05000336/FIN-2009004-01
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Finding | |
|---|---|
| Title | Inadequate and Untimely Corrective Actions Causes Reactor Trip |
| Description | A self-revealing finding of very low safety significance (Green) was identified for Dominion\'s failure to provide timely and effective corrective actions for known degraded conditions on the Unit 2 VR-11 and VR-21 120-volt AC non-vital instrument power supplies. Specifically, VR-11 and VR-21 were known to cycle on and off repeatedly whenever an electrical disturbance on the grid affected the input supply voltages from their respective regulating transformers. The degraded condition on the instrument buses had not been corrected despite numerous prior opportunities and Ultimately led to a reactor trip on July 3, 2009. Dominion entered this issue into their corrective action program (CR340569 and CR340579). Interim corrective actions included the installation of dedicated uninterruptable power supplies (UPS) for the Electro-Hydraulic Control (EHC) system and feedwater level control system loads prior to reactor startup. Final corrective actions to install a larger UPS to power the VR-11 and VR-21 DC buses are under engineering evaluation. This finding is more than minor because it was associated with the Equipment Performance attribute of the Initiating Events cornerstone and affected the cornerstone objective of limiting the likelihood of those events that upset plant stability and challenge critical safety functions during power operations. Dominion did not implement effective interim corrective actions, nor did they take timely final corrective actions to prevent recurrence of the power cycling of the VR-11 and VR-21 instrument buses in time to prevent a reactor trip on July 3, 2009. The inspectors performed a Phase 1 screening, in accordance with fMC 0609, Significance Determination Process, and determined that the finding is of very low safety significance (Green) because it did not contribute to the likelihood that mitigation equipment or functions would not be available. The finding has a cross-cutting aspect in the area of Problem Identification and Resolution, Corrective Action Program because Dominion did not take appropriate corrective actions to address safety issues and adverse trends in a timely manner, commensurate with their safety significance and complexity P.1.d |
| Site: | Millstone  |
|---|---|
| Report | IR 05000336/2009004 Section 4OA3 |
| Date counted | Sep 30, 2009 (2009Q3) |
| Type: | Finding: Green |
| cornerstone | Initiating Events |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | T Moslak B Haagensen D Johnson J Krafty S Shaffer J Tifft R Bellamy C Crisden |
| CCA | P.3, Resolution |
| INPO aspect | PI.3 |
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Finding - Millstone - IR 05000336/2009004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Millstone) @ 2009Q3
Self-Identified List (Millstone)
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