Information Notice 1997-73, Fire Hazard in Use of a Leak Sealant
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
September 23, 1997
NRC INFORMATION NOTICE 97-73: FIRE HAZARD IN THE USE OF A
LEAK SEALANT
Addressees
All holders of operating licenses for nuclear power reactors except those who have
permanently ceased operations and have certified that fuel has been permanently removed
from the reactor vessel.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert
addressees to a potential fire hazard in the use of a leak sealant. 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 contained in this information
notice are not NRC requirements; therefore, no specific action or written response is
required.
Description of Circumstances
Discussion
On July 15, 1997 a steam leak in a main steam isolation valve (MSIV) at Unit 2 of the South
Texas Project plant was being repaired by injecting a leak sealant. The people performing
the work had reached a stopping point to let the injected compounds firm up to create the
seal. The work team left the cubicle in which the work was being performed in order to cool
off, the temperature in the cubicle being too high to allow them to stay there. A patrolling
security guard entered the cubicle and noticed a small flame on the valve. Appropriate
personnel were notified and the flame was put out with a fire extinguisher.
The compounds used to seal the leak were approved products for the application and are in
common use in the industry. Mineral oil is one of the material components of the compound.
When the compound is injected under pressure and gets hot, the mineral oil tends to
separate from the rest of the compound, becoming more fluid and starting to leak out
wherever it can find a path. The leakage may be either as a liquid or as a vapor (smoke)
due to the high temperature.
In this event, the mineral oil leaked out from the sealant-retaining damp as a liquid and
soaked into the fiberglass insulation around the valve. The "wicking" effect from the
penetration into the insulation caused the auto-ignition temperature of the mineral oil to be
PRQ ro-e OCT I t
1-OV 95O3 q q 01 X?
IN 97-73 September 23, 1997 lowered sufficiently to ignite the oil and produce small flames on the insulation pad. Porous
materials, such as blanket-type insulation, exhibit a wicking effect when exposed to a
combustible liquid. When the impregnated insulation is exposed to elevated temperatures, the combustible liquid (in this case mineral oil) may spontaneously ignite even though the
temperature is below the published auto-ignition temperature of the combustible liquid. An
outside ignition source is not required for combustion to occur in oil-soaked insulation.
Auto-ignition temperature is the temperature at which combustion will occur without an
outside ignition source. The flash point is the lowest temperature at which the vapor of a
combustible liquid can be made to ignite momentarily in air, i.e., will bum as long as an open
flame is present and will not continue to bum if the flame is removed. Wicking action actually
lowers the surrounding vapor pressure which results in the lowering of the auto -- :'ion
temperature.
Spontaneous ignition of oil-soaked insulation can occur under the following conditions:
-
the liquid is insufficiently volatile to evaporate rapidly,
-
the insulation is sufficiently porous to allow oxygen to diffuse to the surface of the
absorbed liquid, and
-
the oil leak is slow enough that the pores of the insulation are not blocked so that
oxygen is not excluded from the high-temperature region.
The South Texas Project licensee has taken steps to preclude repetition of this event.
Revisions to engineering standards incorporate information about sealing compounds with
greater-than-minimal percentage of mineral oil and appropriate temperature limitations. Work
instructions related to on-line leak repair activities contain requirements to:
-
ensure that insulation and other materials that may cause a wicking effect are
removed from the work area,
-
ensure that a fire watch is established during work activities and for an hour after work
is complete, and
-
provide adequate ventilation to assist in disbursement of vapors.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Geoffrey P. Homseth, NRR
Joseph I. Tapia, Region IV
301-415-2756
(817) 860-8243 E-mail: gph@nrc.gov
E-mail: jit@nrc.gov
Attachment: List of Recentl Issued NRC Information Notices
Attachment
September 23, 1997 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
97-72
97-71
97-70
97-69
Potential for Failure
of the Omega Series
Sprinkler Heads
Inappropriate Use of
10 CFR 50.59 Regarding
Reduced Seismic Criteria
for Temporary Conditions
Potential Problems with
Seals
Reactor Trip Breakers
and Surveillance Testing
of Auxiliary Contacts
09/22/97
09/22/97
09/19/97
All holders of OLs or
CPs for nuclear power
reactors and fuel
cycle facilities
All holders of OLs for
nuclear power reactors
except those who have
permanently ceased
operations and have
certified that fuel
has been permanently
removed from the
reactor vessel
All holders of OLs for
nuclear power reactors
except those who have
permanently ceased
operations and have
certified that fuel has
been permanently removed
from the reactor vessel
All holders of OLs for
pressurized water reactors
except those who have per- manently ceased operations
and have certified that
fuel has been permanently
removed from the reactor
vessel
.
