05000323/FIN-2013005-02
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Finding | |
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| Title | Reactor Trip due to a Lightning Arrester Flashover |
| Description | The inspectors reviewed a Green self-revealing non-cited violation of 10 CFR 50.65(a)(4), Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants, for failure to implement adequate oversight controls and risk assessment while performing 500kV transmission line insulator maintenance on Unit 2. This caused an initiating event due to a flashover on the main transformer lightning arrester that resulted in a reactor trip. The failure to effectively perform a risk assessment and properly control maintenance activities that resulted in a reactor trip was a performance deficiency. The performance deficiency was more than minor because it was associated with the human performance attribute of the Initiating Events cornerstone and adversely affected the cornerstone objective to limit the likelihood of events that upset plant stability and challenged critical safety functions during power operations, and is therefore a finding. Using Inspection Manual Chapter 0609, Attachment 04, Initial Characterization of Findings, and Appendix A, Exhibit 1, Initiating Events Screening Questions, this finding was determined to be of very low safety significance (Green) because, although it resulted in a reactor trip, it did not result in the loss of mitigating equipment relied upon to transition the plant from the onset of the trip to a stable shutdown condition. Additionally, using Inspection Manual Chapter 0612, Appendix K, Maintenance Risk Assessment and Risk Management Significance Determination Process, this finding was determined to be of very low safety significance (Green). The licensee entered the condition into the corrective action program as Notification 50572800. This finding had a cross-cutting aspect in the area of human performance, associated with the decision-making component, because the licensee did not demonstrate that nuclear safety was an overriding priority during this maintenance activity. Specifically, the licensee did not initially use conservative decision making in not properly categorizing the activity as a reactor trip risk (despite internal and external operating experience to the contrary), and again when the licensee did not terminate the hot washing activities when environmental conditions degraded resulting in excessive water dispersion H.1(b). |
| Site: | Diablo Canyon  |
|---|---|
| Report | IR 05000323/2013005 Section 4OA3 |
| Date counted | Dec 31, 2013 (2013Q4) |
| Type: | NCV: Green |
| cornerstone | Initiating Events |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | A Alen B Parks C Smith G Guerra J Laughlin R Kumana T Hipschman W Walkerb Parksc Smith G Guerra J Laughlin R Kumana T Hipschman W Walker |
| Violation of: | 10 CFR 50.65(a)(4) 10 CFR 50.65 |
| CCA | H.14, Conservative Bias |
| INPO aspect | DM.2 |
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Finding - Diablo Canyon - IR 05000323/2013005 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Diablo Canyon) @ 2013Q4
Self-Identified List (Diablo Canyon)
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