Atmospheric Salt Fog Testing to Evaluate Chloride Induced Stress Corrosion Cracking of Type 304, 304L, and 316L Stainless Steel

Many nuclear plants have begun or will have to start storing spent nuclear waste in onsite dry storage containers, because the room in the spent fuel pools is reaching capacity. Some of these plants are located close to the coast and are in chloride-rich environments. One potential concern for the casks made of austenitic stainless steel is chloride induced stress corrosion cracking.  The objective of this work is to evaluate the stress corrosion cracking susceptibility of austenitic type 304, 304L, and 316L stainless steel to chloride stress corrosion cracking.  U-bend samples were created out of these alloys and assembled in an environmental chamber.  Previously reported testing indicated that direct spraying of simulated sea salt is an unrealistic and highly aggressive condition.  As such, follow on testing was conducted that deposited simulated sea salt on the surface of U-bend samples by means of a salt fog.  U-bend samples were heated to various temperatures and subjected to an accelerated corrosion tests that did not employ the use of any direct spray to the U-bend samples.  Cracking was observed in the lowest temperature 304 and 304L samples, which is where the deposited salt could have deliquesced.  No cracking was observed on any of the 316L U-bends of U-bend samples heated to 80 °C or higher.