05000395/LER-2007-001
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation |
| 3952007001R01 - NRC Website | |
PLANT IDENTIFICATION
Westinghouse - Pressurized Water Reactor
EQUIPMENT IDENTIFICATION
XPP0028D Feedwater Booster Pump "D" XPS0006D Feedwater Booster Pump "D" Recirculation Orifice
IDENTIFICATION OF EVENT
On February 5, 2007 at 0306, the reactor was manually tripped due to a steam leak in the vicinity of the "D" feedwater booster pump recirculation header orifice XPS0006D.
EVENT DATE
02/05/2007
REPORT DATE
04/05/2007 Initial Report 07/26/2007 Revised Report
CONDITIONS PRIOR TO EVENT
Mode 1, 95% Power
DESCRIPTION OF EVENT
"D" Feedwater booster pump had been secured and isolated for maintenance on the pump's inboard mechanical seal. After repairs were complete the pump was filled, vented, unisolated, and warmed per system operating procedure SOP-210. During the initial start of the pump, two banging noises were heard in the vicinity of the Turbine Building (TB) 463' elevation. Water was noticed running back to the TB-412' elevation, and a large plume of steam was observed on the west side of the Deaerator Storage Tank on the TB-463' elevation. Since the actual location of the steam leak could not be readily determined, the Duty Shift Supervisor directed a manual reactor trip.
All systems operated as expected in response to the manual reactor trip. Emergency feedwater actuated on Lo-Lo steam generator water levels. Both motor driven and the turbine driven emergency feedwater pumps started. After review of steam generator parameters, the operating crew secured and reset the turbine driven emergency feedwater pump. Plant management was notified, and the Incident Response Team was activated. A four (4) hour notification to the NRC, as required by 10CFR50.72 (b)(2)(iv), was made at 0638.
CAUSE OF EVENT
Based on results of the Failure Modes Analysis, the failure of the gaskets at XPS0006D was the result of normal aging as well as accelerated aging due to the reduced gasket seating surface caused by an anomaly on the orifice plate seating surface and pipe movement during startup.
ANALYSIS OF EVENT
All systems operated as expected during the event. The emergency feedwater actuated on lo-lo steam generator level. This actuation is expected on a reactor trip.
CORRECTIVE ACTIONS
The gaskets and orifice plate, in the "D" feedwater booster pump recirculation header were replaced. As part of the extent of condition, the maintenance history of the other feedwater booster pump recirculation line orifice connections were evaluated. As a result of this evaluation, the gasket and orifice plate for the "C" feedwater booster pump recirculation line orifice connections were replaced, and the gaskets for the "A" feedwater booster pump recirculation line orifice connections were replaced.
Corrective actions to preclude recurrence were identified in root cause analysis RCA 07-0411 and approved by the Corrective Action Review Board (CARB). These actions include 1) revision of the feedwater system operating procedure (SOP-210) to direct operators to ensure certain system conditions are met prior to starting a feedwater booster pump, 2) redesign and proper sizing of recirculation line orifice plates, 3) reconfiguration of the flanged joint to make it more robust, and 4) revision of maintenance procedures to address use of special tools and surface inspections.
PRIOR OCCURRENCES
There have been no prior occurrences of steam leaks in the secondary plant that required a manual reactor trip in the past several years.