| Water erosion occurs frequently at the last stage blades of saturated steam turbine in PWR power plant. The erosion in blades would induce unexpected transient during plant operation, threatening the safety and economy of plant. The author systematically analyzed the factors affecting erosion rate in the aspects of designing, operation, material, structure and rigidity. Methods for erosion protection were summarized based on the survey of literatures, aiming at maximizing the performance of the nuclear power plant.The objective of this thesis was to find the general means to solve the problem of erosion of last stage blades of QINSHAN Phase II Nuclear Power Plant. By comparison of various methods of erosion protection and repair of the eroded blades, braze welding was decided to be utilized to as the priority method to repair the eroded blades. The process for braze welding was verified in Harbin Turbine Co. Ltd., before on-site execution. Criteria and procedures for evaluation of the extent of erosion on the blade, as well as the process for on-site replacement of the stellite strip and methods for quality assurance of repair activity, have been set before performing the repair action. Accoring to the pre-determined procedures, eroded blade repair and stellite strip replacement action were performed during the previous refueling outage.After one operation cycle, the replaced Stellite strip on the Last Stage Blades were inspected during outage. It was confirmed that degree of water erosion on the replaced strip satisfiable to the technical requirement, proving that the proposed evaluation criteria, repairing process, procedures and quality assurance of the eroded blade are practicable, and can be adopted as the guidance for on-site assessment and repair of eroded turbine last stage blades.
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