Lessons learned from the examination of tubes pulled from Electricité de France steam generators Original Research Article

The laboratory examination of about 200 pulled tubes exhibiting secondary side cracking provides extensive data on the following: • corrosion location, orientation, surface extension, length, depth, density, morphology etc; • tube metallurgical and chemical characteristics; • deposits and oxides composition; • leak rate of the cracks; • burst pressure of the degraded segment; • mechanical properties of segments with or without cracking. The evaluation of the database permits the following: • characterization of degradation; • a better understanding of the phenomena; • validation of the non-destructive examination techniques; • setting alternative plugging criteria; • verification that the plugging criteria are conservative and overly reasonable. Pulled tube examinations are a very convenient way of gathering this essential information to gain more knowledge about the corrosion process. Nowadays, they are implemented in many countries experiencing corrosion of the steam generator bundles in pressurized water reactors. Each year, Electricité de France performs about 15 pulled tube examinations in the hot laboratory located in the nuclear power plant in Chinon.