Information Notice No. 89-26: Instrument Air Supply to Safety-Related Equipment

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                             WASHINGTON, D.C.  20555

                                  March 7, 1989



All holders of operating licenses or construction permits for nuclear power 


This information notice is being provided to alert addressees of instrument 
air inadequacies identified by licensees in response to Generic Letter 88-14, 
"Instrument Air Supply System Problems Affecting Safety-Related Equipment," 
dated August 8, 1988.  It is expected that recipients will review the infor-
mation for applicability to their facilities and consider actions, as appro-
priate, to avoid similar problems.  However, suggestions contained in this 
information notice do not constitute NRC requirements; therefore, no specific 
action or written response is required.

Description of Circumstances:

During a review of the instrument air supply to safety-related equipment, as
requested by Generic Letter 88-14, the Boston Edison Company, licensee for 
Pilgrim Nuclear Power Station, discovered two design inadequacies.  These 
problems affect the integrity of the secondary containment and the primary 

On December 22, 1988, during leak rate testing of the secondary containment, 
the standby gas treatment system was unable to achieve the 0.25-inch water 
vacuum required by the technical specifications because of in-leakage of 
outside air past the inner door of the reactor building trucklock (RBTL).  
The test was being conducted with revised procedures as a result of the 
review requested by Generic Letter 88-14.  The new procedures required the 
test to be conducted with the RBTL outer door open and the RBTL inner door 
closed, but with the inner door's inflatable seal deflated.  Since the plant 
began operating in 1972, previous leak rate testing had been performed with 
the inner door seal inflated by the non-safety-related instrument air system 
and with the non-seismically qualified RBTL outer door closed.

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                                                            March 7, 1989
                                                            Page 2 of 3

The licensee's corrective action involved installing a non-inflatable-type 
rubber gasket to the RBTL inner door frame, which allowed subsequent successful 
completion of the leak rate test.

The same problem of relying on the non-  safety-related instrument air system 
to inflate seals on doors to maintain the integrity of the secondary contain-
ment was identified at Vermont Yankee Nuclear Power Station and Fermi Atomic 
Power Plant, Unit 2, on January 4, 1989, and February 8, 1989, respectively.

The second design inadequacy at the Pilgrim station was discovered on 
January 10, 1989.  The containment isolation valves in the torus-to-reactor 
building vacuum breaker lines, which are redundant to the torus vacuum 
breakers, use instrument air pressure to maintain the valves in the closed 
position.  Upon loss of air pressure, these valves are designed to open to 
allow the vacuum breakers to perform their safety function of preventing 
containment implosion.  When the valves fail open, the isolation function 
of the valves is lost.  At Pilgrim the design requires an adequate supply 
of air pressure to the vacuum breaker isolation valves for 30 days if the 
instrument air system fails.  The licensee for Pilgrim determined by a test 
that the air supply provided by the safety-related accumulators would be 
depleted in less than 1 hour, resulting in the loss of one of the two con-
tainment isolation barriers.  To correct this situation, the licensee 
installed additional larger qualified accumulators and a qualified air line 
that connects to pressurized air bottles.  Portable air bottles can be 
connected to the air line to provide adequate air pressure if needed for the 
long term requirement.  The licensee also instituted surveillance to ensure 
that acceptable accumulator air pressure will be maintained for at least 24 

Similar problems involving the use of non-safety-related instrument air 
systems affecting the integrity of the primary containment have been 
discovered at Oyster Creek Nuclear Power Plant on February 8, 1989, and at 
Browns Ferry Nuclear Power Station, Units 1, 2, and 3, on January 31, 1989.  
At Oyster Creek, the licensee determined that the air accumulators to the main 
steam isolation valves would rapidly depressurize if the normal 
non-safety-related air supply was interrupted.  At Browns Ferry, the 
instrument air system would be relied on without accumulators during a 
design-basis accident to provide the air pressure for the containment 
isolation valves in the suppression pool vacuum relief lines to maintain the 
valves in the closed position. 

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                                                            March 7, 1989
                                                            Page 3 of 3

No specific action or written response is required by this information 
notice.  If you have any questions about this matter, please contact one of 
the technical contacts listed below or the Regional Administrator of the 
appropriate regional office.

                                   Charles E. Rossi, Director
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation

Technical Contacts:  T. Silko, AEOD
                     (301) 492-9059

                     T. Greene, NRR
                     (301) 492-1176

                     J. Lyash, RI
                     (215) 337-5132

Attachment:  List of Recently Issued NRC Information Notices     
.                                                            Attachment 
                                                            IN 89-26
                                                            March 7, 1989
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                             NRC INFORMATION NOTICES
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to________

89-25          Unauthorized Transfer of      3/7/89         All U.S. NRC source,
               Ownership or Control of                      byproduct, and 
               Licensed Activities                          special nuclear 
                                                            material licensees

89-24          Nuclear Criticality Safety    3/6/89         All fuel cycle
                                                            licensees and other
                                                            possessing more 
                                                            than critical 
                                                            mass quantities of
                                                            special nuclear 

89-23          Environmental Qualification   3/3/89         All holders of OLs
               of Litton-Veam CIR Series                    or CPs for nuclear
               Electrical Connectors                        power reactors.

89-22          Questionable Certification    3/3/89         All holders of OLs
               of Fasteners                                 or CPs for nuclear
                                                            power reactors.

89-21          Changes in Performance        2/27/89        All holders of OLs
               Characteristics of Molded-                   or CPs for nuclear
               Case Circuit Breakers                        power reactors.

88-73,         Direction-Dependent Leak      2/27/89        All holders of OLs
Supplement 1   Characteristics of Contain-                  or CPs for nuclear
               ment Purge Valves                            power reactors.

89-20          Weld Failures in a Pump       2/24/89        All holders of OLs
               of Byron-Jackson Design                      or CPs for nuclear
                                                            power reactors.

89-19          Health Physics Network        2/23/89        All holders of OLs
                                                            or CPs for nuclear
                                                            power reactors, and
                                                            the following fuel
                                                            Nuclear Fuel 
                                                            Services of Erwin, 
                                                            General Atomic, UNC
                                                            Montville, B&W LRC
                                                            Lynchburg, and B&W
OL = Operating License
CP = Construction Permit 

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