Electrochemical Method of Nondestructive Testing of the Propensity of Metal Parts of NPP Equipment to Inter-Crystallite Corrosion

Abstract

Standard GOST-regulated method is used to develop a procedure of testing stainless steels (the basic material of operating equipment of nuclear power plants) for inter-crystallite corrosion resistance (ICCR). The methodology includes the methods of surface preparation and environment control, the choice of anode etching parameters and conditions of metallographic evaluation of ICCR. The reliability of the results is confirmed by the data of comparative testing of 08KH18N10T steel specimens after sensitizing and austenite conditioning according to the developed standard (AMU GOST 6032-2003) procedures. The proposed approach to ICCR assessing directly upon viewing the surface is advantages compared to the method of “replicas.” The developed procedure is used to study corrosion of the internal surfaces of the main circulating pumps MCP-195-M at Kalinin and Balakovo NPP to analyze the possibility of extending their lifetime after a 20-year period of their service.