Information Notice 1996-36, Degradation of Cooling Water Systems Due to Icing: Difference between revisions

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{{#Wiki_filter:"JUNITED STATESNUCLEAR REGULATORY COMMISSIONOFYFICE OF NUCLEAR REACTOR REGULATION-WASHINGTON, DC 20555-0001June 12, 1996NRC INFORMATION NOTICE 96-36: DEGRADATION OF COOLING WATER SYSTEMS DUE TOICING
{{#Wiki_filter:"J UNITED STATES NUCLEAR REGULATORY
 
COMMISSION
 
===OFYFICE OF NUCLEAR REACTOR REGULATION===
-WASHINGTON, DC 20555-0001 June 12, 1996 NRC INFORMATION
 
NOTICE 96-36: DEGRADATION
 
OF COOLING WATER SYSTEMS DUE TO ICING


==Addressees==
==Addressees==
All holders of operating licenses or construction permits for nuclear powerreactors.
All holders of operating
 
licenses or construction
 
permits for nuclear power reactors.


==Purpose==
==Purpose==
The U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to potential degradation of facility water intakesystems (circulating, service, and fire water) due to icing conditions.It is expected that recipients will review the information for applicabilityto their facilities and consider actions, as appropriate, to avoid similarproblems. However, suggestions contained in this information notice are notNRC requirements; therefore, no specific action or written response isrequired.
The U.S. Nuclear Regulatory
 
Commission (NRC) is issuing this information
 
notice to alert addressees
 
to potential
 
degradation
 
of facility water intake systems (circulating, service, and fire water) due to icing conditions.
 
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
 
Wolf Creek Between 1:45 a.m. and 2:45 a.m. (all times central standard time) on January 30, 1996, operators
 
at Wolf Creek received alarms indicating
 
that the circulating
 
water system traveling
 
screens were becoming blocked. A visual inspection
 
showed that the traveling
 
screens for bays 1 and 3 were frozen and that water levels in these bays were approximately
 
2.5 m [8 ft] below normal.The emergency
 
service water system was started with the intent to separate this system from the service water system. However, the emergency
 
service water system was incorrectly
 
aligned; flow was directed to the service water system and warming flow to the emergency
 
service water system suction bays was restricted.
 
Operators
 
also shifted to circulating
 
water pump B. At approxi-mately 3:30 a.m., operators
 
received a service water pressure alarm and an electric fire pump started on low service water pressure.
 
The shift super-visor then directed a manual reactor/turbine
 
trip. Circulating
 
water system bays were subsequently
 
determined
 
to be at 3.5 m [12 feet] below normal. The level loss was caused by water from the spray wash system freezing and block-ing the traveling
 
screens.The Train A emergency
 
service water system pump was tripped and declared inoperable
 
at 7:47 a.m. because of low discharge
 
pressure and high strainer differential
 
pressure.
 
At about 8:00 a.m., the supervising
 
operator coming on shift noted the incorrect
 
alignment
 
of the emergency
 
service water system and took action to correct it. At about 5:45 p.m., the operators
 
declared Train A'~P) C-FW 0f bla .pDR :t:-E moric6 6'sVOU 160612 '
1.'K)IN 96-36 June 12, 1996 operable on the basis of an engineering
 
evaluation
 
and placed it in service.However, the pump was again stopped 1-1/2 hours later at approximately
 
7:30 p.m. when the pump exhibited
 
further oscillations
 
in flow and pressure.At approximately
 
8:00 p.m., operators
 
noted that emergency
 
service water system Train B suction bay level was 4.5 m [15 ft] below normal and decreasing
 
slowly. Operators
 
placed additional
 
heat loads on Train B and the suction bay levels subsequently
 
recovered.
 
At 10:14 p.m., the operators
 
again started Train A emergency
 
service water system and secured it at 10:27 p.m. due to decreasing
 
flow and pressure.At about 10:00 a.m. on January 31, divers inspected
 
the suction bay of Train A and noted complete blockage of the trash racks by frazil ice. Train B was not inspected
 
because the pump was running. The ice blockage was cleared by 4:00 p.m. by sparging the trash racks with air. The emergency
 
service water system was designed to have warming flow injected in front of trash racks to increase bulk water temperature
 
and prevent the formation
 
of frazil ice. Due to calculational
 
errors by the architect-engineer
 
and the as-built system configuration, the emergency
 
service water system warming flow was insufficient
 
to prevent frazil ice from forming at the Train A trash racks.FitzPatrick
 
On February 25, 1993, at 1:25 a.m., the electric fire pump started on low fire header pressure.
 
After verifying
 
normal fire header pressure, operators secured the electric fire pump, and the diesel fire pumps subsequently
 
started on low header pressure.
 
It was later determined
 
that the fire jockey pump had lost suction because of the decreasing
 
screenwell
 
level.Over the next several minutes, operators
 
noted an increase in circulating
 
water system motor amperage (which is consistent
 
with decreased
 
suction pressure).
 
Reactor power was also reduced and one circulating
 
water pump was secured. At 1:40 a.m., an operator reported that the screenwell
 
level was approximately
 
3 m [10 ft] below normal and the reactor was manually scrammed.After a second circulating
 
water pump was subsequently
 
secured, the screenwell
 
water level quickly recovered.
 
The licensee concluded
 
that the reduced screenwell
 
level had been caused by ice partially
 
blocking the lake intake structure.
 
