Document: NUREG-0800
Document ID: 38291c4d-6d61-4922-8b44-6af61374cfaa
Document Type: srp
Title: ENGINEERED SAFETY FEATURES MATERIALS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340646.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.1.1
CFR Part: 
CFR Title: 

Content:
spectively. The great majority of tests reported in the Oak Ridge report, Reference 2, were performed with pH of 4.5, and only two tests were conducted with pH values other than 4.5. Some cracking was observed at pH 7.5 in the sensitized 304 stainless steel U-bend specimens after 2 months exposure to pH 7.5 and chloride concentra- tion of 200 ppm. All of the 316 stainless steel specimens showed no evidence of cracking. Considering the fact that in U-bend specimens the material was sensitized, stressed beyond yield, and plastically deformed, we conclude that the reported test conditions were much more severe than the stress conditions likely to exist in the postaccident emergency coolant systems. We agree with the Oak Ridge conclusion that absolute freedom from failure of any complex system such as a spray system can never be guaranteed, but, by proper design, fabrication, and control of the corrosive environment, the probability of failure can be significantly reduced. Our recommended minimum pH is somewhat higher than the Oak Ridge recommendation of a minimum of 6.5. B. Branch Technical Position CMEB criteria for pH level of postaccident emergency coolant water to reduce the probability of stress-corrosion cracking of austenitic stainless steel components, nonsensitized or sensitized, nonstressed or stressed, are as follows: 1. Minimum pH should be 7.0. 2. For the spray water recirculated from the containment sump, the higher the pH in the 7.0 to 9.5 range, the greater the assurance that no stress corrosion cracking will occur. See SRP Section 6.5.2 for additional water chemistry requirements related to fission product removal. 3. If a pH greater than 7.5 is used, consideration should be given to the hydrogen generation problem from corrosion of aluminum in the containment. "All pH values are at 250C. 6.1.1-13 Rev. 2 - July 1981 C. Evaluation Findings The controls on the pH and chemistry of the reactor containment sprays and ECCS solutions meet the staff positions