Areva NP has unveiled a new technique and manipulator to offer off-axis inspection for cracks in boiling water reactor (BWR) core shroud welds.
|Areva NP's new tooling can accurately characterise off-axis cracks (Image: Areva)
The technique, which uses a phased array ultrasound technology paired with a specialised multi-axis manipulator, has been demonstrated during a recent outage at a US BWR, Areva NP said.
BWRs are single-circuit reactors - rather than transfer the heat generated in the reactor's core to a secondary circuit, their coolant water is allowed to boil in the reactor core to produce steam which is transferred directly to electricity generating turbines. Core shrouds are stainless steel cylinders surrounding the fuel inside the reactor pressure vessel used in BWRs to separate upward and downward flows of water.
Utilities are required to perform periodic examinations of the welds in the core shrouds of BWRs. This is regularly done using ultrasound tools to inspect for cracks parallel to the core shroud weld. However, perpendicular or "off-axis" cracking can also occur. Areva NP developed its new consolidated tool to examine accurately detect and characterise all flaws surrounding the weld, regardless of their orientation.
The phased-array technology allows the equipment to perform ultrasonic testing at multiple orientations, helping to accurately detect and characterize all flaws surrounding the weld, while a the delivery manipulator enables the tool to carry out horizontal and vertical weld examinations without having to be removed from the reactor to be reoriented.
Craig Ranson, senior vice president of Installed Base Services at Areva Inc, said the development of the new technique and manipulator would shorten examination times and reduce radiation exposure to personnel. "We are the first supplier to implement a fully demonstrated and documented method for off-axis flaw detection and characterization," he said.
Researched and written
by World Nuclear News