05000400/LER-2003-005, Manual Reactor Trip Following a Trip of the a Condensate Pump Motor
| ML032880460 | |
| Person / Time | |
|---|---|
| Site: | Harris  (NPF-063) |
| Issue date: | 10/09/2003 |
| From: | Waldrep B Progress Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| IINP-03-105 LER 03-005-00 | |
| Download: ML032880460 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4002003005R00 - NRC Website | |
text
OM Progress Energy OCT 0 9 2003 U.S. Nuclear Regulatory Commission ATrN: NRC Document Control Desk Washington, DC 20555 Serial: HNP-03-105 10CFR50.73 SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 DOCKET NO. 50-400/LICENSE NO. NPF-63 LICENSEE EVENT REPORT 2003-005-00 Ladies and Gentlemen:
The enclosed Licensee Event Report 2003-005-00 is submitted in accordance with 10 CFR 50.73. This report describes a manual reactor trip and an auxiliary feedwater actuation following a trip of the "A" condensate pump motor. Event notification EN 40084 previously reported this event in accordance with 10 CFR 50.72.
Please refer any questions regarding this submittal to Mr. John Caves, Supervisor -
Licensing/Regulatory Programs, at (919) 362-3137.
Sincerely, 4X4-. A B. C. Waldrep Plant General Manager Harris Nuclear Plant BCW/jpy Enclosure c:
Mr. R. A. Musser (HNP Senior NRC Resident)
Mr. C. P. Patel (NRC-NRR Project Manager)
Mr. L. A. Reyes (NRC Regional Administrator, Region II)
Progress Energy Carolinas. Inc.
Harris Nuclear Plant P.O. Box 165 New Hill, NC 27562
Abstract
On August 17, 2003 at 1551 with the reactor at approximately 100% power, the Harris Nuclear Plant (HNP) manually tripped the reactor in response to an automatic trip of one of two operating condensate pumps (CPs). The A CP tripped following an electrical short in its motor due to a severe lightning storm. The trip of the WA CP resulted in subsequent trips of the WA condensate booster pump and the UW main feedwater pump (MFP) as designed. As directed by plant procedures, the operations crew manually tripped the reactor upon the trip of a MFP with initial reactor power greater than 90%. The manual reactor trip coupled with the trip of the A" condensate and feedwater train resulted in a reduction of steam generator (SG) water levels. The subsequent low-low SG levels resulted in an auto-start of the auxiliary feedwater pumps as designed. Safety systems functioned as required.
The cause of the unplanned trip of the WA CP motor was a lightning voltage surge that overcame the dielectric strength of the motor winding insulation (i.e., an electrical short). In addition, the grounding system was not effective at protecting the A" CP motor from a lightning strike.
Corrective actions included replacing the WA mCP motor and installing surge protection. In addition, HNP will enhance the A" CP grounding system and install surge protection on the 0B" CP motor.
NRC FORM 366 (7-2000)
(If more space Is required, use add nal copies of (If more space Is requlred use acftional copies of NRC Form MA)
Ill.
SAFETY SIGNIFICANCE
Other than the transient induced by the manual reactor trip, there were no safety significant consequences as a result of this event. The plant was manually tripped by control room operators as directed by plant procedures.
The plant is designed for a loss of main feedwater, and it responded as expected for this condition. The loss of normal feedwater event is classified as an ANS Condition II event, a fault of moderate frequency (i.e., expected to occur, in general, no more than once per year). The initial plant conditions were well within the bounding conditions for the plant design. The event did not involve any release of radioactive material. No design safety limits were exceeded, and no fission product barriers or components were damaged as a result. The plant was promptly stabilized at normal operating no-load RCS temperature and pressure, and no unusual conditions were observed for plant equipment following the manual reactor trip. All safety equipment functioned as required. The operating staff performed the required actions for the trip.
The potential safety consequences under other alternate conditions, such as a loss of both MFPs, may have increased the severity of the transient and may have resulted in an automatic rather than manual reactor trip, but these alternate conditions would not have significantly increased the potential safety consequences of this event.
In general, the severity of the plant transient is reduced at lower power levels, so the same event initiated at a lower power (i.e., less than 100% power) would be expected to result in a smaller transient. This report is submitted pursuant to 10CFR50.73(a)(2)(iv)(A) for the manual reactor trip and automatic actuation of the AFW system.
IV.
CORRECTIVE ACTIONS
Corrective actions included replacing the A" CP motor and installing surge protection. In addition, HNP will enhance the AN CP grounding system and install surge protection on the B" CP motor.
V.
PREVIOUS SIMILAR EVENTS
HNP LER 1999-009-00 (reported 1/13/00)
The 'A' CP motor failed on 12/14/99 and was investigated in AR 10088 (LER 1999-009-00). This previous event was evaluated in the failure analysis for this event to assess the potential of a repeat failure or common cause.
The investigation in 1999 concluded that the motor failure was caused by a voltage surge based on the post-event inspection. The stator failed from a phase-to-phase short at the 1 and 3 coil of the parallel wye winding.
However, the investigation could not determine conclusively the root cause of the voltage surge since the failure site In the motor was destroyed by the arc from the motor Internal fault. Lightning was suspected since there was severe weather at the time of failure, but there was no direct evidence to support that conclusion. Therefore, the most likely root cause of the voltage surge that resulted In the phase-to-phase short was determined to be an internal fault. The corrective action to prevent recurrence was to replace the motor. Based on the historical performance of the Siemens-Allis pumps and current performance data for other pumps in service, the extent of condition was limited to the motor that failed. Therefore, the planned actions did not Include any additional corrective actions to prevent recurrence. So, although the root cause for this previous event is significant in relation to the subject event, the previous corrective actions would not have prevented the event identified by this LER.