ENS 51755
ENS Event | |
|---|---|
20:14 Jan 6, 2016 | |
| Title | Power Reduction Due to Automatic Opening of the Turbine Bypass Valves |
| Event Description | On January 6, 2016, at approximately 1514 EST, with Fermi 2 in Mode 1 operating at 100 percent reactor thermal power, the East and West Turbine Bypass Valves (TBVs) automatically opened for 3 minutes and 32 seconds in response to the number one High Pressure Turbine Stop Valve (TSV) drifting from full open to 25 percent open. Reactor power was subsequently lowered to 91.0 percent reactor thermal power and the bypass valves closed.
Per Technical Specification Bases 3.3.1.1, TBVs must remain shut while reactor thermal power is at or above 29.5 percent to consider the TSV closure and Turbine Control Valve (TCV) fast closure Reactor Protection System (RPS) functions operable. The condition was recognized at the time of the event and the RPS functions were not declared inoperable since the functions were verified to remain enabled. Since the RPS functions were not declared inoperable, Fermi 2 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, after further evaluation, it was determined that this event met the reporting criterion. Accordingly, this event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(A). The licensee informed the NRC Resident Inspector. The cause of the High Pressure Turbine Stop Valve drifting was due to an actuator malfunction that has since been corrected. This event was determined to be reportable at 1200 EST on 02/24/16. See EN #51756 for a similar event that occurred on 02/21/16.
Upon further review, it was determined that this event also meets the reporting criterion of 10CFR50.72(b)(3)(v)(D) for a condition that could have prevented the fulfillment of a safety function of structures or systems that are needed to mitigate the consequences of an accident. Although this event was determined to be reportable at 1200 EST on 02/24/16, it met the reporting requirement on the date of the event (01/06/2016). The licensee informed the NRC Resident Inspector. Notified R3DO (Valos). |
| Where | |
|---|---|
Fermi  Michigan (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+1196.35 h49.848 days <br />7.121 weeks <br />1.639 months <br />) | |
| Opened: | Derek Etue 16:35 Feb 25, 2016 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Mar 2, 2016 |
| 51755 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (91 %) |