United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 81-38: Potentially Significant Equipment Failures Resulting from Contamination of Air-Operated Systems

                                                           SSINS No.: 6835 
                                                           Accession No.: 
                                                           8107230040 
                                                           IN 81-38 

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C.  20555

                              December 17, 1981


Information Notice No.  81-38:  POTENTIALLY SIGNIFICANT EQUIPMENT 
                                   FAILURES RESULTING FROM CONTAMINATION OF 
                                   AIR-OPERATED SYSTEMS 

Description of Circumstances: 

The NRC has reviewed a number of problems related to contamination of air 
systems in operating nuclear plants.  The review indicates that air-operated
components and systems will occasionally become inoperable because they are 
contaminated with oil, water, desiccant, and rust or other corrosion 
products.  The recent instances of inoperable air-operated components 
occurred at the following facilities: 

1.   Palisades Nuclear Station - July 1981, an air-operated control valve 
     failed to stay open.  This resulted in both residual heat removal (RHR)
     trains becoming inoperable.  The failure was attributed to the 
     accumulation of water at the lowest point of the air system lines which
     coincided with the valve location (LER 81-030). 

2.   Rancho Seco Nuclear Station - On July 7, 1981, a pneumatically operated
     globe valve failed to close within the time required by the technical 
     specification.  Investigation revealed the presence of desiccant at the
     air discharge port (LER 81-037). 

3.   Zion Nuclear Station Unit Number 2 - On May 9, 1980, the containment 
     air sample valve failed to close during the monthly containment 
     isolation operability test.  The valve failed to close because of oil 
     contamination of the instrument air lines (LER 80-018). 

4.   San Onofre Nuclear Station Unit Number 1 - On February 4, 1980, the 
     isolation valve for service water to containment failed to close while 
     performing a containment isolation valve test.  The failure of the 
     instrument air filters allowed small particles of desiccant to enter 
     the air lines.  This prevented the solenoid air control valve from 
     operating (LER 80-003). 

No adverse impact on the health and safety of the public has been attributed
to the events listed above.  However, the potential for common mode failure,
combined with the observed frequency of air service related events, 
indicates that added attention to air system reliability is warranted. 
.

                                                           IN 81-38 
                                                           December 17, 1981
                                                           Page 2 of 2 

IE Circular 81-14, "Main Steam Isolation Valve Failures to Close," 
recommended that the holders of operating licenses and construction permits 
review their air systems to assure that measures are taken to prevent air 
quality degradation in the future. 

Listed below are some of the actions known to minimize air system problems: 

1.   Frequent monitoring of the dew point of the instrument air. 

2.   Periodic checking of the desiccant and regeneration or replacement as 
     needed. 

3.   Periodic blowdown of lines to remove oil, moisture, and crud in the 
     instrument air system. 

4.   Periodic inspection of filters downstream of the desiccant cartridges 
     to ascertain that the desiccant has not been pulverized to the point 
     that it is escaping from the cartridge and possibly clogging the 
     filters. 

5.   Avoiding the use of service air as a backup to the instrument air 
     system when alternative backups are available. 

6.   Frequent monitoring of the instrument air system to ensure that it has 
     not been contaminated with oil, moisture, or crud when service air has 
     been used as a backup to the instrument air system. 

This information notice is provided as an early notification of a possibly 
significant matter.  It is expected that recipients will review the 
information for possible applicability to their facilities.  No specific 
action or response is requested at this time. 

If you have any questions regarding this matter, please contact the Regional
Administrator of the appropriate NRC Regional Office. 

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