ML20012C182

LER 85-029-00:on 850520,unusual Motor Vibrations Identified on Svc Water Pump 2PM4A.On 861028,high Vibrations Noted on Upper Motor Bearings of Pump 2PM4B.Caused by Improper Installation.New Bearings installed.W/900312 Ltr

ML20012C182
Person / Time
Site:	Arkansas Nuclear
Issue date:	03/12/1990
From:	Ewing E, Millar D ARKANSAS POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
2CAN039008, 2CAN39008, LER-85-029, LER-85-29, NUDOCS 9003200240
Download: ML20012C182 (4)

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L March 12, 1990 2CANO39008 l

U. S. Nuclear Regulatory Commission Document Control Desk Mail Station P1-137 Washington, D. C. 20555

SUBJECT:

Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6 Licensee Event Report No. 50-368/85-029-00 Gentlemen:

In accordance with 10CFR50.73(a)(2)(v), attached is the ' subject report- '

concerning inadequate quality control:by'the vendor which resulted in the  !

improper installation of service water pump motor bearings. This caused a condition which could have prevented the fulfillment of the safety function of the Service Water system.

Very truly yours, arly C. Ewing General Manager, Technical Support l and Assessment t ECE/DM/abw cc: Regional Administrator Region IV U. S. Nuclear Regulatory Commission

, 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 INP0 Records Center Suite 1500 '

1100 Circle 75 Parkway Atlanta, GA 30339-3064 j,'gRo3200240 900312 g ADOCK 05000368 2

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Form 1062.01A

' NRC Fem '36'6 U.S. Nuclear Regulatory Commission

.(9 83) e proved OM8 No. 3150 0104 L1CENSEE EVENT REPORT (L E R)

FACILITY NAME (1) Arkansas huclear One, Unit Two IDDCAET NUMBER (2) lFAGE (3) 10151010101 31 61 Bill 0Fl013 TITLE (4) Inadequate Quality Control by tee ** Vendor Resulted in Improper Instal?ation of Service Water Pump Motor tB arings Causing a Condition Which Could Have Prevented the Fulfillment of the Safety Tunction of the Service Water System EVENT DATE (5) ER NUMBER (61 REPORT DATE (7) OTHER FACILII]E5 INVOLVED (B) 1 Jequentiali l Revision Month Day Year Year Number Number Month Day Facility Names Year Docket Number (sl 0 b 0 0 0

_ 01 5 21 0 8 5 81 5 --

- 01 21 9 -I 01 0 01 3" 11 21 91 01 0 5 0 0 0 OPERA"ING TH;5 REPORT 15 5UBMITTED PUR5UANT O THE REQUIREMENT 5 OF 10 CFR 5:

MODE L9) 5 (Check one or more of the follt. wino) (11)

F0wtR 20.402(b) 20.40b(c)

LEVEL

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o~, 50.36(c)(1) i 50.73(a (2)(iv) l l 73.71(b)

~ L 20.405(a)(1)(1) ~  ;

~7 50.73(a (2)(v) ~l 73.71(c)

(10) 1 01010 20.405(a) 1)(11) ~1 50.36(c)(2)

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~l Other ($pecify in l~~l 50.73(a)(2)(vii)

- 20.405(a) 1)(111) ~~

1 50.73(a)(2)(i) ~

I 50.73(a (vitt (A) Abstract below and

~ 20.405(a)(1)(lv) ~ l 50.73(a)(2)(11) '"~ $0.73(a (viii (B) in Text NRC Fore 20.405(a)(1)(v) l 50.73(a)(2)(4'i) $0.73(a)(2)(x) 3664)

LICEN5EE CONTALT FOR THIS LER (12)

Name Telephone humber Area Dana Millar, Nuclear $afety and Licensing Specialist , Code

' 51011 916f41-13111010 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (L3)

Reportablei l .

l Reportable,I Caust System Component Manufacturer to NPRDS Cause System Component Manufacturer. to NPRD$

