05000259/FIN-2013003-02
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Finding | |
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| Title | LER 05000296/2013-003-00 and 05000259/2013-002-00 |
| Description | Unresolved Item (URI). A self-revealing issue of concern was identified with the Unit 3 automatic reactor shutdown due to the turbine trip from loss of condenser vacuum on February 25, 2013 and the Unit 1 manual reactor shutdown due to a decreasing vacuum manual scram on March 19, 2013. On February 25, 2013, Unit 3 was operating at approximately 92 percent power following a forced midcycle outage for repairs on the condenser circulating water (CCW) system. At 1313 hours0.0152 days <br />0.365 hours <br />0.00217 weeks <br />4.995965e-4 months <br /> the unit automatically scrammed due to a turbine trip. The turbine trip was caused by low condenser vacuum as a result of a failure of a long cycle return line piping connection to the miscellaneous drain header which connects with the main condenser. Main steam isolation valves (MSIVs) were manually closed and main turbine bypass valves were unavailable due to the loss of condenser vacuum. During the transient all available mitigating equipment performed as designed. The licensee initiated PER 687732 to enter the event into the corrective action program. Licensee investigation revealed the failure of a feedwater long cycle return line connection to the miscellaneous drain header was a result of seat leakage from the reactor feedwater system long cycle return flow control valves (3-FCV-003-0071, 72, and 73). This seat leakage caused the water within the pipe to flash to steam which translated to excessive vibration on the pipe and resulted in fatigue failure of the connection between the 8 inch pipe and 24 inch miscellaneous drain header. On March 19, 2013, Unit 1 was operating at approximately 80 percent power. At 0402 hours0.00465 days <br />0.112 hours <br />6.646825e-4 weeks <br />1.52961e-4 months <br /> the unit was manually scrammed due to decreasing main condenser vacuum. Following the manual scram condenser vacuum recovered and all available mitigating equipment was available and performed as designed. The vacuum degradation was caused by the separation of a 4 inch vent and drain pipe from a 24 inch miscellaneous drain header which connected to the main condenser. The separation was caused by vibration induced cyclic fatigue as a result of the combination of leaking drain valves and repeated operation of dump valves associated with feedwater heaters. The licensee initiated PER 698870 to enter the event into the corrective action program. Additional inspection of the maintenance history, service requests (SRs), problem evaluation reports (PERs), cause analyses and mitigating system responses concerning these two reactor trips are required to provide additional information into the issue. This unresolved item was tracked as URI 05000259, 260, 296/2013003-02. |
| Site: | Browns Ferry  |
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| Report | IR 05000259/2013003 Section 4OA3 |
| Date counted | Jun 30, 2013 (2013Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | D Dumbacher D Jones J Hamman J Montgomery L Pressley M Riches S Shaeffer T Stephena Senguptac Stancil D Dumbacher J Montgomery J Rivera K Miller L Pressley M Riches P Niebaum R Hamilton R Kellner S Shaeffer T Stephen |
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Finding - Browns Ferry - IR 05000259/2013003 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Browns Ferry) @ 2013Q2
Self-Identified List (Browns Ferry)
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