Treatment for corrosion of steam generator primary manway bolt hole in a 600 MW nuclear power unit plant

Serious corrosion was found on surface of steam generator primary manway bolt hole during installation and commissioning of a 600 MW nuclear power plant. Through measurements and calculations carried out by designer, inserts screw threads helical coil was adapted. Because nonstandard material was used in inserts screw threads helical coil, so there isn't any manufacture standard. To determine manufacture technology and acceptance standard, series of tests were conducted refer to American materials standard. Manufacture process was obtained by the tests and used to guide the manufacture of inserts screw threads helical coil which was applied to repair the bolt hole. Three consecutive inspection of the bolt hole gave good results after the treatment. (authors)