EPRI activities on PWSCC of Alloy 600 penetrations

Five domestic and seven foreign PWR type reactors have experienced primary water stress corrosion cracking of Inconel 600 penetrations. To address this problem, EPRI has initiated a research project on control of stress corrosion cracking. To date, a finite element model has been developed to compute residual and operating stresses in pressurizer penetrations and identify potential remedial measures for PWCSS, their advantages, disadvantages, and the practicality of field implementation. Stress analysis of Inconel 600 penetrations showed weld shrinkage and high restraint produced yield strength level stresses in the penetrations. High yield strength and surface cold work result in high residual stresses and hoop stresses are considerably higher than axial stresses, indicating that and cracks will be axial. 2 figs