ML18096A400
| ML18096A400 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 12/23/1991 |
| From: | Vondra C Public Service Enterprise Group |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 91-4, NUDOCS 9112270352 | |
| Download: ML18096A400 (4) | |
Text
Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station 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 91-4 December 23, 1991 This Special Report addresses the circumstances surrounding a valid failure of No. 2B Diesel Generator on Novemeber 22, 1991.
This report is submitted in accordance with the requirements of Technical Specification Surveillance 4.8.1.1.4. pursuant to Technical Specification 6.9.1. It is required within thirty (30) days of event occurrence.
BWL:pc Distribution
.. Si~v,
- yours,
/f%;!fd General Manager -
Salem Operations
I
- I I I UNIT 2 SPECIAL REPORT 91-4 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 Test Failure, Cause Unknown Event Date: 11/22/91 Report Date:
12/23/91 This report was initiated by Incident Report No.91-851..
This special report describes a valid failure involving 2B Diesel Generator {D/G) occurring on November 22, 1991.
It 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, Auqust 1977, Regulatory Position C.3.b..
Surveillance Requirement 4.8.1.1.4 states:
"Reoorts - All diesel generator failures, valid or non-valid, sh~ll be reported to the Commission pursuant to Specification 6.9.1 -~****"*
CONDITIONS PRIOR TO OCCURRENCE:
Mode 5 (Cold Shutdown)
DESCRIPTION OF OCCURRENCE:
On November 22, 1991, at 0238 hours0.00275 days <br />0.0661 hours <br />3.935185e-4 weeks <br />9.0559e-5 months <br />, after performinq the requjred monthly surveillance of 2B DIG, the DIG was declared inoperable because it had failed to reach rated speed (900 RPM) within 10 seconds~
The recorded time was 10.06 seconds.
Technical Surveillance Requirement 4.8.1.1.2.a.2 states:
"Verify the diesel generator starts from ambient conditions arid accelerates to at least 900 RPM in less than or equal to 10 seconds.
The qenerator voltage........ after the start sjqna1".
APPARENT CAUSE OF OCCURRENCE The cause of the DIG valid test failure is unknown.
TI1e most common reasons for failure of a D/G to achieve rated speed within the prescribed time limits are fuel rack binding,
UNIT 2 SPECIAL REPORT 91-4 APPARENT CAUSE OF OCCURRENCE:
(cont'd) faulty/weak air start motors or governor actuators, and low jacket water pressure and speed switches which actuate prematurely to remove the air start motors from the starting sequence.
Troubleshooting included manipulation of the fuel racks for binding and testing the air start motors for operability.
The fuel racks showed no evidence of binding and the air start motors tested satisfactorily.
2B DIG was subsequently started two (2) times and both times the DiG reached 900 RPM in less than 10 seconds.
The associated governor actuators, jacket water pressure and*speed switches operated normally during these runs.
Corrective and preventive maintenance work orders performed on 2B DIG in October and November~ 1991, were reviewed to determine if associated work activities could have affected the starting time.
There were no work activities performed that could have adversely affected the starting time of the DIG.
System Engineering had reviewed the 2B DIG start times which ranged from 7.67 seconds in July, 9.1 and 9.5 seconds in August, 9.1 and 9.2 seconds in September, 8.72 seconds in October, and 9.65 in early November.
The System Engineer recognized the increasing trend in the starting times, but believed that the DIG starting time would decrease following the monthly fuel rack preventive maintenance (PM) as indicated by the trend data.
The PM was performed*prior to the Q!G monthly surevillance run.*
ANALYSIS OF OCCURRENCE:
The failure of 2B DIG to attain a speed of 900 RPM within 10 seconds constitutes a valid failure as described in Regulatory Guide 1.108.
This was the second DIG failure in the last 100 starts f6r all 3 D/Gs.
The previous failure occurred on May 23, 1991, when one or both of the turbo boost solenoid valves on 2B DIG remained open allowing the air receivers to depressurize to approximately 40 psi (the minimum allowable pressure for operability is 100 psi).
In Mode 5, Technical Specifications require only two (2) operable D/Gs.
During this event, 2A and 2C D/Gs were operable.
Therefore, this event did not impact the health and safety of the general publjc.
CORRECTIVE ACTION:
Surveillance Procedure SP(0)4.R.1.1.2 was performed satisfactorily and 2B D/G was returned to service on November 23, 1991, at 1042 hours0.0121 days <br />0.289 hours <br />0.00172 weeks <br />3.96481e-4 months <br />.
UNIT 2 SPECIAL REPORT 91-4 CORRECTIVE ACTION:
(cont'd)
The operability test frequency was in6reased in accordance with Technical Specification Table 4.8-1, Diesel Generator Test Schedule, which requires that after the second test failure in the last 20 tests, the surveillance test frequency be increased to once every 7 days.
Data from prior DIG starts will be reviewed as well as the results from the 18 month mechanical surveillance testing (scheduled to be performed during the current refueling outage) to help determine the root cause of the DIG increased start times.
An inquiry will made through Nuclear Network to obtain industry data relative to DIG starting times.
The vendor will also be contacted to determine if there are any known concerns with the starting system.
.bwJ : pc SORC Mtq.91-129 General Manager -
sa*lem Operations