05000483/FIN-2012004-03
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Finding | |
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| Title | Review the Cause of the Failure of Inverter NN14 |
| Description | On August 19, 2012, safety-related inverter NN14 failed. After determining the cause of the failure, the length of time to repair, test, and return to service; the licensee requested enforcement discretion since activities would extend beyond the allowed outage time specified in technical specifications. An unresolved item was identified to assess whether the cause for the noncompliance, for which a Notice of Enforcement Discretion was granted, involved a violation. On July 27 and August 13, 2012, safety related inverter NN14 auto-transferred to the backup source. The licensee entered Technical Specification 3.8.7, Action A.1, which required returning the inverter to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or place the plant in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Troubleshooting efforts concluded that the most likely cause for the inadvertent auto-transfer was a degraded card associated with the automatic static transfer switch. This card was replaced along with successful completion of post-maintenance testing. On August 19, 2012, inverter NN14 failed again. The licensee entered Technical Specification 3.8.7, Action A.1. Troubleshooting revealed that the constant-voltage transformer phase B secondary windings were shorted to ground. The most probable cause of the short was determined to be degradation of the transformer windings/insulation. In consultation with the vendor, the licensee determined that following replacement of the transformer, post-maintenance testing and temperature/voltage stabilization would exceed the time allowed by technical specifications. Therefore, the licensee contacted the NRC on August 20, 2012, to request enforcement discretion to extend the allowed outage time of Technical Specification 3.8.7, Action A.1, for an additional 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> (a total of 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br />). The NRC staff evaluated the information provided by the licensee and granted Notice of Enforcement Discretion 12-4-002 (ADAMS ML12237A010). An unresolved item was identified to assess whether the cause for the noncompliance, for which a Notice of Enforcement Discretion was granted, involved a violation URI 05000483/2012004-03, Review Cause of the Failure of Inverter NN14. |
| Site: | Callaway  |
|---|---|
| Report | IR 05000483/2012004 Section 4OA3 |
| Date counted | Dec 31, 2012 (2012Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | L Ricketson P Elkmann L Carson L Willoughby N O'Keefe T Hartman N Greene Z Hollcraft N Makrisp Elkmannt Hartman G Apger L Willoughby N Makris N O'Keefe |
| INPO aspect | |
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Finding - Callaway - IR 05000483/2012004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Callaway) @ 2012Q4
Self-Identified List (Callaway)
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