05000445/LER-2003-002
| Event date: | |
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| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4452003002R00 - NRC Website | |
I. DESCRIPTION OF REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION
Any event or condition that resulted in manual or automatic actuation of the Reactor Protection System (RPS) including reactor trip or reactor scram.
B. PLANT OPERATING CONDITIONS PRIOR TO THE EVENT
was in Mode 1, Power Operation, operating at 100 percent power.
C. STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT
WERE INOPERABLE AT THE START OF THE EVENT AND THAT
CONTRIBUTED TO THE EVENT
There were no inoperable structures, systems, or components that contributed to the event.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND
APPROXIMATE TIMES
On March 16, 2003, CPSES Unit 1 was in Mode 1, Power Operation, operating at 100 percent power. At 2149 hours0.0249 days <br />0.597 hours <br />0.00355 weeks <br />8.176945e-4 months <br />, Condensate pump 1-01 motor breaker [EIIS: (SD)(P)(M0)(BRK)] unexpectedly tripped and Operators (utility, licensed) in the Unit 1 Control Room received a "Condensate Pump 1 Breaker Open" alarm [HIS: (SD)(P)(BKR)(ALM)]. Eleven seconds later, Main Feedwater pump 1-02 [EIIS: (SJ)(P)] tripped on low suction pressure and one second later Main Feedwater Pump 1-01 [EIIS: (SJ)(P)] also tripped on low suction pressure. The loss of both Main Feedwater pumps resulted in the automatic start as expected of both Motor Driven Auxiliary Feedwater pumps (BA)(P)]. Operators (utility, licensed) in the Unit 1 Control Room initiated a manual reactor trip based upon the loss of the Main Feedwater pumps and the rapidly decreasing feedwater levels in all four Steam Generators.
The Turbine Driven Auxiliary Feedwater pump [EIIS: (BA)(P)] also Generators [EIIS: (SB)(SG)]. All control rods fully inserted and the plant response to the manual trip was as expected.
On March 17, 2003, the Condensate pump 1-01 motor [EIS: (SD)(P)(MO)] returned to limited power operations (approximately 55% power) on March 17, 2003, utilizing the remaining Condensate pump 1-02 and operated at a reduced power level until March 31, 2003, when the repaired Condensate pump motor 1-01 was reinstalled and Unit 1 was returned to 100% power.
E. THE METHOD OF DISCOVERY OF EACH COMPONENT OR
SYSTEM FAILURE, OR PROCEDURAL OR PERSONNEL ERROR
Operators (utility, licensed) in the Unit 1 Control Room received a "Condensate Pump 1 Breaker Open" alarm.
II. COMPONENT OR SYSTEM FAILURES
A. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE
A phase to phase fault within the Condensate pump motor 1-01 windings occurred due to a manufacturing defect. The manufacturing defect was lack of a clearance or air gap between the two winding coils. Because the Condensate pump motors at CPSES are not classified as safety related, they were not purchased under the provisions of 10CFR21 and this defect is therefore not reportable per 10CFR21.
B. FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED
COMPONENT
Lack of a clearance or air gap between the two winding coils caused rubbing and abrasion to occur between the coils over a period of years. The rubbing of the two coils caused localized insulation degradation over time and ultimately led to a phase to phase fault.
C. SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED
BY FAILURE OF COMPONENTS WITH MULTIPLE FUNCTIONS
Not applicable – No failures of components with multiple functions were identified.
D. FAILED COMPONENT INFORMATION
Electric Machinery Manufacturing Co.
4000 hp, Frame 6380, Three Phase, Electric Motor HI. ANALYSIS OF THE EVENT
A. SAFETY SYSTEM RESPONSES THAT OCCURRED
The Reactor Protection System and the Auxiliary Feedwater System actuated during the event. The loss of both Main Feedwater pumps resulted in the automatic start as expected of both Motor driven Auxiliary Feedwater pumps, and the Turbine Driven Auxiliary Feedwater pump also automatically started as fully inserted and the plant response to the manual trip was as expected.
B. DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY
Not applicable -- No safety system was rendered inoperable.
C. SAFETY CONSEQUENCES AND IMPLICATIONS
This event is specifically bounded by the Final Safety Analysis Report (FSAR) accident analysis of the loss of feedwater flow presented in Section 15.2.7 of the CPSES FSAR. The loss of normal feedwater transient is classified as an ANS Condition II event, a fault of moderate frequency. In the March 16, 2003 event, the Auxiliary Feedwater System responded as expected and maintained the necessary Steam Generator heat transfer capability. There were no other malfunctions or equipment failures which complicated the plant response or otherwise elevated risk beyond the event analysis data. There were no safety system functional failures associated with this event.
Based on the above, it is concluded that the event of March 16, 2003, did not adversely affect the safe operation of CPSES Unit 1 or the health and safety of the public.
IV. CAUSE OF THE EVENT
The Unit 1 manual reactor trip resulted from the unexpected trip of Condensate pump motor 1-01 and subsequent loss of both Main Feedwater pumps. The trip of Condensate pump motor 1-01 was caused by a phase to phase fault within the motor windings which occurred due to a manufacturing defect. The manufacturing defect was the lack of a clearance or air gap between the two winding coils.
V. CORRECTIVE ACTIONS
Condensate pump motor 1-01 was repaired, reinstalled, and returned to service. As a part of the CPSES Corrective Action Program, the condition of the winding coils on the other three Condensate pump motors will be evaluated. In addition, an evaluation of the Predictive Analysis Program, specifically for large electric motors, will be performed to determine the adequacy of the current program scope, monitoring practices, and overall effectiveness.
VI. PREVIOUS SIMILAR EVENTS
In 1995, CPSES Unit 1 experienced a manual reactor trip due to the loss of both Condensate pumps and both Main Feedwater pumps (see LER 445/95-003). However, the loss of both Condensate pumps in the 1995 event was due to a different cause than the March 16, 2003 event.