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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 56846 | 10 November 2023 08:14:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Scram | The following information was provided by the licensee via email: At 0118 EST, with Unit 1 in Mode 1 at 100 percent power, the reactor was manually scrammed due to degrading main condenser vacuum. The scram was not complex, with all systems responding normally post-scram. The main turbine bypass valves opened automatically to maintain reactor pressure. Operations responded and stabilized the plant. Reactor water level is being maintained via feedwater pumps. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. Unit 2 is not impacted. Due to Reactor Protection System actuation while critical, this event is being reported as a four-hour and eight-hour non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). Unit 1 reactor is currently stable in mode 3. An investigation is in progress into the cause of the degrading condenser vacuum. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | Feedwater Reactor Protection System Main Condenser | |
| ENS 55909 | 23 May 2022 21:16:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Automatic Reactor Scram | The following information was provided by the licensee via email: At 1716 hours EDT on May 23, 2022, Susquehanna Steam Electric Station Unit 1 reactor automatically scrammed. Unit 1 reactor was being operated at approximately 100 percent (Rated Thermal Power) RTP. The Control Room received indication that both divisions of (Reactor Protection System) RPS actuated from (Reactor Pressure Vessel) RPV high pressure signals and all control rods fully inserted. The Main Turbine bypass valves opened automatically to control reactor pressure. Reactor water level lowered to -42 inches causing Level 3 and Level 2 isolations. (High Pressure Coolant Injection) HPCI (Emergency Core Cooling System) ECCS actuation occurred as designed at -38 inches and injected to the Reactor Vessel. No other ECCS system actuations occurred. (Reactor Core Isolation Cooling) RCIC automatically initiated as designed at -30 inches. The Operations crew subsequently maintained reactor water level at the normal operating band using Feedwater pumps. The reactor is currently stable in Mode 3. An investigation is in progress into the cause of the Automatic SCRAM. The NRC Senior Resident Inspector was notified. A voluntary notification to (Pennsylvania Emergency Management Agency) PEMA will be made. This event requires a 4 hour ENS notification in accordance with 10 CFR 50.72(b)(2)(iv)(A) & 10 CFR 50.72(b)(2)(iv)(B) and an 8 hour ENS notification in accordance with 10 CFR 50.72(b)(3)(iv)(A). | Feedwater Control Rod | |
| ENS 55616 | 30 November 2021 17:54:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unit 1 Automatic Scram | At 1254 EST on November 30, 2021, Susquehanna Steam Electric Station Unit 1 reactor automatically scrammed during Turbine Valve Cycling surveillance activities. Unit 1 reactor was being operated at approximately 80 percent rated thermal power with turbine valve cycling surveillance activities in progress. The Control Room received indication that both divisions of RPS (reactor protection system) actuated from turbine valve closure signals and all control rods fully inserted. The Main Turbine was manually tripped, and turbine bypass valves opened automatically to control reactor pressure. Reactor water level lowered to -35 inches causing Level 3 and Level 2 isolations. No ECCS (emergency core cooling systems) actuations occurred. RCIC (reactor core isolation cooling) automatically initiated as designed at -30 inches. The Operations crew subsequently maintained reactor water level at the normal operating band using Feedwater pumps and RCIC was placed in a standby lineup. The reactor is currently stable in Mode 3. An investigation is in progress into the cause of the turbine valve closure signals. The NRC Senior Resident Inspector was notified. A voluntary notification to PEMA (Pennsylvania Emergency Management Agency) will be made. This event requires a 4-hour ENS notification in accordance with 10CFR50.72(b)(2)(iv)(B) and an 8-hour ENS notification in accordance with 10CFR50.72(b)(3)(iv)(A). Unit 2 was not affected and remains at 100 percent power, Mode 1. | Feedwater Main Turbine Control Rod | |
| ENS 55514 | 11 October 2021 17:21:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Automatic Reactor Scram After Main Turbine Trip | 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 hour ENS notification in accordance with 10 CFR 50.72(b)(2)(iv)(A), 10 CFR 50.72(b)(2)(iv)(B) and an 8 hour ENS notification in accordance with 10 CFR 50.72(b)(3)(iv)(A). | Main Steam Isolation Valve Main Turbine Reactor Recirculation Pump Main Steam Line Control Rod | |
