AREVA NP said Monday it had developed and demonstrated, during a recent nuclear plant outage in the United States, a new ultrasonic testing technique that successfully included off-axis inspection for cracks in a boiling water reactor's (BWR's) core shroud welds. The new approach, the company said, pairs a phased array technique and a specialized multi-axis manipulator.
Core shrouds, made of stainless steel, are used in BWRs to control coolant water inside the reactor pressure vessel.
The nuclear energy industry regularly uses ultrasonic tools to inspect for cracks parallel to the core shroud weld. However, some core shroud weld exams indicated a perpendicular or “off-axis” cracking, the company said. In response, AREVA NP developed a new consolidated tool to generate ultrasonic testing and multiple orientations, helping to accurately detect and characterize all flaws surrounding the weld.
“AREVA NP's development of this new technique and manipulator will save our customers significant examination time and, more importantly, personnel radiation exposure,” said Craig Ranson, senior vice president of Installed Base Services at AREVA. “We are the first supplier to implement a fully demonstrated and documented method for off-axis flaw detection and characterization,” he said.
With the new delivery manipulator for enhanced ultrasonic inspections, technicians can examine the core shroud welds on a rotational and extending feature, which enables horizontal and vertical weld inspections without removing the tool from the reactor for orientation.
In alignment with industry best practices, this new technique incorporates the latest interim guidance on off-axis flaw detection and sizing from the Electric Power Research Institute’s BWR Vessel and Internals Project, AREVA NP said.