it has been successfully used practically.%大亚湾核电站汽轮机转子末级叶片是采用GEC-A设计制造的MARKII型叶片枞树型叶根。由于GEC-A未改进前的末级叶片在其它电厂发现过裂纹，大亚湾核电站很早就开始实施反馈性预防检查，但需要拆除末级叶片，而一次拆装检查需要8～9d，成为核电厂常规换料大修中的关键瓶径，并可能产生因拆卸而带来的机械损伤风险。因此，找到延长低压缸拆装叶片的周期的方法，将可以实现在保证核电厂汽轮机组可靠性的同时进一步提高经济性。通过多年的调研及试验，相控阵超声波原位检查技术可以满足此目的，并已在现场得到成功应用。