Information Notice No. 82-14: TMI-1 Steam Generator/Reactor Coolant System Chemistry/Corrosion Problem
8202040133 SSINS No.: 6835 IN 82-14 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 May 12, 1982 Information Notice No. 82-14: TMI-1 STEAM GENERATOR/REACTOR COOLANT SYSTEM CHEMISTRY/CORROSION PROBLEM Addressees: All nuclear power reactor facilities holding an operating license (OL) or construction permit (CP). Purpose: This information notice is provided as a notification of an event that may have safety significance. It is expected that recipients will review the information for applicability to their facilities. No specific action or response is required at this time. Description of Circumstances: During a long-term cold shutdown, radioactivity was detected in the secondary side of both steam generators at Three Mile Island (TMI), Unit 1. Subsequent examinations and testing of the steam generators has revealed corrosion damage to thousands of the steam generator tubes and primary to secondary leakage at more than 100 tubes. Chemical analysis of the reactor coolant revealed the presence (approaching 1 ppm) of sulfur compounds, which in some reduced forms can cause rapid corrosion of some reactor coolant system materials, including steam generator tubing. Although the exact cause of the corrosion is still under investigation, preliminary indications are that a sulfur compound was inadvertently introduced into the reactor coolant system during the outage. Since this type of corrosion is particularly aggressive, even during cold conditions, the licensee has deemed it advisable to conduct an examination of reactor coolant materials throughout the primary system. Discussion: Current pressurized water reactor plant standard technical specifications require periodic sampling of the reactor coolant for chloride and fluoride during cold shutdown or refueling. Typically, many PWRs also monitor pH and conductivity under these conditions. This analysis indicates an impurity by a mismatch between measured pH and conductivity when compared with predicted pH and conductivity characteristic of the amount of boric acid and base additive which is present. When any of the above conditions exist, it is advisable to perform further analyses to determine what impurities are present which will facilitate appropriate corrective measures. . IN 82-14 May 12, 1982 Page 2 of 2 In the case discussed above, chemistry data are still being reviewed, so it cannot yet be concluded that the normal reactor coolant chemistry analyses would have indicated the problem. Four potential sources for sulfur introduction are being reviewed. These include: 1. Inadvertent addition of sulfuric acid to the reactor coolant chemical addition tank as a personnel error via the waste neutralization tank. 2. System or operator malfunction to introduce sodium thiosulfate (present in tanks on site from past application as a containment spray additive). 3. Release of ion exchange resins which have a sulfonic base, from letdown or makeup systems. 4. Malfunction of the makeup system ion exchange regeneration process which utilizes sulfuric acid. If you have any questions regarding this matter, please contact the Regional Administrator of the appropriate NRC Regional Office, or this office. Sincerely, Edward L Jordan, Director Division of Engineering and Quality Assurance Office of Inspection and Enforcement Technical Contact: T. E. Chapman 301-492-4550 Attachment: Recently issued IE Information Notices
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021