05000446/LER-2003-001
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4462003001R00 - 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
On July 9, 2003, Comanche Peak Steam Electric Station (CPSES) Unit 2 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 July 9, 2003, Comanche Peak Steam Electric Station (CPSES) Unit 2 was in Mode 1, Power Operation, operating at 100% power. At 0109 hours0.00126 days <br />0.0303 hours <br />1.802249e-4 weeks <br />4.14745e-5 months <br />, the 2-04 Reactor Coolant Pump (RCP) motor breaker [Ell.S: (AB)(P)(MO)(BICR)] unexpectedly opened which resulted in loss of the 2-04 RCP. Operators (utility, licensed) in the Unit 2 Control Room automatic reactor trip. All control rods fully inserted, all Auxiliary Feedwater pumps [EIIS: (BA)(P)1 automatically started as expected, and the unit was stabilized in Mode 3.
E. THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM
FAILURE, OR PROCEDURAL OR PERSONNEL ERROR
Operators (utility, licensed) in the Unit 2 Control Room received a "Rx > 48 percent I of 4 loop flow low trip" alarm.
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II. COMPONENT OR SYSTEM FAILURES
A. FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED
COMPONENT
TXU Energy's evaluation of this event determined that a "B" phase stator to ground short occurred in the 244 RCP motor.
B. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE
The "B" phase stator to ground short occurred in the 2-04 RCP motor due to degradation of the stator ground wall insulation.
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
Westinghouse SIN 89P969 Model #CS-VSS 7000 HP, 6600 volt, 6 pole. Reactor Coolant Pump Motor
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ANALYSIS OF THE EVENT
A. SAFETY SYSTEM RESPONSES THAT OCCURRED
The Reactor Protection System and the Auxiliary Feedwater System actuated as expected during the event. Both Motor Driven Auxiliary Feedwater pumps and the Turbine Driven Auxiliary Feedwater pump automatically started as expected and the plant response to the automatic trip was as expected.
B. DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY
Not applicable — No safety system was rendered inoperable.
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C. SAFETY CONSEQUENCES AND IMPLICATIONS
This event is specifically bounded by the accident analysis of the partial loss of forced reactor coolant flow discussed in Section 15.3.1 of the CPSES Final Safety Analysis Report (FSAR). The partial loss of forced reactor coolant flow is classified as an ANS Condition II event, a fault of moderate frequency. In the July 9, 2433 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 this analysis, it was concluded that this event did not adversely affect the safe operation of CPSES Unit 2 or the health and safety of the public.
IV. CAUSE OF THE EVENT
'MU Energy believes that the cause of the event was the opening of the 2-04 RCP motor breaker due to a "B" phase stator to ground short in the 2-04 RCP motor. The "8" phase stator to ground short occurred in the 2-04 RCP motor due to degradation of the stator ground wall insulation.
V. CORRECTIVE ACTIONS
Corrective actions include repair of the 2-04 RCP motor stator and, as previously discussed in Licensee Event Report 03-002-00 for CPSES Unit 1, an evaluation of the Predictive Analysis Program specifically for large electric motors will be performed to assess the current program scope, monitoring practices, and overall effectiveness.
VL � PREVIOUS SIMILAR EVENTS In 1996, CPSES Unit 2 experienced a reactor trip due to the loss of a Reactor Coolant Pump (see LER 446/96-007). However, the Reactor Coolant Pump loss during the 1996 event was due to the loss of the power supply, which was different than the July 9, 2003 event.
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