Either frazil ice formed around or in front of the heated intake bar racks, or slush ice was present in front of the bar racks.Fermi On February 5, 1996, at approximately
 
2:30 p.m., diesel generator
 
service water pump C failed to develop normal discharge
 
pressure, flow, and motor current during a surveillance.
 
This made Division I emergency
 
diesel generator (EDG) 12 inoperable.
 
After several unsuccessful
 
attempts to start the pump, an air purge of the pump column on the discharge
 
of the pump was initiated
 
in an attempt to clear any obstruction
 
in the column or the pump inlet. The licensee detected blockage when it tried to blow air through the pipe. At 8:21 p.m., the pump was started and after 3 to 5 seconds an erratic discharge
 
pressure was noted. In a short time, pump flow, discharge
 
pressure, and motor amps were normal. The following
 
day, on February 6, diesel generator
 
service water pump B was started. The pump, which cools Division II
 
K> < IN 96-36 June 12, 1996 EDG 13, showed no flow, no pressure, and low amperage for the first 30 seconds. After approximately
 
90 seconds, normal flow discharge
 
pressure and motor current were achieved.
 
The remaining
 
safety-related
 
pumps were tested satisfactorily.
 
The diesel generator
 
service water pumps are all deep-draft
 
pumps and take suction from the ultimate heat sink reservoir
 
which is a segregated
 
pool. The licensee evaluation
 
concluded
 
that although the reservoir
 
temperatures
 
are maintained
 
above 5 eC [41 OF], part of the pump column and two of the linear guide bearings are located above the water level and are exposed to ambient air temperature
 
conditions.
 
The failure of the diesel generator
 
service water pump C was attributed
 
to ice buildup around the shaft and spider bearing from leakage past the discharge
 
check valve and the cold weather. The licensee also concluded
 
that under some credible meteorological
 
conditions, the functions
 
of both divisions
 
could have been affected.Discussion
 
Frazil icing is a phenomenon
 
that affects the operation
 
of intake structures
 
in regions that experience
 
cold weather. The accumulation
 
of frazil ice on intake trash racks can completely
 
block the flow of water into the intake.The process starts when the water flowing into the intake is supercooled (a condition
 
where the water is below the freezing point). The supercooling
 
may be very small, on the order of a few hundredths
 
of a degree.The supercooling
 
occurs with a loss of heat from a large surface area such as a lake with open water and clear nights. High winds contribute
 
to the problem by providing
 
mixing of the supercooled
 
water to depths as great as 6 to 9 m[20 to 30 ft]. The frazil ice, which is composed of very small crystals (1-15 mm) with little buoyancy because of their size, is carried along in the water and mixed all through the supercooled
 
water.The suction of the supercooled
 
water and the suspended
 
frazil ice crystals through an intake structure
 
brings the frazil ice crystals in contact with the trash rack bars. Frazil ice crystals easily adhere to any object with which they collide. The ice collects first on the upstream side of the trash racks, then steadily grows until the space between the trash racks is bridged. This bridging rapidly blocks the trash racks. The accumulation
 
of ice can with-stand high differential
 
pressures;
effectively
 
damming the intake suction.Facility vulnerability
 
to icing events is a function of plant design. Frazil and other ice formation
 
is dependent
 
on specific environmental
 
conditions
 
and represents
 
a potential
 
common-mode
 
failure that can cause the loss or degrada-tion of multiple cooling water systems, including
 
the potential
 
loss of the ultimate heat sink.
 
IN 96-36 June 12, 1996 Related Information
 
NUREG/CR-0548, "Ice Blockage of Water Intakes." 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
 
project manager.I i -..--.....-.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
Contacts: John R. Tappert, NRR (301) 415-1167 Internet:jrtlnrc.gov
 
Bruce Jorgensen, RIII (708) 829-9615 Internet:blj@nrc.gov
 
Attachment:
List of Recently Issued NRC Information
 
Notices I k W (0%0%J4-c- -d I
 
K>Attachment
 
IN 96-36 June 12, 1996 LIST OF RECENTLY ISSUED NRC INFORMATION
 
NOTICES Information
 
Date of Notice No. Subject Issuance Issued to 96-35 Failure of Safety Systems on Self-Shielded
 
Irradia-tors Because of Inadequate
 
Maintenance
 
and Training Hydrogen Gas Ignition during Closure Welding of a VSC-24 Multi-Assembly
 
Sealed Basket 06/11/96 05/31/96 All U.S. Nuclear Regulatory
 
Commission
 
irradiator
 
licensees
 
and vendors All holders of OLs or CPs for nuclear power reactors 96-34 96-33 Erroneous Defective Results ii Data From Thermocouple
 
i a Fire 05/24/96 All material and fuel cycle licensees
 
that monitor tem-perature with thermocouples
 
96-32 96-31 96-30 Implementation
 
of 10 CFR 50.55a(g)(6)(ii)(A),"Augmented
 
Examination
 
of Reactor Vessel" Cross-Tied
 
Safety Injec-tion Accumulators
 
Inaccuracy
 
of Diagnostic
 
Equipment
 
for Motor-Operated Butterfly
 
Valves Requirements
 
in 10 CFR Part 21 for Reporting
 
and Evaluating
 
Software Errors Suggested
 
Guidance Relating to Development
 
and Imple-mentation
 
of Corrective
 
Action Potential
 
Clogging of High Pressure Safety Injection Throttle Valves During Recirculation
 
06/05/96 05/22/96 05/21/96 05/20/96 05/01/96 05/01/96 All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for pressurized
 
water reactors All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for nuclear power reactors All material and fuel cycle licensees All holders of OLs or CPs for pressurized
 
water reactors 96-29 96-28 96-27 OL -Operating
 
License CP = Construction
 
Permit
 
.I IN 96-36 June 12, 1996 Related Information
 
NUREG/CR-0548, "Ice Blockage of Water Intakes." 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


