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Case Study: Finding Stress – Corrosion Cracks in Stainless Steel Canisters

Finding corrosion cracks in the stainless steel canisters used to contain nuclear material for long-term storage is an essential, yet time consuming process, especially as these canisters are usually stored by the thousands. These canisters may develop atmospherically-induced stress corrosion cracking (AISCC) and it is this cracking that requires periodic inspection of the canisters.

How is AISCC caused? Absorbing moisture from the air, particle deposits on the sides of the canisters can cause a thin layer of salt solution to develop. If there is already a high enough level of residual stress in the canister, this salt solution may cause AISCC.

The Challenge

Many businesses are now turning to robotic options to inspect the canisters simply due to the time it takes to inspect each individual canister. But it is not just the time factor that is seeing many businesses turn to robotic inspection options. These cracks can be extremely small, 2 – 3mm in length, or quite large. Eddify recently ran testing to find the best option for robotically identifying cracks in stainless steel canisters used to store nuclear material.

The Solution

The Eddy current array (ECA) has proven to be one of the better options above other technologies. The ECA is an adaptable, powerful and cost-effect technology which lends itself well to robotization. Electromagnetic testing has long been used in various industries to detect cracks on or near the surface on materials such as stainless steel.

The ECA arranges several coils in rows which allows for a wider inspection area while the probes are more stable than the more conventional pencil probes, offering a higher tolerance level to coupling. All round, this makes the ECA more suited to robotization than many other products.

Eddyfi used a range of testing methods on their test cannister to see which product worked the best, and with those methods they discovered plenty of benefits to changing to robotization for inspections.

The ECA is easy to integrate into a robotic system, meaning industries may not need to undergo large upgrades. The ECA test results are repeatable and intuitive, ensuring that industries will be able to test multiple stainless steel canisters without worrying about downtime, and that there is no surface preparation required, so testing can be done a lot quicker and with a lot less fuss. The ECA probe can also stand up to heavy use making it one of the best choices for industry users.

ECA probes have been designed to meet the needs of those in the oil & gas, power generation and aerospace industries.

Nexxis are proud to offer the Eddyfi eddy current inspection system and has a team of industry professionals will evaluate your operation’s inspection requirements and your unique applications to work out the most appropriate, cost-effective and flexible solution.  Upgrading from your current inspection model to an ECA will cut down on the time your staff spend checking the stainless steel canisters in use on site. Check out our extensive range of technical equipment at and make some advantageous changes to your inspection programme today.


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