United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-04, Supplement 1: Inadequate Qualification and Documentation of Fire Barrier Penetration Seals

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

                                 August 9, 1988

                                                 DOCUMENTATION OF FIRE BARRIER
                                                 PENETRATION SEALS 


All holders of operating licenses or construction permits for nuclear power 


This information notice supplement is being provided to alert addressees to 
problems caused by potential misapplication of silicone foam material used in 
penetration openings at nuclear power plants.  It is expected that recipients 
will review the information for applicability to their facilities and consider 
actions, as appropriate, to avoid similar problems.  However, suggestions con-
tained in this information notice do not constitute NRC requirements; 
therefore, no specific action or written response is required.  

Description of Circumstances:

Diablo Canyon.  Since August 9, 1979, Diablo Canyon has experienced four fires 
in which the penetration seal material ignited and burned:  

�    On May 10, 1988, during the performance of a diesel generator 24-hour 
     load test, the Dow Corning silicone foam material, through which the 
     diesel generator exhaust pipe passes, caught fire.  The penetration 
     design provides for isolation of the foam from the pipe by metal-clad 
     insulation.  This insulation was degraded by the pressure oscillations 
     from repeated thermal expansion and contraction of the pipe.  The 
     licensee observed dense smoke and two-to three-foot flames coming from 
     the penetration seal material.  

�    On February 11, 1983, after 1.7 hours of diesel engine operation, the 
     penetration seal material for another diesel generator exhaust pipe was 
     involved in rapid combustion.  

�    On September 21, 1982, during a diesel generator 24-hour load test, the 
     penetration seal material burned under similar circumstances.  One mea-
     surement with a pyrometer indicated that the exhaust pipe temperature was 
     about 600�F.  

.                                                       IN 88-04, Supplement 1
                                                       August 9, 1988
                                                       Page 2 of 3

�    On August 9, 1979, the penetration seal material burned under similar 

Davis-Besse.  On March 25, 1986, the licensee, Toledo Edison, reported that 
the silicone foam sealant in a fire barrier penetration in the main steam line 
room appeared to have baked and pulled away from the pipe (Licensee Event 
Report 50-346/86-17).  This penetration was filled with low-density silicone 
foam (SF-20), which is rated for a maximum temperature of 425�F.  The main 
steam lines normally operate near 600�F.  The licensee's corrective actions 
were to stuff ceramic fiber (Kaowool) into the seal for increased fire 
resistance and to expand the existing fire watch.  The licensee determined 
that a high-temperature boot seal could not be properly installed because of 
interferences.  The licensee revised the fire barrier penetration test from a 
check that a seal is intact to a comparison of an as-built seal to a 
fire-tested seal configuration.  


The NRC requirements and guidelines for fire barrier penetration seals are 
contained in various documents, including Appendix R to 10 CFR 50, Appendix A 
to Branch Technical Position (BTP) APCSB 9.5-1, "Guidelines for Fire 
Protection for Nuclear Power Plants Docketed Prior to July 1, 1976," and 
NUREG-0800, Standard Review Plan.  These requirements and guidelines are 
summarized in Appendix A of Information Notice No. 88-04, "Inadequate 
Qualification and Documentation of Fire Barrier Penetration Seals."  In 
addition, as stated in Section D.1 (I) of Appendix A to BTP APCSB 9.5-1, 
"Interior wall and structural components, thermal insulation materials and 
radiation shielding materials and sound-proofing should be noncombustible."  

The silicone foam seal material in the diesel generator exhaust pipe penetra-
tions at Diablo Canyon was used as replacement material for the combustible 
foam plastic-type seals, which were involved in the 1975 fire at the Browns 
Ferry nuclear power plant.  In addition to diesel generator exhaust pipe 
penetrations, some main steamline penetrations may be sealed with this ma-
terial.  The material is apparently designed to withstand maximum ambient 
temperatures of 400�F and temporary exposure to 500�F, but not long-term 
exposure to higher temperatures.  Although the measurement at Diablo Canyon in 
1982 indicated a pipe temperature of about 600�F, average pipe temperatures 
are probably much higher.

The licensee for Diablo Canyon determined that only six penetrations (all 
associated with diesel generator exhaust pipes) potentially exposed the sili-
cone foam penetration seal material to high temperatures.  For these penetra-
tion openings, the licensee plans to install a penetration seal material 
designed to withstand long-term exposure to high temperatures.

This subject is also discussed in Information Notice No. 88-56, "Potential 
Problems With Silicone Foam Fire Barrier Penetration Seals."  The present 
notice is being issued separately to highlight the potential misapplication 
.                                                       IN 88-04, Supplement 1
                                                       August 9, 1988
                                                       Page 3 of 3

of silicone foam sealant material for uses in which the sealant must withstand 
significant exposure to high temperature.  Information Notice No. 88-56 
focuses on nonconforming conditions of silicone foam sealing materials that 
have been found in inspections of fire barriers.  

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 techni-
cal 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:  Chuck Ramsey, RV
                     (415) 943-3767

                     Dennis Kubicki, NRR
                     (301) 492-0825

Attachment:  List of Recently Issued NRC Information Notices
.                                                       Attachment
                                                       IN 88-04, Supplement 1
                                                       August 9, 1988
                                                       Page 1 of 1

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

88-59          Main Steam Isolation Valve    8/9/88         All holders of OLs
               Guide Rail Failure at                        or CPs for nuclear
               Waterford Unit 3                             power reactors. 

88-58          Potential Problems with       8/8/88         All holders of OLs
               ASEA Brown Boveri ITE-51L                    or CPs for nuclear
               Time-Overcurrent Relays                      power reactors. 

88-57          Potential Loss of Safe        8/8/88         All holders of OLs
               Shutdown Equipment Due to                    or CPs for nuclear
               Premature Silicon Controlled                 power reactors. 
               Rectifier Failure 

88-56          Potential Problems with       8/4/88         All holders of OLs
               Silicone Foam Fire Barrier                   or CPs for nuclear
               Penetration Seals                            power reactors. 

88-55          Potential Problems Caused     8/3/88         All holders of OLs
               by Single Failure of an                      or CPs for nuclear
               Engineered Safety Feature                    power reactors. 
               Swing Bus 

88-54          Failure of Circuit Breaker    7/28/88        All holders of OLs
               Following Installation of                    or CPs for nuclear
               Amptector Direct Trip                        power reactors. 

88-53          Licensee Violations of NRC    7/28/88        All manufacturers 
               Regulations, Which Led to                    and distributors 
               Medical Diagnostic                           of radio-
               Misadministrations                           pharmaceuticals 
                                                            for human use, 
                                                            pharmacies, and 
                                                            medical licensees.

88-52          Failure of Intrauterine       7/27/88        Medical licensees.
               Tandem of Fletcher 
               Applicator Brachytherapy 
               Devices During Patient 
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Friday, May 22, 2015