ML20199J834

Final Deficiency Rept CDR 86-00-01 Re Design of Diesel Generator Air Start Sys.Initially Reported on 860220.Colt Industries Reset Electric Governor & Revised Starting Air Design to Vent Booster Air Via Pilot Air Connection

ML20199J834
Person / Time
Site:	Seabrook
Issue date:	03/31/1986
From:	Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
CDR-86--1, CDR-86-00-01, SBN-978, NUDOCS 8604090584
Download: ML20199J834 (3)

Text

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SEABROOK STATION Engineering Office Pubec SeMce of New Hompshbe March 31, 1986 Naw Hornpshire Yankse Division SBN-978 T.F. Q2.2.2 Itited States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prunnia, FA 19406 Attention: Mr.111 chard W. Starostecki, Director Division of Project and Resident Programs

References:

(a) Construction Permits CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444 (b) Telephone Conversation, February 20, 1986, "50.55 (e) -

Diesel Generator Air Start System Deficiency,"

W. J. Cloutier (YNSD) and W. J. Daley (YNSD) to J. Beall (NF.C Region I)

Subject:

10CFR50.55(e) Final Report: Deficiency in the Design of the Diesel Generator Air Start System (CDR 86-00-01)

Dear Sir:

On February 20, 1986, we reported a 10CFR50.55(e) item to Region I (Reference (b)). The following information is being filed to clone this item.

A. Description of Deficiency A design deficiency in the Diesel Generator, 1-DG-SKD-7B, starting air system was discovered during startup testing. During this testing, the diesel engine tripped on overspeed. Investigation of the problem indicated that the primary vent path, the starting air distributor, bled the fuel rack booster air pressure too slowly to prevent engine overspeed. This required the lube oil shuttle valve, a accondary vent path, to bleed residual booster air pressure in order to prevent overspeed.

B. Analysis of Safety Implications Overspeed and subsequent trip of the diesel generators on a cold start would result in the unavailability of the emergency back-up power supply until manual restart efforts were succenaful. Both A and B diesel generators could overspeed and trip due to this common deficiency and could result in a plant ac power " black out" during normal or accident conditions.

P.O Box 300 Soobrock.NHO3574

• Totophone(603)474 9521 0604090584 860331 PDR ADOCK 05000443 i S PDR l 3 , g jt.

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United States Nuclear Regulatory Commission Attention: Mr. Richard W. Starostecki Page 2 C. Corrective Action To correct this condition and prevent future overspeed trips, Colt Industries revised the starting air design to vent booster air vim 1 the pilot air connection. We have rerouted the booster vent to the main air start pilot connections per Colt's revised design requirements.

In addition, Ccit Industries Engineering reset the electric governor. The voltage gain on the EGA control is now set higher than before. This causes the electric governor to react more quickly and, thereby, the engine is less prone to overspeed.

Following these changes, both dies.els were tested and no overspeed tripping occurred.

This work has been completed on both Unit I diesels. Modification to the Unit 2 diesels is covered by a nonconformance report. We will notify Region I i when Unit 2 modifications are completed.

This is our final report on this item for Unit 1.

Very truly y urs, f/+--/ 62#

John DeVincentis, Director Engineering and Licensing cc: Atomic Safety and Licensing Board Service List Director, Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, i 20555 a

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,r Diane curran Peter J. Mathews, Mayne Harmon & Wales City Hall 20001 S. Streit, W.W, Newburyport, MA 01950 Euite 430 -

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