==Description of Circumstances==
contacts listed below or the appropriate
Wolf CreekBetween 1:45 a.m. and 2:45 a.m. (all times central standard time) onJanuary 30, 1996, operators at Wolf Creek received alarms indicating that thecirculating water system traveling screens were becoming blocked. A visualinspection showed that the traveling screens for bays 1 and 3 were frozen andthat water levels in these bays were approximately 2.5 m [8 ft] below normal.The emergency service water system was started with the intent to separatethis system from the service water system. However, the emergency servicewater system was incorrectly aligned; flow was directed to the service watersystem and warming flow to the emergency service water system suction bays wasrestricted. Operators also shifted to circulating water pump B. At approxi-mately 3:30 a.m., operators received a service water pressure alarm and anelectric fire pump started on low service water pressure. The shift super-visor then directed a manual reactor/turbine trip. Circulating water systembays were subsequently determined to be at 3.5 m [12 feet] below normal. Thelevel loss was caused by water from the spray wash system freezing and block-ing the traveling screens.The Train A emergency service water system pump was tripped and declaredinoperable at 7:47 a.m. because of low discharge pressure and high strainerdifferential pressure. At about 8:00 a.m., the supervising operator coming onshift noted the incorrect alignment of the emergency service water system andtook action to correct it. At about 5:45 p.m., the operators declared Train A'~P) C-FW 0f bla .pDR :t:-E moric6 6'sVOU 160612 '
1.'K)IN 96-36June 12, 1996 operable on the basis of an engineering evaluation and placed it in service.However, the pump was again stopped 1-1/2 hours later at approximately7:30 p.m. when the pump exhibited further oscillations in flow and pressure.At approximately 8:00 p.m., operators noted that emergency service watersystem Train B suction bay level was 4.5 m [15 ft] below normal and decreasingslowly. Operators placed additional heat loads on Train B and the suction baylevels subsequently recovered. At 10:14 p.m., the operators again startedTrain A emergency service water system and secured it at 10:27 p.m. due todecreasing flow and pressure.At about 10:00 a.m. on January 31, divers inspected the suction bay of Train Aand noted complete blockage of the trash racks by frazil ice. Train B was notinspected because the pump was running. The ice blockage was cleared by4:00 p.m. by sparging the trash racks with air. The emergency service watersystem was designed to have warming flow injected in front of trash racks toincrease bulk water temperature and prevent the formation of frazil ice. Dueto calculational errors by the architect-engineer and the as-built systemconfiguration, the emergency service water system warming flow wasinsufficient to prevent frazil ice from forming at the Train A trash racks.FitzPatrickOn February 25, 1993, at 1:25 a.m., the electric fire pump started on low fireheader pressure. After verifying normal fire header pressure, operatorssecured the electric fire pump, and the diesel fire pumps subsequently startedon low header pressure. It was later determined that the fire jockey pump hadlost suction because of the decreasing screenwell level.Over the next several minutes, operators noted an increase in circulatingwater system motor amperage (which is consistent with decreased suctionpressure). Reactor power was also reduced and one circulating water pump wassecured. At 1:40 a.m., an operator reported that the screenwell level wasapproximately 3 m [10 ft] below normal and the reactor was manually scrammed.After a second circulating water pump was subsequently secured, the screenwellwater level quickly recovered. The licensee concluded that the reducedscreenwell level had been caused by ice partially blocking the lake intakestructure. Either frazil ice formed around or in front of the heated intakebar racks, or slush ice was present in front of the bar racks.FermiOn February 5, 1996, at approximately 2:30 p.m., diesel generator servicewater pump C failed to develop normal discharge pressure, flow, and motorcurrent during a surveillance. This made Division I emergency dieselgenerator (EDG) 12 inoperable. After several unsuccessful attempts to startthe pump, an air purge of the pump column on the discharge of the pump wasinitiated in an attempt to clear any obstruction in the column or the pumpinlet. The licensee detected blockage when it tried to blow air through thepipe. At 8:21 p.m., the pump was started and after 3 to 5 seconds an erraticdischarge pressure was noted. In a short time, pump flow, discharge pressure,and motor amps were normal. The following day, on February 6, dieselgenerator service water pump B was started. The pump, which cools Division II


