05000425/LER-2014-002
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4252014002R00 - NRC Website | |
A. REQUIREMENT FOR REPORT
This report is required per 10CFR 50.73(a)(2)(i)(B) due to a condition prohibited by TS in that the 2B CS pump failed to meet TS 3.6.6 Condition A. The TS required action completion time to enter Mode 3 was exceeded without meeting the requirement to be in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 in 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br />.
B. UNIT STATUS AT TIME OF EVENT
Mode 1, 100 percent rated thermal power
C. DESCRIPTION OF EVENT
On August 19, 2014 at 02:00 EDT, the 2B CS pump was removed from service for routine preventive maintenance and testing activities. During post-maintenance testing on August 20, 2014 at 03:14, it was noted that the pump inboard (drive side) mechanical seal was overheating. Although a repair plan was developed and initiated, there was Insufficient time remaining for the TS 3.6.6 Condition A completion time to implement the repairs, complete post-maintenance testing and return the pump to service. Disassembly of the pump involved a number of activities that would require exceeding the TS 3.6.6 Condition A. The overall risk of a plant shutdown was evaluated against the risk significance of extending LCO 3.6.6, and based on the risk evaluation enforcement discretion was requested for extending the TS 3.6.6 Condition A by 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br /> due to the time required for maintenance activities. During a teleconference on August 21, 2014 at 18:00 EDT, the NRC granted Vogtle's verbal request for enforcement discretion to extend the completion time from 02:00 on August 22, 2014 to 14:00 on August 24, 2014. Restoration of the pump continued and on August 24, 2014 at 01:57, the pump was returned to service and TS 3.6.6 was exited.
D. CAUSE OF EVENT
The cause of the 2B CS pump inoperability was failure of the pump inboard mechanical seal due to a loss of seal cooling. This determination was based on engineering judgment and vendor input during the event investigation.
E. SAFETY ASSESSMENT
While the 2B CS pump was being restored no other safety-related or non-safety-related risk significant systems were out of service. Since the 2A CS train was protected and one train of CS is adequate to perform the CS function, maintenance activities to restore the pump to operable status were not considered to pose a risk of an unnecessary transient. Other work activities that could have posed a risk to the plant were deferred. Furthermore, on-line risk management was utilized to monitor risk thresholds and ensure margin was maintained. Therefore, this event had no adverse effect on the health and safety of the public. This event is of very low safety significance.
F. CORRECTIVE ACTION
Mechanical seals, bearings, and couplings were installed along with replacement and alignment of the rotating element. Subsequent inspection and post maintenance testing was performed satisfactorily. The pump was returned to service at 01:57 on August 24, 2014, The NOED to restore operability of the pump was a one-time only extension. It was determined and agreed upon with the NRC during teleconference on August 21, 2014 that a follow-up license amendment is not required.
G. ADDITIONAL INFORMATION
1. Failed Components:
Containment Spray pump (mechanical seal), [P] Pump 2. Previous Similar Events:
On June 23, 2008, during similar surveillance testing on the 2B CS pump, the inboard mechanical seal overheated and began smoking. However, the 2008 event's failure mechanism was improper pump shaft alignment. All corrective actions were completed in regards to the 2008 event. An emergency amendment to the TS was requested for this shaft alignment event with approval granted on June 25, 2008. [ML081770464S] 3. Energy Industry Identification System Code:
[BE] — Containment Spray System (PWR) NRC FORM 3613A (02-2014)