ML18096A084

Special Rept:On 910523 & 910525,valid Failure Re 2B Diesel Generator Occurred When pre-lube Pump Heater Circuit de-energized & non-valid Failure Occurred on 910525 Re Jacket Water Leak

ML18096A084
Person / Time
Site:	Salem
Issue date:	06/20/1991
From:	Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9106260250
Download: ML18096A084 (4)

Text

.. ~~ P. S.t&G e .e

~~- E..

Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station

• June 20, 1991 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCKET NO. 50-311 UNIT NO. 2 SPECIAL REPORT 91-2 This Special Report addresses the cir.cumstances surrounding a valid failure and a non-valid failure of No. 2B Diesel Generator on May*

23, 1991 and May 25, 1991, respectively. This report is submitted

• in accordance with the requirements of Technical Specification

• surveillance 4.8.1.1.4. pursuant to ~echnical Specification 6.9.1.

It is required within thirty (30) days of event occurrence.

Sincerely yours, EZ/la-

c. A. Vondra

• General Manager -

Salem Operations MJP:pc Distribution 9106260250 910620 95-2189 (10M) 12-89 PDR ADOCK 05000311 S PDR

UNIT 2 SPECIAL REP0~91-2 PLANT IDENTIFICATION:

\

Salem Generating Station - Unit 2 Public Service Electric & Gas Company Hancock's Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

2B Diesel Generator; Valid and non-valid failure due to equipment failure Event Date: 5123191 and 5125191 Report Date: 6/20191 This report was initiated by Incident Report No.(s)91-381 and 91-385.

This special report describes a valid.failure involving 2B Diesel Generator {DIG) occurring on May 23, 1991 and a non-valid failure on May 25, 1991.

This report is submitted for informational purposes in accordance with Technical Specification Surveillance Requirement 4.8.1.1.4 and contains the information required by Regulatory Guide 1.108, Revision l, August 1977, Regulatory Position C.3.b.

Surveillance Requirement 4. 8 .1*.1. 4 states:

"Reports - All diesel generator failures, valid or non-valid, shall be reported to the Commission pursuant to Specification 6.9.1 . . . . . "

CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 - Reactor Power 75% - Unit Load 800 MWe DESCRIPTION OF-OCCURRENCE:

On May 23, 1991, at 0245 hours0.00284 days <br />0.0681 hours <br />4.050926e-4 weeks <br />9.32225e-5 months <br />, an alarm associated with the pre-lube pump flow control switch was received which caused the pre-lube pump heater circuit to be de-energized. At 0356 hours0.00412 days <br />0.0989 hours <br />5.886243e-4 weeks <br />1.35458e-4 months <br />, 2B DIG was started to ensure that the DIG oil temperature would remain above 100 degrees. During the start of the DIG, one or both of the turbo boost solenoid valves remained open allowing the air receivers to depressurize to approximately 40 psi {the minimum allowable pressure is 100 psi). The DIG was declared inoperable and Technical Specification 3.8.1.1.b Action Statement "a" was entered.

Technical Specification 3.8.1.1 states:

"As a minimum, the following A.C. electrical power sources shall be OPERABLE:

a. Two physically independent circuits between the offsite transmission network and the onsite Class lE distribution system (vital bus system) and

UNIT .2 SPECIAL REP0-91:.._.2 -.2-

b. Three separate and independent diesel generators with:

\'

Technical Specification 3.8.1.1 Action Statement a states:

With either an offsite circuit or diesel generator of the above required A.C. electrical power sourceE? inoperable, demonstrate the OPERABILITY of the remaining A.C. sources by performing Surveillance Requirement~ 4.8.1.1.1.a. and 4.8.1.1 . .2.a * .2 within one hour and at least once per 8 .hours thereafter; restore at least two offsite circuits and three diesel generators to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."

On May 25, 1991, following trouble-shooting and maintenance testing associated with the turbo boost solenoid valves, a jacket water leak occurred on a threaded connection to the .2B D/G ttirbocharger during the perf6rmance of Surveillance Procedure, SP(O) 4.8.1.1 . .2., "Electrical Power Systems - Emergency Diesels". The Operations Department elected to stop the surveillance until the leak could be repaired.

APPARENT CAUSE OF OCCURRENCE:

The cause of the D/G valid test failure has been attributed to an equipment failure. Troubleshooting revealed that a defective

. relay (1 STG) in the switching tachometer circuit caused the turbo boost solenoid valves to remain open.

The cause of the D/G non-valid test failure has been attributed to an equipment failure. A 3/8" NPT nipple, approximately 2 inches long, cracked in the root of the thread. The cause of the crack has been attributed to vibration induced fatique. The cracked fitting did not fail catastrophically. Although the le~kage was within the system make-up capability and the D/G surveillance could have continued, the D/G surveillance was terminated to allow immediate repair.

ANALYSIS OF OCCURRENCE:

The failure of the air receivers to maintain greater than 100 psi constitutes a valid failure as described in Regulatory Guide 1.108. This is the first D/G failure in the last 100 starts for all three (3) D/Gs. The last 100 valid tests performed date back to July 24, 1990.

With one diesel inoperable, the remaining diesels are capable of providing power to the minimum saf egaurds equipment required for analyzed accident and transient conditions. Therefore, this event did not impact the health and safety of the general public.

1-

! l\ UNIT 2 SPECIAL REP0.91-2 CORRECTIVE ACTION:

The defective relay and cracked nipple were replaced and Surveillance Procedur~ SP(0)4.8.1.1.~ was successfully performed. 2B D/G was declared operable on May 25, 1991 at 2045 hours0.0237 days <br />0.568 hours <br />0.00338 weeks <br />7.781225e-4 months <br /> at which time Technical Specification Action Statement 3.8.1.1.b. was exited.

A review of the equipment history for the D/Gs indicates that the failure of the relay is a first time occurance and no further analysis is required. The failure of the jacket water piping has occurred previously. Unit 11B DIG experienced.this type of failur_e in May 1988 and Unit 2 2B D/G in September 1989. As identified in the Unit 2 Special Report 90-6, the schedule 40 nipple was replaced with a schedule 80 nipple. This is the first failure of a schedule 80 nipple.

• The Technical Department is continuing its review of the jacket

• water piping system configuration to determine if a configuration change, (e.g. selected replacement of portions of the system with flexible hoses) would provide a more reliable system.

Technical Specification Table 4.8-1, Diesel Generator Test Schedule, requires that the test frequency be increased to "At least once per 31 days" for "less than or Equal to 1" failure in the last 20 valid tests. This is the first failure for the D/G, therefore, no increase in surveillance frequency is.required.

General Manager -

Salem Operations bwl:pc SORC Mtg.91-070