ML20045E149

LER 93-010-00:on 930526,discovered That Screen Drive Coupling on Essential Cooling Water Traveling Screen 2A Damaged.Caused by Aging of Elastomeric Element.Couplings Replaced & Preventive Maint initiated.W/930625 Ltr

ML20045E149
Person / Time
Site:	South Texas
Issue date:	06/25/1993
From:	Groth J, Pinzon J HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-010-01, LER-93-10-1, ST-HL-AE-4494, NUDOCS 9307010182
Download: ML20045E149 (7)

Text

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' The Light c o mp a ny South Texas Project Electric Generating P. O.Station Box 289 Wadsworth. Texas 77483

' Houston Lighting & Power T

June'25, 1993 ST-HL-AE-4494 File No.: G26'

'10CFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Unit 2 .

Docket No. STN 50-499 Licensee Event Report 93-010 Failure of an Essential Cooling Water Travelina Screen Drive Couplina Pursuant to 10CFR50.73, Houston Lighting & Power (HL&P) submits the attached Unit 2 Licensee Event Report 93-010 regarding a failure of an Essential Cooling Water traveling screen drive coupling. This event did not have an adverse effect on the health and safety of the public.

If you should have Jany questions on this ' matter, .please contact Mr. J. M. Pinzon at (512) 972- 7 or me at (512) 972-8664.

f a .

. GYe Vice President, duclear Generation JMP/pa

Attachment:

LER 93-010 (South Texas, Unit 2) 300004 LER-93\L93010RO.02 - l j Project Manager on Behalf of the Participants in the South Texas Project I

9307010102 930625 PDR ADOCK 05000499 "m ,

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Houston Lighting & Power Company ST-HL--A' E-4 4 9 4

- South Texas Project Electric Generating Station- File.No.: G 2 6'-

10CFR50.73 Page 2 c::

Regional Administrator, Region IV .Rufus S. Scott Nuclear ~ Regulatory Commission Associate' General Counseli 611 Ryan Plaza Drive, Suite 400 Houston' Lighting & Power Company Arlington, TX 76011 P. O.~ Box 61867 Houston, TX '77208-L. E. Kokajko ,

Project Manager U.S. Nuclear Regulatory Commission Institute of. Nuclear, Power Washington, DC 20555 Operations'- Records' Center.

700 Galleria' Parkway.

• J .- I . Tapia Atlanta,.GA' 30339-5957 Senior Resident Inspector .

c/o U. S. Nuclear Regulatory Dr. Joseph M. Hendrie Commission 50 Bellport Lane P. O. Box 910 Bel] port, HY 11713 Bay City, TX 77414 D. K. Lacker J. R. Newman, Esquire Bureau of Radiation Control .'

Newman & Holtzinger, P.C., STE 1000 Texas' Department of Health 1615 L Street, N.W. 1100 West.49th Street Austin, TX '78756-3189- 3 Washington, DC 20036 U.S. Nuclear Regulatory Comm. l D. E. Ward /T. M. Puckett Central Power and Light Company Attn: Document Control-Desk'

-P. O. Box 2121- Washington', D.C. 20555 Corpus Christi, TX 78403 J. C. Lanier/M. B. Lee 1 City of Austin-Electric Utility Department 721 Barton Springs Road Austin, TX 78704

'K . J. Fiedler/M. T.'Hardt '

City'Public Service P. O. Box 1771  ;

San Antonio, TX 78296 1

LER 93\t,93010RO.U2

~l

NRC FOR'1366 U.S. OJCLEA3 REGULATORY CCMMISSION APPROVED BY OMB NO. 3150-0104 (5-92) . EXPIRES 5/31/95 ESilMATED BURDEN PER RESPONSE TO COMPLY WITH I I3 LtECTl " "

LICENSEE EVENT REPORT (LER) $gn"l""*gg 0"S REGAp9xNG BURDEN ESTI ATE D THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, (See reverse for required number of digits / characters for each block) WAShlNGTON, DC 20555 0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) PAGE (3)

South Texas, Unit 2 05000 499 1 OF 4 TITLE (4) Failure of an Essential Cooling Water Traveling Screen Coupling EVENT DATE (5) LER NtMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