09/19/97 OL = Operating License
CP = Construction Permit
IN 97-73 KJ; September 23, 1997 lowered sufficiently to Ignite the oil and produce small flames on the insulation pad. Porous
materials, such as blanket-type insulation, exhibit a wicking effect when exposed to a
combustible liquid. When the impregnated insulation is exposed to elevated temperatures, the combustible liquid (in this case mineral oil) may spontaneously ignite even though the
temperature is below the published auto-ignition temperature of the combustible liquid. An
outside ignition source is not required for combustion to occur in oil-soaked insulation.
Auto-ignition temperature Is the temperature at which combustion will occur without an
outside ignition source. The flash point is the lowest temperature at which the vapor of a
combustible liquid can be made to ignite momentarily in air, i.e., will bum as long as an open
flame is present and will not continue to bum if the flame is removed. Wicking action actually
lowers the surrounding vapor pressure which results in the lowering of the auto-ignition
temperature.
Spontaneous ignition of oil-soaked insulation can occur under the following conditions:
-
the liquid is insufficiently volatile to evaporate rapidly,
-
the insulation is sufficiently porous to allow oxygen to diffuse to the surface of the
absorbed liquid, and
-
the oil leak is slow enough that the pores of the insulation are not blocked so that
oxygen is not excluded from the high-temperature region.
The South Texas Project licensee has taken steps to preclude repetition of this event.
Revisions to engineering standards incorporate information about sealing compounds with
greater-than-minimal percentage of mineral oil and appropriate temperature limitations. Work
instructions related to on-line leak repair activities contain requirements to:
-
ensure that insulation and other materials that may cause a wicking effect are
removed from the work area,
-
ensure that a fire watch is established during work activities and for an hour after work
is complete, and
-
provide adequate ventilation to assist in disbursement of vapors.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
original signed by D.B. Matthews for
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Geoffrey P. Homseth, NRR
Joseph I. Tapia, Region IV
301-415-2756
(817) 860-8243 E-mail: gph@nrc.gov
E-mail: jit@nrc.gov
DOCUMENT NAME: 97-73.1N
- SEE PREVIOUS CONCURRENCES
Attachment: List of Recently Issued NRC Information Notices
Tech Editor 08/26/97 OFC
PECB:DRPM
C:EMCBlDE
(A)C:PECB
(A)D:DRPM
NAME
RBenedict*
JStrosnider*
RDennig*
JRO
GHomseth*
____ ___
JTapia*_
_
_
_
_
_
_
_
DATE
08/28/97
09/03/97
09/08197
//I/97
[IOFFICIAL RECORD COPY]
IN 97-xx
/
September xx, 1997 lowered sufficiently to ignite the oil and produce small flames on the insulation pad. Porous
materials, such as blanket-type insulation, exhibit a wicking effect when exposed to a
combustible liquid. When the impregnated insulation is exposed to elevated temperatures, the combustible liquid (in this case mineral oil) may spontaneously ignite even though the
temperature is below the published auto-ignition temperature of the combustible liquid. An
outside ignition source Is not required for combustion to occur in oil-soaked insulation.