K> < IN 96-36June 12, 1996 EDG 13, showed no flow, no pressure, and low amperage for the first30 seconds. After approximately 90 seconds, normal flow discharge pressureand motor current were achieved. The remaining safety-related pumps weretested satisfactorily.The diesel generator service water pumps are all deep-draft pumps and takesuction from the ultimate heat sink reservoir which is a segregated pool. Thelicensee evaluation concluded that although the reservoir temperatures aremaintained above 5 eC [41 OF], part of the pump column and two of the linearguide bearings are located above the water level and are exposed to ambientair temperature conditions. The failure of the diesel generator service waterpump C was attributed to ice buildup around the shaft and spider bearing fromleakage past the discharge check valve and the cold weather. The licenseealso concluded that under some credible meteorological conditions, thefunctions of both divisions could have been affected.DiscussionFrazil icing is a phenomenon that affects the operation of intake structuresin regions that experience cold weather. The accumulation of frazil ice onintake trash racks can completely block the flow of water into the intake.The process starts when the water flowing into the intake is supercooled (acondition where the water is below the freezing point). The supercooling maybe very small, on the order of a few hundredths of a degree.The supercooling occurs with a loss of heat from a large surface area such asa lake with open water and clear nights. High winds contribute to the problemby providing mixing of the supercooled water to depths as great as 6 to 9 m[20 to 30 ft]. The frazil ice, which is composed of very small crystals(1-15 mm) with little buoyancy because of their size, is carried along in thewater and mixed all through the supercooled water.The suction of the supercooled water and the suspended frazil ice crystalsthrough an intake structure brings the frazil ice crystals in contact with thetrash rack bars. Frazil ice crystals easily adhere to any object with whichthey collide. The ice collects first on the upstream side of the trash racks,then steadily grows until the space between the trash racks is bridged. Thisbridging rapidly blocks the trash racks. The accumulation of ice can with-stand high differential pressures; effectively damming the intake suction.Facility vulnerability to icing events is a function of plant design. Fraziland other ice formation is dependent on specific environmental conditions andrepresents a potential common-mode failure that can cause the loss or degrada-tion of multiple cooling water systems, including the potential loss of theultimate heat sink.
Office of Nuclear Reactor Regulation


IN 96-36June 12, 1996 Related InformationNUREG/CR-0548, "Ice Blockage of Water Intakes."This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation project manager.Ii -..--.....-.Brian K. Grimes, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical Contacts:John R. Tappert, NRR(301) 415-1167Internet:jrtlnrc.govBruce Jorgensen, RIII(708) 829-9615Internet:blj@nrc.govAttachment:List of Recently Issued NRC Information NoticesIk W (0%0%J4-c- -dI
project manager.Original signed by Brian K. Grimes Brian K. Grimes, Acting Director Division of Reactor Program Management


K>AttachmentIN 96-36June 12, 1996 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to96-35Failure of Safety Systemson Self-Shielded Irradia-tors Because of InadequateMaintenance and TrainingHydrogen Gas Ignitionduring Closure Weldingof a VSC-24 Multi-AssemblySealed Basket06/11/9605/31/96All U.S. Nuclear RegulatoryCommission irradiatorlicensees and vendorsAll holders of OLs or CPsfor nuclear power reactors96-3496-33ErroneousDefectiveResults iiData FromThermocouplei a Fire05/24/96All material and fuel cyclelicensees that monitor tem-perature with thermocouples96-3296-3196-30Implementation of 10 CFR50.55a(g)(6)(ii)(A),"Augmented Examinationof Reactor Vessel"Cross-Tied Safety Injec-tion AccumulatorsInaccuracy of DiagnosticEquipment for Motor-Operated Butterfly ValvesRequirements in 10 CFRPart 21 for Reporting andEvaluating Software ErrorsSuggested Guidance Relatingto Development and Imple-mentation of CorrectiveActionPotential Clogging of HighPressure Safety InjectionThrottle Valves DuringRecirculation06/05/9605/22/9605/21/9605/20/9605/01/9605/01/96All holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor pressurized waterreactorsAll holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor nuclear power reactorsAll material and fuel cyclelicenseesAll holders of OLs or CPsfor pressurized waterreactors96-2996-2896-27OL -Operating LicenseCP = Construction Permit
===Office of Nuclear Reactor Regulation===
Technical


.IIN 96-36June 12, 1996 IN 96-XXJune XX, 1996 Related informationNUREG/CR-0548, *Ice Blockage of Water Intakes"This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation project manager.Brian K. Grimes, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical Contacts:John R. Tappert, NRR(301) 415-1167Internet:Jrt@nrc.govBruce Jorgensen, RIII(708) 829-9615Internet:bl Jnrc.govAttachment:List of Recently Issued NRC Information NoticesDOCUMENT NAME:G:\JRT\WOLFICE.INTech Editor reviewed 5/1/96To receive a copy of this document, indicate in the box: ACTattachment/enclosure 'El -Copy with attachment/enclosure* see orevious concurrences-Copy withoutON" -No copyOFFICE
Contacts: John R. Tappert, NRR (301) 415-1167 Internet:jrt@nrc.gov
 
Bruce Jorgensen, RIII (708) 829-9615 Internet:blj@nrc.gov
 
Attachment:  
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME: 96-36.IN Tech Editor reviewed 5/1/96 To receive a copy of attachment/enclosure
 
* s this document, indicate in the box: "C""EN -Copy with attachment/enclosure
 
ee Drevious concurrences
 
-Copy without"N" -No co OFFICE


==CONTACT==
==CONTACT==
S C C/SRXB:DSSA I C/PECB:DRPM I D/DRPMNAME JTappert
S IC C/SRXB:DSSA
 
I C/PECB:DRPM
 
D/JT(S, i NAME JTappert


* LMarsh
* LMarsh


* AChaffeer,(, IBGrimesBJorgensen *DATE 5 /2/96 5/14/96 6 _ _ _6/ _/96UrIU-lAL KLLUKU WO/WY-,*-)
* AChaffee*
-IN 96 dMay XX, 1995 IN 96-XXMay XX, 1995 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation project manager.Brian K. Grimes, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical Contacts:John R. Tappert, NRR(301) 415-1167Internet:jrt~nrc.govBruce Jorgensen, RIII(708) 829-9615Internet:bl Jnrc.govAttachment:List of Recently Issued NRC Information NoticesDOCUMENT NAME:G:\JRT\WOLFICE.INTech Editor reviewed 5/1/96To receive a copy of this document, Indicate in the box: "C'attachment/enclosure HEN -Copy with attachment/enclosure* see nrevinus concurrences-Copy withoutON" -No copy--r-V. ---*OFFICE
BKf1Tntee'
l BJorgensen
 
