ENS 47181
ENS Event | |
|---|---|
18:03 Aug 23, 2011 | |
| Title | Alert Declared Due to an Earthquake in the Area and a Loss of Offsite Power |
| Event Description | At 1403 hrs. EDT, North Anna Power Station declared an Alert due to significant seismic activity onsite. The Alert was declared under EAL HA6.1. Both units experienced automatic reactor trips from 100% power and are currently stable in Mode 3. All offsite electrical power to the site was lost. All four emergency diesel generators (EDG) automatically started and loaded and provided power to the emergency buses.
While operating, the 2H EDG developed a coolant leak and was shutdown. As a result, the licensee added EAL SA1.1 to their declaration. All control rods inserted into the core. Decay heat is being removed via the steam dumps to atmosphere. No personnel injuries were reported.
The licensee has downgraded the Alert to a Notification of Unusual Event based on equipment alignments and inspection results. The licensee notified R2 IRC. Notified IRD (Marshall), NRR (Thorp), FEMA (Hollis), DHS (Inzer), USDA (Ferezan), HHS (Willis) and DOE (Parsons).
The licensee has exited the Notification of Unusual Event at 1315 EDT. The exit criteria was that all inspections and walkdowns were completed and plant conditions no longer meet the criteria for a NOUE. Notified R2DO (Widmann), IRD (Marshall), NRR (Thorp), FEMA (Hollis), DHS (Inzer), USDA (Ferezan), HHS (Willis) and DOE (Jackson).
This notification is to report new information identified post event that a condition existed which met the emergency plan criteria but was not declared. On August 23 at 1403 EDT, North Anna Power Station declared an Alert due to seismic activity onsite. The Alert was declared under Emergency Action Level (EAL) HA6.1 "Other conditions existing which in the judgment of the SM warrant declaration of an alert. Initial review of seismic response data from the earthquake on 8/23/11 (1348 hours0.0156 days <br />0.374 hours <br />0.00223 weeks <br />5.12914e-4 months <br />) indicates that design spectrum input assumptions (i.e. Design Basis Earthquake [DBE] limits) may have been exceeded above 5 HZ. This would have resulted in classification of an Alert under EAL HA1.1. No significant equipment damage to safety related systems (including class I structures) has been identified through site walk-downs nor has equipment degradation been detected through plant performance and surveillance testing following the earthquake. The licensee notified the NRC Resident Inspector. The licensee also plans on notifying the State Emergency Operations Center and the Louisa County County Administrator. Notified R2DO (Widmann) and NRR EO (Bahadur). |
| Where | |
|---|---|
North Anna  Virginia (NRC Region 2) | |
| Reporting | |
| Emergency class: | Alert |
| 10 CFR 50.72(a) (1) (i), Emergency Class Declaration | |
| Time - Person (Reporting Time:+-3.65 h-0.152 days <br />-0.0217 weeks <br />-0.005 months <br />) | |
| Opened: | Lee Baron 14:24 Aug 23, 2011 |
| NRC Officer: | Eric Simpson |
| Last Updated: | Aug 26, 2011 |
| 47181 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
WEEKMONTHYEARENS 560882022-09-04T23:39:0004 September 2022 23:39:00
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