05000364/LER-1994-001, :on 940805,main Turbine Was Manually Tripped Due to Degrading Condenser Vacuum.Caused by Equipment Failure of Local Pressure Gauge.Local Pressure Indicator Was Replaced
| ML20072U099 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 09/02/1994 |
| From: | Hill R, Dennis Morey ALABAMA POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-94-001, LER-94-1, NUDOCS 9409160118 | |
| Download: ML20072U099 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3641994001R00 - NRC Website | |
text
South;rn Nucl:ar Operating Company s
Post Omce Box 1295 Birmingham, Atacama 35201 Tetephone (205) 868-5131 h
Southern Nuclear Operating Company Dave Morey Vice President Far!ey Project the southem electnc system September 2,1994 Docket No: 50-364 10 CFR 50.73 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Joseph M. Farley Nuclear Plant - Unit 2 Licensee Event Report No.94-001 Reactor Trio Gentlemen:
Joseph M. Farley Nuclear Plant Licensee Event Report No.94-001 Unit 2 - Reactor Trip is being submitted in accordance with 10 CFR 50.73. If you have any questions, please advise.
Respectfully submitted, f
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Dave Morey DRC/ cit.lcreactp. doc Enclosure cc: Mr. S. D. Ebneter Mr. B. L. Siegel Mr. T. M. Ross j
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TITLE (4)
Manual Turbine / Reactor Trip Due to Loss of Condenser Vacuum EVENT DATE (5)
LEF NUMBER (6)
REPORT DATE (7)
OTHER FACluTIES INVOLVED (8) j MONTH DAY YEAR YEAR MgpAL
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[No DATE(15) f l-kBSTRACT (Larut to 1400 spaces. a e, aptwoxunatory ween ausgen-spece typewntlen tones)(16) t At 1459 on August 5,1994, with the Unit in Mode 1 and operating at approximately 100 percent reactor power, the main turbine was manually tripped due to degrading condenser vacuum. This manual trip of the main turbine from 100 pe.rcent power initiated a reactor trip as designed.
i Previous to the trip, work had been performed on a low pressure turbine gland seal regulator to repair a steam leak. Upon valving the regulator in after the repair, it was noted that the gland seal steam pressure was being maintained slightly above the normal band as indicated on the local pressure indicator. The regulator was adjusted to lower the gland seal pressure to the proper range
- - as indicated on the local pressure gauge. This adjustment was made by an Instmment and Controls technician who was assisted by an Operations systems operator. The local pressure indicator was subsequently determined to be inaccurate and actual gland seal pressure was too low to prevent air in-leakage into the main condenser. Shortly after completion of the above adjustments, condenser vacuum degraded rapidly, and upon reaching the administrative main turbine manual trip criteria of 2.7 psia, the control room operators tripped the main turbine. This initiated an automatic reactor trip per design. The Operations crew responded to the reactor trip as directed by plant procedures. The faulty gauge was replaced and the Unit was returned to service.
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FORM 36 U.S. NUCLEAR QEGULATOWY COMMISSION LPPRO BN
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PLANT AND SYSTEM IDENTIFICATION
Westinghouse - Pressurized Water Reactor.
Energy Industry Identification System codes are identified in the test as [XX]
SUMMARY OF EVENT A loss of condenser vacuum due to inadequate steam pressure being supplied to a gland seal [TC] on the main turbine occurred on August 5,1994, at 1459. Condenser vacuum degraded to the point that the procedural trip criteria for the main turbine was reached. The Operations crew tripped the main turbine manually per procedure and then responded to the automatic reactor trip which was initiated per design. All plant systems functioned as designed in response to the reactor trip.
DESCRIPTION OF EVENT
Repairs were made to a leak discovered in the gland seal regulator supplying gland sealing steam to the number four gland on the Unit 2 main turbine. During the time the repairs were in progress number four gland sealing steam was supplied by bypassing the gland regulator. ARer completing the repairs, the number four regulator was placed in service. Upon placing the regulator in service the observed gland seal pressure, based on the locally installed gauge (PI-510), was noted to be above the norm:
1erating band of between 1 and 5 psig. The local gauge, which had been calibrated du-a previous refueling outage, indicated a pressure of approximately 6 psig. In addition, a.
gland sealing steam annunciator (high/ low inputs) alarmed in the control room.
