Information Notice 1994-76, Recent Failures of Charging/Safety Injection Pump Shafts

Recent Failures of Charging/Safety Injection Pump Shafts

ML031060430
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:	10/26/1994
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-94-076, NUDOCS 9410200153
Download: ML031060430 (12)

4 UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 October 26, 1994 NRC INFORMATION

NOTICE 94-76: RECENT FAILURES OF CHARGING/SAFETY

INJECTION PUMP SHAFTS

Addressees

All holders of operating

licenses or construction

permits for pressurized

water rekctors.

Purpose

The U.S. Nuclear Regulatory

Commission (NRC) is issuing this information

notice (IN) to alert addressees

to recent failures of charging/safety

injection

pump shafts at facilities

designed by the Westinghouse

Electric Corporation (Westinghouse).

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.Background

4 At Westinghouse-designed

facilities, charging/safety

injection

pumps have three funct ons: (1) to deliver seal iri 4 ction flow to the reactor coolant pumps, (2) .o eliver makeup water flcv ) the reactor coolant system, and (3) to deliver high head safety injection

and recirculation

flow to the reactor coolant system during and after a loss-of-coolant

accident.

During normal operation, one of two, or in some cases, one of three pumps is always in operation

to deliver seal injection

and makeup water flow. The loss of an inservice

charging/safety

injection

pump creates a condition

that may challenge

reactor coolant pump seal integrity

and, if makeup water flow is not restored in a timely manner, can result in a loss of coolant inventory.

On February 29, 1980, the NRC issued IN 80-07, "Pump Shaft Fatigue Cracking," to alert recipients

to failures of charging/safety

injection

pump shafts that occurred during the 1970s. All of the charging/safety

injection

pump shafts addressed

in that notice were procured by Westinghouse

from the Pacific Pump Division of Dresser Industries (now Ingersoll-Dresser

Pump Co). Actions taken at that time to correct the problem included design modifications, changes in the heat treatment

of the shaft material, and the use of formed cutting tools during fabrication.

Also, abnormal operation

of the pumps such as operation with a partial or complete loss of fluid or with high vibration

present was found to be a significant

contributor

to the shaft failures.

The Westinghouse

Nuclear Service Division issued Technical

Bulletins

TB-77-", TB-78-1, and TB-79-6, to provide guidance on vibration

monitoring, operation

and maintenance

of the pumps, and allowable

vibration

amplitude

limits.9410200153 gf 4 okC 4 P4R On C AI 0+ic 4V Iae

vJ IN 94-76 October 26, 1994 Recent events indicate that failures of charging/safety

injection

pump shafts continue to be a problem.Description

of Circumstances

Sequoyah Unit 1 On February 18, 1991, plant operators

for Sequoyah Unit 1 received indications

of decreasing

flow and increasing

motor current on charging pump IB-B. When efforts to restore full flow failed, they declared the pump inoperable

and began shutting down the reactor as required by plant technical

specifications.

Charging pump lB-B had been in operation

for several months and had shown no previous signs of degradation.

The licensee disassembled

the pump, found heavy wear on the impeller shoulders

and the balance drum, and found a 280-degree

crack in the shaft near the 11th stage impeller.

Westinghouse

analyzed the shaft and determined

that the crack had been in the shaft for several months (possibly

years) and that the rotating element was of the improved type referred to in IN 80-07. The licensee replaced +he rotating element and, after testing the pump successfully, returned the pump to service. [Licensee

Event Report (LER) 50-327/91-003]

Callaway On February 2, 1992, the Union Electric Company Callaway Plant was at power and charging pump B was in service to support operations.

Plant operators received indications

of zero flow in the charging header and at the reactor coolant pump seal. The operators

placed charging pump A iA service to restore normal flow, and pump B tripped. Plant personnel

inspected

pump B and found that the shaft had sheared on the outboard end between the balance drum lock nut an, balance drum mating area. le licensee documented

the failure in Suggestion

Occurrence

Solution 92-10 and replaced the failed shaft.Shearon Harris On March 18, 1993, operators

at the Shearon Harris plant received indications

of a shaft failure on charging/safety

injection

pump B. The indications

were high motor current, low charging flow, and low pump discharge

pressure.