Auto-ignition temperature Is the temperature at which combustion will occur without an
outside ignition source. The flash point is the lowest temperature at which the vapor of a
combustible liquid can be made to ignite momentarily in air, i.e., will bum as long as an open
flame is present and will not continue to bum if the flame is removed. Wicking action actually
lowers the surrounding vapor pressure which results in the lowering of the auto-ignition
temperature.
Spontaneous ignition of oil-soaked insulation can occur under the following conditions:
-
the liquid is insufficiently volatile to evaporate rapidly,
-
the insulation is sufficiently porous to allow oxygen to diffuse to the surface of the
absorbed liquid, and
-
the oil leak is slow enough that the pores of the insulation are not blocked so that
oxygen is not excluded from the high-temperature region.
The South Texas Project licensee has taken steps to preclude repetition of this event.
Revisions to engineering standards incorporate information about sealing compounds with
greater-than-minimal percentage of mineral oil and appropriate temperature limitations. Work
instructions related to on-line leak repair activities contain requirements to:
-
ensure that insulation and other materials that may cause a wicking effect are
removed from the work area,
-
ensure that a fire watch is established during work activities and for an hour after work
is complete, and
-
provide adequate ventilation to assist In disbursement of vapors.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Geoffrey P. Homseth
Joseph I. Tapia, Region IV
301-415-2756
(817) 860-8243 E-mail: gphenrc.gov
E-mail: jit@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\RABlSEALFIRE.IN
- SEE PREVIOUS CONCURRENCES
OFC
PECB:DRPM
C:EMCB/DE
(A)C:PECB
(A)D:DRPM
NAME
RBenedict*
JStrosnider
RDennig*
JRoe
GHomseth*
JTapia*
DATE
08/28/97
09/03/97
09/08/97 I /97 FUICHIAL KRUUU L;UIJ
At
9*1?7
- .7-xx
September xx, 1997 temperature is below the published auto-ignition temperature of the combustible liquid. An
outside ignition source is not required for combustion to occur in oil-soaked insulation.
Auto-ignition temperature is the temperature at which combustion will occur without an
outside ignition source. The flash point is the lowest temperature at which the vapor of a
combustible liquid can be made to ignite momentarily in air, i.e., will bum as long as an open
flame is present and will not continue to bum if the flame is removed. Wicking action actually
lowers the surrounding vapor pressure which results in the lowering of the auto-ignition
temperature.
Spontaneous ignition of oil-soaked insulation can occur under the following conditions:
-
the liquid is insufficiently volatile to evaporate rapidly,
-
the insulation is sufficiently porous to allow oxygen to diffuse to the surface of the
absorbed liquid, and
-
the oil leak is slow enough that the pores of the insulation are not blocked so that
oxygen is not excluded from the high-temperature region.
The South Texas Project licensee has taken steps to preclude repetition of this event.
Revisions to engineering standards incorporate information about sealing compounds with
greater-than-minimal percentage of mineral oil and appropriate temperature limitations. Work
instructions related to on-line leak repair activities contain requirements to:
-
ensure that insulation and other materials that may cause a wicking effect are
removed from the work area,
-
ensure that a fire watch is established during work activities and for an hour after work
is complete, and
-
provide adequate ventilation to assist in disbursement of vapors.
This information notice requires no specific action or written response. If you have any
questions about the information in this notice, please contact one of the technical contacts
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Jack W. Roe, Acting Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Geoffrey P. Homseth
Joseph I. Tapia, Region IV
301-415-2756
817-860-8243 E-mail: gph@nrc.gov
E-mail: jit@nrc.gov
Attachment: List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\RAB1\\SEALFIRE.IN
OFC
PECB:DRPM
C:EMCBIDE
(A)C:
(A)D:DRPM
NAME
R~enedh
e
RD yni
JRoe
GHOms th~f
~
e
JTapia
__
_
__
_
__
_
DATE
4 /*97
/3 /97
4' /97
1 /97
[OFFICIAL RECO RD COPY]