* lDATE 5 /2/96 5/14/96 6/5/96 6//(/96 OFFICIAL RECORD COPY
 
IN 96-XX June XX, 1996 Related information
 
NUREG/CR-0548, *Ice Blockage of Water Intakes" 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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
Contacts: John R. Tappert, NRR (301) 415-1167 Internet:Jrt@nrc.gov
 
Bruce Jorgensen, RIII (708) 829-9615 Internet:bl
 
Jnrc.gov Attachment:
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME:G:\JRT\WOLFICE.IN
 
Tech Editor reviewed 5/1/96 To receive a copy of this document, indicate in the box: ACT attachment/enclosure
 
'El -Copy with attachment/enclosure
 
* see orevious concurrences
 
-Copy without ON" -No copy OFFICE


==CONTACT==
==CONTACT==
S IC C/SRXB:DSSA [_ C/PECB:DRPM I D/DRPMNAME JTappert
S C C/SRXB:DSSA
 
I C/PECB:DRPM
 
I D/DRPM NAME JTappert


* LMarsh
* LMarsh


* AChaffee BGrimesBJorgensen *DATE 5 12/96 5/14/96 5 / /96 5 / /96.- -----------. bOFFICIAL KLLRCD COPY so&sect;S
* AChaffeer,(, IBGrimes BJorgensen
 
*DATE 5 /2/96 5/14/96 6 _ _ _6/ _/96 UrIU-lAL KLLUKU WO/WY-,*-)
-IN 96 d May XX, 1995 Related-Information
 
NUREG/CR-0548, "Ice Blockage of Water Intakes" 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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
Contacts: John R. Tappert, NRR (301) 415-1167 Internet:jrt@nrc.gov
 
Bruce Jorgensen, RIII (708) 829-9615 Internet:blj@nrc.gov
 
Attachment:
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME:G:\JRT\WOLFICE.IN


IN 96-XXMay XX, 1995 This information notice requires no specific action or writtenyou have any questions about the information In this notice, plone of the technical contacts listed below or the appropriate 0Nuclear Reactor Regulation project manager..actofTechnical Contacts:John R. Tappert,(301) 415-1167Internet :Jrt~nrcBrian K. Grimes Acting DirectorDivision of Resctor Program ManagementOffice of Nu ear Reactor RegulationNRR uce Jorgensen, RGN III(708) 829-9615:.gov Internet:blj@nrc.govNRC I iormation NoticesAttachment:List of Recently IssuedDOCUMENT NAME:G:\JRT\WO 4ICE.INTech Editor reviewed /1/96To receive a copy p this documiattachment/enclosyre "E -Coiseep nrpvinu!ent, indicate in the box: IC'py with attachment/enclosureI concurrences= Copy withoutON, -No copyOFFICE CONTSCTS IC C/SRXB:DSSA _ C/PECB:DRPM l/DRPMNAME JT pert
Tech Editor reviewed 5/1/96 To receive a copy of this document, indicate in the box: "C" attachment/enclosure "E" = Copy with attachment/enclosure
 
* _ nrvin_ , concurrences
 
= Copy without"N" = No copy OFFICE
 
==CONTACT==
S IC C/SRXB:DSSAl
 
C/PECB:DRPM
 
l D/DRPM H NAME JTappert


* LMarsh
* LMarsh


* AChaffee BGrimesAB4rgensen *DATE /2/96 5/14/96 5 / /96 5 / /967 ArTTA I &#xa3;'LFIL rIILvrv -'WI I AULOISI.WWI 5 JP4\  
* AChaffee BGrimes BJorgensen
IN 96-XXMay XX, 1995
 
}}
*DATE 5 /2/96 5/14/96 5 / /96 5 / /96 OFFICIAL RECORD COPY
 
IN 96-XX May XX, 1995 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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
Contacts: John R. Tappert, NRR (301) 415-1167 Internet:jrt~nrc.gov
 
Bruce Jorgensen, RIII (708) 829-9615 Internet:bl
 
Jnrc.gov Attachment:
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME:G:\JRT\WOLFICE.IN
 
Tech Editor reviewed 5/1/96 To receive a copy of this document, Indicate in the box: "C'attachment/enclosure
 
HEN -Copy with attachment/enclosure
 
* see nrevinus concurrences
 
-Copy without ON" -No copy--r-V. ---*OFFICE
 
==CONTACT==
S IC C/SRXB:DSSA
 
[_ C/PECB:DRPM
 
I D/DRPM NAME JTappert
 
* LMarsh
 
* AChaffee BGrimes BJorgensen
 
*DATE 5 12/96 5/14/96 5 / /96 5 / /96.- -----------. b OFFICIAL KLLRCD COPY so&sect;S
 