The operators

secured pump B from service and placed pump A in service. Plant personnel

uncoupled

the pump from the motor and found that the pump shaft had sheared under the balancing

drum lock nut. This was the same location as in three failures that occurred in the 1970s. (LER 50-400/93-005)

D.C. Cook Unit 2 In July 1993, at D.C. Cook Unit 2, a charging pump failed a surveillance

test when it could not deliver the required 454 liters [120 gallons] per minute.The rotating element in that pump had been installed

in 1987. The licensee disassembled

the pump and found a 10 centimeter

[4 inch!, 180 degree circumferential

crack through the number 9 impeller shaft keyway. Smaller cracks were found in two other impeller keyway areas. (LER 50-316/93-006)

IN 94-76 October 26, 1994 Braidwood

Unit 1 and Sequoyah Unit 2 The NRC staff has received information

on two other recent failures of charging/safety

injection

pump shafts: (1) on September

15, 1993, at the Braidwood

Nuclear Station Unit 1 (Braidwood), a charging/safety

injection

pump shaft sheared between the 10th and 11th stage impellers, and (2) on February 7, 1994, at Sequoyah Unit 2, a charging\safety

injection

pump shaft failed, resulting

in a reactor shutdown as required by plant technical specifications.

The licensee for Braidwood

replaced the pump shaft and documented

the failure on Problem Investigation

Report 456-200-93-03600.

The licensee for Sequoyah reported that the affected pump had not exhibited

any indication

of degradation

before the shaft failure and that, similar to many of the other shaft failures, the shaft had failed near the location of the balancipng

drum lock nut. (LER 50-328/94-002)

Discussion

Charging/safety

injection

pumps are important

for normal plant operation

and for core cooling during accidents

such as a small break loss-of-coolant

accident.

Fcr most of the failure events described

above, determination

of the root cause of the failure was inconclusive.

However, the operational

histories

of many of the failed shafts showed that they had been operated with void formation, gas entrainment, or other abnormal conditions

within a few years of the failure. Operation

of the pumps under these conditions

may have caused or contributed

to the later failure of the shafts. Avoiding operation of charging pumps under abnormal conditions

and maintaining

vibration

levels within manufacturer

recommendations

may increase pump reliability.

To increase the benefit of predictive

maintenance

programs, Wbstinghouse

recommends

that pump vibrations

be monitored

at least monthly; preferably, every two weeks. This is more frequent than is required by Section XI of the ASME B iler and Pressure Vessel Code. V'stinghouse

will provide recommended

vibration

limits upon request.Industry experience

in detecting

shaft failures in pumps such as the reactor coolant pump and the recirculation

pump is relevant to monitoring

programs of charging/safety

injection

pumps because the precursors

to shaft failure are similar. For those pumps, monitoring

phase angles as well as monitoring

vibration

amplitude

is considered

to be important

in detecting

shaft degradation.

These data are routinely

trended by some licensees

for detection of impending

shaft failures.A description

of the analyses and conclusions

for some of the above events follows: Westinghouse

evaluated

seven possible root causes for the shaft failure at Callaway, including

material defects, design flaws, errors in fabrication

or processing, assembly or installation

defects, off-design

or unintended

service conditions, maintenance

deficiencies, and improper operation.

Westinghouse

concluded

that the shaft failure was most likely the result of a 1986 event in which the pump had experienced

a loss of suction water flow for approximately

seven minutes. The loss of suction flow increased

the vapor-to-liquid

ratio in the pump and caused a dynamic imbalance.

Events of this type could cause

K>~IN 94-76 October 26, 1994 immediate

pump failure or cause cyclic fatigue damage that could lead to premature

shaft failure at a later date.A gas entrainment

event that occurred on August 20, 1990, was determined

to be the probable cause of the shaft failure at Sequoyah Unit 2. Problems caused by gas entrainment

are discussed

in NRC Information

Notice 88-23, "Potential

for Gas Binding of High-Pressure

Safety Injection

Pumps During a Design Basis Accident," and its supplements.

Westinghouse

considers

an operational

phenomenon, such as gas entrainment, may have led to the shaft failure at Shearon Harris, although the licensee found no evidence of gas pockets in the charging system. In May 1991 (two years before-the

shaft failure), the licensee reported to the NRC that the charging system had been in a degraded condition

during the previous operating

cycle.An NRC Special Inspection

Team reviewed the event and determined

that several water hammer events could have occurred in the system as a result of weaknesses

in the design of the alternate

minimum flow system. The NRC issued IN 92-61, "Loss of High Head Safety Injection," and its supplement

regarding that event. Another concern at Shearon Harris was the fact that the A and B charging/safety

injection

pumps are alternated

at approximately

2-week intervals.

Therefore, each pump is started about 25 to 30 times each year.Westinghouse

believes the high number of starts also could contribute

to early shaft failure. Problems associated

with excessive

pump starts include galled wear rings, increased

vibration, and decreased

pump performance.

