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 Office of Nuclear Reactor Regulation
To:
References
IN-93-051, NUDOCS 9307010233
Download: ML031070374 (12)

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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

nuclear power

All holders of operating licenses or construction permits for

reactors.

Purpose

information

The U.S. Nuclear Regulatory Commission (NRC) is issuing this of turbine- notice to alert addressees to the problem of repetitive tripping

Project Electric

driven auxiliary feedwater pumps (TDAFWPs) at the South Texas the

Generating Station. It is expected that recipients will review

actions, as

information for applicability to their facilities and consider contained in

appropriate, to avoid similar problems. However, suggestions no specific

this information notice are not NRC requirements; therefore, action or written response is required.

Description of Circumstances

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

performed a monthly surveillance test on its Unit 1 TDAFWP. After The

start signal, the pump immediately tripped on an overspeed condition.

local manual

operators repeated the surveillance test after a successful the licensee

start. On this attempt the pump successfully started, and

subsequently considered the pump operable.

water level

On January 23, 1993, Unit 2 tripped from 100-percent power on low

in one of the steam generators. The trip occurred because electro-hydraulic

was lost. The

control oil to the steam generator main feedwater pump turbine longer required.

secured when no

Unit 2 TDAFWP started on demand and was later attempted to

After the pump was secured, problems occurred when operators

from the control room. (See

relatch MOV-514 (the TDAFWP trip/throttle valve) a

The licensee conducted

Figure 1.) The pump was declared inoperable. to resolve the

significant amount of troubleshooting and testing on the TDAFWP was identified

MOV-514 relatch problem and another speed control problem that

was completed

during the testing. After the operability surveillance test was restarted on

successfully, the TDAFWP was declared operable and the unit

January 25, 1993.

a routine monthly

On January 28, 1993, the Unit 1 TDAFWP was tested as part of

immediately tripped on an overspeed

surveillance. When started, the TDAFWP 28 through

condition and was subsequently declared inoperable. From January

9307010233 P PC w3 9t - oSI 915 I

-I

IN 93-51 July 9, 1993 and

January 30, 1993, the licensee undertook an extensive testing with the TDAFWP.

troubleshooting effort to determine the cause of the problem

Several problems (overspeed tripping, Numerous pump starts were completed. full- and inability to maintain rated

lack of speed control, oscillations, the Unit 1 load, steady-state speed) were identified. On January 30, 1993, and

TDAFWP was declared operable following extensive maintenance activities

the successful completion of the surveillance test.

direction of

On February 1, 1993, the Unit 1 TDAFWP was tested again at the considering the

the Unit 1 operations manager in order to ensure operability, signal, the

numerous problems encountered previously. After receiving a start

pump tripped on an overspeed condition and was declared inoperable.

Two steam- On February 3, 1993, Unit 2 was operating at 100-percent power. feedwater

driven steam generator main feedwater pumps and one electric startup

feedwater

pump were providing feed flow to the steam generators. The startup being

pump tripped when the pump lubricating oil duplex strainers were to avoid

shifted. Operators began to manually ramp down power but were unable

initiated a manual

the low steam generator level. The operators subsequently system trip

reactor trip before receiving an automatic reactor protection Unit 2 signal on low steam generator level. Following the plant trip, the

the steam generators.

TDAFWP received an automatic signal to supply water to

The pump started but immediately tripped on an overspeed condition.

in the

On February 4, 1993, Unit 1 commenced a shutdown to place the reactor had not been

mode required by the Technical Specifications because the TDAFWP

allowed by the

restored to an operable condition within the outage time

Technical Specifications.

NRC

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

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 of

overspeed trips, the proximate cause was determined to be the intrusion

water into the TDAFWP turbine that adversely affected its performance.

tests

However, this cause was effectively masked for several surveillance

because the surveillance test program established to satisfy the operability

to

requirements of the Technical Specifications was not sufficiently rigorous conditions.

assure that the testing was performed under suitable environmental

of the

The TDAFWP was not returned to its normal standby condition before each

TDAFWP surveillance tests performed on December 27, 1992, and

normal

January 30, 1993. Because of this, the pump was not tested in its not

standby condition and degraded conditions affecting operability were

revealed.

IN 93-51 July 9, 1993 Unit 2 The licensee determined that the root cause of the February 3, 1993,with an

TDAFWP overspeed trip was an incorrect valve lineup in conjunction

located

Inoperable or degraded steam trap. The valves and the steam trap are TDAFWP

admission line. (See Figure 1.) The

in the drain line from the steam supply

overspeed trip was caused by excessive condensate buildup in the steam

(MOV-514 in Figure 1). The excessive

line upstream of the trip/throttle valve was

condensate had accumulated because the steam trap bypass valve, MS-517, an

the steam trap had degraded to such

incorrectly positioned (closed) and condenser.

extent that it was no longer capable of passing condensate to the

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.

