05000244/FIN-2013007-01
From kanterella
Jump to navigation
Jump to search
Finding | |
|---|---|
| Title | Required Voltage and Timing Criteria for Load Tap Changer Controls and Motor |
| Description | The team identified a finding of very low safety significance involving a non-cited violation (NCV) of 10 CFR Part 50, Appendix B, Criterion III, Design Control, in that, Constellation did not ensure the automatic load tap changer (LTC) controls and motor for the #7 transformer and the circuit 767 voltage regulator associated with the #6 transformer had adequate voltage to operate during design basis events. Specifically, LTC operation is credited to restore vital bus voltage during design basis events under minimum grid voltage conditions. Additionally, appropriate acceptance criteria had not been translated into periodic LTC timing tests to ensure design assumptions were being maintained. Failure of the automatic LTC controls and motor to operate, as credited, due to inadequate voltage or timing would result in the 480V safeguard buses disconnecting from one of its credited sources of power. Constellation entered the issue into their corrective action program, performed preliminary voltage calculations, and tested a spare LTC motor at voltage levels below the vendor minimum voltage ratings to ensure the offsite power source would remain operable to the safeguard buses. The finding was more than minor because it was similar to Example 3.j of NRC IMC 0612, Appendix E, and was associated with the Design Control attribute of the Mitigating Systems Cornerstone and affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. The team determined the finding was of very low safety significance because the issue was a design deficiency that did not result in the loss of the preferred source of power to the 480V safeguard buses. This finding had a cross-cutting aspect in the area of Problem Identification and Resolution, Operating Experience, because in 2011 Ginna had previously recognized operating experience information noting that the station may be vulnerable to the issue of evaluating LTC control voltage. However, Constellation had not implemented this operating experience into their station processes to ensure they had correctly analyzed the issue. |
| Site: | Ginna  |
|---|---|
| Report | IR 05000244/2013007 Section 1R21 |
| Date counted | Sep 30, 2013 (2013Q3) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | P Kaufman F Arner J Brand J Ayala G Gardner J Nicely P Krohn |
| Violation of: | 10 CFR 50 Appendix B Criterion III, Design Control |
| CCA | P.5, Operating Experience |
| INPO aspect | CL.1 |
| ' | |
Finding - Ginna - IR 05000244/2013007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Finding List (Ginna) @ 2013Q3
Self-Identified List (Ginna)
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||