05000388/FIN-2015002-05
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Finding | |
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| Title | Loss of Main Condenser Vacuum When Transitioning Steam Seals to Auxiliary Steam |
| Description | A self-revealing finding of very low safety significance (Green) and associated NCV of SSES Unit 2 TS 5.4.1, Procedures, was identified because Susquehanna incorrectly implemented procedures for operation of the auxiliary steam and main turbine steam sealing systems. Specifically, on April 10, 2015, while Unit 2 was being shut down for a RFO, operators secured main turbine steam seals resulting in degraded main condenser vacuum. The degraded main condenser vacuum resulted in a main turbine trip, which caused an automatic reactor scram from approximately 37% power. Susquehanna restored main condenser vacuum by reestablishing steam seals, performed off-normal and emergency operating procedures to stabilize the plant post-scram and entered the issue into the corrective action program (CAP) as CR-2015-09890. The finding was more than minor because it was associated with the Human 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, not understanding the impact of securing auxiliary steam to the main turbine steam seals resulted in the degradation of main condenser vacuum, automatic trip of the main turbine and associated reactor scram. The inspectors evaluated the finding in accordance with IMC 0609, Appendix A "The SDP for Findings At-Power," Exhibit 1, for the Initiating Events cornerstone, dated June 19, 2012. The inspectors determined the finding was of very low safety significance (Green) because it did not cause a reactor trip and the loss of mitigation equipment. Specifically, though a reactor scram occurred, operators were able to restore main condenser vacuum prior to MSIV closure and the main condenser and reactor feed pumps remained functional during the event. This finding has a cross-cutting aspect in the area of Human Performance, Avoid Complacency, because Susquehanna did not implement appropriate error reduction tools. Specifically, operators did not effectively implement human error prevention tools (e.g. pre-job briefing, stop-think-act-review) in accordance with station processes. |
| Site: | Susquehanna  |
|---|---|
| Report | IR 05000388/2015002 Section 4OA3 |
| Date counted | Jun 30, 2015 (2015Q2) |
| Type: | NCV: Green |
| cornerstone | Initiating Events |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | F Bower H Gray J Greives J Kulp N Graneto T Daun A Turilin B Smith C Graves |
| Violation of: | Technical Specification - Procedures Technical Specification |
| CCA | H.12, Avoid Complacency |
| INPO aspect | QA.4 |
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Finding - Susquehanna - IR 05000388/2015002 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Susquehanna) @ 2015Q2
Self-Identified List (Susquehanna)
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