Information Notice 1993-51, Repetitive Overspeed Tripping of Turbine-Driven Auxiliary Feedwater Pumps

Repetitive Overspeed Tripping of Turbine-Driven Auxiliary Feedwater Pumps

ML031070374
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, 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:	07/09/1993
From:	Grimes B K Office of Nuclear Reactor Regulation
To:
References
IN-93-051, NUDOCS 9307010233
Download: ML031070374 (12)

r -UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 July 9, 1993 NRC INFORMATION

NOTICE 93-51: REPETITIVE

OVERSPEED

TRIPPING OF TURBINE-DRIVEN

AUXILIARY

FEEDWATER

PUMPS

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 the problem of repetitive

tripping of turbine-driven auxiliary

feedwater

pumps (TDAFWPs)

at the South Texas Project Electric Generating

Station. 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

On December 27, 1992, Houston Lighting & Power Company (the licensee)performed

a monthly surveillance

test on its Unit 1 TDAFWP. After receiving

a start signal, the pump immediately

tripped on an overspeed

condition.

The operators

repeated the surveillance

test after a successful

local manual start. On this attempt the pump successfully

started, and the licensee subsequently

considered

the pump operable.On January 23, 1993, Unit 2 tripped from 100-percent

power on low water level in one of the steam generators.

The trip occurred because electro-hydraulic

control oil to the steam generator

main feedwater

pump turbine was lost. The Unit 2 TDAFWP started on demand and was later secured when no longer required.After the pump was secured, problems occurred when operators

attempted

to relatch MOV-514 (the TDAFWP trip/throttle

valve) from the control room. (See Figure 1.) The pump was declared inoperable.

The licensee conducted

a significant

amount of troubleshooting

and testing on the TDAFWP to resolve the MOV-514 relatch problem and another speed control problem that was identified

during the testing. After the operability

surveillance

test was completed successfully, the TDAFWP was declared operable and the unit was restarted

on January 25, 1993.On January 28, 1993, the Unit 1 TDAFWP was tested as part of a routine monthly surveillance.

When started, the TDAFWP immediately

tripped on an overspeed condition

and was subsequently

declared inoperable.

From January 28 through 9307010233 P 9t PC w3 -oSI 9 15 I

-I IN 93-51 July 9, 1993 January 30, 1993, the licensee undertook

an extensive

testing and troubleshooting

effort to determine

the cause of the problem with the TDAFWP.Numerous pump starts were completed.

Several problems (overspeed

tripping, lack of speed control, oscillations, and inability

to maintain rated full-load, steady-state

speed) were identified.

On January 30, 1993, the Unit 1 TDAFWP was declared operable following

extensive

maintenance

activities

and the successful

completion

of the surveillance

test.On February 1, 1993, the Unit 1 TDAFWP was tested again at the direction

of the Unit 1 operations

manager in order to ensure operability, considering

the numerous problems encountered

previously.

After receiving

a start signal, the pump tripped on an overspeed

condition

and was declared inoperable.

On February 3, 1993, Unit 2 was operating

at 100-percent

power. Two steam-driven steam generator

main feedwater

pumps and one electric startup feedwater pump were providing

feed flow to the steam generators.

The startup feedwater pump tripped when the pump lubricating

oil duplex strainers

were being shifted. Operators

began to manually ramp down power but were unable to avoid the low steam generator

level. The operators

subsequently

initiated

a manual reactor trip before receiving

an automatic

reactor protection

system trip signal on low steam generator

level. Following

the plant trip, the Unit 2 TDAFWP received an automatic

signal to supply water to the steam generators.

The pump started but immediately

tripped on an overspeed

condition.

On February 4, 1993, Unit 1 commenced

a shutdown to place the reactor in the mode required by the Technical

Specifications

because the TDAFWP had not been restored to an operable condition

within the outage time allowed by the Technical

Specifications.

Further details can be found in License Event Report 50-498/93-007 and NRC Inspection

Reports 50-498; 50-499/93-05 and 50-498; 50-499/93-07.

Discussion

Although the licensee did not identify the root cause of the Unit 1 TDAFWP overspeed

trips, the proximate

cause was determined

to be the intrusion

of water into the TDAFWP turbine that adversely

affected its performance.

However, this cause was effectively

masked for several surveillance

tests because the surveillance

test program established

to satisfy the operability

requirements

of the Technical

Specifications

was not sufficiently

rigorous to assure that the testing was performed

under suitable environmental

conditions.

