05000416/FIN-2013002-05
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Finding | |
|---|---|
| Title | Automatic Reactor Scram Caused by Ground Condition on the A Phase Neutral Current Transformer |
| Description | The inspectors reviewed a self-revealing finding for the failure to ensure the current transformer structure, the neutral bus housing, and the associated mounting hardware were installed with adequate clearance to accommodate thermal expansion. This failure resulted in an automatic reactor scram on December 29, 2012, and a subsequent scram on January 4, 2013. Following the second scram on January 4, 2012, the licensee determined the cause of the scram was a trip of the phase A unit differential relay because of a ground fault on the A phase of the generator neutral current transformer, due to inadequate clearances. Immediate corrective actions included removing the damaged current transformer and modifying the neutral bus housing. The plant scrams were entered into the corrective action program as Condition Reports CR-GGN- 2012-13290 and CR-GGN-2013-00083. The failure to install micarta plate bolts in accordance with manufacturer specifications and ensure that the current transformer structure, the neutral bus housing, and the associated mounting hardware had adequate clearance is a performance deficiency. This finding is more than minor because it is associated with the Initiating Events Cornerstone attribute of human performance and adversely affected the cornerstone objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown and power operations. Using NRC Inspection Manual Chapter 0609, Attachment 4, Initial Characterization of Findings, the inspectors determined that the issue affected the Initiating Events Cornerstone. In accordance with NRC Inspection Manual Chapter 0609, Appendix A, The Significance Determination Process (SDP) for Findings at Power, the inspectors determined that the issue has very low safety significance (Green) because it caused only a reactor trip and did not cause a loss of mitigating equipment relied upon to transition the plant from the onset of the trip to a stable shutdown condition. The finding has a cross-cutting aspect in the human performance area associated with the resources component because the licensee failed to provide adequate work instructions. |
| Site: | Grand Gulf  |
|---|---|
| Report | IR 05000416/2013002 Section 4OA3 |
| Date counted | Mar 31, 2013 (2013Q1) |
| Type: | Finding: Green |
| cornerstone | Initiating Events |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | B Rice D Proulx J Braisted J Laughlin R Smith S Achen S Hedger S Makor |
| CCA | H.7, Documentation |
| INPO aspect | WP.3 |
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Finding - Grand Gulf - IR 05000416/2013002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Grand Gulf) @ 2013Q1
Self-Identified List (Grand Gulf)
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