05000387/FIN-2010004-04
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Finding | |
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| Title | Failure to Accurately Model the Simulator for RPV Level Control Using the Integrated Control System |
| Description | A self-revealing NCV of 10 CFR 55.46(c)(1), Plant Referenced Simulators, was identified because the Susquehanna simulator did not accurately model integrated control system (ICS) response to reactor pressure vessel (RPV) level transients. This violation was due to an error in the simulator modeling that caused RPV level control in the simulator to respond more rapidly than the actual plant resulting in the simulation of a more _stable response and smaller overall changes in RPV level during level transients in the simulator. This error contributed to the decision to proceed with an extended power uprate (EPU) required condensate pump trip test during reactor power ascension activities. As a result on May 14, 2010, when the condensate pump trip test was performed, the ICS system was unable to adequately control reactor vessel water level and operators inserted a manual reactor scram prior to a high level turbine trip at level 8. PPL completed corrective actions to update the simulator model to accurately reflect the feedwater flow component of ICS and has ensured that the simulator reflects actual plant performance and re-performed the condensate pump trip test. This issue was entered in PPL\'s corrective action process as AR/CR 1257781. The performance deficiency is more than minor because it is associated with the Human Performance attribute of Mitigating Systems and affects the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the modeling of the Susquehanna simulator introduced negative operator training that affected the ability of the operators to take the appropriate actions during an actual event. The finding was determined to be of very low safety significance because it is not related to operator performance during requalification, it is related to simulator fidelity, and it had a negative impact on the timeliness of operator actions during an actual plant transient. This finding has a cross-cutting aspect in the area of Human Performance, Resources, because PPL did not ensure that equipment and other resources were available and adequate to assure safety. Specifically, simulator fidelity was inadequate in that modeling information provided by the simulator vendor was not reviewed by PPL nor was an alternate methodology used to validate simulator performance prior to use in operator training and predictions of actual plant response. In addition, ICS adjustments made after the April 22, 2010, scram provided another opportunity to verify the validity of ICS gain settings. |
| Site: | Susquehanna  |
|---|---|
| Report | IR 05000387/2010004 Section 4OA2 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | A Rosebrook D Molteni J Furia J Greives P Finney P Krohn R Mckinley |
| CCA | H.1, Resources |
| INPO aspect | LA.1 |
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Finding - Susquehanna - IR 05000387/2010004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Susquehanna) @ 2010Q3
Self-Identified List (Susquehanna)
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