ENS 47798
ENS Event | |
|---|---|
20:11 Apr 2, 2012 | |
| Title | Autostart Of Division 3 Diesel Generator Following 4160 Volt Line Outage |
| Event Description | On 4/2/12 at 1511 [CDT], GGNS [Grand Gulf Nuclear Generating Station] received a valid ESF actuation for emergency AC power to Division 3 4160V bus due to degraded voltage.
One of the two 500KV offsite feeders (Tech Spec Offsite Power Source) tripped causing a drop in grid voltage which resulted in a trip of the ESF feeder breaker for 4160 Volt Division 3 bus. The HPCS (High Pressure Core Spray) Diesel Generator automatically started and energized the bus. The HPCS system was not running and no ECCS initiation occurred during this event. The plant was in Mode 5 with RHR A in shutdown cooling. Divisions 1 and 2 ESF power monitoring instrumentation responded to the grid voltage transient but no actuation setpoints were reached. Division 1 and 2 ESF 4160V buses remained energized and shutdown cooling remained in service. The 500KV offsite feeder (Tech Spec Offsite Power Source) and additional 115 KV feeder (Tech Spec Offsite Power Source) remained in service. The 500KV feeder that tripped was restored by the dispatcher at approximately 1515 CDT. The Division 3 bus was subsequently transferred back to offsite power and the HPCS Diesel Generator was secured. This event is reportable per 10 CFR 50.72(b)(3)(iv). A lightning strike resulted in a voltage transient on the GGNS electrical distribution system. Due to this transient, the 'A' Control Room Air Conditioning Unit (CRAC 'A') tripped and had to be manually restarted. CRAC 'A' was not running for approximately two minutes. During this timeframe CRAC 'B' was tagged out of service. This was evaluated and determined to not be a loss of safety function. The licensee has notified the NRC Resident Inspector. |
| Where | |
|---|---|
Grand Gulf  Mississippi (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+2.75 h0.115 days <br />0.0164 weeks <br />0.00377 months <br />) | |
| Opened: | Frank Weaver 22:56 Apr 2, 2012 |
| NRC Officer: | Pete Snyder |
| Last Updated: | Apr 2, 2012 |
| 47798 - NRC Website
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