A MONTH DAY YEAR YEAR MONTH DAY YEAR NtmBER NUMBER 05000 05 26 93 93 -- 010 -- 00 06 25 93 O O OPERATING THIS REP RT IS SUBMITTE PURSUANT T THE RE UIREMENTS F1 CFR $: (Check one or more) (11)

MODE (9) N'/ A 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)

MMW McW X MamW M c)

POWER g LEVEL (10) 20.405(a)(1)(ii) 50.36(c)(2) 50,73(a)(2)(vii) OTHER 20.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(viii)(A) (Specify in ow 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) A((ac 20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x) NRC Form 366A)

LICENSEE CONTACT FOR THIS Lf R (12)

NAME TELEPHONE NUMBER (Include Area Code)

Jairo Pinzon - Senior Engineer (512) 972 - 8027 CfMPLETE ONE LINE FOR E ACH COMPONE NT F AILURE DESCRIBED IN THIS REPORT (13)

COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM fD p X BI CPLG R235 NO SUPPLEMENT At RFPORT EXPECTED (14) EXPE CTED MONTH DAY YEAR YES(If yes, complete EXPECTED SUBMISSION DATE). X No g5 AUSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On May 26, 1993, Unit 2 was defueled during a refueling outage. During a post-maintenance run of the Essential Cooling Water (ECW) 2A traveling screen, Maintenance personnel discovered that the screen drive coupling was damaged. The coupling transfers motive force from the drive motor to the traveling screen speed reducer while allowing for equipment misalignment.

Coupling inspections of Unit 2 Trains B and C indicated similar coupling damage, with half of the couplings exhibiting cracks while the other half appeared normal. The failure of the couplings affected all three Unit 2 trains of ECW, thus rendering all Standby Diesel Generators (SDG) technically inoperable (but still functional). Unit 2 declared an Unusual Event. Unit 1 ECW Trains A, B and C couplings were satisfactory. The cause of this event was failure to inspect / replace the traveling screen couplings. Information regarding nominal expected lifetime was not in the vendor manual. Corrective actions include developing preventive maintenance activities to inspect / replace the couplings, incorporating vendor information detailing expected life of the couplings into the vendor manual and performing a review to identify other mild environment Equipment Qualification Program Preventive Maintenance activities that may have been cancelled based on incomplete information.

NRC FORM 366 (5-92)

LER-93\t93010RO.U2

NRC F(QM,366A U.S. CJCLEAR REGULATORY COMMIS$1C APPROVED BY 0M8 NO. 31V0-0104

{$-92) . EXPIRES 5/31/95-ESilMATED BURDEN PE:1 SESPONSE TO COMPLY WITH THl! 'l INFORMAYlON COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBE TEXT CONTINUATION 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001 AND TO THE PAPERWORN REDUCTION PROJECT (31500104), OFFICE Of MAN AGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAMC (1) DOCKET WlMBER (2) LER NUMBER (6S PAGE (3)

YEAR SEQUENTIAL REVISION South Texas, Unit 2 05000 499 2 OF 5 93 -- 010 -- 00 TEXT 111 more space is required. use ndditional copies of NRC Form 3664) (17)

DESCRIPTION Of EVENT:

On May 26, 1993, Unit 2 was defueled during its third refueling outage. The Reactor Cooling System was depressurized and vented. During a post-maintenance run of the Essential Cooling Water (ECW) 2A traveling screen, Maintenance personnel discovered that the screen drive coupling was damaged.

The coupling transfers motive force from the drive motor to the traveling screen speed reducer while allowing for equipment misalignment. The elastomeric element of the flexible coupling contained through-wall cracks around half of its circumference. The other half of the coupling was in satisfactory condition. Coupling inspections of Unit 2 Trains B and C indicated similar coupling damage, with half of the coupling exhibiting cracks while the other half appeared normal. Unit 1 ECW Trains A, B and C couplings were satisfactory.

Previously, Equipment Qualification Program Preventive Maintenance (PM) activities existed to replace these couplings but had been cancelled due to being in a mild environment. A review was performed prior to cancellation of these PM activities which took into consideration information available at that time.