However, Westinghouse

concluded

that the available

data were insufficient

to directly link the failure of the shaft to the high number of pump starts.Although Westinghouse

could not conclusively

determine

the root cause of the shaft failure at Shearon Harris, West 'nghouse made recommendations

which could help pre-ent or detect impendine

shaf fa;lures.

Westinghou- suggested

that the liceasee conduct a detailed review, of the possibility

that gas could become entrained

in the charging pump suction piping and the cross connczts to other systems. Westinghouse

also recommended

that, when the rotating element of the pump is replaced, consideration

be given to installing

the latest shaft design which has an improved one-piece

balance drum lock nut. Westinghouse

included recommendations

for vibration

monitoring

in Westinghouse

Technical Bulletin TB-79-6. Westinghouse

has not specified

a limitation

on the number of pump starts but recommends

that pump starts be minimized

to maintain pump reliability.

In addition to the industry actions described

above, Westinghouse

and the Westinghouse

Owners Group (WOG) are implementing

a program to address these pump shaft failures.

The program includes:

(1) a survey of WOG member utilities

for pump service operating

history data, (2) a pump design review, and (3) a shaft material enhancement

evaluation.

The program is intended to identify any weaknesses

in design, maintenance, or operation

of the pumps in order to improve shaft reliability.

I .S : ..I IN 94-76 October 26, 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 (NRR) project manager.Brian K. Grimes, Director Division of Project Support Office of Nuclear Reactor Regulation

Technical

contact: D. Roberts, RII (919) 362-0601 Attachment:

List of Recently Issued NRC Information

Notices daret4s

Attachment

IN 94-76 October 26, 1994 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 93-60, Supp. 1 94-75 94-74 94-73 94-72 94-71 94-70 94-69 94-68 Reporting

Fuel Cycle and Materials

Events to the NRC Operations

Center Minimum Temperature

for Criticality

Facility Management

Responsibilities

for Purchased

or Contracted

Services for Radiation Therapy Programs Clarification

of Critical-ity Reporting

Criteria Increased

Control Rod Drop Time from Crud Buildup Degradation

of Scram Solenoid Pilot Valve Pressure and Exhaust Diaphragms

Issues Associated

with Use of Strontium-89 and Other Beta Emitting Radiopharma- ceuticals Potential

Inadequacies

in the Prediction

of Torque Requirements

for and Torque Output of Motor-Operated

Butterfly

Valves Safety-Related

Equip-ment Failures Caused by Faulted Indicating

Lamps 10/20/94 10/14/94 10/13/94 10/12/94 10/05/94 10/04/94 09/29/94 09/28/94 09/27/94 All 10 CFR Part 70 fuel cycle licensees.

All holders of OLs or CPs pressurized-water

reactors (PWRs).All U.S. Nuclear Regulatory

Commission

Medical Licensees.

All fuel fabrication

facilities.

All'holders

of OLs or CPs for pressurized

water reactors All holders of OLs or CPs for boiling water reactors (BWRs).All U.S. Nuclear Regulatory

Commission

Medical Licensees.

All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs For nuclear power reactors.OL = Operating

License CP = Construction

Permit

..I IN 94-76 October 26, 1994 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact technical

contact listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.Original signed by Brian K. Grimes Brian K. Grimes, Director Division of Project Support Office of Nuclear Reactor Regulation

Technical

contact: D. Roberts, RII (919) 362-0601 Attachment:

List of Recently Issued NRC Information

Notices**See previous concurrence

Mamn dated Mav 27 1994 OFFICE REGION II REGION II REGION II NAME DRoberts*

JRJohnson**

BBoger*DATE 08/18/94 05/27/94 08/19/94 OFFICE EMEB:DE C/EMEB:DE

D/DE:NRR NAME JRajan* RWessman*

BWSheron*nATF fl/19194 1 08/26/94 08/30/94 Wu.-t .I -I L*, *- _ , -., -X OFFICE TECHED:RPB

OGCB:DORS:NRR

C/OGCB:DORS:NRR

D NAME JMain* JBirmingham*

ELDoolittle*

DATE 07/20/94 08/17/94 09/08/94 10t{/94 OFFICIAL DOCUMENT1 NAME: V4-/0. IN

IN 94-xx October 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 technical

contact 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

contact: D. Roberts, R11 (919) 362-0601 Attachment:

