ML20090M603
| ML20090M603 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 03/20/1992 |
| From: | Woodard J SOUTHERN NUCLEAR OPERATING CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9203250022 | |
| Download: ML20090M603 (7) | |
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March 20, 1992 10 CFR 50.36 Docket Nos. 50-348 50-364 U. S. Nucicar Regulatory Commission ATIN:
Document Control Desk Washington, DC 20555 Joseph M. Farley Nuclear Plant Annual Diesel Generator Reliability Data _Repati Gentlemen: is the Annual Diesel Generator Reliability Data Report which is submitted in accordance with Techr.ical Specification 6.9.1.12.
This report provides the number of tests (valid or invalid) and the number of failures for each diesel generator at farley Nuclear Plant for 1991 provides the information identified in Regulatory Position C.3.b of Regulatory Guide 1.108, Revision 1,1977, for each failure.
In August of 1991, Southern Nuclear assembled a Diesel Generator Task Force to assess diesel performance.
The Task force has reviewed diesel operating records, maintenance problems, and procurement problems in an effort to improve diesel reliability and availability. A number of corrective actions have been taken to date to improve performance and several more actions are still in progress.
In the attached report it is noted that as uf September 1991, there were six failures in the last 100 valid tests.
At of February 21, 1992, the failure rate associated with the 1-2A, IB, and 2B diesels was two failures in the last 100 valid tests.
Respectfully submitted, b
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m J. b Woodard
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4 ATTACHMENT 1 AN!NAL DIESEL GENERATOR RELIABILITY DATA REPORT POR 1991
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ANNUAL DIESEL GENERATOR RELIABILITY DATA REPORT FOR 1991 Diesel Generator 1 2A IB 2B IC 20 Total Valid Successful 58 49 50 37 37 231 Tests Invalid Tests 30 19 15 10 10 84 Valid Failures-2 3
2 0
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Invali' Failures 0
0 0
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This diesel generator (DG) reliability data report for the year 1991 is submitted fri accordance with Technical Specification 6.9.1.12.
The table above shows the nurther of tests (valid or invalid) and the number of failures for each of the five DGs at Farley Nuclear Plant.
- 4 I
A'ITACHMENT 2 i
INFORMATION IDENTir1ED IN REGULATORY POSITION C.3.B 0F REGUIATORY GUIDE 1.108, REVISION 1, 1977
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1B DG FAILURE ON 04-19-91 At 0448 on 0419 91, the 111 DG was started per 1:NP 1 STP 80.1 and I;NP 1 SOP 38.0. The output breaker was closed at 0450 and the DG was then loaded to 1 MW. Shortly thereafter, the Plant Operator (PO) observed load oscillations at the !?mergency Power lloard (liPil) and attempted to stabilire voltage without success. The load began to decrease until it dropped to zero, at which point the PO opened the output breaker. The Diesel fluilding Systems Operator (50) reported to the PO that the low fuel oil pressure annunciator had alarmed and fuel oil pressure indicated zero, na,cd on the SO's report and since the voltage and the frequency never came up to 4160 Volts and 60 liertz after the output breaker was opened, the PO tripped the DG at 0455.
Initially an electrical problennvas suspected, however, electrical checks were performed and no problem was found. Mechanical Maintenance then investigated the fuel oil system. The fuel oil day tank foot valve was checked, and no problem was found. Per a vendor recommendation, the fuel oil pump and orifice plate were replaced. The diesel was restarted and tested satisfactorily.
The diesel was returned to service on 4 2191. The 4-19-91 failure was the third failure in the last 100 valid tests. The surveillance test interval was changed to once per 7 days.
(Sce the NOTE after the til DG Failure on 05 24 91 descri,ition) 1-2A DG FAILURE ON 05-17-91 At 1014 on 0517 91, the 12A diesel generator tripped on low lube oil pressure during normal surveillance. Imw lube oil pressure was caused by a high differential pressure across the lube oil strainer, The strainer differential pressure rapidly increased after the diesel generator start. The SO attempted to swap the on service lube oil strainer, but the swap was not made before the diesel tripped. The rapid increase in differential pressure was caused by water in the oil due to a lobe oil heat exchanger tube leak found subsequent to the diesel generator trip. This leak also caused rising lobe oil level in the lube oil sump.
The leak was repaired and the heat exchanger pressure tested satisfactorily, Pre trip oil sample analysis results were reviewed and no indications were found that a heat exchanger tube leak problem was developing. Ilased on normal oil level checks prior :a the event, it is believed that the tube leak developed during this event.
The 1-2A DG was returned to service on 519 91. The 517 91 failure was the fourth failure in the last 100 valid tests. The surveillance schedule remained at once per 7 days.
