ENS 51756
ENS Event | |
|---|---|
05:30 Feb 21, 2015 | |
| Title | Power Reduction Due to Automatic Opening of a Turbine Bypass Valve |
| Event Description | On February 21, 2015, at approximately 0030 EST, with Fermi 2 in Mode 1 operating at 100 percent reactor thermal power, the West Turbine Bypass Valve (TBV) automatically opened in response to the number two High Pressure Turbine Stop Valve (TSV) cycling from full open to closed and then to 22 percent open. Reactor power was subsequently lowered to 91.5 percent reactor thermal power and the bypass valve 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 declared inoperable. The Limiting Condition for Operation was exited at 0031 EST following TBV closure. Since the RPS functions were verified to remain enabled, 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, this event was subsequently determined to meet the reporting criterion and 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 cycling was due to a communication card failure that has since been corrected. This event was determined to be reportable at 1200 EST on 02/24/16. See EN #51755 for a similar event that occurred on 01/06/16.
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 (02/21/2015). 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:+8867.08 h369.462 days <br />52.78 weeks <br />12.146 months <br />) | |
| Opened: | Derek Etue 16:35 Feb 25, 2016 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Mar 2, 2016 |
| 51756 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (91 %) |