05000389/LER-2008-003
| Docket Number Sequential Revmonth Day Year Year Month Day Yearnumber No. | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3892008003R00 - NRC Website | |
DOCKETFACILITY NAME (1) LER NUMBER (6) PAGE (3)NUMBER (2) St. Lucie Unit 2 05000389 2008 - 003 - 00
Description of the Event
On June 7, 2008, A St. Lucie Unit 2 was operating in Mode 1 at 100% power when Operators observed that the 2B Condensate Pump [EII:SD] and 2B Steam Generator Feedwater Pump [EII:SJ] had tripped and steam generator water levels were rapidly decreasing. An The plant was manually tripped in accordance with plant procedures.
investigation determined the 2B condensate pump "B" phase motor leads had overheated and failed. All safe shutdown equipment operated as designed and there was no adverse impact on the health and safety of the public.
Cause of the Event
The event investigation determined that the 2B Condensate Pump "B" phase motor lead lugs overheated and melted due to high resistance at the lug crimp connections. The high resistance was caused by undetected epoxy resin in the motor lead cables. The motor lead lugs were installed with undetected epoxy resin in the motor lead cables because a vendor inadvertently impregnated the motor lead cables with epoxy resin during the Vacuum Pressure Impregnation (VPI) process. The root cause for the undetected epoxy resin was the motor rewind specification did not have specific hold points to detect epoxy resin in motor leads.
Several contributing factors were identified including the vendor inadvertently contaminating the motor lead cables with epoxy and site personnel's unawareness of the adverse results of motor leads contaminated during the VPI process.
Analysis of the Event
This event is reportable under 10 CFR 50.73(a)(2)(iv)(A), as any event or condition that resulted in a manual or automatic reactor trip.
Analysis of Safety Significance The Condensate system is a composite of several subsystems that work in conjunction with one another to supply pre-heated and deaerated high pressure feedwater to the steam generators for steam production. The Condensate System is not Safety Related except for the condensate storage tank (CST) which is the source of water for the auxiliary feedwater system. Failure of the 2B Condensate Pump would have ultimately led to a low steam generator level auto-trip of the Unit. Actions taken by the Operators to manually trip the Unit precluded that action. The Condensate System has no credited safety function and was able to achieve a safe shutdown without impacting the health and safety of the public.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)
Corrective Actions
The corrective actions and supporting actions are entered into the site corrective action program. Any changes to the proposed actions will be managed under the commitment management change program.
1.Revise motor rewind specification (SPEC-E-008) to ensure epoxy is not applied to the motor leads during the Vendor's vacuum pressure impregnation process.
2.Revise motor rewind specification (SPEC-E-008) to add inspection hold points to inspect for epoxy and other contaminates.
Similar Events A search of the corrective action database for St. Lucie was performed to identify events related to a condensate pump/reactor trip and none were found. This event is not considered a repeat event.
Failed Components
Condensate Pump Motor; manufacture Allis-Chalmers - Machine Type "ANVOD"