A Design Change Notice (DCN) was issued in September, 1991 to incorporate information from the environmental reports into the vendor manual to obtain complete maintenance requirements. However this DCN was not reviewed by the cognizant group responsible for concurrence / impact, and therefore not reviewed for possible incorporation into a PM activity.

At the time of the event, Standby Diesel Generator (SDG) 22 was available for operation. Loss of the ECW 2B train rendered SDG 22 technically inoperable (but still functional) which led to a situation where all Unit 2 SDGs were inoperable. Unit 2 declared an Unusual Event at 1702 hours0.0197 days <br />0.473 hours <br />0.00281 weeks <br />6.47611e-4 months <br />, on May 26, 1993.

The ECW train 2B flexible coupling was replaced and SDG 22 was returned to operability. The Unit 2 Train A and C couplings were replaced. The Unusual Event was terminated at 2204 on May 26, 1994.

CAUSE OF EVENT:

The flexible coupling failed apparently due to aging of the elastomeric element.

l LER-93\L9301DRO.U2

llRC f0RM 366A. U.S. C33 CLEAR REGULATORY COMMISSI C APPROVED BT OMB Wo. 3'i50-0104 (5-92) '

EXPIRES 5/3V95 ESTIMATED BURDEN PER RESPONSE 10 COMPLY W11H 1H15 INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE LICENBEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBE TEXT CONTINUATION 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001 AND TO THE PAPERWORs REDUC 110N PROJECT (31$0-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACit1TY NAME (1) DOCKET NUMRER (2) LFR NUMBER (61 PAGE (3)

YEAR SEQUENTIAL REVISION

"#8" "#8" South Texas, Unit 2 05000 499 '3 OF 5 j 93 -- 010 -- 00 TEXT (if more space is reautred. use edditional copies of NRC Form 366A) (17)

CAUSE OF EVENT: (Cont'd)

The cause of this event was failure to inspect / replace the traveling screen couplings. Per recent discussions with the manufacturer, the flexible couplings have a nominal expected lifetime of five years. However, this information was not contained in the vendor manual for the coupling.

Therefore, the replacement PMs were deleted because there was no reason to suspect a failure due to aging.

A contributing cause was that the initial review which cancelled the mild environment Equipment Qualification PMs did not include all available Equipment Qualification information. A second contributing cause was that the DCN to incorporate maintenance information of the couplings into the vendor manual was not reviewed by the cognizant group. This review would have addressed the impact on PM activities.

ANALYSIS OF EVENT:

Failure of the traveling screens affects the operation of the ECW-system.

The ECW system removes heat from various safety related loads during accident conditions. This heat is dispersed in the Ultimate Heat Sink (the Essential Cooling Pond) . The ECW traveling screens filter water from the Essential Cooling Pond to I- uve debris which could damage pumps or foul heat exchanger tubes. During normal operation there is no debris in the cooling pond which could affect its operation. This function-is necessary after a design basis flood or other extreme weather conditions which would deposit debris into the Essential Cooling Pond. Since the Essential Cooling Pond is fed from well water and it is chemically treated there is no reason'to suspect that the screens would be required to operate under normal conditions. Since initial operation of the plant, there have been no failures of the screens due to debris. Therefore, loss of the screens in this case did not impact the actual operation of the ECW system or its ability to cool the SDGs.

The failure of the couplings affected all three Unit 2 trains of ECW and l therefore, could have prevented the fulfillment of the safety function of the  !

ECW system during an accident condition. This event is reportable pursuant j to 10CFR50. 73 (a) (2) svi) since a common failure affected independent trains.

LER-93\L93010RD.U2

. ~

yac, FQRy. 366A u.s. NUCLEAR REGJLATORY COm!SSION APPROVED SY OMB NO. 3150-0104 (5 92)

EXPIRES 5/31/95 ESilMATED BURDEN PER RESPC"SE TO COMPLY WITH THi!

INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMFENTS REGARDING BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBE 7714), U.S. NUCLEAR REGULATORY COMMISSION, TEXT CONTINUATION WASHINGTON, DC 20555-0001 AND TO THE PAPERWORM REDUCTION PROJECT (31'$0-0104), OFFICE OF MANAGEMENT AND BUDGET, WASNINGTON, DC 20503.

