Decreasing thermal stresses in steam generator collector welds area using external cooling

Abstract

Presented paper deals with possibility of external cooling of steam generator welds area to decrease internal tensile thermal stresses which are one of the causes of cracking in this area. On various WWER-440 nuclear power plants (NPP) steam generators (SG) occurred quite serious problem of cracking in weld joints connecting primary collectors to the SG vessels nozzle. The cause of this cracking is stress corrosion cracking (SCC) mechanism. Results of these analyses showed that by proper external cooling of the weld area it is possible not just to decrease significantly existing tensile stresses, but to change them into compressive ones. This of course would have great impact on crack occurrence and growth.Presented paper deals with possibility of external cooling of steam generator welds area to decrease internal tensile thermal stresses which are one of the causes of cracking in this area. On various WWER-440 nuclear power plants (NPP) steam generators (SG) occurred quite serious problem of cracking in weld joints connecting primary collectors to the SG vessels nozzle. The cause of this cracking is stress corrosion cracking (SCC) mechanism. Results of these analyses showed that by proper external cooling of the weld area it is possible not just to decrease significantly existing tensile stresses, but to change them into compressive ones. This of course would have great impact on crack occurrence and growth.