ENS 48598
ENS Event | |
|---|---|
06:56 Dec 16, 2012 | |
| Title | Reactor Scram from 98% Power During Turbine Control Valve Testing |
| Event Description | At approximately 01:56 hours on December 16, 2012, Susquehanna Steam Electric Station Unit 2 reactor automatically scrammed while performing testing of the number 2 control valve per the station surveillance testing program. The number 2 control valve closure initiated a 1/2 scram in the reactor protection system as designed; specifically the 'B1' channel. Evaluation of plant data indicates that an 'A' scram channel signal was activated during the time period the number 2 control valve scram signal was active, thereby causing a full reactor scram. The cause of the 'A' scram channel signal is not understood at this time and is under investigation.
A second reactor scram signal was received at approximately 02:10 hours due to reactor water level lowering to 13 inches. Reactor water level was restored above the trip setpoint. All control rods inserted and both reactor recirculation pumps tripped at -38 inches. Reactor water level lowered to -48.5 inches causing Level 3 (+13 inches) and level 2 (-38 inches) isolations. HPCI and RCIC both automatically initiated and were overridden by control room operators after water level was restored. All isolations and initiations at this level occurred as expected. No steam relief valves opened. Pressure was controlled via turbine bypass valve operation. All safety systems operated as expected. This report is being made per 10 CFR 50.72(b)(2)(iv)(A) and 10 CFR 50.72(b)(2)(iv)(B) for 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> reports, and 10 CFR 50.72(b)(3)(iv)(A) for an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> report. The unit 2 reactor is currently stable in Mode 3. An investigation into the cause of the reactor scram is underway. Unit 1 continued power operation. The NRC resident inspectors were notified. A press release will occur." The licensee will be notifying the State authorities. |
| Where | |
|---|---|
Susquehanna  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000388/LER-2012-003 |
| Time - Person (Reporting Time:+-2.28 h-0.095 days <br />-0.0136 weeks <br />-0.00312 months <br />) | |
| Opened: | Alex Mcllellan 04:39 Dec 16, 2012 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Dec 16, 2012 |
| 48598 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (98 %) |
| After | Hot Shutdown (0 %) |