05000461/FIN-2008004-02
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Finding | |
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| Title | Failure to Evaluate an Unexpected and Unknown Cause for Stray Voltage in the End-of-Cycle Recirculation Pump Trip Circuit During Post Modification Testing Resulted in a Reactor Recirculation Pump Trip |
| Description | The inspectors identified a finding of very low safety significance associated with a self-revealed event that resulted in the unexpected loss of a reactor recirculation pump. The licensee failed to evaluate an unexpected and unknown cause for stray voltage in the End-of-Cycle Recirculation Pump Trip (EOC-RPT) circuit during post-modification testing during the Cycle 11 refueling outage that concluded in February 2008. This resulted in the unexpected loss of a reactor recirculation pump and the subsequent plant transient that led to a reactor scram. As an immediate and interim corrective action, the licensee implemented a design change to the EOC-RPT circuitry that should prevent inadvertent relay actuation causing recirculation pump trips due to the stray voltage problem. No violation of regulatory requirements was identified. The finding was of more than minor significance because this issue was associated with the Equipment Performance attribute of the Initiating Events Cornerstone and adversely affected the cornerstone objective of limiting the likelihood of events that upset plant stability and challenge critical safety functions during power operations. Specifically, the failure to evaluate an unexpected and unknown cause for stray voltage in the EOC-RPT circuit during post modification testing resulted in the unexpected loss of a reactor recirculation pump and the subsequent plant transient that led to a reactor scram. The finding was of very low safety significance because the issue: (1) did not contribute to the likelihood of a primary or secondary system loss-of-coolant-accident initiator, (2) did not contribute to both the likelihood of a reactor trip AND the likelihood that mitigation equipment or functions would not be available, and (3) did not increase the likelihood of a fire or internal/external flooding event. The inspectors concluded that this finding affected the cross-cutting area of human performance. Specifically, the licensee failed to appropriately incorporate risk insights in investigating and resolving an unexplained source of voltage in a circuit that had a high risk consequence (i.e., reactor recirculation pump trip). (IMC 0305 H.3(a)) (Section 1R12.b.2) |
| Site: | Clinton  |
|---|---|
| Report | IR 05000461/2008004 Section 1R12 |
| Date counted | Sep 30, 2008 (2008Q3) |
| Type: | Finding: Green |
| cornerstone | Initiating Events |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.12 |
| Inspectors (proximate) | D Melendez-Colon D Reeser B Kemker A Barker S Mischke D Lords N Feliz-Adomo C Acosta Acevedoe Coffman |
| CCA | H.5, Work Management |
| INPO aspect | WP.1 |
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Finding - Clinton - IR 05000461/2008004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Clinton) @ 2008Q3
Self-Identified List (Clinton)
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