| ENS 55370 | 21 July 2021 22:26:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor SCRAM | At 1826 EDT on July 21, 2021, Susquehanna Steam Electric Station Unit 1 reactor automatically scrammed due to a trip of the Main Turbine. Unit 1 reactor was operating at 100 percent reactor 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. The Reactor Recirculation Pumps tripped on EOC-RPT (end of cycle recirculation pump trip). Reactor water level lowered to +8 inches causing Level 3 (+13 inches) isolations. No ECCS (Emergency Core Cooling Systems) or RCIC (Reactor Core Isolation Cooling system) actuations occurred. The Operations crew subsequently maintained reactor water level at the normal operating band using Reactor Feed Water. The reactor is currently stable in Mode 3 with main condenser available. Investigation into the trip of the Main Turbine is in progress. The NRC Resident Inspector was notified. A voluntary notification to PEMA will be made. This event requires a 4 hour ENS notification in accordance with 10CFR50.72(b)(2)(iv)(B) and an 8 hour ENS notification in accordance with 10CFR50.72(b)(3)(iv)(A) and 10CFR50.72(b)(3)(iv)(B). | Main Turbine Reactor Recirculation Pump Main Condenser Control Rod | |
| ENS 54691 | 3 May 2020 12:21:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Scram Due to Main Turbine Trip | At 0821 EDT on May 3, 2020, the Susquehanna Steam Electric Station Unit 1 reactor automatically scrammed due to a trip of the Main Turbine. The Unit 1 reactor was operating at 76 percent reactor power following a ramp schedule to full power subsequent to a maintenance outage. The Control Room received indication of a Main Turbine trip with both divisions of the Reactor Protection System actuated and all control rods inserted. The Reactor Recirculation Pumps tripped on End of Cycle - Recirculation Pump Trip. Reactor water level lowered to -1 inch causing Level 3 (+13 inches) isolations. No Emergency Core Cooling System or Reactor Core Isolation Cooling actuations occurred. The operations crew subsequently maintained reactor water level at the normal operating band using Reactor Feed Water. No Steam Relief Valves opened. The reactor is currently stable in Mode 3. Investigation into the trip of the Main Turbine is in progress. The NRC Resident Inspector was notified. A voluntary notification to the Pennsylvania Emergency Management Agency and press release will occur. This event requires a 4-hour Emergency Notification System (ENS) notification in accordance with 10 CFR 50.72(b)(2)(iv)(B) and an 8-hour ENS notification in accordance with 10 CFR 50.72(b)(3)(iv)(A) and 10 CFR 50.72(b)(3)(iv)(B). | Reactor Protection System Reactor Core Isolation Cooling Main Turbine Reactor Recirculation Pump Emergency Core Cooling System Control Rod | |
| ENS 54525 | 14 February 2020 05:25:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Scram Due to Rising Condenser Backpressure | At 0025 EST on February 14, 2020, Susquehanna Steam Electric Station Unit 2 reactor was manually scrammed due to rising Main Condenser backpressure caused by a loss of the Unit 2 Offgas Recombiner. Unit 2 reactor was being operated at maximum facility output, approximately 98% RTP, when at 0012 EST, Unit 2 Recombiner 0C145 Panel Trouble and 2C198 HWC Panel Trouble alarms were received along with rising Main Condenser backpressure. Initial Main Condenser backpressure was 2.6 in HgA and was rising at approximately 0.3 HgA/min. A Recirc Lim 2 was inserted to lower reactor power and condenser backpressure continued to rise following the reduction in reactor power. A manual scram was inserted at 0025 EST by placing the Mode Switch to Shutdown when condenser backpressure rose to 6 in HgA. All control rods inserted. Reactor water level lowered to -30 inches causing Level 3 (+13 inches) isolation and partial (Division 2) Level 2 (-38 inches) isolation. No ECCS actuations occurred and RCIC initiated. The Operations crew subsequently maintained reactor water level at the normal operating band using Reactor Feed Water. No steam relief valves opened. The Reactor Recirculation Pumps remained in service. The reactor is currently stable in Mode 3. Investigation into the cause of the loss of Unit 2 recombiner is underway. The NRC Senior Resident Inspector was notified. A voluntary notification to PEMA and press release will occur. | Reactor Recirculation Pump Main Condenser Control Rod | |
