Information Notice 1996-36, Degradation of Cooling Water Systems Due to Icing

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
Issue date:	06/12/1996
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-96-036, NUDOCS 9606070097
Download: ML031060039 (11)

"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

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• LMarsh

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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:

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

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• 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:

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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

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CONTACT

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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:

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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

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• 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:

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• 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:

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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

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