HPCI,

• IE Information Notice 86-14, Supplement 1, "Overspeed Trips of AFW,

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 If

This information notice requires no specific action or written response.

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 PIPE CAP WITH ORIFICE

LINE DRAIN If (UNIT I ONLY)

VALVES

MS

371 MS

370 MS TURBINE CASING

FO 7537B 373 DRAIN VALVE

~1 II

STEAM TRAP STEAM FO 7537A--

BYPASS

VALVE

TRAP

Yl (D% %Dn

w I1

°% I'-

CONDENSER I-a%0 w r

0D

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 MS TURBINE CASING

FO 7537B 373 DRAIN VALVE

MS

515 STEAM TRAP SPOOL

BYPASS PIECE m'z ~ --

VALVE

MS " MD3%Dt

HAQ

516 %O D

CONDENSER " D

Wa "

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 Extended Storage of 07/08/93 All licensees authorized

Sealed Sources to possess sealed sources.

93-49 Improper Integration of 07/08/93 All holders of OLs or CPs

Software into Operating for nuclear power reactors.

Practices

93-48 Failure of Turbine- 7/6/93 All holders of OLs or CPs

Driven Main Feedwater for nuclear power reactors.

Pump to Trip Because of

Contaminated Oil

92-06, Reliability of ATWS 07/01/93 All holders of OLs or CPs

Supp. 1 Mitigation Systems and for nuclear power reactors.

Other NRC-Required Equip- ment not Controlled by

Plant Technical Specifica- tion

93-47 Unrecognized Loss of 06/18/93 All holders of OLs or CPs

Control Room Annunciators for nuclear power reactors.

93-46 Potential Problem with 6/10/93 All holders of OLs or CPs

Westinghouse Rod Control for Westinghouse (W)-

System and Inadvertent designed nuclear power

Withdrawal of A Single reactors.

Rod Control Cluster Assembly

93-45 Degradation of Shutdown 06/16/93 All holders of OLs or CPs

Cooling System Performance for nuclear power reactors.

93-44 Operational Challenges 06/15/93 All holders of OLs or CPs

During A Dual-Unit for nuclear power reactors.

Transient

93-43 Use of Inappropriate 06/10/93 All holders of OLs or CPs

Lubrication Oils in for nuclear power reactors.

Safety-Related Applications

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 *DRP:RIV *TECH ED. *SC:DRP:RIV *D:DRP:RIV

NAME PCWen/vsb l MASatorius MFMejac WDJohnson ABBeach

DATE 06/01/93 l 06/02/93 06/02/93 06/04/93 06/04/93

• PM:PDV:NRR *C:SPLB:DSSA:NRR *D:DSSA:NRR *C:OGCB:DORS:NRR D

LEKokaJko CEMcCracken ACThadani GHMarcus dd____

06/08/93 06/09/93 06/10/93 06/16/93 DOCUMENT NAME: 93-51.IN

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

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 l *C:SPLB:DSSA:NRR *D:DSSA:NRR C:OGCB:DORS:NRR D

LEKokaiko CEMcCracken l ACThadani GHMarcus( r lines

06/08/93 1 06/09/93 06/10/93 06//6/93 06/,z/93 DOCUMENT NAME: INTDAFWP.WP 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 l

PM PDV:NRR

LEKokaiko

06/1 /93 P

CEMcCI

e

J E

dThadani

BC:OGCB:DORS:NRR

GHMarcus

D:DORS:NRR

BKGrimes

06/ "/93 06/f/L93 06/ /93 06/ /93 DOCUMENT NAME: INTDAFWP.WP

06/04/93 15:05 R I'J US NRC FTS 728-327'3

002

06-S12-1119 14t130 ;301

5 34 37 NRC WHZTEl LINT F

. .1 P.02 IN 93-xx

Junt Xx, 1993 rhis iofwmtion 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

Brian K. Gripes, Director

Division of OPerating Reactor Support

Office of Nuclear Reactor Regulation

Toc"ial contatts: 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 and Exhaust

9 t

1. FlKrp 2, Modified South Texas Project TDA4I P Steam Supply and Exhaust

S.stoe

. ist tf Recently Issued NRC Information Noice~s

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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 BC:OGCB:DORS:NRR D:DORS:NRR

CEMcCracken ACThadani GHMarcus BKGrimes

06/ /93 06/ /93 06/ /93 06/ /93 UMUWMMI NAMt: IN IUDAWFW. WF