Irradiation-Assisted Stress Corrosion Cracking of Heat-Affected Zones of Austenitic Stainless Steel Welds

Irradiation assisted stress corrosion cracking is known to appear in the internal components of boiling water reactors such as core shrouds. Although the behaviour of austenitic stainless steels base material has been thoroughly investigated, few studies were dedicated to the weld metal and heat affected zones (HAZ). The goal of this study is a contribution to better understand the welding and neutron-irradiation induced changes in the HAZ that may promote intergranular cracking. The evolution of residual stresses, microstructure, microchemistry, mechanical properties, and the stress corrosion behaviour of two welded austenitic stainless steels have been investigated, before and after irradiation. Slow Strain Rate Tensile (SSRT) tests were performed. Flat tensile samples, containing the weld and HAZ were fabricated from type AISI 304 and AISI 347 stainless steels. SSRT corrosion tests were performed at 290ºC in low conductivity water with 200 ppb dissolved oxygen. Reference tests were performed in inert gas (argon). The irradiated HAZs presents typical irradiation-induced defects with slightly increased density. The tensile tests reveal a significant hardening of the material that is clearly related to the irradiation induced microstructure. Finally no intergranular fracture is observed for the irradiation dose and deformation conditions studied.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen