05000348/LER-2005-002
| Joseph M. Farley Nuclear Plant - Unit 1 05000 348 1)Of 4 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3482005002R00 - NRC Website | |
Westinghouse -- Pressurized Water Reactor Energy Industry Identification Codes are identified in the text as [XX]
Description of Event
On November 11, 2005 at 1149, operators were taking routine bus voltage readings. When the voltmeter selector switch was operated, the voltmeter went blank. It was determined that an LCO existed with respect to TS Table 3.3.5-1 Function 3 for loss of 4kv bus degraded grid alarm capability, and the Required Action for this condition was met. It was not recognized at that time that the synchroscope for the 1F (Unit I Train A Engineered Safety Features or ESF) 4kv bus [EK] was also affected. Therefore TS 3.8.1 Required Action B.1 to verify operability of offsite power sources per Surveillance Requirement (SR) 3.8.1.1, was not met at this time.
During troubleshooting of the voltmeter on November 14, 2005 it was determined that the voltmeter was failed due to blown fuses, and that the blown fuses also disabled the synchroscope. The synchroscope is required per TS Surveillance Requirement (SR) 3.8.14 for the ability to synchronize the 1-2A Train A Emergency Diesel Generator (EDG) to an offsite source following power restoration after an LOSP. The 1-2A EDG was declared inoperable for Unit 1 only, per TS 3.8.1 on November 14, 2005 at 1647. Required actions per TS 3.8.1.B, notably to verify operability of offsite power sources per Surveillance Requirement (SR) 3.8.1.1, were then met.
The fuses were replaced restoring power to the voltmeter and the synchroscope. The 1-2A EDG was declared operable on November 14, 2005 at 2200.
The voltmeter selector switch was caution tagged not to operate the switch until troubleshooting of the cause of the blown fuses could be completed and corrected.
The voltmeter selector switch has been replaced.
Cause of Event
The failed voltmeter and synchroscope were caused by fuses blown by a short in a degraded voltmeter phase selector switch. When changing switch positions, momentary simultaneous contact of two phases occurred, resulting in a short that blew the fuses in the two phases.
The operation in a condition prohibited by TS was caused by cognitive personnel error and knowledge deficiency in that it was unclear to the operating crew that loss of the voltmeter indicated that the synchroscope might also be inoperable. In this case the only apparent loss was the bus voltmeter. Loss of the synchroscope, which is not normally in use, was not apparent to the operators.
Safety Assessment The ability of the 1-2A EDG to start, load, and supply ESF loads in a Loss of Site Power (LOSP) event was unaffected by this event. The only effect was loss of the ability to synchronize the EDG to an available offsite source following power restoration after an LOSP. This is a manual action with no time constraints. The loss of the synchroscope was repaired well within the 7 day mission time of the EDG and the function restored.
was unaffected by this event.
Since the B Train ESF power supply was unaffected by this event, it does not represent a Safety System Functional Failure.
Corrective Action The fuses were replaced restoring power to the voltmeter and the synchroscope. The 1-2A EDG was declared operable on November 14, 2005 at 2200.
The voltmeter selector switch was tagged to prevent operation pending switch repair or replacement.
The voltmeter selector switch has been replaced.
A night order was issued to Operations shift crews emphasizing the significance of loss of indication and the standard for investigation of loss of power available indications.
Guidance on actions to take based on loss of certain unique Emergency Power Board indications has been made.
Additional Information
The following LERs have been submitted in the past two years on Technical Specification violations:
Failure Troubleshooting Water Inoperable Inoperable