Information Notice 1996-36, Degradation of Cooling Water Systems Due to Icing: Difference between revisions
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| issue date = 06/12/1996 | | issue date = 06/12/1996 | ||
| title = Degradation of Cooling Water Systems Due to Icing | | title = Degradation of Cooling Water Systems Due to Icing | ||
| author name = Grimes B | | author name = Grimes B | ||
| author affiliation = NRC/NRR | | author affiliation = NRC/NRR | ||
| addressee name = | | addressee name = | ||
Line 14: | Line 14: | ||
| page count = 11 | | page count = 11 | ||
}} | }} | ||
{{#Wiki_filter:" | {{#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 | All holders of operating licenses or construction permits for nuclear power | ||
reactors. | |||
==Purpose== | ==Purpose== | ||
The U.S. Nuclear Regulatory Commission (NRC) is issuing this | 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== | ==Description of Circumstances== | ||
Wolf | Wolf Creek | ||
1.'K)IN 96- | |||
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) bla 0f . | |||
C-FW | |||
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 06/11/96 All U.S. Nuclear Regulatory | |||
on Self-Shielded Irradia- Commission irradiator | |||
. | tors Because of Inadequate licensees and vendors | ||
Maintenance and Training | |||
96-34 Hydrogen Gas Ignition 05/31/96 All holders of OLs or CPs | |||
during Closure Welding for nuclear power reactors | |||
of a VSC-24 Multi-Assembly | |||
Sealed Basket | |||
96-33 Erroneous Data From 05/24/96 All material and fuel cycle | |||
Defective Thermocouple licensees that monitor tem- Results ii i a Fire perature with thermocouples | |||
96-32 Implementation of 10 CFR 06/05/96 All holders of OLs or CPs | |||
50.55a(g)(6)(ii)(A), for nuclear power reactors | |||
"Augmented Examination | |||
of Reactor Vessel" | |||
96-31 Cross-Tied Safety Injec- 05/22/96 All holders of OLs or CPs | |||
tion Accumulators for pressurized water | |||
reactors | |||
96-30 Inaccuracy of Diagnostic 05/21/96 All holders of OLs or CPs | |||
Equipment for Motor- for nuclear power reactors | |||
Operated Butterfly Valves | |||
96-29 Requirements in 10 CFR 05/20/96 All holders of OLs or CPs | |||
Part 21 for Reporting and for nuclear power reactors | |||
Evaluating Software Errors | |||
96-28 Suggested Guidance Relating 05/01/96 All material and fuel cycle | |||
to Development and Imple- licensees | |||
mentation of Corrective | |||
Action | |||
96-27 Potential Clogging of High 05/01/96 All holders of OLs or CPs | |||
Pressure Safety Injection for pressurized water | |||
Throttle Valves During reactors | |||
Recirculation | |||
OL - Operating License | |||
CP = Construction Permit | |||
IN 96-36 | |||
. I 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 this document, indicate in the box: "C"- Copy without | |||
attachment/enclosure "EN - Copy with attachment/enclosure "N"- No co | |||
* s ee Drevious concurrences | |||
OFFICE | |||
==CONTACT== | ==CONTACT== | ||
S | S IC C/SRXB:DSSA I C/PECB:DRPM D/JT(S, i | ||
NAME JTappert * LMarsh * AChaffee* BKf1Tntee' l | |||
BJorgensen * l | |||
DATE 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 Bruce Jorgensen, RIII | |||
(301) 415-1167 (708) 829-9615 Internet:Jrt@nrc.gov 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 - Copy without | |||
attachment/enclosure 'El - Copy with attachment/enclosure ON" - No copy | |||
* see orevious concurrences | |||
OFFICE | |||
==CONTACT== | ==CONTACT== | ||
S | S C C/SRXB:DSSA I C/PECB:DRPM 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 | |||
* AChaffee | Division of Reactor Program Management | ||
IN 96- | |||
}} | Office of Nuclear Reactor Regulation | ||
Technical Contacts: John R. Tappert, NRR Bruce Jorgensen, RIII | |||
(301) 415-1167 (708) 829-9615 Internet:jrt@nrc.gov 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" = Copy without | |||
attachment/enclosure "E" = Copy with attachment/enclosure "N" = No copy | |||
, | |||
* _ nrvin_ concurrences | |||
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 Bruce Jorgensen, RIII | |||
(301) 415-1167 (708) 829-9615 Internet:jrt~nrc.gov 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'- Copy without | |||
attachment/enclosure HEN - Copy with attachment/enclosure ON" - No copy | |||
* see nrevinus | |||
--- * | |||
- - r-V. | |||
concurrences | |||
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 | |||
§S | |||
OFFICIAL KLLRCD COPY so | |||
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 .act | |||
one of the technical contacts listed below or the appropriate 0 of | |||
Nuclear Reactor Regulation project manager. | |||
Brian K. Grimes Acting Director | |||
Division of Resctor Program Management | |||
Office of Nu ear Reactor Regulation | |||
Technical Contacts: John R. Tappert, NRR uce Jorgensen, RGN III | |||
(301) 415-1167 (708) 829-9615 Internet :Jrt~nrc :.gov Internet:blj@nrc.gov | |||
Attachment: List of Recently Issued NRC I Notices | |||
iormation | |||
DOCUMENT NAME:G:\JRT\WO 4ICE.IN | |||
Tech Editor reviewed /1/96 To receive a copy p this documient, indicate in the box: IC'= Copy without | |||
attachment/enclosyre "E - Coi py with attachment/enclosure ON, - No copy | |||
seep nrpvinu! I concurrences | |||
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 I I £'LFIL rIILvrv | |||
'WArTTA 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 N" - No copy | |||
OFFICE | |||
==CONTACT== | |||
S IC C SRXB:DSSA I ?lC/PECB:DRPM D/DRPM | |||
NAME JTappert [7LMarsh ftv AChaffee BGrimes | |||
. ~BJorgensel;V 8 DATE 5 /2/96/ 5/0t/96 5 / /96 5 //96 OFFICIAL RECORD COPY}} | |||
{{Information notice-Nav}} | {{Information notice-Nav}} |
Latest revision as of 04:38, 24 November 2019
"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) bla 0f .
