05000353/LER-1993-009
| ML20056D958 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 08/13/1993 |
| From: | Boyce R, Kantner J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-93-009-01, LER-93-9-1, NUDOCS 9308190078 | |
| Download: ML20056D958 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| 3532093009R00 - NRC Website | |
text
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. PHILADELPHIA ELECTRIC COMPANY LIMERICK GENERATING STATION P. O. BOX 2300 SANATOGA, PA 19464-2300 C15) 327-1200 EXT. 2(W August 13, 1993 Docket No. 50-353 ROBERT W. BOYCE License No. NPF-85 PLANT MAh%ER LIMERICK GENERATING STATION U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
Licensee Event Report Limerick Generatina Station, Unit 2 This LER reports an inadvertent actuation of the Primary Containment and Reactor Vessel Isolation Control System, an Engineered Safety Feature, that resulted in a condition which j could have prevented the High Pressure Coolant Injection (HPCI) l system from performing its intended safety function. {
Specifically, the HPCI system steam supply line outboard )
isolation valve inadvertently isolated due to the failure of a Rosemount differential pressure transmitter.
Reference:
Docket No. 50-353 Report Number: 2-93-009 Revision Number: 00 Event Date: July 16,1993 Report Date: August 13, 1993 Facility: Limerick Generating Station P.O. Box 2300, Sanatoga, PA 19464 This LER is being submitted pursuant to the requirements of 10CFR50. 73 (a) (2) (iv) and 10CFR50.73 (a) (2) (v) .
Very truly yours, L -
- M GHS/
cc: T. T. Martin, Administrator, Region I, USNRC N. S. Perry, USNRC Senior Resident Inspector, LGS I I
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,im On July 16, 1993, at 1228 hours0.0142 days <br />0.341 hours <br />0.00203 weeks <br />4.67254e-4 months <br />, the High Pressure Coolant Injection (HPCI) system steam supply line outboard primary containment isolation valve isolated due to an inadvertent HPCI steam line high steam flow isolation signal. Isolation of this valve is controlled by the Primary Containment and Reactor Vessel >
Isolation Control System which is an Engineered Safety Feature.
The isolation signal was the result of an unexpected failure of differential pressure transmitter, PDT-055-2N057B (Rosemount, Model No. 1153DB6 PAN 0016). The cause of the transmitter failure is currently under investigation. The consequences of this event were minimal and there was no release of radioactive material to the environment. The HPCI system isolated as designed in response to the isolation signal. All other Emergency Core Cooling Systems were operable at the time of the event to mitigate the consequences of an accident. Following troubleshooting, the transmitter was replaced and the HPCI system was declared operable at 0720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> on July 17, 1993. Corrective actions to prevent recurrence, if necessary, will be determined based on the results of the failure analysis by the manufacturer.
A supplement to this report will be submitted if any significant results are identified from the failure analysis.
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l U S NUCLf. AR REGUL ATORY COMMISSION swAC Feem ash l LICENSEE EVENT REPORT (LER) TEXT CONTINUATION arenovio ous no. siw-om-j Exemes sm n sacy.gT V NAME til DOCA ET NUMet p L2l ggg gyggg a ggg pagg g33 s*a l"$!OP. OT.*JO Limerick Generating Station, Unit 2 OF o l5 l D l 0 l 0 l 315 l 3 9l 3 0]0l9 -
0 l0 0l 2 OJ3 ren a -. . - - uc i .mv.i n7, Unit Conditions Prior to the Event Unit 2 was in Operational Condition 1 (Power Operation) at 100%
power at the time of this event.
i There were no structures, systems, or components out of service l
that contributed to this event.
l Description of the Event '
On July 16, 1993, at 1228 hours0.0142 days <br />0.341 hours <br />0.00203 weeks <br />4.67254e-4 months <br />, the Unit 2 High Pressure Coolant Injection (HPCI) system (EIIS:BJ) steam supply line outboard primary containment isolation valve, HV-055-2F003, (EIIS:ISV) isolated due to an inadvertent Division II HPCI steam line high steam flow isolation signal. Isolatian of this valve is controlled by the Primary Containment and Reactor Vessel Isolation Control System (PCRVICS) (EIIS :JM) which is an Engineered Safety Feature (ESF). The HPCI system was not operating at the time of the isolation.
