ML17289A898

LER 92-025-02:on 920522,during Insp of HPCS Pump Motor,Small Piece of Aluminum Upper Air Deflector Found Lodged Inside Motor Stator.Caused by Personnel Error.Evaluation of ECCS Will Be Performed to Prevent Future damage.W/921002 Ltr

ML17289A898
Person / Time
Site:	Columbia
Issue date:	10/02/1992
From:	John Baker, Reis M WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-92-233, LER-92-025, LER-92-25, NUDOCS 9210080192
Download: ML17289A898 (7)

Text

Acczr,za~rzD ryrxIam row Dzvro~a~riox svsrzrur REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

"ACCESSION NBR:9210080192 DOC.DATE: 92/10/02 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION REISiM.P. Washington Public Power Supply System BAKER,J.W. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 92-025-02:on 920522,during insp of HPCS pump motor, small piece of aluminum upper air deflector found lodged inside motor stator. Caused by personnel error. Evaluation of ECCS will be performed to prevent future damage.W/921002 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR t ENCL / SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 DEANiW. 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 '

NRR/DOEA/OEAB l. 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB8H3 1 1 NRR/DSDPLB8Dl 1 1 NRR/DST/SRXB 8E 1 1 EG FILE Q 02 1 1 RES/DSIR/EIB 1 1 RGNS~. EKE Ol 1 1 EXTERNAL: EG&G BRYCEiJ.'H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYgG.A 1 1 NSIC POOREiW 1 1 NUDOCS FULL TXT 1 1 YOTE TO ALL RIDS RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK.

ROOiM PI-37 (EXT. 504-2065) TO ELIMIYATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 31 ENCL 31

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 October 2, 1992 G02-92-233 Docket No. 50-397 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555

SUBJECT:

NUCLEAR PLANT WNP-2, OPERATING LICENSE NPF-21 LICENSEE EVENT REPORT NO. 92-025-02 Transmitted herewith is Licensee Event Report No. 92-025-02 for the WNP-2 Plant. This report is submitted in response to the report requirements of 10CFR50.73 and discusses the items of reportability, corrective action taken, and action taken to preclude recurrence. This supplement is provided. in order to augment details of the root cause statement and clarify statements made regarding historical aspects of this event.

Sincerely,

. W. Baker WNP-2 Plant Manager (Mail Drop 927M)

JWB/RJP/lr Enclosure cc: Mr. J. B. Martin, NRC - Region V Mr. C. Sorensen, NRC Resident Inspector (Mail Drop 901A, 2 Copies)

INPO Records Center - Atlanta; GA Mr. D. L. Williams, BPA (Mail Drop 399) 9210080192 5'21002 PDR ADOCK 0500039'7 S PDR

LICENSEE EVEN REPORT (LER)

FACILITY NAME (I) DOCKET NUMB R ( ) PAGE (3)

Washin ton Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 I OF TITLE (4)

INOPERABILITY OF HIGH PRESSURE CORE SPRAY SYSTEM DUE TO PARTIAL FAILURE OF PUMP MOTOR UPPER AIR DEFLECTOR EVENT DATE (5 LER NUMBER 6 REPORT DATE 7 OTHER FACILITIES INVOLVED (8)

HONTM DAY YEAR YEAR SEQUENTIAL EVISION MONTH OAY YEAR FACILITY NAHES OCKET NUMBERS(S)

NUMBER NUHBER 0 5 0 0 0 0 5 2 8 9 2 9 2 0 2 5 0 2 I 0 0 2 9 2 0 5 0 0 0 P ERAT ING MIS REPORT IS SUBHITTEO PURSUANT TO THE REQUIREHENTS OF 10 CFR 5: (Check one or more of the following) (11)

ODE (9) 5 PONER LEVEL 20.402(b) 20.405(C) 50.73(a)(2)(iv) 77.71(b) 20.405(a)(1)(i) 50.36(c)(1) X 50.73(a)(2)(v) 73.73(c) 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) THER (Specify in Abstract 20.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(viii)(A) below and in Text, NRC 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) Form 366A) 20.405(a)(l)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x)

LICENSEE CONTACT FOR THIS LER (12)

TELEPKONE HUMBER NAME REA CODE M.P. Reis, Compliance Supervisor 5 0 9 7 7 - 4 1 5 2 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COHPONEHT HANUFACTURER EPORTABLE CAUSE SYS'EM COMPONENT MANUFACTURER REPORTABLE 0 NPRDS TO NPRDS 8 G 0 G 0 8 (14) EXPECTED SUBMISSION HON'TH DAY YEAR SUPPLEMENTAL REPORT EXPECTED ATE (15)

YES (If yes, complete EXPECTED SUBMISSION DATE) X NO BSIRAC1 nB)

On May 22, 1992, during an inspection of the High Pressure Core Spray (HPCS) pump motor, a small piece of the aluminum upper air deflector was found lodged inside the motor stator. Several cracks were also discovered in the air deflector. After further investigation, this problem was determined to be reportable because it could have affected operability of the HPCS System.