The Instam
. Controls (I&C) group was contacted to adjust the regulator. The turbine building syst.. operator (SO) and I&C personnel were sent to the number four gland I&C technicians adjusted the pressure control equipment while the SO monitored the number four gland sealing steam supply pressure at PI-510. Several adjustments were made until the local pressure gauge indicated approximately midrange in the normal operating band. At this point the SO observed that the number four gland seal supply pressure was satisfactory and reported this to the control room. The SO was told by the Operator At The Controls (OATC) that the gland sealing
- - steam alarm, which had momentarily cleared, had returned and was in alarm. The SO returned to the -
i local PI-510 and noted that pressure was still in the normal operating band. The SO indicated to the I&C technicians that no further adjustments would be necessary. The SO again called the OATC l
while the I&C personnel returned to the maintenance shop. The OATC requested the SO have I&C j
perform additional adjustments to clear the alarm condition. The OATC was told by the SO that j
I&C had len the area. The OATC observed the control room vacuum indication which was stable at
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the time. Although the OATC was concerned about the alarm condition which still existed, he did i
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Joseph M. Farley Nuclear Plant - Unit 2 0l5l0l0l0l316l4 9l4 0l0l1 010 l3 oF l4 TLXT (If more space na roquand, use nadWonal NRC form 3064's)(17) not believe the problem to be urgent due to the stable indication of condenser vacuum. The SO left the area at this point to perform other duties. The OATC intended to discuss with the Shift Supervisor the need to have the 1&C personnel return to make additional adjustments to clear the alarm. Shortly afterwards, before the OATC talked with the Shift Supervisor, the Unit Operator (UO) observed a rapid degradation of condenser vacuum. This condition was communicated to the turbine building SO, the OATC and the Shift Supervisor. The turbine building SO immediately proceeded to the number four gland. Upon arrival the SO noted the gland seal supply pressure local indication was still in the normal operating band. Even though the indication was within the normal operating band, the SO began to open the bypass steam supply around the number four gland regulator believing it to be the most likely cause of the loss ofvacuum. During this same time frame the Shift Supervisor implemented the Loss of Vacuum Abnormal Operating Procedure. When the turbine vacuum degraded to the administrative limit of 2.7 psia (i.e., back pressure increased) the Shift Supervisor directed the operator to trip the turbine. The turbine was tripped just before the SO was able to increase the gland steam pressure. The reactor trip response procedure (EEP-0) was then entered and completed satisfactorily.
CAUSE OF EVENT
A root cause evaluation was conducted and identified the following causes:
1)
Equipment failure of the local pressure gauge (PI-510) which was found to be unreliable and inaccurate. This was evidenced by post trip calibration of the gauge.
2)
The OATC and SO did not adequately consider the significance of conflicting indications, and did not take contingency actions while resolving those indications. The OATC-recognized an alarm condition was still being annunciated in the control room. However, since the local indication was reported as being in the normal band, and the vacuum indication in the control room was stable, the urgency of the main control room alarm was not apparent. Also, based on the local pressure indication and report of stable vacuum from the control room, the SO believed the number four gland seal pressure regulator to be stable and left the area to perform other duties.
NRC Form 866A(449l =
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PAGE(8) 1
" E ***EF"' E "Nu ER Joseph M. Farley Nuclear Plant - Unit 2 0l5101010l3l6l4 914 0l0l1 0l0 l4 oF l4 i
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REPORTABILITY ANAL,YSIS AND SAFETY ASSESSMENT
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This event is reportable due to the actuation of the reactor protection system. All systems operated -
as designed in response to the reactor trip j
There was no e Tect on the health and safety of the public.
CORRECTIVE ACTION
The local pressure indicator was replaced. FNP will evaluate the use of this type gauge for this particular application.
The OATC and SO were coached on dealing with situations in which there is conflicting information present.
A training advisory notice will be sent to appropriate plant personnel to emphasize how failure to
.l take contingency actions while resolving conflicting information resulted in a reactor trip in this -
event.
l These actions will be completed by October 1,1994.
ADDITIONAL INFORMATION
5 No similar events have been reported for Farley Nuclear Plant.
No plant system failed to function as designed during this event, and the event would not have been '
more severe ifit had occurred under different operating conditions.
I The Reactor was taken critical again on August 6,1994 at 0511, and the main generator was.
synchronized to the grid at 22.10 that same day.-
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NRC Penn 80th18459
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