Subsequent investigation revealed that the isolation was the j result of the failure of differential pressure transmitter, PDT-l 055-2N057B, (EIIS:PDT) which caused a gross failure indication at the associated trip units. Gross failure, in this case, refers to a signal that is below the calibrated range of the transmitter I during normal plant conditions. The function of the transmitter is to measure the differential pressure across a flow orifice in the HPCI turbine steam supply line. A large differential pressure would indicate a potential leak or break in the steam supply line, resulting in an isolation signal being generated to close the outboard primary containment isolation valve.
Following troubleshooting, the transmitter 5'as replaced and the HPCI system was declared operable at 0720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> on July 17, 1993.
The HPCI system was inoperable for approximately 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> and 52 minutes.
A four hour notification to the NRC was made at 1345 hours0.0156 days <br />0.374 hours <br />0.00222 weeks <br />5.117725e-4 months <br /> on July 16, 1993, in accordance with the requirements of 10CFR50. 72 (b) (2) (ii) and 10CFR50.72 (b) (2) (iii) since this event resulted in an ESF actuation and a condition which could have prevented the HPCI system from performing its intended safety function to mitigate the consequences of an accident.
Accordingly, this report is being submitted in accordance with the requirements of 10CFR50.73 (a) (2) (iv) and 10CFR50.73 (a) (2) (v) .
Analysis of the Event l
The consequences of this event were minimal and there was no release of radioactive material to the environment as a result of 1
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this event. The HPCI system isolated as designed in response to l the inadvertent isolation signal. All-remaining Emergency Core i Cooling Systems, including the Automatic Depressurization System, the Low Pressure Coolant Injection system, and the Core Spray system, and the Reactor Core Isolation Cooling system were ;
operable at the time of this event to mitigate the consequences :
of an accident. .
Cause of the Event :
The cause of the event is an unexpected failure of differential pressure transmitter, PDT-055-2N057B (Rosemount, Model No.
1153DB6 PAN 0016). The failure of this transmitter caused an !
inadvertent downscale differential pressure signal resulting in ;
tripping of differential pressure switch, PDS-055-2N660B, which l caused the HPCI system steam supply line outboard isolation valve
~
, to close. ,
The cause of the transmitter failure is currently under !
investigation. The failure mode of the transmitter was not '
symptomatic of a loss of fill-oil condition as described in NRC Bulletin No. 90-01, " Loss of Fill-Oil in Transmitters i Manufactured by Rosemount"; however, the exact cause of the transmitter failure has not yet been determined. The transmitter is being sent to the manufacturer for a failure analysis. ;
Corrective Actions
- The transmitter was replaced and the HPCI system was declared i operable at 0720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> on July 17, 1993. Further corrective ,
actions to prevent recurrence will be developed, if necessary, i based on the results of the transmitter failure analysis by the r manufacturer. A supplement to this report will be-submitted if i any significant results are identified from the failure analysis.
2 Previous Similar Occurrences l LER 2-90-008 reported an inadvertent isolation of the HPCI system l steam supply line inboard primary containment isolation valve, !
. HV-055-2F002, due to the intermittent downscale failure of differential pressure transmitter, PDT-055-2N057D (Rosemount, j Model No. 1153DB6RJ). The transmitter was returned to Rosemount I for failure analysis, during which the transmitter functioned normally, and the cause of the transmitter failure could not be determined. Therefore, this event was considered an isolated occurrence, and no further actions to prevent recurrence were developed at that time.
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