List of Recently Issued NRC Information

Notices* See previous concurrence

• • Memo dated May 27 1994 OFFICE REGION II REGION II REGION II NAME DRoberts*

JRJohnson**

BBoger*DATE , 08/18/94 [05/27/94 j 08/19/94 OFFICE [ EMEB:DE C/EMEB:DE

I D/DE:NRR NAME JRajan* RWessman*

I BWSheron*DATE 08/22/94 08/26/94 08/30/94 OFFICE TECHED:RPB

OGCB:DORS:NRR

C/OGCB:DORS:NRR

D/DORS:NRR

NAME JMain* JBirmingham*

ELDoolittle*

BKGrimes DATE , 07/20/94 1 08/17/94 , 09/08/94 1 10/ /94 vo .-.-. -^llrg *e- A o n Tl1 UV ILIAL UULUMtNl NAMt: U:\UMF 14N.JLU 4t14L

IN 94-xx October 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 technical

contact 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

contact: D. Roberts, RII (919) 362-0601 Attachment:

List of Recently Issued NRC Information

Notices* See previous concurrence

• • Memo dated May 27 1994 OFFICE REGION II l REGION II REGION II NAME DRoberts*

JRJohnson**

BBoger*DATE 08/18/94 05/27/94 08/19/94 OFFICE EMEB:DE C/EMEB:DE

D/DE:NRR NAME JRajan* RWessman*

BWSheron*DATE 08/22/94 08/26/94 08/30/94-,

• _, , , ,-,, OFFICE TECHED:RPB

OGCB:DORS:NRR

C/OGCB:DORS:NRR

D/DORS:NRR

NAME JMain* JBirmingham*

ELDoolittle*

BKGrimes DATE ,07/20/94

[08/17/94

1 09/08/94 110/ /94 U-ILIAL DULUMLNI NAM: U:\FUMF 1N.JLU

IN 94-xx September

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 technical

contact 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

contact: D. Roberts, RII (919) 362-0601 Attachment:

List of Recently Issued NRC Information

Notices* See previous concurrence

• • MPm= dated May 27. 1994 OFFICE REGION II REGION II REGION II NAME DRoberts*

JRJohnson**

BBoger*DATE 108/18/94

,05/27/94

08/25/94 OFFICE EMEB:DE C/EMEB:DE

D/DE:NRR NAME JRajan* RWessman*

BWSheron&nATC 08/22/Q9 nR/26/94 08/2 v/94 ulIL. I --I --. _ .OFFICE TECHED:RPB

OGCB:DORS:NRR

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NAME JMain* JBirmingham*l

Ek6V2 ittle BKGrimes DATE 1 07/20/94 -1 08/17/94 j P'Z' 94 08/ /94----- .---'OF-FICIAL

DOCUMEN NAME: b:\FUMr IN.VLb

.r IN 94-xx September

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 technical

contact 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

contact: D. Roberts, R11 (919) 362-0601 Attachment:

List of Recently Issued NRC Information

Notices* See previous concurrence

• • Memo dated May 27 1994 OFFICE REGION II REGION I1 REGION II NAME I DRoberts*

JRJohnson**

BBoger*DATE l 08/18/94 [05/27/94 J 08/19/94 OFFICE EMEB:DE C/EMEB:DE

ID I iD IIRR NAME JRajan* RWessman*

I B S on W DATE 08/22/94 08/26/94 08/S6/94 OFFICE TECHED:RPB

OGCB:DORS:NRR

C/OGCB:DORS:NRR

D/DORS:NRR

NAME JMain* JBirmingham*

ELDoolittle

BKGrimes DATE 07/20/94 08/17/94 08/ /94 08/ /94 sors~a rvral~I.-

Plte ^. nstl ti. of ^UMtILIAL UUUUMtNI NAML: b: \FUMr 1N.ULV

IN 94-xx August 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 technical

contact 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

contact: D. Roberts, RII (919) 362-0601 Attachment:

List of Recently Issued NRC Information

Notices* See previous concurrence

• • Memo dated May 27 1994 __41 OFFICE REGION II REGION II lEMED( C/EME l D/DE:NRR NAME DRoberts JRJohnson**

JRajw" RWes ke rBWSheron DATE 08/ /94 05/27/94 0 8 /,/94 089f4/94 9 08/ /94 OFFICE 1 TECHED:RPB

J OGCB:DORS:NRR

C/OGCB:DORS:NRR

D/DORS:NRR

NAME l JMain* JBimnghim*

It ELDoolittle

BKGrimes DATE l 07/20/94 l 08/17/94 08/ /94 08/ /94 OFFICIAL DOCUMENT NAME: G:\PUMPIN.JLB