1B DG FAILURE ON 05-17-91 At 2018 on 517 91, the til DG alarmed on low fuel oil pressure. When the fuel oil pressure was read locally, both pressure indicators (Pis) 637 and 638 read zero. The fuel oil strainer was shifted but this action did not restore fuel oil pressure. The diesel was then manually primed and the fuel oil pressure returned to normal. The diesel was shut down and inspected. Investigation indicated the fuel oil suction line had become air bound, and priming the diesel while it was operating had corrected the problem. The diesel was restarted with normal pressures indicated. The STP was completed satisfactorily.
The til DG was returned to service on 517 91. Prior to the 517 91 test on the 111 DG, there had been 4 failures of the large DGs in the last 100 valid tests. If the 517 91 test had been successful, tbc failure rate would have dropped to 3 in the last 100 valid tests. Since the 5-17 91 test was a failure, the failure rate remained at 4 in the last 100 valid tests.
(See the NOTE after the til DG 1:ailure on 05 24 91 description)
IB DG FAILURE ON 05-24-91 At 0825 on 05 24 91, after starting for normal surveillance, the diesel generator was secured due to low fuel oil pressure. The low fuel oil pressure was caused by a leak in the fuel oil line at the day tank which allowed air to enter the system.
Per MWR 220387, Mechanical Maintenance found the day tank foot valve in satisfactory condition, hov ever, a pressuce test of the fuel pump suction piping indicated a leak through cut threads on the foot valve pipe fitting at the top of the day tank. Investigation revealed the threads were probably damaged during preventive maintenance on the foot valve on 12-17-90 during removal or reinstallation of the foot valve pipe.
The foot valve pipe inside the day tank, and the foot valve, were replaced. The til DG ws returned to service on 5 25 91. The 5 24 91 failure was the fifth failure in the last 100 vahd tests. The surveillance schedule remained at once per 7 days.
NOTE: In retrospect,it is now believed that the unloading of the diesel, the failure of the voltage to increase, and the low fuel oil pressure observed in the 4-19-91,517 91 and 5 24 91 lil DG failures were all caused by fuel depletion. The fuel depletion was due to air binding of the fuel pump caused by air being drawn through cut threads on the foot valve pipe fitting at the top of the day tank. The problem was corrected when the foot valve pipe inside the day tank, and the foot valve, were replaced on 05 24-91, The day tank foot valve inspection PMs for all 5 DGs have been revised to require a pressure test of the fuel oil suction piping after the foot valve inspection.
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1-2A DG FAILURE ON 08-13-91 At 1807 on 08-13 91, after starting the diesel for routine surveillance, the diesel was shut down due to a body to bonnet leak on the llobert Shaw intercooler thermostatic bypass valve. The body to bonnet leak was repaired when the thermostatic bypass valve was disassembled for the replacement of its poppet valve assembly and load spring and reassembled with new gaskets on 819 91.
The 12A DG was returned to service on 8 2191. The length of this outage was due to the length of time required to obtain a replacement valve. This was the fourth failure in the last 100 valid tests. The surveillance test intermi remained at once per 7 days.
2B DG FAILbRE ON 09-02-91 At 1030 on 9 2 91, after starting the 211 DG for normal surveillance, closing the output breaker and increasing the load, the DG was unloaded due to oscillations of 500 kW. The DG was run unloaded while maintenance ch.cked the EGA controller and the governor.
It was reloaded after 30 minutes and the topJ increased steadily to 1 MW, but smoke began coming from the turbo charger area. The DG was then unloaded and secured.
An investigation of the DG was conducted which resulted in adjustment of the EGA controller by maintenance personnel and the governor by the vendor. The DG was restarted on a dual header start and was loaded satisfactorily. The smoke appeared to be the result of the DG being freshly painted ar.d an oil build up in the exhaust header caused by running the DG unloaded for 30 minutes.
The 213 DG was returned to service on 9 2-91. The 9-2-91 failure was the fifth failure in the last 100 valid tests. The surveillance schedule remained at once per 7 days.
2B DG FAILURE ON 09-17-91 At 0055 on 0917 91, during the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> load run, with the DG paralleled to the grid, voltage control of the DG was lost which caused a loss of reactive load control. The diesel-generato* vas rapidly removed from operation. The loss of voltage control was found to be a failure of a control transformer (T54) in the feedback circuit of the voltage regulator.
The defective component was replaced and has been sent to the manufacturer for diagnostic testing.
There has only been one other failure of a T54 transformer at FNP This occurred in 1985 (MWR 116762) on the ill DG.
The 213 DG was returned to service on 9-17 91. The 917 91 failure was the sixth failure in the last 100 valid tests. The surveillance schedule remained at once per 7 days, i
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