0 Bl i NI Of f GI 61 81 3 i l' j l l l l 1 i

I l l I l l 1 1 I I i I I i l l l SUPPLEMEN" REPORT EXPECTFD (14) EXPECTED Month Day tear SUBMIS$10N ,

l~l Yes (if ves. Complete Expected Submission Date) lIl No DATE (15) I l I i AB5TRACI (Limit to 1400 spaces, i.e. , approximately fif teen single space typewristen lines) (: 6)

As a result of a detailed review of the Service Water (SW) system during an NRC inspection, Arkansas Nuclear One (ANO) has performed a historical review of these events and conservatively detemin6J them to be reportable. On April 10, 1985, a motor, which had newly installed bearings and had been rewound by the vendor, General Electric (GE), was installed on 'A' SW pump (2P4A). After approximately 40 days of pump operation on May 20, 1985, unusual motor vibrations were identified on 2PM4A. It was determined that the upper motor bearings were degraded. The bearings were replaced and the pump returned to service on May 21, 1985. On May 25, 1985, a motor, which GE had returned after rewinding and replacing the motor bearings, was installed on 2P48. On October 28, 1986, high vibrations were identified on the upper actor bearings of 2PM4B. The bearings which were degraded were replaced and the pump returned to service. The root cause of the failure of the bearings on 2PM4A was the installation of the incorrect bearings by CE at the service facility. The failure of the bearings in 2PM4B was due to improper {

installation (incorrect orientation) of the bearings at the GE service facility. Bearing replacements have been performed by AND maintenance personnel since 1985. In each failure the redundant train of SW was avaliable to shutdown the plant, therefore, this event was not safety significant.

i

Form 1062.01B NRC Fem 366A ** U.S. Nuclear Regulatory Commission (9 83) Approved DMB No. 3150-0104 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1) lDOCAET NUMBER (2) l LER NUMBER (6) l FAGE (3) l l l 15tquentiall l Revision!

Arkansas Nuclear One, Unit Two l l Year Number Number l 1015I010101 31 61 81 61 F --

01 21 9 --

01 0101210F1013 ItU (If more space is required, use additional NRC Form 366A's) (17)

A. Plant $tatus At the time of occurrence of this event. Arkansas Nuclear One Unit Two (ANO-2) was operating in Mode 5 (Cold Shutdown). A plant heatup was in progress from 2R4 refueling outage (March 15, 1985 to May 26, 1985).

B. Event Description ,

The Service Water (SW) system [BI) consists of two independent, but interconnected, seismic Category 1, redundant flow paths which furnish cooling water to two independent trains of Engineered Safety Feature (ESF) equipment under normal and emergency conditions. Three pumps are provided such that each is capable of supplying 100 percent of the required cooling water supply for one train of ESF equipment during a Design Basis Accident (i.e., Loss of Coolant Accident with a Concurrent Loss of Offsite Power). Examples of E!F systems supplied with SW include: Containment Cooling (BK), Emergency Diesel Generator (EK), High Pressure Safety injection (BQ), and Low Pressurs SafetyInjection[EP). The normal water supply to the SW system is from the Lake Dardanelle Reservoir.

The SW pump motors are vertical high thrust motors manufactured by General Electric (CE) [Gef3).

The motors are designed with two upper bearings mounted in tendem for a high continuous downward thrust application and with a lower bearing which functions as a guide bearing. The upper bearings are angular contact ball bearings and the lower bearing is a radial bearing. The motor is designed for a continuous downward thrust and a momentary upthrust.

On April 10, 1985, 6 motor, which had newly installed baurings and had been rewound by the vendor L (CE), was installed on 2P4A and the pump was placed in service. After approximately forty days of

, pump operation on May 20, 1985, unusual vibrations were identified on 'A' SW pump motor (2PM4A).

l The pump, which was running at the time, was secured. Af ter an inspection it was determined that j the upper motor bearings had degraded causing the high vibrations. A subsequent evaluation revealed that the incorrect bearings had been installed in the motor during work performed at the

! GE service facility. The upper motor bearings were replaced with the correct bearings and the pump l returned to service on May 21, 1985.

l t

On May 25, 1985, a motor, which GE had returned af ter rewinding and replacing the motor bearings, was installed on 2P4B. With the plant operating in Mode 1. on October 28, 1986, high vibrations l were identified on the upper motor bearings of 2PM48. The bearings which were degraded were replaced and the pump returned to service.

