ST-HL-AE-2767, Final Deficiency Rept Re Cracking of ESF Diesel Generator Heads.Initially Reported on 880801.Precautions Added to ESF Diesel Generator Instruction Manual to Ensure Engine Timing Checked Out Prior to Operation Following Maint

Final Deficiency Rept Re Cracking of ESF Diesel Generator Heads.Initially Reported on 880801.Precautions Added to ESF Diesel Generator Instruction Manual to Ensure Engine Timing Checked Out Prior to Operation Following Maint

ML20153F517
Person / Time
Site:	South Texas
Issue date:	08/30/1988
From:	Goldberg J HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
ST-HL-AE-2767, NUDOCS 8809070324
Download: ML20153F517 (4)

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llouston Lighting A: Power August 30, 1988 ST HL AE 2767 File No. C12.440 10CFR50.55(e)

U. S. Nuclear Regulatory Coc::nission Attention: Document Control Desk Washington, DC 20555 South Texas Project Elsetric Generating Station Unit 2 Docket No. STN 50 499 Final Report Concerning Cracking of ESF Diesel Generator Heads On August 1, 1988, Houstoa Lighting and Power Company notified your office pursuant to 10CFR50.55(e), of an item concerning Cracking of ESF Diesc1 Generator Heads. Enclosed is our Final Report concerning this subject. We have determined that this item is reportable pursuant to 10CFR50.55(e).

If you should have any questions on this matter, please contact Mr.

M. F. Polishak at (512) 972-7071.

.A .Al J. H. Goldberg Group Vice President, Nuclear SDP/RHT/hg Attacament: Final Report Concerning Cracking of ESF 01esel Generator Heads 8809070324 880830 PDR S ADOCK 05000499 pm L4/NRC/by p A Subsidiary of Ilouston Industries incorporated

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Regional Administaator, Region IV Rufus S. Scott _ I Nuclear Regulatory Commission Associate General Counsel ,

611 Ryan flaza Orive. Suite 1000 Houston Lighting & Power Company i Arlington, TK 76G11 P.~ 0. Box 1700 i Houston, TX 77001 ,

George Dick, Project Manager l U.S. Nuclear Regulatory Commission INPO  ;

Washington, DC 20555 Records Center 1100 Circle 75 Parkway Jack E. Boss Atlanta, CA 30339 3064 i Resident Inspector / Operations .

i c/o U.S. Nuclear Regulatory Dr. Joseph M. Hendrie l commission 50 Be11 port Lane 3 P. O. Box 510 Be11 port, NY 11713  ;

Bay City TX 77414 Don L. Carrison  !

Resident Inspector / Construction  !

c/o U.S. Nuclear Regulatory j Commission i P. O. Box 910 i Bay City, TX 77414 J. R. Newman, Esquire [

Newman & Holtzinser, P.C.

l 1615 L Street, N.W. '

Washington, DC 20036 q l

R. L. Rsnge/R P. Verret l Central Power & Light Company P. 9. Box 2121 Corpus Christi, TX 78403 l

R. John Miner (2 copies)

Chief Operating Officer  !

City of Austin Electric Utility '

721 Barton Springs Road Austin, TX 78704 4

, R. J. Costello/M. 7. H^rdt City Public Servics Board P. O. Box 1771 j San Antonio, TX 78296 i

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Aeeachment ST HL AE 2767 File No. G12.440, G2.2 Page 1 of 2 Final Report Concerning Cracking of ESF Diesel Generator Heads I . Summary Ou August 1, 1988, HL6P notified the N.tC concerning cracking in Unit 2 ESF diesel generator cylinder heads that had been determined to be reportable pursuant to 10CFR50.55(e). The cracked diesel generator cylinder heads resulted from engine operation with advanced timing. The ESF diesel generators provide emergency power to the ESF buses in the event of a Design Basis Accident. If this out of time condition had remained uncorrected, concinued operation of the ESF diesel generator could have resulted in a failure that would render the diesel generator's ESF function inoperable.

II. Description of Deficiency During start up testing of the Unit 2 Train "C" Standby Diesel Generator (DC), jacket water was discovered in the combustion chamber of two cylinders. Subsequent removal and inspection of the twenty (20) cylinder heads showed eighteen (18) to be cracked.

Further field investigation revealed that the timing for the DG was advanced approximately twenty-five degrees, allowing the engine to fire at approximataly fifty-fivo degrees before top dead center. The timing advancement most likely occurred vaen the chain tightener oil supply hose was replaced. Apparently, during replacement of the hoses the timing '

chain was loosened. Later, during reinstallacion of the chain tensioner, the slack in the timing chain was taken up, unknowingly advancing the timing chain by two links on the crank shaft gear.

III. Corrective Action

1) The timing chains on the Train "A" and Train "B" Unit 2 EST dieset generators were inspected to ensure they were properly adjusted. The timing of "A" DG was found to be slightly retarde1. Although the reason for the retarded condition can not be conclusively determined, it was not attributable to unknowingly rotating the timing chain on the crank shaft gear. The rets eded timing condition of "A" DG was corrected prior to its initial opetation. The tiaing on the Train "B" DG wa" found to be properly adjusted.

2) Pistons, connecting :nia, bushings, pins, and bearings for cylinders 6 and 7 of the Train "C" diesel generator were inspected to identify areas which exhibited cridence of thermal dams.ge In addition, one cy1!nder liner was removed and inspected for ther:.d damage. The inspected components are acceptable with the exception of the l pistons, which exhibited cracks and eron!.nn in the crown arc s. From 1

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Attachment ST HL AE-2767 File No. G12.440, G2.2 Page 2 of 2 these inspections, HL&P has concluded that the areas subject to thermal damage are limited to the cylinder heads and pistons. All twenty (20) cylinder heads will be replaced. The pistons will be removed, inspected, and rework completed prior to. engine restart.

3) The timing of the repaired engine will be properly adjusted prior to restart.

IV. Recurrence Control

1) Precautions have been added to the ESF Diesel Generator Instruction Manual to ensure that the engine e.iming is checked prior to i operation following maintenance in the timing chain area.

2) In addition, plant maintenance procedures are being reviewed to ensure that adequate precautions are taken when maintenance is performed in tis timing chain area.

. Revisions to the appropriate procedures will be completed by November 15, 1988.

V. Safety Analysis The ESF diesel generators provide emergency pcwer to the ESF buses in the event of a Design Basis Accident. Had this deficiency remained uncorrected and a loss of offsite power (LOOP), or other design basis accident occu-red, in combination with a single failure of either the Train "A" or "B" DGs to start, a safety hazard could result. Therefore, the deficiency has been determined to be reportable pursusnt to 10CFR50.55(e).

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