IN 96-XX May XX, 1995 This information
 
notice requires no specific action or written you have any questions
 
about the information
 
In this notice, pl one of the technical
 
contacts listed below or the appropriate
 
0 Nuclear Reactor Regulation
 
project manager..act of Technical
 
Contacts: John R. Tappert, (301) 415-1167 Internet :Jrt~nrc Brian K. Grimes Acting Director Division of Resctor Program Management
 
===Office of Nu ear Reactor Regulation===
NRR uce Jorgensen, RGN III (708) 829-9615:.gov Internet:blj@nrc.gov
 
NRC I iormation
 
Notices Attachment:
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*DATE /2/96 5/14/96 5 / /96 5 / /96 7 ArTTA I &#xa3;'LFIL rIILvrv -'WI I AULOISI.WWI 5 JP4\  
IN 96-XX May XX, 1995 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
 
project manager.Brian K. Grimes, Acting Direc r Division of Reactor Program anagement Office of Nuclear Reactor egulation Technical
 
Contacts:
John R. Tappert, NRR Bruc Jorgensen, RGN III (301) 415-1167 (7 ) 829-9615 Internet:jrt~nrc.gov
 
I ernet:blJ~nrc.gov
 
Attachment:
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{{Information notice-Nav}}
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Revision as of 14:07, 31 August 2018

Degradation of Cooling Water Systems Due to Icing
ML031060039
Person / Time
Site: Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant  Entergy icon.png
Issue date: 06/12/1996
From: Grimes B K
Office of Nuclear Reactor Regulation
To:
References
IN-96-036, NUDOCS 9606070097
Download: ML031060039 (11)
v • d • e


"J UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFYFICE OF NUCLEAR REACTOR REGULATION

-WASHINGTON, DC 20555-0001 June 12, 1996 NRC INFORMATION

NOTICE 96-36: DEGRADATION

OF COOLING WATER SYSTEMS DUE TO ICING

Addressees

All holders of operating

licenses or construction

permits for nuclear power reactors.

Purpose

The U.S. Nuclear Regulatory

Commission (NRC) is issuing this information

notice to alert addressees

to potential

degradation

of facility water intake systems (circulating, service, and fire water) due to icing conditions.

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

Wolf Creek Between 1:45 a.m. and 2:45 a.m. (all times central standard time) on January 30, 1996, operators

at Wolf Creek received alarms indicating

that the circulating

water system traveling

screens were becoming blocked. A visual inspection

showed that the traveling

screens for bays 1 and 3 were frozen and that water levels in these bays were approximately

2.5 m [8 ft] below normal.The emergency

service water system was started with the intent to separate this system from the service water system. However, the emergency

service water system was incorrectly

aligned; flow was directed to the service water system and warming flow to the emergency

service water system suction bays was restricted.

Operators

also shifted to circulating

water pump B. At approxi-mately 3:30 a.m., operators

received a service water pressure alarm and an electric fire pump started on low service water pressure.

The shift super-visor then directed a manual reactor/turbine

trip. Circulating

water system bays were subsequently

determined

to be at 3.5 m [12 feet] below normal. The level loss was caused by water from the spray wash system freezing and block-ing the traveling

screens.The Train A emergency

service water system pump was tripped and declared inoperable

at 7:47 a.m. because of low discharge

pressure and high strainer differential

pressure.

At about 8:00 a.m., the supervising

operator coming on shift noted the incorrect

alignment

of the emergency

service water system and took action to correct it. At about 5:45 p.m., the operators

declared Train A'~P) C-FW 0f bla .pDR :t:-E moric6 6'sVOU 160612 '

1.'K)IN 96-36 June 12, 1996 operable on the basis of an engineering

evaluation

and placed it in service.However, the pump was again stopped 1-1/2 hours later at approximately

7:30 p.m. when the pump exhibited

further oscillations

in flow and pressure.At approximately

8:00 p.m., operators

noted that emergency

service water system Train B suction bay level was 4.5 m [15 ft] below normal and decreasing

slowly. Operators

placed additional

heat loads on Train B and the suction bay levels subsequently

recovered.

At 10:14 p.m., the operators

again started Train A emergency

service water system and secured it at 10:27 p.m. due to decreasing

flow and pressure.At about 10:00 a.m. on January 31, divers inspected

the suction bay of Train A and noted complete blockage of the trash racks by frazil ice. Train B was not inspected

because the pump was running. The ice blockage was cleared by 4:00 p.m. by sparging the trash racks with air. The emergency

service water system was designed to have warming flow injected in front of trash racks to increase bulk water temperature

and prevent the formation

of frazil ice. Due to calculational

errors by the architect-engineer

and the as-built system configuration, the emergency

service water system warming flow was insufficient

to prevent frazil ice from forming at the Train A trash racks.FitzPatrick

On February 25, 1993, at 1:25 a.m., the electric fire pump started on low fire header pressure.

After verifying

normal fire header pressure, operators secured the electric fire pump, and the diesel fire pumps subsequently

started on low header pressure.

It was later determined

that the fire jockey pump had lost suction because of the decreasing

screenwell

level.Over the next several minutes, operators

noted an increase in circulating

water system motor amperage (which is consistent

with decreased

suction pressure).

Reactor power was also reduced and one circulating

water pump was secured. At 1:40 a.m., an operator reported that the screenwell

level was approximately

3 m [10 ft] below normal and the reactor was manually scrammed.After a second circulating

water pump was subsequently

secured, the screenwell

water level quickly recovered.

The licensee concluded

that the reduced screenwell

level had been caused by ice partially

blocking the lake intake structure.