The root cause of this event was improper work practices that were outside the scope of instructions provided to perform work on the HPCS pump throttle bushing during the pre-operational flushing phase of plant construction. This condition resulted in tearing of the upper air deflector due to excessive The tear propagated along surface indications that were residual from manufacturing during uplift'orces.

subsequent operating cycles due to a high frequency, low stress fatigue mechanism. It has been determined that the indications alone could not have initiated air deflector failure. This event involved a personnel error.

As corrective action, inspection and testing of the HPCS pump motor was performed, the upper air deflector was replaced, and the lower air deflector was inspected. Additionally, air deflectors for the Service Water pumps, which are similarly designed, were inspected. An evaluation of Emergency Core Cooling System (ECCS) pump/motor maintenance procedures will be performed in order to determine if adequate guidance is provided to prevent similar damage in the future. This event did not adversely affect the health and safety of the public or Plant personnel..

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NANE (I) OOCKET NUMBER (2) LER NUNBER (8) AGE (3) ear umber ev. No.

Washington Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 2 0 2 5 0 2 2 OF 5 TITLE (4)

INOPERABILITY OF HIGH PRESSURE CORE SPRAY SYSTEM DUE TO PARTIAL FAILURE OF PUMP MOTOR UPPER AIR DEFLECTOR Plant Condi i n Plant Mode - 5 (Refueling)

Power Level - 0%

Event De cri ion On May 22, 1992, during an inspection of surge ring support brackets and fasteners on the HPCS System Pump Motor (HPCS-M-P/1), a piece of the aluminum upper air deflector was found lodged inside the motor stator. On May 28, 1992, after further investigation, this problem was determined to be reportable because it could have affected operability of pump,HPCS-P-1 and the HPCS System. At the time of the event the Plant was shutdown for the annual maintenance and refueling outage.

The inspection that identified this condition was being performed in response to a recommendation in a General Electric Service Information Letter (SIL 484) pertaining to pump/motor surge ring support brackets and fasteners. Although no problems were noted with these brackets and fasteners, the 5-inch by 4-inch (nominally 3/32-inch thick) piece of the deflector that was discovered could have resulted in localized areas

. of motor damage or there could have been excessive heating of the motor windings due to a reduction of proper air flow during operation of the pump. If the entire annulus portion of the deflector would have failed during pump operation, it most probably would have resulted in motor failure. The purpose of the air deflector is to direct cooling air to the motor windings.

The HPCS pump/motor is a 3,000 hp, 1800 RPM, 4140 volt, squirrel-cage induction motor that is mounted vertically above the HPCS pump (General Electric, Model 5K6357XC10A/PZ55). The degradation or failure of this pump/motor combination could have affected the safety function of the HPCS System, which is to maintain vessel inventory and cool the reactor core during accident conditions.

Immediate rrective Action As immediate corrective action, an investigation into the cause of this event was initiated. No other immediate actions were required because the Plant was shutdown for the annual maintenance and refueling outage at the time of discovery.

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY MAME (I) DOCKET NUMBER (2) LER MUMBER (8) PAGE (3)

Year umber ev. Ko.

Washington Nuclear Plant - Unit 2 5 0 0 0 3 9 7 0

2 025 02 3 OF 5 TITLE (4)

INOPERABILITY OF HIGH PRESSURE CORE SPRAY SYSTEM DUE TO PARTIAL FAILURE OF PUMP MOTOR UPPER AIR DEFLECTOR Fu her Ev luation and Correc ive Action Further Evaluation This event is reportable in accordance with the requirements of 10CFR50.73(a)(2)(v) as an event or condition that alone could have prevented the fulfillment of the safety function of a system that is needed to mitigate the consequences of an accident. This event was also verbally reported to the NRC in accordance with the requirements of 10CFR50.72 as a four-hour, nonemergency notification on May 28, 1992.

Physical examinations and analyses of the failed upper air deflector have been performed by the Supply System's Materials Engineering Group. The scope of these examinations and analyses included fractographic and metallurgical examinations, chemical and modal analyses, and finite element analysis of the static loading condition. Fracture'mechanics analysis of the dynamic loading condition was not deemed necessary due to the conclusive nature of results acquired from other examinations and analyses.

Examination of the upper air deflector identified one instance of tearing and several instances of indentation-type deformation corresponding with air deflector hold-down bracket locations. The tearing was several inches long, and formed a part of. the main fracture. Other observed features included: 1) fatigue symptoms in the principal cracks that merged with the tear, and 2) surface indications that were residual from the air deflector manufacturing process.

It has been determined that the indentation-type deformations noted at air deflector hold-down bracket locations were the result of normal bracket preload stresses. The existence of air deflector tearing has been attributed to a previous event involving improper uplift of the HPCS pump/motor assembly. A review of equipment history records for the HPCS pump/motor indicates that an event involving excessive uplift force on the rotor of the HPCS pump motor occurred in 1983 during the preoperational flushing phase of plant construction.

