Nuclear power generation continues to be an attractive and reliable solution providing carbon-free electricity around the world. But with great power comes the great responsibility to operate safely through rigorous maintenance and inspection routines. Since its early days, Eddyfi Technologies has been present in nuclear power plants by proposing innovative Eddy Current Array (ECA) solutions that excel at detecting near-invisible surface flaws in a wide variety of components. This article presents a few key applications where ECA continues to shine year after year, either as custom solutions tailored to address very specific geometries, or as standard and versatile products. 

Eddy current array probes come in all shapes and sizes. From the paper-thin P-Flex to complex automated scanner systems, the same fundamental principles apply: eddy currents propagate in the surface under examination and are disturbed by the presence of discontinuities such as cracks and voids. However, inspections in nuclear power plants often come with unique requirements. To be suitable for use in a reactor, ECA probes must meet strict specifications in terms of materials compatibility and radiation resistance while still offering the usual high performance and adaptability. 

At Eddyfi Technologies, even when off-the-shelf doesn’t cut it, a turnkey inspection solution is just around the corner. Harnessing the full potential of the Ectane® 3 means adapting ECA coil sensors to specific applications. An optimal coil configuration is selected, and a mechanical solution is designed around it. The probe is then manufactured, tested, and fine-tuned with the power of Magnifi®. Here are a few examples of recent applications that benefited from our ECA technology. 

A computer monitor with a screen and a control panel
Description automatically generated

Fuel Rods 

The rods that contain nuclear fuel pellets are typically made of zirconium or stainless-steel alloys, with a very thin wall and a diameter of less than 16mm (5/8in). An array of high-resolution eddy current sensors encircling the rod can detect sub-millimeter cracks and dents in both the external and internal surfaces. The rods only need to be pushed through the probe: a replaceable centering device helps with the alignment and scan repeatability. 

  • Diameter-specific probe design to inspect fuel rods 
  • Waterproof and radiation-resistant probe body 
  • Highest resolution for the inspection of both sides of the wall 

A close-up of a metal cylinder
Description automatically generated

Structural Welds in Steam Generators 

Weld defects can compromise the structural integrity of a tank, posing safety hazards, leaks, and costly repairs. Inspecting complex tank welds is vital for safety, compliance, and equipment longevity. Eddyfi has developed ECA probes capable to detect axial and transverse defects, fatigue cracking, and lack of fusion. These probes can mount on robotic arms and scanners, are PMUC compliant (products and materials used in nuclear power plants) and feature a padded array of sensors that conforms to weld caps. 

  • Flexible padded design  
  • Weld inspection (fatigue crack, lack of fusion, etc.) 
  • Early detection of flaw propagation in the dome of the steam generator 

J-weld Inspection 

The Reactor Pressure Vessel Head (RPVH) in Pressurized Water Reactors (PWRs) is crucial for maintaining the integrity of the reactor coolant pressure boundary, ensuring safe plant operation. ECA custom probes have been engineered to securely fit onto both the nozzle and shell J-weld surfaces. These probes are specifically designed to detect circumferential and axial flaws in one single scan. 

  • Gel-filled compliant probe 
  • Underwater weld inspection 
  • Detection of weld defects in nuclear environments inaccessible to human operators 


Turbine Rotor Assembly 

Turbine blades exert a tremendous amount of stress on the rotor assembly to which they are attached through dovetail-shaped slots. The integrity of such a system can be assessed with the cutting-edge printed coil eddy current technology (P-Flex), which can be attached to probe heads of almost any shape (see the picture below). This technology allows inspectors to meticulously scrutinize complex shapes for any hidden flaws or irregularities that could compromise operations.  

  • Probe parameters optimized based on the component’s geometry and the inspection condition 
  • Printed coil technology allows a perfect fit between probes and components 
  • Detection of submillimeter cracks anywhere along the dovetail slot 

A few men working in a factory
Description automatically generated


A black and gold device with a black cable
Description automatically generated with medium confidence

A close-up of a machine
Description automatically generated

Transportation Casks for Spent Nuclear Fuel 

Spent Nuclear Fuel (SNF) is transported in nuclear flasks designed to keep their content safe during transportation and prevent leakage to the outside world. When the time comes to inspect and ensure that these containers operate safely, ECA probes are customized to inspect hard-to-reach areas in flasks of all shapes and sizes. With the right operating frequency, it is also possible to penetrate the wall and detect flaws on its far side. 

  • Geometry-specific custom ECA probe     
  • Far-side and near-side defect detection in hard-to-reach areas 
  • Ergonomic and easy to use for repeatable scans 

License: CC BY 3.0 Deed. 

Nuclear Waste Canisters 

Cracks in nuclear waste canisters pose severe risks that can lead to radioactive environmental contamination and health hazards. Cleanup is costly, and incidents damage public trust, highlighting the need for rigorous safety measures. These canisters need to be inspected thoroughly, usually with a rigid ECA probe that fits snuggly into the corner, slot, or surface to inspect. 

  • Rigid probe body tailored to the geometry to inspect 
  • Capability to inspect all surfaces of nuclear waste canisters 
  • Easy to attach to a robotized scanner or inspection crawler 


Smooth operation of nuclear facilities is made possible through routine inspection and early flaw detection. To examine the integrity of critical components, ECA remains an essential tool that makes asset life extension possible and can prevent the costly replacement of suitable parts. New ways of engineering custom ECA solutions develop every day to meet the ever-changing needs of the nuclear industry. Standard probes like the I-Flex and P-Flex paired with the Ectane 3 continue to provide a valuable testing ground for demonstrating the potential of ECA for surface defect detection, but when the next step must be “made to spec”, Eddyfi Technologies always has a solution. 

Shop ECA Probes by Eddyfi Technologies PNG

Check out the Eddyfi Academy to stay ahead of the curve and Beyond Current and get in touch with our experts to discuss your next inspection challenge!