FACIIITY NAME (1) DOCKET NUMBER (2) LER WUMBER (61 PAGE (3)

SEQUENTIAL REVISION YEAR South Texas, Unit 2 05000 499 4 OF 5 93 -- 010 -- 00 TEXT (If mr;re soace is reauired. use additional copies of NRC Form 366A) (17)

CORRECTIVE ACTIONS:

1. Unit 2 Trains A, B and C ECW traveling screen elastomeric couplings were replaced. The Unit 1 ECW traveling screen elastomeric couplings were inspected and found to be satisfactory.

2. Pertinent vendor information detailing the expected life of the couplings has been incorporated into the vendor manual.

3. Preventive Maintenance activities have been initiated to inspect / replace the flexible couplings and work instructions will be developed prior to their next performance.

4. This event will be discussed with the personnel responsible for reviewing the DCN for impact on PM activities. This action will be completed by July 29, 1993.

5. A review will be performed to identify if there are generic implications associated with the review of DCNs. This review will be completed by July 29, 1993. A revision to the LER will be submitted if any significant findings are discovered.

6. HL&P will perform a review to identify whether other mild environment Preventive Maintenance activities had been cancelled based on incomp. ate reviews of available Equipment Qualification information. If any deficient conditions are found, PM activities will be reactivated in a timely fashion. The evaluation will be completed by September 14, 1993.

Additional corrective actions will be developed as necessary.

ADDITIONAL INFORMATION:

The degraded couplings are manufactured by Rexnord and the coupling elastomeric elements are the Tru-Flex type.

During the past two years, three LERs have been submitted to the NRC which attributed failures as the result of deleted or non-existent Preventive Maintenance activities. These LERs are as follows:

. Unit 1 LER 92-012 - entry into Technical Specification 3.0.3 due to both channels of the Digital Rod Position Indication (DRPI) system bccoming inoperable. This LER attributed one of the causes to non-existent Preventive Maintenance activities.

LER-93\t93010RO.U2

jaRC FORR 366A U.S. sAJCLEAR REGULATC2Y COMMISSION APPROVED BY OMB No. 3150-0104 (5 ,92) .

EXPIRES 5/31/95 ESTIMATED BU2 DEN PER RESPONSE TO COMPLY WITH THl!

• INFORMATION COLLECTION REQUEST: 50.0 NRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE LICENSEE EVENT REPORT (LER) INFORMATION AND RECORDS MANAGEMC.NT BRANCH (MNB5 TEXT CONTINUATION 7714), u.S. NUCLEAR REGUL ATORY COMMISSION, WASHINGTON, DC 20555-0001 AND TO THE PAPERWORK REDUCTION PROJEC1 (3150-0104), OFFICE Of MANAGEMENT AND DVDGET, WASHINGTON, DC 20503.

FACILITY NAMF (1) DOCK 7 NUMBER (2) LER WUMBER (61 PAGE (3)

YEAR SEQUENTIAL REVISION South Texas, Unit 2 05000 499 5 OF 5 93 -- 010 -- 00 TEXT IJ!f pore space is reautred, use addi+1onal copies of NRC Form 36 36 (IT)

ADDITIONAL INFORMATION: (Cont'd) o Unit-1 LER 92-016 - unplanned Engineered Safety Features (ESF) actuation of a Component Cooling Water pump. During this event an alarm was inoperative due to a loose microswitch connection. The level switch that generates the alarm had not been calibrated since 1987 and the Preventive Maintenance activity for both units had been deleted.

o Unit 1 LER 93-017 - inappropriate extension of Feedwater Isolation Bypass positioner and solenoid Equipment Qualification life. In this event Preventive Maintenance were de-activated - as a result of Engineering personnel incorrectly interpreting design documents.

HL&P's assessment of the PM program, as well -as the NRC Diagnostic Evaluation, identified weaknesses in the scope of STPEGS PM activities. HL&P is addressi.4 this concern in response to the Diagnostic Evaluation results.

LER-93\t93010RO.U2 l