United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-35: Fire in Compressible Material at Dresden Unit 3

                                                           SSINS No:  6835 
                                                           IN 86-35        

                                UNITED STATES
                           WASHINGTON, DC 20555

                                May 15, 1986

                                   UNIT 3 


All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP) 


This notice is being issued to advise recipients of the circumstances 
surrounding a fire which occurred at Dresden Unit 3 on January 20, 1986 It 
is expected that recipients will review the information for applicability to
their facilities and consider actions, if appropriate, to determine whether 
a similar fire hazard exists at their facilities No specific action or 
response is required by this notice 

Description of Circumstances: 

Dresden Unit 3 is a 773 MWe BWR with a typical "light bulb" Mark I drywell, 
which includes a free-standing steel containment vessel A reinforced 
concrete shield wall surrounds the containment vessel To allow for thermal 
and pressure expansion and contraction under design-basis conditions, an 
annular space of about 2 inches is provided between the vessel and the 
shield wall After the vessel was erected and pressure tested, a composite 
urethane foam and fiberglass sheet was glued to the external surfaces of the 
vessel This method of application provides a compressible fill in the space 
between the vessel and the concrete to ensure that adequate freedom for 
motion is maintained 

Dresden Unit 3 is replacing certain pipe that is part of the reactor coolant
pressure boundary In connection with this work, a pipe which penetrates the
shield wall was being removed using a arc-air cutting technique The sleeve 
in the shield wall through which the pipe passes slopes downward from the 
outside; hot slag from the pipe cutting inadvertently ran through the sleeve
and contacted the urethane foam The small fire which started was thought to
have been promptly extinguished 

Some time later, personnel working inside the drywell noted that the inner 
surface of the vessel was heated by a continuing fire such that the paint 
was discolored in sizeable local areas The station fire brigade reviewed 
plant records and identified the presence of the combustible foam in the 
annular space Water was applied through the penetration where the fire 

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                                                            May 15, 1986  
                                                            Page 2 of 2   

started as well as through adjacent penetrations The temperature of the 
inside surface of the steel drywell was monitored and was determined to have
returned to normal about 12 1/2 hours after the fire was first detected 


The licensee is committed to provide to the NRC an extensive evaluation of 
damage that may have been done by the fire and the repairs (if any) that may
be required, the methods of accomplishment, the consequences of a recurrence
of a fire in this or any similar space where a significant fraction of the 
local volume may be occupied by combustible foam, and methods of detection 
and suppression of any potential future fire The NRC also has requested 
that the licensee consider and discuss the matter of conformance to Appendix 
R of 10 CFR 50 When the requested information is received the NRC will 
consider whether further action is required 

The reactor was shut down and defueled at the time of the fire, and 
resolution of NRC concerns will be required before restart The event is 
discussed in greater detail in NRC Inspection Report No 56-249/86006 

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

                              Edward L Jordan, Director 
                              Division of Emergency Preparedness 
                                and Engineering Response 
                              Office of Inspection and Enforcement 

Technical Contact:  James Henderson, IE 
                    (301) 492-9654 

Attachment:    List of Recently Issued IE Information Notices 

*NRC Inspection Report 50-249/86006 (DRSS), available for review at the NRC 
Public Document Room, 1717 H St NW, Washington, DC; the NRC Local Document 
Room, Morris Public Library, 604 Liberty St, Morris, IL 60450; and the NRC 
Region III Document Room, 799 Roosevelt Road, Glen Ellyn, IL 60137 

Page Last Reviewed/Updated Friday, May 22, 2015