The uplift event transpired during installation of a pump throttle bushing for the HPCS pump.

During this event, workers exceeded the scope of their instructions and used a ten ton porta-power hydraulic jack to lift the rotor of the HPCS pump motor. Lifting the rotor in this manner resulted in failure of the HPCS pump motor thrust collar due to overstress, and allowed the rotor to impact the upper air deflector.

LICENSEE EVENT REPORT (L R)

TEXT CONTINUATION FACILITY NAHE (I) DOCKET NUHBER (2) LER NUHBER (8) PAGE (3)

Year Number ev. No.

Washington Nuclear Plant - Unit 2 3'

0 5 0 0 0 7 2 025 2 4 F 5 ITLE (4)

INOPERABILITY OF HIGH PRESSURE CORE SPRAY SYSTEM DUE TO'PARTIAL FAILURE OF PUMP MOTOR UPPER AIR DEFLECTOR Based upon the results of examinations and analyses, it was concluded that failure of the upper air deflector was precipitated by stress risers that were created by tom material in the vicinity of the air deflector hold-down brackets. Actual failure of the air deflector resulted when fatigue cracks were initiated at these stress risers and propagated along existing surface indications during succeeding plant operating cycles due to a high-frequency, low-load mechanism. Although manufacturing related surface indications contributed to fatigue crack propagation and subsequent failure of the upper air deflector, it has been determined that these indications alone could not have caused air deflector failure.

The root cause of this event was improper maintenance work practices that were outside the scope of instructions provided to perform repair work on the HPCS pump throttle bushing during the pre-operational flushing phase of plant construction. The excessive uplift forces experienced during this repair work introduced a tear in the upper air deflector. Fatigue cracks were later initiated and propagated along stress risers associated with the tear, and ultimately resulted in failure of the upper air deflector. This event involved a personnel error.

Failure of the HPCS pump upper air deflector did not result directly from a manufacturing defect, and is not considered to be reportable under 10CFR21. This event was not contributed to by any systems, structures or components that were inoperable at the start of the event.

Further Corrective Action As corrective action, visual inspection of the HPCS motor stator windings, and megger and DC high-potential tests of the HPCS motor stator insulation were performed. The visual inspection confirmed that HPCS pump/motor stator windings had not been damaged, and megger and DC high-potential tests demonstrated that the HPCS pump/motor stator insulation had not be'en degraded.

The failed upper air deflector was replaced with a new deflector, and the HPCS pump/motor lower air deflector was visually inspected. Additionally, air deflectors for the Service Water System Pump Motors, which are similarly designed,,were visually inspected. No evidence of cracking was I identified during inspection of the HPCS pump lower air deflector or Service Water System pump air deflectors. Based upon these air deflector inspections and discussions with the vendor, it was determined that inspection of air deflectors for Residual Heat Removal (RHR) and Low Pressure Core Spray (LPCS) motors, which are also of a similar design, was not necessary. An evaluation of Emergency Core Cooling System (ECCS) pump/motor maintenance procedures will be performed in order to verify that adequate guidance exists to prevent similar air deflector damage in the future.

Completion of this evaluation is scheduled for March 31, 1993.

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER (8) AGE (3) ear umber ev. No.

Washington Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 2 025 2 5 F 5 TITLE (4)

INOPERABILITY OF 'HIGH PRESSURE CORE SPRAY SYSTEM DUE TO PARTIAL FAILURE OF PUMP MOTOR UPPER AIR DEFLECTOR nEfnfifE f HPCS is a partfof the ECCS. Its purpose is to supply water to the reactor vessel over a wide range of accident conditions. For small-break Loss of Coolant Accidents (LOCAs) that do not result in rapid reactor depressurization, the system is designed to maintain reactor water -level. For large breaks, the system provides core spray cooling. The ECCS has built-in redundancy, and is comprised of HPCS, LPCS, ADS, and the RHR - LPCI Mode. Failure of HPCS is bounded within the ECCS single failure analysis.

The condition described in this report did not result in actual failure of HPCS during an event where it was required to operate. Consequently, this event did not affect the health and safety of either the public or Plant personnel. However, even if failure or unavailability of the ECCS function associated with HPCS had occurred during the period when air deflector damage was unrecognized, either the RCIC or ADS System could have been used as a backup to the HPCS System.

Similar Events There have been LERs written due to the inoperability of the HPCS System; however, none of these reports pertained to failure of pump/motor air deflectors.

E~fi f

~eadem ~om onent High Pressure Core Spray (HPCS) System BG Motor HPCS-M-P/1 BG MO

. Pump HPCS-P-I BG Emergency Core Cooling System (ECCS) BM Reactor Core Isolation Cooling (RCIC) System BN Low Pressure Core Spray (LPCS) System BM Residual Heat Removal (RHR) System BO Automatic Depressurization System (ADS) BG