05000388/FIN-2013011-01
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Finding | |
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| Title | Reactor Scram due to Loss of Integrated Control System |
| Description | A finding of very low safety significance (Green) for failure to evaluate and incorporate the operating experience PPL received regarding the integrated control system (ICS) was self-revealed when Unit 2 lost control of reactor vessel level on November 9, 2012, requiring insertion of a manual scram. The cause of the loss of level control was the lockup of one of the two ICS network core switches due to a data storm, a condition which had been described in various operating experience communications from April 2007 through September 2012. PPLs immediate corrective actions included entering the issue into their corrective action program as condition report 1640540, making changes to Unit 2s core switches to prevent a similar condition, and developing a procedure to allow operators to diagnose and respond to a similar condition in Unit 1. The performance deficiency is more than minor because it was associated with the equipment performance attribute of the Initiating Events cornerstone and affected its objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. Specifically, in this case, had the operating experience been reviewed appropriately, compensatory actions could have been taken that would have reasonably prevented the scram with loss of main feedwater. The inspectors evaluated the finding in accordance with IMC 0609, \"Significance Determination Process,\" Appendix A, \"The Significance Determination Process (SDP) for Findings At-Power,\" Exhibit 1, for the Initiating Events cornerstone. The Senior Reactor Analyst (SRA) used the SSES Standardized Plant Analysis Risk (SPAR) model, Revision 8.16, for Unit 2 and SAPHIRE 8 to conduct the detailed risk evaluation and determined the increase in core damage frequency (ACDF) for internal initiating events was 5E-7yr (Green). Specifically, to account for the increased chance for a loss of main feedwater, the initiating event frequency was increased by one order of magnitude. Additionally, model modifications were made to account for the plant specific depressurization strategy. The dominant sequence was a loss of main feedwater with a failure of all injection coupled with a failure to vent containment and control residual heat removal (RHR). The increase in risk from both external events and for a large early release was found to be negligible. This finding was determined to have a cross-cutting aspect in the area of Corrective Action Program, Operating Experience (OE), because PPL staff did not systematically collect, evaluate, and communicate to affected internal stakeholders in a timely manner relevant internal and external OE. Specifically, PPL did not enter the vendor advisories into the stations OE program and therefore, management was unaware of the core switch issues, no formal evaluation was conducted, and no corrective actions were specified to mitigate the vulnerability. |
| Site: | Susquehanna  |
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| Report | IR 05000388/2013011 Section 4OA3 |
| Date counted | Sep 30, 2013 (2013Q3) |
| Type: | Finding: Green |
| cornerstone | Initiating Events |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | C Newport F Bower J Grieves |
| CCA | P.5, Operating Experience |
| INPO aspect | CL.1 |
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Finding - Susquehanna - IR 05000388/2013011 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Susquehanna) @ 2013Q3
Self-Identified List (Susquehanna)
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