Residual stress measurements on sleeves and nozzles

Investigation of the Calvert Cliffs-2 heater sleeve failures confirmed the presence of axial throughwall stress corrosion cracks near the J-weld. It was determined that the primary water stress corrosion cracking (PWSCC), a condition that requires significant tensile stress in order to occur, was caused by a fabrication step which resulted in high residual stresses. In order to quantify these stresses, mock-ups were prepared with four conditions: with weld in reamed area, with weld in non-reamed area, with weld in non-reamed area followed by severe reaming, and in reamed are followed by stress relief. It was concluded that fabricated sleeves in reamed areas away from welds did not have sufficient tensile stresses to initiate PWSCC, J-welds induced high tensile stresses in a circumferential direction on the sleeve sufficient to initiate PWSCC. Reaming permitted development of higher residual stresses because of the presence of a cold worked layer of material and reaming after welding produces compressive stresses which would hinder PWSCC initiation. It was also found that stress relief reduced tensile stresses. 5 figs