The TDAFWP was not returned to its normal standby condition

before each of the TDAFWP surveillance

tests performed

on December 27, 1992, and January 30, 1993. Because of this, the pump was not tested in its normal standby condition

and degraded conditions

affecting

operability

were not revealed.

IN 93-51 July 9, 1993 The licensee determined

that the root cause of the February 3, 1993, Unit 2 TDAFWP overspeed

trip was an incorrect

valve lineup in conjunction

with an Inoperable

or degraded steam trap. The valves and the steam trap are located in the drain line from the steam admission

line. (See Figure 1.) The TDAFWP overspeed

trip was caused by excessive

condensate

buildup in the steam supply line upstream of the trip/throttle

valve (MOV-514 in Figure 1). The excessive condensate

had accumulated

because the steam trap bypass valve, MS-517, was incorrectly

positioned (closed) and the steam trap had degraded to such an extent that it was no longer capable of passing condensate

to the condenser.

The licensee took the following

corrective

actions related to the hardware modifications

for both units:* The trip/throttle

valves and governors

were sent to the respective

vendors for complete refurbishment

and testing. The gearing arrangement

of the trip/throttle

valve was modified to ensure slower stroke time, thus enabling a more positive governor response.* The TDAFWP drain system was modified to remove the steam traps in the steamline

drain system, replacing

them with a spool piece. Also, the trip/throttle

valve high-pressure

steam leakoff was separated

from the turbine casing drain line and rerouted to the sump to prevent possible intrusion

of steam into the turbine casing. (See Figure 2.)Related Generic Communications

• NRC Information

Notice 86-14, Supplement

2, "Overspeed

Trips of AFW, HPCI, and RCIC Turbines," dated August 26, 1991.* NRC Information

Notice 88-09, "Reduced Reliability

of Steam-Driven

Auxiliary

Feedwater

Pumps Caused by Instability

of Woodward PG-PL Type Governors," dated March 18, 1988.* IE Information

Notice 86-14, Supplement

1, "Overspeed

Trips of AFW, HPCI, and RCIC Turbines," dated December 17, 1986.* IE Information

Notice 86-14, "PWR Auxiliary

Feedwater

Pump Turbine Control Problems," dated March 10, 1986.

• .IN 93-51 July 9, 1993 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 (NRR) project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts:

Mark A. Satorius, RIV (817) 860-8141 William D. Johnson, RIV (817) 860-8148 Peter C. Wen, NRR (301) 504-2832 Attachments:

1. Figure 1, Existing South Texas Project TDAFWP Steam Supply and Exhaust System 2. Figure 2, Modified South Texas Project TDAFWP Steam Supply and Exhaust System 3. List of Recently Issued NRC Information

Notices

MOV-143 STEAM EXHAUST LINE STEAM ADMISSION LINE MOV-514 TERRY TURBINE (STEAM ADMISSION LINE DRAIN VALVES PIPE CAP WITH ORIFICE If (UNIT I ONLY)MS 371 MS 370 FO 7537B~1 I I FO 7537A--Yl MS TURBINE CASING 373 DRAIN VALVE STEAM TRAP BYPASS VALVE STEAM TRAP w I1°% I'-(D% %D n 0D w I-a%0 r CONDENSER FIGURE 1 TDAFWP STEAM SUPPLY AND EXHAUST SYSTEM (UNMODIFIED)

MOV-143 STEAM EXHAUST LINE STEAM ADMISSION LINE MOV-514 TERRY TURBINE C STEAM ADMISSION UNE DRAIN VALVES MS 370 FO 7537B MS TURBINE CASING 373 DRAIN VALVE MS 515 STEAM TRAP BYPASS VALVE SPOOL PIECE m 'z--~HAQ %D t" MD3%O D" D Wa " MS 516 CONDENSER FIGURE 2 TDAFWP STEAM SUPPLY AND EXHAUST SYSTEM (MODIFED)

Attachment

3 IN 93-51 July 9, 1993 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 93-50 93-49 93-48 92-06, Supp. 1 93-47 Extended Storage of Sealed Sources Improper Integration

of Software into Operating Practices Failure of Turbine-Driven Main Feedwater Pump to Trip Because of Contaminated

Oil Reliability

of ATWS Mitigation

Systems and Other NRC-Required

Equip-ment not Controlled

by Plant Technical

Specifica- tion Unrecognized

Loss of Control Room Annunciators

Potential

Problem with Westinghouse

Rod Control System and Inadvertent

Withdrawal

of A Single Rod Control Cluster Assembly Degradation

of Shutdown Cooling System Performance

Operational

Challenges

During A Dual-Unit Transient Use of Inappropriate

Lubrication

Oils in Safety-Related

Applications

07/08/93 07/08/93 7/6/93 07/01/93 06/18/93 6/10/93 06/16/93 06/15/93 06/10/93 All licensees

authorized

to possess sealed sources.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for Westinghouse (W)-designed nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.93-46 93-45 93-44 93-43 OL = Operating

