U-tube local damage analysis and preventable method for AP1000 steam generator during local post weld heat treatment

AP1000 steam generator support plate temporary slope can cause u-tube permanent deformation (local depression) during local stress relieving post weld heat treatment due to small clearance between tube and support plate hole. The deformation trend of steam generator components and secondary air temperature distribution can be tested and simulated by analysis model during actual post weld heat treatment of round seam between tube sheet and channel head. Air heating and cooling blower system is designed for internal temperature balance during post weld heat treatment. The analysis model can simulate the steam generator component deformation trend which is verified by actual post heat treatment. And the tube local damage by permanent deformation is prevented by using air heating and cooling blower system.