ML20128N073
| ML20128N073 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 02/12/1993 |
| From: | Tuckman M DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9302220478 | |
| Download: ML20128N073 (3) | |
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['ike nnrr Company AlS Tluw CatuaLa Nudear Generation Department lice President 1
%00 Coacord Road (803)&113205 0ifice nrt, SC nts (M3)MI 3426 h1 l
i DUKEPOWER Febmary 12, 1993 J
U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 4
Subject:
Catawba Nuclear Station, Unit 2 Docket No. 50-414 Special Repott Invalid Failures of Diesel Generator 2B Pursuant to Technical Specification 4.8.1.1.3 and 6.9.2, find attached a Special Repon concerning the two Unit 2 Diesel Generator B (DG 2B) invalid failures that occurred on January 13, 1993.
4 Very truly yours, h Y(\\4-4 M. S. Tuckman CRUDG2B212.92 Attachment xc: S. D. Ebneter Regional Administrator, Region II W. T. Orders Senior Resident Inspector R. E. Manin, ONRR 22001'?
9302220478 930212 gor Anockosoog4
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4 SPECIAL REPORT CATAWBA NUCLEAR STATION DIESEL GENERATOR 2B INVALID FAILURE i
DUE TO HIGH CRANKCASE PRESSURE Two invalid failures of Diesel Generator (DG) 2B occurred on January 13,1993 due to a high crank. case pressure trip. This was caused by a failure of the Calcon sensor that is utilized in this application. Unit 2 was at 100% power at the time this failure occurred.
The failures occurred during the performance of Operations (OPS) monthly Periodic Test (PT). DG 2B was on a monthly test frequency at the time this failure occurred. There j
have been 0 valid failures in the last 20 valid tests and 1 valid failure in the last 100 valid tests. DG 2B remains on a monthly operability test schedule in accordance with Technical Specification 4.8.1.1.2 Table 4.8-1. There is no unavailability time associated with these failures.
DG 2B was manually started (Start #705) on January 13,1993 at 1350 for the OPS PT.
Instmmentation and Electrical personnel (IAE) were scheduled to perform a functional i
verification on the crankcase pressure sensor, 2LDPT5420, which had been replaced on December 12, 1992, following spurious annunciator actuation. After the engine ran for approximately 60 seconds, it automatically tripped. All of the Group II trip annunciators i
were received at the time the trip occurred. OPS restarted the engine at approximately i
1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> for IAE troubleshooting purposes.
It was immediately noticed that the pneumatic logic system was losing air pressure. A check of the crankcase pr:ssure sensor revealed that it was the source of the problem. Air was found to be blowing from its vent port, thus preventing the remainder of the system from pressurizing. The engine tripped again after the 60 second Group II lockout was removed.
To further verify that l
2LDPT5420 was the cause of the problem, IAE capped the instrutncnt tubing line to the sensor to block the air leakage and had OPS start the engine again. The engine ran without problems and the PT was completed.
A new crankcase pressure sensor was acquired from stock and calibrated to the proper trip point. After the engine was shutdown, IAE replaced the failed sensor with the newly calibrated one. The engine was restarted for the functional verification and no problems were observed.
In checking the calibration of the sensor removed from the engine, it was found that the-l setpoint was now approximately 2 inches of water column above atmospheric pressure (INWC). Prior to this sensor being installed on December 15,1992, it had been calibrated to the design setpoint of 5 INWC. It was noted that this sensor and the one that was installed were fairly sensitive to mechanical agitation.
Because of the concerns with the reliability of the pneumatic shutdown logic system, corrective actions have already taen initiated to replace this system with a more reliable electrical system. Nuclear Station Modifications (NSMs) CN-ll104 and CN-20486 were i
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completed on Unit I and Unit 2 DGs, respectively during IEOC3 and 2EOC2 outages to replace the safety-related pneumatics with electrical components. NSM CN-ill49 was i
completed on Unit i DGs during IEOC6 outage, to remove all the non-emergency pneumatic trip instnimentation, including the crankcase pressure trip sensor, and replace j
it with an electrical system. This same modification (CN-20528) will be performed on Unit i
2 during the present 2EOC5 outage.
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