License CP -Construction

Permit

\,-IN 93-51 July 9, 1993 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 (NRR) project manager.orig /s/'d by BKGrimes Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts: Mark A. Satorius, RIV (817) 860-8141 William D. Johnson, RIV (817) 860-8148 Peter C. Wen, NRR (301) 504-2832 Attachments:

1. Figure 1, Existing South Texas Project TDAFWP Steam Supply and Exhaust System 2. Figure 2, Modified South Texas Project TDAFWP Steam Supply and Exhaust System 3. List of Recently Issued NRC Information

Notices*SEE PREVIOUS CONCURRENCE

OFFICE *OGCB:DORS

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NAME PCWen/vsb

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ABBeach DATE 06/01/93 l 06/02/93 06/02/93 06/04/93 06/04/93*PM:PDV:NRR

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IN 93-xx June 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 one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts: Mark A. Satorius, RIV (817) 860-8141 William D. Johnson, RIV (817) 860-8148 Peter (301)C. Wen, NRR 504-2832 Attachments:

1. Figure 1, Existing South Texas Project TDAFWP Steam System 2. Figure 2, Modified South Texas Project TDAFWP Steam System 3. List of Recently Issued NRC Information

Notices Supply and Exhaust Supply and Exhaust*SEE PREVIOUS CONCURRENCE

OFFICE *OGCB:DORS

• DRP:RIV *TECH ED. *SC:DRP:RIV

• D:DRP:RIV

N.ME PCWen/vsb

MASatorius

MFMejac WDJohnson

ABBeach DATE 06/01/93 06/02/93 06/02/93 06/04/93 06/04/93*PM:PDV:NRR

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6 IN 93-xx June 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 one of the technical

contacts listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts: Mark A. Satorius, RIV (817) 860-8141 William D. Johnson, RIV (817) 860-8148 Peter C. Wen, NRR (301) 504-2832 Attachments:

1. Figure 1, Existing South Texas Project TDAFWP Steam Supply and Exhaust System 2. Figure 2, Modified South Texas Project TDAFWP Steam Supply and Exhaust System 3. List of Recently Issued NRC Information

Notices*SEE PREVIOUS CONCURRENCE

OFFICE *OGCB:DORS

• DRP:RIV *TECH ED. *SC:DRP:RIV

• D:DRP:RIV

NAME PCWen/vsb

MASatorius

MFMejac WDJohnson

ABBeach DATE 06/01/93 06/02/93 06/02/93 06/04/93 06/04/93 PM PDV:NRR P e E BC:OGCB:DORS:NRR

D:DORS:NRR

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notice requires no specific act on or written response.

If yew ton & questions

about the information

in his notice, please contact*a of tochnical

contacts listed bolow or th appropriate

Office of btlw lector Regulation (NRR) project manager Toc"ial contatts: Brian K. Gripes, Director Division of OPerating

Reactor Support Office of Nuclear Reactor Regulation

MKrk A. Satorius, RI'(817) 660-4141 William D. Johnton, RIV (817) B6O-814B Peter C. Win NRR (301) 504-28i2 fttocwtsz:1

1. fig" It Existing South Texas Project TDAfWP Steam Supply 9 t 1. FlKrp 2, Modified South Texas Project TDA4I P Steam Supply S. stoe.ist tf Recently Issued NRC Information

Noice~s and Exhaust and Exhaust I Q2I fIaCURR E _.__ I___-(, 0 1 93 PCmn/sb tSu:D~ohnn

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IN 93-xx June xx, 1993 Page 3 of 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 (NRR) project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts: Mark A. Satorius, RIV (817) 860-8141 William D. Johnson, RIV (817) 860-8148 Peter C. Wen, NRR (301) 504-2832 Attachment:

List of Recently Issued NRC Information

Notices_. __I OFFICE OGCB:DORS

DRP:RIV TECH ED. SC:DRP:RIV

D:DRP:RIV NAME PCWen/vsb

MASatorius

A. WDJohnson

ABBeach DATE .06/ I /93 _ 06/ /93 06/-L193 f06/ /93 l 06/ /93....BC:SPLB:DSSA:NRR

D:DSSA:NRR

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