ML20112F792

Special Rept:On 960507,D22 EDG Declared Inoperable.Caused by D22 EDG Crankcase Overpressurization Exhaust Backpressure. D22 EDG Exhaust Stack Scraped & Ion Oxide Scale Sheets Removed from Sidewalls

ML20112F792
Person / Time
Site:	Limerick
Issue date:	06/06/1996
From:	Boyce R PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9606100118
Download: ML20112F792 (3)

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R:btrt W.Ccyce Plant Manager

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. Limerick Generating Staton

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' PECO NUCLEAR nc0 eno c-Limerick Generatire Station A Unit of P5CO Energy. PO Box 2300 Sanatoga, PA 19464-0920 610 718 200C T.S. 6.9.2 June 6, 1996 Docket No. 50-353 License No. NPF-85 U.S. Nuclear Regulatory Commission Attn: . Document Control Desk Washington, DC 20555

SUBJECT:

Limerick Generating Station, Unit 2-Special Report for a Valid Emergency Diesel Get.arator Test Failure

REFERENCE:

Technical. Specifications Sections 4.8.1.1.3 and 6.9.2 This Special Report is submitted pursuant.to the requirements of Technical Specifications (TS) Section 6.9.2 as required by TS Surveillance Requirement 4.8.1.1.3. TS Surveillance Requirement-4.8.1.1.3 requires reporting of all diesel generator failures, valid or non-valid, within 30 days. The report is required to include the information recommended in Regulatory Position C.3.b of Regulatory Guide (RG) 1.108, " Periodic Testing of Diesel Generator Units as Onsite Electric Power Systems at Nuclear Power Plants,"

Revision 1, August 1977.

On May 7, 1996, with Unit 2 at 100% power, Operations perc&nnel were performing Surveillance Test (ST) Procedure ST-6-092-312-2, "D22 Diesel Generator Slow Start Operability Test Run." The D22 Emergency Diesel Generator (EDG) was started at 1029 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.915345e-4 months <br /> and brought up to full speed and full load by 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />. During.this time all observed EDG parameters were normal. Upon reaching full load, the Equipment Operator (EO) removed the crankcase dipstick to checat lube oil level per procedure. When the dipstick was removed a second time, lube oil streamed out of the dipstick pipe. The EO reinserted the dipstick, and subsequently, the D22 EDG high crankcase pressure alarm annunciated on the local control panel.

The EO notified the Main Control Room (MCR) of the condition and MCR Operations personnel shutdown the'D22 EDG at 1103 hours0.0128 days <br />0.306 hours <br />0.00182 weeks <br />4.196915e-4 months <br /> on May 7, 1996, and declared the D22 EDG inoperable.

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9606100118 960606 PDR ADOCK 05000353 S PDR

Juns 6, 1996 Page Two During the D22 EDG operability run, debris was observed being expelled from the EDG exhaust stack on the roof of the EDG building. The debris, which fell on the EDG building roof and the currounding ground, consisted of iren oxide flakes approximately one to two inches in diameter and one eighth of an inch thick.

There was no change in smoke quantity or color coming from the D22 EDG exhaust stack during the burst of debris.

An extensive investigation concluded that the D22 EDG crankcase overpressurization was exhaust backpressure caused by momentary plugging of the exhaust stack birdscreen by iron oxide scale sheets which broke away from the exhaust stack sidewall and entered the exhaust stream air flow.

The following corrective actions have been completed:

1. The D22 EDG exhaust stack was scraped and iron oxide scale sheets were removed from its sidewalls. The remaining Unit 1 and Unit 2 EDG exhaust stacks were also scraped and cleaned to address the potential generic implications of this event. i

2. In accordance with vendor recommendations, the D22 EDG was further inspected for other sources of crankcase pressurization. As a result, two cylinder liners, one piston and its associated rings, one connecting rod bearing, the lube oil, the crankcase vacuum manometer, and the crankcase vacuum / pressure switch were all replaced. Also, the generator windings and the crankcase vacuum eductor were cleaned. None of the items identified above contributed to the D22 EDG j crankcase overpressurization event.

3. At 1945 hours0.0225 days <br />0.54 hours <br />0.00322 weeks <br />7.400725e-4 months <br /> on May 14, 1996, the D22 EDG was satisfactorily tested and declared operable.

The future actions planned as a result of this event are as follows:

1. An assessment is expected to be completed by December 15, 1996, to identify appropriate long term corrective actions for the Unit 1 and Unit 2 EDG exhaust stack iron oxide scaling conditions.

2. Review and provide any necessary amendments to the Special Report dated December 28, 1996, which addressed crankcase overpressurization events for the Unit 1 D14 EDG and the Unit 2 Dal EDG, in light of the findings of this event.

The D22 EDG failure was classified as a valid failure using the guidance of RG 1.108, Revision 1, August 1977, Section C.2.e(5).

Since this D22 EDG valid failure is the first failure in the last 20 valid demands, the ST procedure monthly frequency is not required to be changed in accordance with TS Section 4.8.1.1.2.a.

• Junn 6, 1996 s Page Three If you have any questions, please do not hesitate to contact Mr.

James L. Kantner at (610) 718-3400.

Very truly yours, d,"

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DMS:cah I cc: T. T. Martin, Administrator Region I, USNRC N. S. Perry, USNRC Senior Resident Inspector, IGS l

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