Defect characterization in pipe-to-pipe welds in large-diameter stainless-steel piping

Metallurgical evaluation of pipe-to-pipe welds in large-diameter, Type 304 stainless-steel piping used to construct the moderator/coolant water systems for Savannah River Site reactors has demonstrated that small weld defects found in this 1950-vintage system do not compromise the integrity of the system. The weld defects were too small for detection by the preservice standard radiographic inspection, but were found through systematic ultrasonic testing and penetrant testing evaluations of piping that had been removed during upgrades to the piping system. The defects include lack of weld penetration, slag inclusions, and other weld metal discontinuities. These discontinuities typically did not propagate during more than 35 years of service. The defects examined were too small and isolated to degrade the mechanical properties of the pipe-to-pipe weldments and, therefore, did not compromise the integrity of the piping system.