C-FW
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
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 06/11/96 All U.S. Nuclear Regulatory
on Self-Shielded Irradia- Commission irradiator
tors Because of Inadequate licensees and vendors
Maintenance and Training
96-34 Hydrogen Gas Ignition 05/31/96 All holders of OLs or CPs
during Closure Welding for nuclear power reactors
of a VSC-24 Multi-Assembly
Sealed Basket
96-33 Erroneous Data From 05/24/96 All material and fuel cycle
Defective Thermocouple licensees that monitor tem- Results ii i a Fire perature with thermocouples
96-32 Implementation of 10 CFR 06/05/96 All holders of OLs or CPs
50.55a(g)(6)(ii)(A), for nuclear power reactors
"Augmented Examination
of Reactor Vessel"
96-31 Cross-Tied Safety Injec- 05/22/96 All holders of OLs or CPs
tion Accumulators for pressurized water
reactors
96-30 Inaccuracy of Diagnostic 05/21/96 All holders of OLs or CPs
Equipment for Motor- for nuclear power reactors
Operated Butterfly Valves
96-29 Requirements in 10 CFR 05/20/96 All holders of OLs or CPs
Part 21 for Reporting and for nuclear power reactors
Evaluating Software Errors
96-28 Suggested Guidance Relating 05/01/96 All material and fuel cycle
to Development and Imple- licensees
mentation of Corrective
Action
96-27 Potential Clogging of High 05/01/96 All holders of OLs or CPs
Pressure Safety Injection for pressurized water
Throttle Valves During reactors
Recirculation
OL - Operating License
CP = Construction Permit
. I 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 this document, indicate in the box: "C"- Copy without
attachment/enclosure "EN - Copy with attachment/enclosure "N"- No co
- s ee Drevious concurrences
OFFICE
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S IC C/SRXB:DSSA I C/PECB:DRPM D/JT(S, i
NAME JTappert * LMarsh * AChaffee* BKf1Tntee' l
BJorgensen * l
DATE 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 Bruce Jorgensen, RIII
(301) 415-1167 (708) 829-9615 Internet:Jrt@nrc.gov 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 - Copy without
attachment/enclosure 'El - Copy with attachment/enclosure ON" - No copy
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CONTACT
S C C/SRXB:DSSA I C/PECB:DRPM 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 Bruce Jorgensen, RIII
(301) 415-1167 (708) 829-9615 Internet:jrt@nrc.gov 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" = Copy without
attachment/enclosure "E" = Copy with attachment/enclosure "N" = No copy
,
- _ nrvin_ concurrences
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 Bruce Jorgensen, RIII
(301) 415-1167 (708) 829-9615 Internet:jrt~nrc.gov 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'- Copy without
attachment/enclosure HEN - Copy with attachment/enclosure ON" - No copy
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--- *
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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
§S
OFFICIAL KLLRCD COPY so
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 .act
one of the technical contacts listed below or the appropriate 0 of
Nuclear Reactor Regulation project manager.
Brian K. Grimes Acting Director
Division of Resctor Program Management
Office of Nu ear Reactor Regulation
Technical Contacts: John R. Tappert, NRR uce Jorgensen, RGN III
(301) 415-1167 (708) 829-9615 Internet :Jrt~nrc :.gov Internet:blj@nrc.gov
Attachment: List of Recently Issued NRC I Notices
iormation
DOCUMENT NAME:G:\JRT\WO 4ICE.IN
Tech Editor reviewed /1/96 To receive a copy p this documient, indicate in the box: IC'= Copy without
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seep nrpvinu! I concurrences
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 I I £'LFIL rIILvrv
'WArTTA 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 N" - No copy
OFFICE
CONTACT
S IC C SRXB:DSSA I ?lC/PECB:DRPM D/DRPM
NAME JTappert [7LMarsh ftv AChaffee BGrimes
. ~BJorgensel;V 8 DATE 5 /2/96/ 5/0t/96 5 / /96 5 //96 OFFICIAL RECORD COPY