Surface Mitigation System: Ultra-High-Pressure Cavitation Peening
Expanding Your Options
Imagine that you had a way to stop primary water stress corrosion cracking (PWSCC) with a risk-free process that uses only water — a solution that does absolutely no harm to the surface of your components and provides a depth of compression that exceeds MRP requirements. It’s here — AREVA’s Ultra High Pressure (UHP) Cavitation Peening. Our mission is to develop timeless solutions to stop plant aging — all while meeting your cost, schedule, safety, and performance goals.
AREVA’s UHP cavitation peening process is a surface mitigation solution that is applicable to the key components of the primary system — reactor vessel head (RVH) nozzle penetrations, bottom mounted nozzle (BMN) instrumentation penetrations, and reactor vessel primary nozzles. These components — comprised of Alloy 600 welded with Alloy 82/182 — are highly susceptible to PWSCC, caused by a combination of three factors:
- A susceptible material — in this case Alloy 600 and Alloy 82/182
- A corrosive environment — in this case the primary system borated water at high temperatures and pressures
- Tensile stresses at the wetted surface created during the manufacturing process — specifically, welding heat-affected zones
Industry-wide, inspections have continued to reveal indications of PWSCC in these aging components. Plant operators have historically had two options — component replacement or repairs — both of which are costly and significantly impact outage critical path.
As the industry addresses these challenges to ensure safe extended operation, AREVA brings the right experts to the table to provide a real, highly cost-effective new option — surface mitigation — to stop PWSCC before it starts without draining your capital budget.
A Timeless Solution to Stop Plant Aging
AREVA’s UHP cavitation peening process uses submerged, ultra-high-pressure water jets to work the surface of reactor vessel components. The high-pressure water flow creates vapor bubbles. As these vapor bubbles collapse on the component’s surface, shock waves travel into the material and create compressive residual stresses. Rather than allowing operational stresses to create multiple, random fractures on a component’s surface, cavitation peening creates compressive stresses on the surface of the material in a controlled manner, preventing PWSCC initiation.
AREVA’s innovative new process operates at a higher pressure with less restrictive parameters than other mitigation alternatives, achieving a higher depth of compression and allowing a more efficient overall implementation schedule.
The long-term value of cavitation peening far outweighs the initial investment. You can always do a component replacement, or keep addressing indications with expensive repair methods. Or you can deploy one simple mitigation technique to significantly reduce risk. Mitigation of all susceptible components is less expensive than future repairs, and you minimize the risk of extended plant shutdown and additional capital expenses.
Features & Benefits
- Prevents primary water stress corrosion cracking (PWSCC)
- Provides asset life extension by stopping the degradation process
- Compressive stress depths exceed MRP requirements
- Reduces the risk of emergent repairs
- Lower cost than future repairs or replacements
- All wetted nozzle surfaces are mitigated
- Additional schedule and cost savings when in-service inspection (ISI) and surface mitigation scopes are combined
- No harm to component surfaces
- Process uses only water; no FME concerns
- Does not leave abrupt edges between peened and non-peened regions
- Mitigation with inspection provides asset warranty which could help with asset capitalization