^ Cavitation peening was recognised in 2017 as one of the Top Innovative Practices for work completed on the Byron and Braidwood reactor vessel closure heads.

Text & image by Framatome

Framatome applied a cutting-edge maintenance technique on reactor vessel primary nozzles at Dominion Energy’s Millstone Power Station (Conneticut, USA) during the plant’s spring 2019 outage. This was the first application of Framatome’s ultra-high pressure (UHP) cavitation peening process on reactor pressure vessel nozzles to primary pipe welds. Because it is deployed directly to the inner surface, it is uniquely suited to remediate the component regardless of external space restrictions or dose constraints.
“Framatome’s innovative solutions are ensuring the efficient and reliable operation of today’s reactor fleet,” said Catherine Cornand, Framatome’s senior executive vice president in charge of the Installed Base Business Unit. “This new underwater application of UHP cavitation peening on a primary nozzle is another example of our team’s expertise and dedication to innovation and continuous improvement in servicing our customers worldwide.”

Full-scale mock-up

To prepare for the work, Framatome demonstrated the qualified reactor vessel primary nozzle cavitation peening technology on a full-scale mock-up at the company’s world-class Technical Training Center in Lynchburg, Virginia, in early 2019.
UHP cavitation peening is designed to prevent primary water stress corrosion cracking. The process uses ultra-highpressure water jets to generate vapour bubbles that collapse with enough force to create beneficial compression of the components’ surfaces. This surface compression improves components’ material properties and enhances resistance to corrosion and other types of degradation, which reduces the effects of ageing.

“UHP cavitation peening can extend the life of components by up to 40 years”

UHP cavitation peening can extend the life of nuclear reactor primary components, including the hot leg primary nozzles, for up to 40 additional years. Additionally, the process reduces outage time and saves money by eliminating the need to replace components or address indications with traditional repair methods. UHP cavitation peening can be used for several different applications in most reactor designs.
“Cavitation peening is an industry game-changer that was recognised in 2017 as one of the Top Innovative Practices for work completed on the Byron and Braidwood reactor vessel closure heads,” said Craig Ranson, senior vice president of Framatome’s North America Installed Base Business Unit. “We are proud to work with Dominion to expand our proven capabilities and engineer a solution for this unique primary nozzle repair.”
Located in Waterford, Connecticut, the Millstone Power Station’s two pressurized water reactors produce enough electricity to power 2.1 million homes.

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