Either frazil ice formed around or in front of the heated intake bar racks, or slush ice was present in front of the bar racks.Fermi On February 5, 1996, at approximately

2:30 p.m., diesel generator

service water pump C failed to develop normal discharge

pressure, flow, and motor current during a surveillance.

This made Division I emergency

diesel generator (EDG) 12 inoperable.

After several unsuccessful

attempts to start the pump, an air purge of the pump column on the discharge

of the pump was initiated

in an attempt to clear any obstruction

in the column or the pump inlet. The licensee detected blockage when it tried to blow air through the pipe. At 8:21 p.m., the pump was started and after 3 to 5 seconds an erratic discharge

pressure was noted. In a short time, pump flow, discharge

pressure, and motor amps were normal. The following

day, on February 6, diesel generator

service water pump B was started. The pump, which cools Division II

K> < IN 96-36 June 12, 1996 EDG 13, showed no flow, no pressure, and low amperage for the first 30 seconds. After approximately

90 seconds, normal flow discharge

pressure and motor current were achieved.

The remaining

safety-related

pumps were tested satisfactorily.

The diesel generator

service water pumps are all deep-draft

pumps and take suction from the ultimate heat sink reservoir

which is a segregated

pool. The licensee evaluation

concluded

that although the reservoir

temperatures

are maintained

above 5 eC [41 OF], part of the pump column and two of the linear guide bearings are located above the water level and are exposed to ambient air temperature

conditions.

The failure of the diesel generator

service water pump C was attributed

to ice buildup around the shaft and spider bearing from leakage past the discharge

check valve and the cold weather. The licensee also concluded

that under some credible meteorological

conditions, the functions

of both divisions

could have been affected.Discussion

Frazil icing is a phenomenon

that affects the operation

of intake structures

in regions that experience

cold weather. The accumulation

of frazil ice on intake trash racks can completely

block the flow of water into the intake.The process starts when the water flowing into the intake is supercooled (a condition

where the water is below the freezing point). The supercooling

may be very small, on the order of a few hundredths

of a degree.The supercooling

occurs with a loss of heat from a large surface area such as a lake with open water and clear nights. High winds contribute

to the problem by providing

mixing of the supercooled

water to depths as great as 6 to 9 m[20 to 30 ft]. The frazil ice, which is composed of very small crystals (1-15 mm) with little buoyancy because of their size, is carried along in the water and mixed all through the supercooled

water.The suction of the supercooled

water and the suspended

frazil ice crystals through an intake structure

brings the frazil ice crystals in contact with the trash rack bars. Frazil ice crystals easily adhere to any object with which they collide. The ice collects first on the upstream side of the trash racks, then steadily grows until the space between the trash racks is bridged. This bridging rapidly blocks the trash racks. The accumulation

of ice can with-stand high differential

pressures;

effectively

damming the intake suction.Facility vulnerability

to icing events is a function of plant design. Frazil and other ice formation

is dependent

on specific environmental

conditions

and represents

a potential

common-mode

failure that can cause the loss or degrada-tion of multiple cooling water systems, including

the potential

loss of the ultimate heat sink.

IN 96-36 June 12, 1996 Related Information

NUREG/CR-0548, "Ice Blockage of Water Intakes." 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

project manager.I i -..--.....-.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

Contacts: John R. Tappert, NRR (301) 415-1167 Internet:jrtlnrc.gov

Bruce Jorgensen, RIII (708) 829-9615 Internet:blj@nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices I k W (0%0%J4-c- -d I

K>Attachment

IN 96-36 June 12, 1996 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 96-35 Failure of Safety Systems on Self-Shielded

Irradia-tors Because of Inadequate

Maintenance

and Training Hydrogen Gas Ignition during Closure Welding of a VSC-24 Multi-Assembly

Sealed Basket 06/11/96 05/31/96 All U.S. Nuclear Regulatory

Commission

irradiator

licensees

and vendors All holders of OLs or CPs for nuclear power reactors 96-34 96-33 Erroneous Defective Results ii Data From Thermocouple

i a Fire 05/24/96 All material and fuel cycle licensees

that monitor tem-perature with thermocouples

96-32 96-31 96-30 Implementation

of 10 CFR 50.55a(g)(6)(ii)(A),"Augmented

Examination

of Reactor Vessel" Cross-Tied

Safety Injec-tion Accumulators

Inaccuracy

of Diagnostic

Equipment

for Motor-Operated Butterfly

Valves Requirements

in 10 CFR Part 21 for Reporting

and Evaluating

Software Errors Suggested

Guidance Relating to Development

and Imple-mentation

of Corrective

Action Potential

Clogging of High Pressure Safety Injection Throttle Valves During Recirculation

06/05/96 05/22/96 05/21/96 05/20/96 05/01/96 05/01/96 All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for pressurized

water reactors All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for nuclear power reactors All material and fuel cycle licensees All holders of OLs or CPs for pressurized

water reactors 96-29 96-28 96-27 OL -Operating

License CP = Construction

Permit

.I IN 96-36 June 12, 1996 Related Information

NUREG/CR-0548, "Ice Blockage of Water Intakes." 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

project manager.Original signed by Brian K. Grimes Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

Contacts: John R. Tappert, NRR (301) 415-1167 Internet:jrt@nrc.gov

Bruce Jorgensen, RIII (708) 829-9615 Internet:blj@nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME: 96-36.IN Tech Editor reviewed 5/1/96 To receive a copy of attachment/enclosure

