United States Nuclear Regulatory Commission - Protecting People and the Environment

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 

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