05000339/FIN-2016002-02
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Finding | |
|---|---|
| Title | Adequacy of Class 1E 120VAC Vital Bus Design |
| Description | The NRC identified an NCV of 10 CFR Part 50, Appendix B, Criterion III, Design Control, for the licensees failure to verify the adequacy of design for the protection devices at the 120VAC vital instrumentation buses. Specifically, the licensees failure to verify that the protective devices at the Unit 1 and Unit 2 120VAC vital instrumentation buses would isolate failed equipment when supplied by the voltage regulating transformer in accordance with IEEE 308-1971 was a PD. The licensee entered this issue into their CAP as CRs 1006865 and 1013278. At the time of the inspection, the licensee was evaluating the issue to determine appropriate corrective actions. This does not present an immediate safety concern because the performance deficiency is related to a non-conformance with a design standard upon which only one train would be affected by a postulated single failure and the other train would remain available and capable to respond to the design basis accident. The performance deficiency was determined to be more than minor because it adversely affected the Design Control attribute of the Mitigating Systems cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, failing to isolate failed equipment could lead to tripping the associated 120VAC vital bus, causing unnecessary loss of other safety related equipment connected to the bus. The finding was determined to be of very low safety significance (Green), because it was a deficiency affecting the design or qualification of a structure, system, or component (SSC) and the SSC maintained its operability. This finding was not assigned a cross-cutting aspect because the issue did not reflect current licensee performance. |
| Site: | North Anna  |
|---|---|
| Report | IR 05000339/2016002 Section 1R21 |
| Date counted | Jun 30, 2016 (2016Q2) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | G Croon G Eatmon G Ottenberg J Panfel J Rivera M Riley R Kellner S Rose |
| Violation of: | 10 CFR 50 Appendix B Criterion III, Design Control 10 CFR 50 Appendix B |
| INPO aspect | |
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Finding - North Anna - IR 05000339/2016002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (North Anna) @ 2016Q2
Self-Identified List (North Anna)
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