ENS 51423
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ENS Event | |
|---|---|
16:22 Sep 17, 2015 | |
| Title | Valid Actuation of Uv Relays Following Loss of Unit 2 Startup Transformer |
| Event Description | On September 17, 2015, at 1222 hours0.0141 days <br />0.339 hours <br />0.00202 weeks <br />4.64971e-4 months <br />, with Unit 2 in Mode 5 at the beginning of a refueling outage, an electrical fault on the 2A 6.9 kV bus resulted in the loss of the 2A startup transformer and its associated non-safety related 2A2 and safety related 2A3 busses. At the time of the event, the 2A Emergency Diesel Generator (EDG) had been properly removed from service for scheduled maintenance. The loss of the 2A start up transformer initiated the under voltage relays, which resulted in a valid actuation signal that would have started the 2A EDG.
Additionally, the 2A train of shutdown cooling (SDC) was de-energized; the 2B (protected) train of SDC was not affected by the event and remained in service to remove decay heat. The 2A shutdown cooling train was restored and made available on September 19, 2015 at 0030. The 2B EDG and 2B startup transformer remained operable. St. Lucie did not report this event within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> of occurrence, however, this event was subsequently determined to be reportable pursuant to 10CFR50.72(b )(3)(iv)(A). During this event, Unit 1 experienced a loss of the 1A startup transformer. There was no effect on Unit 1 operation, as its associated non-safety and safety-related busses remained powered by the auxiliary transformer. The 1A startup transformer returned to service on September 18, 2015 at 2103. The licensee informed the NRC Resident Inspector. |
| Where | |
|---|---|
Saint Lucie  Florida (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+168.2 h7.008 days <br />1.001 weeks <br />0.23 months <br />) | |
| Opened: | J. Breen 16:34 Sep 24, 2015 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Sep 24, 2015 |
| 51423 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
WEEKMONTHYEARENS 560872022-09-03T02:48:0003 September 2022 02:48:00
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