05000458/FIN-2010004-06
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Finding | |
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| Title | Inadequate Maintenance Results in Unplanned Opening of Main Turbine Bypass Valve |
| Description | A self-revealing finding of very low safety significance (Green) was identified when turbine bypass valve number 1 opened unexpectedly causing the reactor to exceed 100 percent core thermal power. Operators promptly lowered core thermal power to 90 percent to preserve margin to fuel thermal limits. A failed power supply and inadequate calibration and testing of the steam bypass and pressure regulation system and electro-hydraulic control system caused the event. Corrective actions include replacing system power supplies and revising applicable calibration and test instructions. The licensee entered this issue into their corrective action program as Condition Report CR-RBS-2010-03343. This finding was more than minor because it was associated with the equipment performance attribute of the Mitigating Systems Cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, technical specification mitigation equipment (main turbine bypass system, end-of-cycle recirculation pump trip function, and rod block instrumentation functions) became inoperable. Using Manual Chapter 0609, Significance Determination Process, Phase 1 Worksheet, the inspectors determined that the finding was of very low safety significance (Green) because the finding did not represent an actual loss of safety function of the system or train; did not result in the loss of one or more trains of nontechnical specification equipment; and did not screen as potentially risk significant due to a seismic, flooding, or severe weather initiating event. The inspectors determined that this finding did not represent current licensee performance because the preventative maintenance schedule and calibration procedure were developed and approved over two years ago. Therefore, no crosscutting aspect was assigned to this finding (Section 1R20) |
| Site: | River Bend  |
|---|---|
| Report | IR 05000458/2010004 Section 1R20 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | Finding: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71111.2 |
| Inspectors (proximate) | P Elkmann C Osterholtz R Hagar G Larkin V Gaddy C Norton D Strickland R Kumana C Stancil G Guerra |
| INPO aspect | |
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Finding - River Bend - IR 05000458/2010004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (River Bend) @ 2010Q3
Self-Identified List (River Bend)
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