05000482/FIN-2008002-08
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Finding | |
|---|---|
| Title | Transformer trip resulted in an unplanned eractor trip and forced outage. |
| Description | On March 17, 2008, plant operators observed that steam generator water level was lowering and main feed pump speed was decreasing. Based on these indications, Wolf Creek operators manually tripped the plant. Posttrip immediate actions and followup actions were completed without deviation. An auto actuation of auxiliary feed water occurred due to low/low steam generator water levels as expected but no other ECCS or engineered safety feature actuations occurred. All plant equipment responded as expected. Following the trip, control room operators observed indications that the plant had experienced a loss of the XPB03 13.8 kV to 4.16 kV nonsafety transformer which powers PB003 4.16 kV nonsafety bus. Approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> prior to the transformer trip, Wolf Creek had removed from service XPB04 transformer for planned maintenance and cross connected XPB04 transformer PB004 bus loads to the XPB03 transformer PB003 bus. This arrangement powered all three condensate pumps from the PB003 4.16 kV bus. The PB003 bus powers condensate Pumps A and C and the PB004 bus powers condensate Pump B. The XPB03 transformer trip resulted in losing power to all three condensate pumps which tripped the main feed pumps on low suction pressure. The licensees initial draft investigation of the cause of the transformer trip determined that two phases of the XPB03 transformer 4.16 kV output cables had overheated and failed. Additional investigation into the cable failures discovered that two multidirectional conductor connectors used to terminate two phases of the 1000 million circular mils (MCM) 4.16 kV bus cables were installed using the incorrect configuration. The cable connector had been installed using a 1500-2000 MCM configuration which resulted in the conductor connector bottoming out before applying sufficient compression to ensure adequate connection to the cable. Pending completion of the licensees root cause determination and consequence assessment by a Region IV Senior Reactor Analyst, additional inspection of the finding is needed to determine significance. This issue is considered unresolved pending additional NRC review of Wolf Creek root cause determination. This issue will be tracked as: Unresolved Item (URI)05000483/2008002-08, Transformer Trip Resulted in an Unplanned Reactor Trip and Forced Outage |
| Site: | Wolf Creek  |
|---|---|
| Report | IR 05000482/2008002 Section 4OA3 |
| Date counted | Mar 31, 2008 (2008Q1) |
| Type: | URI: |
| cornerstone | No Cornerstone |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | C Long D Stearns G Pick S Cochrum V Gaddyk Claytonp Elkmann L Ellershaw S Cochrum C Long V Gaddy |
| INPO aspect | |
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Finding - Wolf Creek - IR 05000482/2008002 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Wolf Creek) @ 2008Q1
Self-Identified List (Wolf Creek)
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