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)

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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

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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

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< 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

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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

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

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

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-

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

• 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