  • s this document, indicate in the box: "C""EN -Copy with attachment/enclosure

ee Drevious concurrences

-Copy without"N" -No co OFFICE

CONTACT

S IC C/SRXB:DSSA

I C/PECB:DRPM

D/JT(S, i NAME JTappert

  • LMarsh
  • AChaffee*

BKf1Tntee'

l BJorgensen

  • lDATE 5 /2/96 5/14/96 6/5/96 6//(/96 OFFICIAL RECORD COPY

IN 96-XX June XX, 1996 Related information

NUREG/CR-0548, *Ice Blockage of Water Intakes" 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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

Contacts: John R. Tappert, NRR (301) 415-1167 Internet:Jrt@nrc.gov

Bruce Jorgensen, RIII (708) 829-9615 Internet:bl

Jnrc.gov Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME:G:\JRT\WOLFICE.IN

Tech Editor reviewed 5/1/96 To receive a copy of this document, indicate in the box: ACT attachment/enclosure

'El -Copy with attachment/enclosure

  • see orevious concurrences

-Copy without ON" -No copy OFFICE

CONTACT

S C C/SRXB:DSSA

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I D/DRPM NAME JTappert

  • LMarsh
  • AChaffeer,(, IBGrimes BJorgensen
  • DATE 5 /2/96 5/14/96 6 _ _ _6/ _/96 UrIU-lAL KLLUKU WO/WY-,*-)

-IN 96 d May XX, 1995 Related-Information

NUREG/CR-0548, "Ice Blockage of Water Intakes" 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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

Contacts: John R. Tappert, NRR (301) 415-1167 Internet:jrt@nrc.gov

Bruce Jorgensen, RIII (708) 829-9615 Internet:blj@nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME:G:\JRT\WOLFICE.IN

Tech Editor reviewed 5/1/96 To receive a copy of this document, indicate in the box: "C" attachment/enclosure "E" = Copy with attachment/enclosure

  • _ nrvin_ , concurrences

= Copy without"N" = No copy OFFICE

CONTACT

S IC C/SRXB:DSSAl

C/PECB:DRPM

l D/DRPM H NAME JTappert

  • LMarsh
  • AChaffee BGrimes BJorgensen
  • DATE 5 /2/96 5/14/96 5 / /96 5 / /96 OFFICIAL RECORD COPY

IN 96-XX May XX, 1995 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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

Contacts: John R. Tappert, NRR (301) 415-1167 Internet:jrt~nrc.gov

Bruce Jorgensen, RIII (708) 829-9615 Internet:bl

Jnrc.gov Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME:G:\JRT\WOLFICE.IN

Tech Editor reviewed 5/1/96 To receive a copy of this document, Indicate in the box: "C'attachment/enclosure

HEN -Copy with attachment/enclosure

  • see nrevinus concurrences

-Copy without ON" -No copy--r-V. ---*OFFICE

CONTACT

S IC C/SRXB:DSSA

[_ C/PECB:DRPM

I D/DRPM NAME JTappert

  • LMarsh
  • AChaffee BGrimes BJorgensen
  • DATE 5 12/96 5/14/96 5 / /96 5 / /96.- -----------. b OFFICIAL KLLRCD COPY so§S

IN 96-XX May XX, 1995 This information

notice requires no specific action or written you have any questions

about the information

In this notice, pl one of the technical

contacts listed below or the appropriate

0 Nuclear Reactor Regulation

project manager..act of Technical

Contacts: John R. Tappert, (301) 415-1167 Internet :Jrt~nrc Brian K. Grimes Acting Director Division of Resctor Program Management

Office of Nu ear Reactor Regulation

NRR uce Jorgensen, RGN III (708) 829-9615:.gov Internet:blj@nrc.gov

NRC I iormation

Notices Attachment:

List of Recently Issued DOCUMENT NAME:G:\JRT\WO

4ICE.IN Tech Editor reviewed /1/96 To receive a copy p this documi attachment/enclosyre "E -Coi seep nrpvinu!ent, indicate in the box: IC'py with attachment/enclosure

I concurrences

= Copy without ON, -No copy OFFICE CONTSCTS IC C/SRXB:DSSA

_ C/PECB:DRPM

l/DRPM NAME JT pert

  • LMarsh
  • AChaffee BGrimes AB4rgensen
  • DATE /2/96 5/14/96 5 / /96 5 / /96 7 ArTTA I £'LFIL rIILvrv -'WI I AULOISI.WWI 5 JP4\

IN 96-XX May XX, 1995 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

project manager.Brian K. Grimes, Acting Direc r Division of Reactor Program anagement Office of Nuclear Reactor egulation Technical

Contacts:

John R. Tappert, NRR Bruc Jorgensen, RGN III (301) 415-1167 (7 ) 829-9615 Internet:jrt~nrc.gov

I ernet:blJ~nrc.gov

Attachment:

List of Recently Issued NRC Informat1o

otices DOCUMENT NAME:G:\JRT\WOLFICE.1I

Tech Editor reviewed 5/1/96 To receive a copy of this ocument, indicate in the box: OCR -Copy without attachment/enclosure

-C y with ttachment/enclosure

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CONTACT

S IC C SRXB:DSSA

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V 8 DATE 5 /2/96/ 5 /0t/96 5 / /96 5 //96 OFFICIAL RECORD COPY


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