ENS 52057
ENS Event | |
|---|---|
22:15 Jun 30, 2016 | |
| Title | Multiple Valid Specified System Actuations Due to Loss of Service Transformer 21 |
| Event Description | On June 30, 2016 at 1715 CDT, Grand Gulf Nuclear Station (GGNS) experienced an electrical power supply loss from Service Transformer 21 which resulted in power supply being lost to Division 2 (16AB Bus) and Division 3 (17AC Bus) ESF buses. This resulted in a valid actuation of Division 2 and Division 3 Diesel Generators on bus under voltage. They both automatically started and energized their respective ESF buses as designed.
During this event, the loss of power to the Division 2 (16AB Bus) resulted in a Division 2 RPS bus power loss, which actuated a Div 2 RPS half SCRAM signal. The power loss also resulted in a loss of the Instrument Air pressure resulting in some Control Rod Scram Valves to drift open. This in turn caused the Scram Discharge Volume to fill to the point where a Div 1 RPS half SCRAM signal was initiated from Scram Discharge Volume level high on Channel 'A'. This resulted in a valid full RPS Reactor SCRAM while not critical. Instrument Air pressure was restored and the SCRAM signal was reset at 1733 CDT. Appropriate off normal event procedures were entered to mitigate the transient. No ECCS initiation signals were reached. All safety systems performed as expected. GGNS was in Mode 4, Cold Shutdown, with MSIVs closed at the time of the event. Reactor water level was maintained in the normal water level band by Control Rod Drive system throughout this event. RHR 'A' was maintained in Shutdown Cooling operation and it was not affected by this event. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Grand Gulf  Mississippi (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000416/LER-2016-006 |
| Time - Person (Reporting Time:+0.65 h0.0271 days <br />0.00387 weeks <br />8.9037e-4 months <br />) | |
| Opened: | Joe Graham 22:54 Jun 30, 2016 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | Jun 30, 2016 |
| 52057 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |