Information Notice No. 86-35: Fire in Compressible Material at Dresden Unit 3
SSINS No: 6835
IN 86-35
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, DC 20555
May 15, 1986
Information Notice No. NO 86-35: FIRE IN COMPRESSIBLE MATERIAL AT DRESDEN
UNIT 3
Addressees:
All nuclear power reactor facilities holding an operating license (OL) or a
construction permit (CP)
Purpose:
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
apparently
IN 86-35
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
Discussion:
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
(DRSS)*
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
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