ENS 55514
ENS Event | |
|---|---|
17:21 Oct 11, 2021 | |
| Title | Automatic Reactor Scram After Main Turbine Trip |
| Event Description | At 1321 EDT on October 11, 2021, Susquehanna Steam Electric Station Unit 2 reactor automatically scrammed due to a trip of the Main Turbine.
Unit 2 reactor was being operated at approximately 95 percent RTP [rated thermal power] with no evolutions in progress. The Control Room received indication of a Main Turbine trip with both divisions of RPS [Reactor Protection System] actuated and all control rods inserted. Turbine bypass valves opened automatically to control reactor pressure and subsequently failed open causing the reactor to depressurize. When reactor pressure reached approximately 560 psig, the operations crew manually closed the Main Steam Isolation Valves (MISVs) to stop the depressurization. Reactor water level lowered to -31 inches causing Level 3 (+13 inches) isolations. No [automatic] ECCS [Emergency Core Cooling System] actuations occurred. HPCI [High Pressure Coolant Injection] and RCIC [Reactor Core Isolation Cooling] were manually initiated to control reactor water level. The Operations crew subsequently maintained reactor water level at the normal operating band using RCIC and reactor pressure was controlled with HPCI in pressure control mode and main steam line drains. The Reactor Recirculation Pumps tripped as designed on EOC-RPT [end of cycle recirculation pump trip]. The reactor is currently stable in Mode 3. An investigation into the cause of the turbine trip is underway. The NRC Resident Inspector was notified. A voluntary notification to PEMA will be made. This event requires a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> ENS notification in accordance with 10 CFR 50.72(b)(2)(iv)(A), 10 CFR 50.72(b)(2)(iv)(B) and an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> ENS notification in accordance with 10 CFR 50.72(b)(3)(iv)(A). |
| Where | |
|---|---|
Susquehanna  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000388/LER-2021-003-01 Automatic Reactor Scram Due to Main Turbine Trip Caused by Inadvertent Trip of the Main Generator Output Breakers |
| Time - Person (Reporting Time:+-0.27 h-0.0113 days <br />-0.00161 weeks <br />-3.69846e-4 months <br />) | |
| Opened: | Charles Yoder 17:05 Oct 11, 2021 |
| NRC Officer: | Lloyd Desotell |
| Last Updated: | Oct 11, 2021 |
| 55514 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (95 %) |
| After | Hot Standby (0 %) |