NRC: Watch for Stainless Steel Corrosion from Chlorides in PWRs

The NRC recently notified licensees that chlorides – usually from the air at nuclear plants near the ocean, worker sweat or adhesives – have caused cracking on stainless steel piping in pressurized-water reactors.

NRCLast week’s notice doesn’t require action on the part of plant operators, but it suggests they watch for similar problems. According to the notice, workers at the Callaway plant in Missouri found a small leak beneath a clamp on a stainless 2-inch pressurized spray pipe. In 2009 and 2010, personnel at San Onofre Nuclear Generating Station detected leaks in similar piping at two of their reactors.

Studies of the replaced sections of pipe and previous research indicate chlorides and stagnant flow conditions can increase the risk of stress corrosion cracking (SCC) in PWRs. Sources of chlorides include sea spray, tapes, marking fluid, threaded joint compounds, sweat and insulation.

The notice was sent to all PWR licensees and applicants. There are 69 PWRs currently licensed in the U.S., according the NRC website. The notice said “the operating experience described above shows that, as nuclear plants age, SCC can potentially become an emergent degradation mechanism in PWRs for environments that contain chlorides or stagnant flow conditions. Licensees should be aware of the potential for SCC to occur in stainless steel in PWR applications.”


- Read the full NRC notice here.

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