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EXPERIMENTAL RESIDUAL STRESS EVALUATION OF
HYDRAULIC EXPANSION TRANSITIONS IN ALLOY 690
STEAM GENERATOR TUBING
Rod McGregor, Babcock & Wilcox International, Doug Hornbach, Lambda Research
Usama Abdelsalam, McMaster University, Paul Doherty, Babcock & Wilcox International
ABSTRACT expansion are less than 25% of the local yield stress
and are found on the transition in a narrow
Nuclear Steam Generator (SG) service reliability and circumferential band at the immediate tube surface
longevity have been seriously affected worldwide by (<.0002 inch/ mm depth). The measurements
corrosion at the tube-to-tubesheet joint expansion. otherwise indicate a predominance pressive
Current SG designs for new facilities and replacement stresses on and below the secondary-side surface of
projects enhance corrosion resistance through the use the transition zone. Excellent resistance to
of advanced tubing materials and improved joint initiation is offered by the low levels of tensile stress
design and fabrication techniques. Alloy 690TT and cold work. Propagation of any possible cracking
tubing has demonstrated outstanding laboratory would be deterred by pressive stress field that
performance in accelerated primary water surrounds this small volume of tensile material.
chemistries. Resistance to Secondary Water Stress
Corrosion Cr