Technical Improvement of Shims and Its Procedure for Gap Measurement and Adjustment for CPR1000 Steam Generator Upper Horizontal Support

Taking China Modified Pressure Reactor 1000 MW nuclear electrical station（CPR1000）steam generator（SG） as an example, the origin for the difference between gap measured and real gap for the thermal expansion of SG upper horizontal support is analyzed, and the optimized schemes ware proposed to improve the shim structure and the procedure about gap measurement and adjustment. The results show that the scheme is an effective way to solve the difficulties met during gap measurement and adjustment.