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SCC Behavior Of Alloy 52M Weld Butter On SA-508 LAS From The Double-Repair Dissimilar Metal Weld In A PWR Environment

This paper presents the results of a confirmatory research program conducted with the purpose of evaluating the susceptibility of Nickel-base Alloy 690 and 52/152 and variant welds to stress corrosion cracking (SCC) with a focus on the SCC response of Alloy 52/152 weldments with repairs.Nickel-base Alloy 690 and the associated weld Alloys 52 and 152 are typically used for nozzle penetrations in replacement heads for pressurized water reactor (PWR) vessels, repairs of existing components as well as for designs of advanced nuclear reactors because of their increased resistance to stress corrosion cracking (SCC) relative to Alloys 600, 82, and 182. 

Product Number: ED22-17283-SG
Author: Bogdan Alexandreanu, Yiren Chen
Publication Date: 2022
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The Alloy 52M narrow gap temper bead double repair weld was fabricated by EPRI with three repair regions - a 40% depth repair, a 20% depth repair, and an overlapping region with the 20% depth repair on top of the 40% depth repair - temper bead protocol. Two specimens were tested from the regions with the double repair and the region with a single 40% depth repair. SCC CGR testing found both specimens to be susceptible to IG SCC, with significant levels of IG fracture morphology. The fracture surface of the specimen from the region with the single 40% depth repair was highly IG-engaged (71%) and propagated unperturbed beyond Cr-diluted regions near the LAS and reached the regions with nominal 29-30 wt. % Cr concentration, likely beyond the 1st weld butter layer. The average crack advance was substantial, making the resulting data consistent with the criteria of acceptance for the industry-proposed Alloy 82/182 disposition curve. The factor of improvement vs. the 75th Percentile MRP-115 curve is approximately 20. The industry-proposed Alloy 52/152 curve does not appear to bound the data points obtained from this double repair weldment.

The Alloy 52M narrow gap temper bead double repair weld was fabricated by EPRI with three repair regions - a 40% depth repair, a 20% depth repair, and an overlapping region with the 20% depth repair on top of the 40% depth repair - temper bead protocol. Two specimens were tested from the regions with the double repair and the region with a single 40% depth repair. SCC CGR testing found both specimens to be susceptible to IG SCC, with significant levels of IG fracture morphology. The fracture surface of the specimen from the region with the single 40% depth repair was highly IG-engaged (71%) and propagated unperturbed beyond Cr-diluted regions near the LAS and reached the regions with nominal 29-30 wt. % Cr concentration, likely beyond the 1st weld butter layer. The average crack advance was substantial, making the resulting data consistent with the criteria of acceptance for the industry-proposed Alloy 82/182 disposition curve. The factor of improvement vs. the 75th Percentile MRP-115 curve is approximately 20. The industry-proposed Alloy 52/152 curve does not appear to bound the data points obtained from this double repair weldment.