Information Notice 1994-29, Charging Pump Trip During a Loss-of-Coolant Event Caused by Low Suction Pressure

Charging Pump Trip During a Loss-of-Coolant Event Caused by Low Suction Pressure

ML031060474
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, 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, 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:	04/11/1994
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-94-029, NUDOCS 9404060036
Download: ML031060474 (9)

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 April 11, 1994 NRC INFORMATION NOTICE 94-29: CHARGING PUMP TRIP DURING A LOSS-OF-COOLANT

EVENT CAUSED BY LOW SUCTION PRESSURE

Addressees

All holders of operating licenses or construction permits for pressurized- water reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information

notice to alert addressees to the possibility of a charging pump trip caused

by inadequate suction pressure because too many pumps may be aligned to a

single suction path during accident mitigation. 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

During a steam generator tube rupture event at Palo Verde Unit 2 on March 14,

1993 (NRC Inspection Report 50-279/93-14), a charging pump tripped off on low

suction pressure when the operators switched the charging pump suction source

from the volume control tank to the refueling water tank. During the

subsequent evaluation of the event, the licensee determined that four pumps, three charging pumps and a boric acid makeup pump, were all taking suction

through the same 7.6-cm [3-in.] diameter pipe. The licensee also determined

that the high rate of flow through the suction pipe that resulted from the

simultaneous operation of all four pumps caused a sufficient pressure

reduction at the suction of the pumps to lower this pressure below the low

suction trip setpoints of the charging pumps.

Two charging pumps were already running when the tube rupture occurred. In

addition, the operators were running a boric acid pump to circulate the

refueling water through filters to purify it for an upcoming outage; The

boric acid pump flow was being recirculated back to the refueling water tank

and did not contribute to the makeup water going into the reactor coolant

system. The operators started the third charging pump early in the event in

an effort to restore the pressurizer level, which was decreasing because of

the tube rupture. At that time all of the charging pumps were taking suction

from the volume control tank, which is the normal source of makeup water for

the reactor coolant system. Approximately 30 minutes later, in accordance

with emergency procedures, the operators opened the suction valve from the

9404060036 po-rXE qq-D29 qqoqI

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IN 94-29

- V April 11, 1994 refueling water tank and then closed the suction valve from the volume control

tank.

At this point one of the charging pumps tripped off. The operators were able

to restore the tripped charging pump to operation by realigning the suction of

the charging pumps to other suction paths from the refueling water tank.

Discussion

Following this event the licensee calculated that, with the boric acid pump

running, the remaining flow capacity of the refueling water tank suction

source that was in use was Just sufficient for two charging pumps. With all

four pumps running the suction pressure was below the low suction trip set

points (81.0 kPa to 87.2 kPa [11.75 psia to 12.65 psia]) for the charging

pumps. Because the trip set points are set at slightly different pressures, only one pump tripped. Once this first pump tripped, the resulting rise in

suction pressure allowed the remaining pumps to keep running.

The licensee concluded that, if recirculation by the boric acid pump is not in

progress, sufficient suction pressure exists for all three charging-pumps.

Consequently, the licensee revised the emergency procedures that involve the

charging pumps to specify that any ongoing recirculation of the refueling

water by the boric acid pump is to be terminated when refueling water is

needed for emergency makeup.

Licensees of pressurized-water reactors use the charging systems in a number

of ways for accident mitigation, such as including the charging system as a

part of the automatic safety injection system. Charging systems are also used

as a source of pressurizer spray to depressurize the reactor when the reactor

coolant pumps are shut down. Emergency operating procedures often refer to

the charging systems for other uses as well.

Some licensees do not isolate the volume control tank (or its equivalent) when

the charging system source is switched to the refueling water tank (or its

equivalent), but depend on the static pressure in the refueling water tank to

keep the volume control tank from draining. Should the volume control tank

empty in response to lower-than-expected suction pressure, hydrogen cover gas

normally contained in this tank could enter the charging system suction and

cause the pumps to malfunction.

IN 94-29 April 11, 1994 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation project manager.

Brian K. Gr es, Director ter- Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: Warren C. Lyon, NRR

(301) 504-3892 Attachment:

List of Recently Issued NRC Information Notices

Ak-1achment

IN 94-29 April 12, 1994 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

92-51, Misapplication and 04/12/94 All holders of OLs or CPs

Supp. 1 Inadequate Testing of for nuclear power reactors.

Molded-Case Circuit

Breakers

94-28 Potential Problems with 04/05/94 All holders of OLs or CPs

Fire-Barrier Penetration for nuclear power reactors.

Seals

94-27 Facility Operating 03/31/94 All holders of OLs or CPs

Concerns Resulting from for nuclear power reactors.

Local Area Flooding

94-26 Personnel Hazards and 03/28/94 All holders of OLs or CPs

Other Problems from for nuclear power reactors.

Smoldering Fire-Retard- ant Material in the

Drywell of a Boiling- Water Reactor

93-17, Safety Systems Response 03/25/94 All holders of OLs or CPs

Rev. 1 to Loss of Coolant and for nuclear power.

Loss of Offsite Power

94-25 Failure of Containment 03/25/94 All holders of OLs or CPs

Spray Header Valve to for nuclear power reactors.

Open due to Excessive

Pressure from Inertial

Effects of Water

94-24 Inadequate Maintenance 03/24/94 All holders of OLs or CPs

of Uninterruptible Power for nuclear power reactors.

Supplies and Inverters

94-23 Guidance to Hazardous, 03/25/94 All NRC Licensees.

Radioactive and Mixed

Waste Generators on the

Elements of a Waste

Minimization Program

OL - Operating License

CP - Construction Permit

. I If IN 94-29 April 11, 1994 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation project manager.

orig /s/'d by CIGrimes

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: Warren C. Lyon, NRR

(301) 504-3892 Attachment:

List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OFFICE *OGCB *TECH ED *SRXB/DSSA *C:SRXB/DSSA

NAME DCKirkpatrick RSanders WCLyon RJones

DATE 111/30/93 111/30/93 , 12/20/93 12/22/93

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01/04/94 01/11/94 04/L/94 VULUMMN NAME: 4-M. IN

IN 94-xx

March xx, 1994 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact: Warren C. Lyon, NRR

(301) 504-3892

• SFF PREVOUS CONCURRENCE

OFFICE *OGCB *TECH ED *SRXB/DSSA *C:SRXB/DSSA

NAME DCKirkpatrick RSanders WCLyon RJones

DATE 11/30/93 11/30/93 12/20/93 1 12/22/93

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AThadani GHMarcus BKGrimes

01/04/94 01/11/94 03/ /94 DOCUMENT NAME: CHARGING.DCK I=01tw

O IN 94-xx

January xx, 1994 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Warren C. Lyon, NRR

(301) 504-3892

• SEE PREVIOUS CONCURRENCE

OFFICE *OGCB *TECH ED *SRXB/DSSA *C:SRXB/DSSA

NAME DCKirkpatrick I RSanders WCLyon RJones

DATE I1/30/93 >/BYJ 11/30/93 112/20/93 12/22/93 D:DSSA Okl C:OGCB/DORS D:DORS/NRR c ll

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01/04/94 01/ti/94 01/ /94 DOCUMENT NAME: CHARGING.DCK

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IN 93-xx

December xx, 1993 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Warren C. Lyon, NRR

(301) 504-3892

• SEF PREVIOUS CONCURRENCE Af. -.-/ ,

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December xx, 1993 This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate Office of Nuclear

Reactor Regulation project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Warren C. Lyon, NRR

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