C. Safety Significance The SW system serves two identical full capacity trains of ESF equipment. Only one train of ESF equipseent is required for shutdown of the plant af ter any postulated accident condition. Each $W I system train is capable of supplying 100 percent of the required cooling water flows thus meeting l the single failure criterion. If one SW pump falls, the standby pump, if available, may be l brought into service to provide 100 percent of the required cooling water flow for that train.

In the May 1985 event and October 1986 event with the failure of the upper motor bearings on 2PM4A and 2PM48, respectively, only one train of the SW system was affected. If a failure of a SW pump on the redundant train had occurred, this event would be considered safety significant.

However, one train of SW remained operable throughout both events, therefore, this event was not l safety significant.

I D. Root Cause The root cause of the failure (May 1985) of the upper motor bearings on 2PM4A was that the incorrect motor bearings were installed by GE apparently due to inadequate quality control measures at the service facility.

The cause of the October 1986 failure of the upper motor bearings on 2PM4B was also attributed to inadequate quality control by GE. When the motor was received from GE and installed in May 1985, the upper motor bearings had been installed in the incorrect orientation.

E

Fore 1062.01B NRC Fore 366A' ', . U.S. huelear Regulatory Commission (9-83) Approved OMB No. 3150-01D4 Expires: 8/31/85 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY KAME (1) lDOCAET NUMBER (2) l  ;[R NOMF.f R (6) l PAGE (3) l l l lJequential '

l Revision)

Arkansas Nuclear One, Unit Two i l_Yearl Number Number l 10I51010f01 31 61 81 81 bi-- 01 21 9 --

01 Ol01310F1013 TEXT (If more space is. required, use edditional NRC Form 366A's) (17)

E. Basis for Reportability As a result of a detailed review of the $V system during an NRC inspection, AND performed a historical review of these events. On February 9, 1990, these events were conservatively determined to be reportable pursuant to 10CFR50.73(a)(2)(v) as a condition that alone could have prevented the fulfillment of the safety function of the SW system. The failure of a train of the SW system results in a loss of a full train of ESF equipment.

F. Corrective Action

, The correct bearings were installed in 2PM4A after the bearing failures. The bearings in 2PM4B were installed in the correct orientation af ter the bearing f ailures.

The pump motors were sent to the GE service facility for rewinding of the motors. AND also requested that new bearings be installed. Af ter the beering f ailure (May 1985 event) AND apparently did not notify GE of the installation of the incorrect bearings, therefore, 90 actions were taken by CE. At the time of occurrence CE's tuality assurance program was acceptable. The AND Quality Assurance group will evaluate the GE quality assurance program specific to this situation for generic implications. The results of the evaluation will be completed by June 1,1990. Maintenance activities on the $W pump motors (i.e., bearing replacement) have been performed by AND maintenance personnel since the May 1985 and October 1986 bearing failures.

Following the failure of the upper motor bearings on 2PM4B which had been serviced by GE, the GE designers were consulted. It was concluded after further Investigation that the SW pump motors were designed for a face to back bearing orientation. This design configuration allows for two load carrying surfaces for the downward thrusts experienced by the bearings. The original ANO maintenance procedure for bearing installation in the SW pump motors did not depict a specific orientation for the installation of the bearings. The standard maintenance practice for bearing installation was to place the new bearings in the motor in the same orientation as the old bearings were found. This did not provide an assurance that the bearings were being properly installed.

The AND maintenance procedures for bearing installation in the SW pump motors were revised in October 1986 to reflect the correct orientation for bearing installation and to provide an assurance that the bearings would be correctly installed in the future.

G. Additional Information

+There are no previously reported events concerning incorrect bearing installations on 5W pump motors.

Energy Industry Identificotion System (Ell 5) codes are identified in the text as (XX].

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