| ENS 52795 | 8 June 2017 19:27:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Automatic Reactor Scram After Main Turbine Control Logic Loss of Power | At 1527 hrs (EDT) on June 8, 2017, Susquehanna Steam Electric Station Unit 1 reactor automatically scrammed due to a loss of Main Turbine Electro-Hydraulic Control (EHC) logic power causing a High Flux Reactor Power RPS (Reactor Protection System) trip. All control rods (fully) inserted and both reactor recirculation pumps tripped due to reaching reactor water level 2. Reactor water level lowered to -49 inches causing Level 3 (+13 inches) and Level 2 (-38 inches) isolations. HPCI (High Pressure Coolant Injection) and RCIC (Reactor Core Isolation Cooling) automatically initiated and were overridden by control room operators after RPV (Reactor Pressure Vessel) water level was restored to the normal band with feedwater. HPCI and RCIC injected to the Reactor Coolant System during reactor level stabilization. All isolations and initiations occurred as expected. No main steam relief valves opened. Pressure was controlled via main turbine bypass valve operation. All safety systems operated as expected. Secondary Containment Zone 1, 2, and 3 differential pressure lowered to 0 inch WG (Water Gauge) due to a trip of the Reactor Building Ventilation system that resulted from Unit 1 Level 2 isolation. Differential pressure was restored to Zones 1, 2, and 3 by the initiation of Standby Gas Treatment System on the Unit 1 Level 2 initiation. Unit 1 reactor is currently stable in Mode 3. Investigation into the loss of Main Turbine EHC logic power is underway. The NRC Resident Inspector has been notified. A voluntary notification to PEMA and press release will occur. The suspected cause of the loss of power to the EHC logic circuit is ongoing maintenance on the system. | Reactor Coolant System Feedwater Secondary containment Main Turbine Reactor Recirculation Pump Reactor Building Ventilation Standby Gas Treatment System Control Rod Main Steam | 05000387/LER-2017-005 |
| ENS 51925 | 13 May 2016 05:10:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Manual Reactor Scram Due After Loss of an Essential Motor Control Center | At approximately 0110 hours (EDT) on May 13, 2016, Susquehanna Steam Electric Station Unit Two reactor was manually scrammed by plant operators due to a sustained loss of AC power to essential plant loads. Power to MCC 2B246 was lost at 2355 on May 12, 2016, resulting in a loss of Drywell cooling. Drywell pressure increased to 1.3 psig when operators placed the mode switch to the shutdown position to manually SCRAM the reactor. All rods inserted as expected. Reactor water level lowered to -27 inches and was immediately restored by normal feedwater level control. Level 3 (+13 inch) PCIS isolations occurred, along with an initiation of the RCIC system (-30 inches). Once adequate level was verified, RCIC was overridden. Pressure was controlled with turbine bypass valves, and subsequently main steam line drains. All safety systems functioned as expected. The power loss also tripped Reactor Building HVAC, causing a loss of secondary containment differential pressure resulting in a loss of safety function. Due to the loss of drywell cooling, high drywell pressure actuations and a second reactor SCRAM signal, this signal was automatic, occurred at 0314 hours. HPCI (which automatically initiated on high drywell pressure) was subsequently overridden and declared inoperable, resulting in a loss of safety function. (HPCI did not inject into the vessel). The reactor is currently stable in Mode 3. Initial reports from the field indicate a phase to phase fault on the MCC 2B246 bus bars. The licensee has notified the NRC Resident Inspector and will be issuing a press release. | Feedwater Secondary containment HVAC Main Steam Line | |
| ENS 51532 | 12 November 2015 16:32:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram | At 1132 hours (EST) on November 12, 2015, Susquehanna Steam Electric Station Unit 1 reactor automatically scrammed due to one Main Steam Isolation Valve (MSIV) unanticipated closure causing a High Pressure RPS (Reactor Protection System) trip. All control rods inserted and both reactor recirculation pumps tripped due to reactor water level 2. Reactor water level lowered to -37 inches causing Level 3 (+13 inches) and level 2 (-38 inches) (Division 2 only) isolations. RCIC (Reactor Core Isolation Cooling) automatically initiated and was overridden by control room operators after RPV (Reactor Pressure Vessel) water level was restored to the normal band with feedwater. All isolations and initiations occurred as expected. No main steam relief valves opened. Pressure was controlled via main turbine bypass valve operation. All safety systems operated as expected. The Unit 1 reactor is currently stable in Mode 3. Investigation into the cause of the MSIV closure is underway. Unit 2 was unaffected and continues power operation. The NRC Resident Inspector has been notified. A voluntary notification to PEMA (Pennsylvania Emergency Management Agency) and press release will occur. The plant is in its normal shutdown electrical lineup. | Feedwater Main Steam Isolation Valve Reactor Recirculation Pump Control Rod Main Steam | |
| ENS 50973 | 11 April 2015 03:46:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram Caused by Main Turbine Trip Due to Degrading Main Condenser Vacuum | At 2346 EDT on April 10, 2015, Susquehanna Steam Electric Station Unit 2 reactor automatically scrammed due to a main turbine trip caused by loss of turbine steam seals and degrading main condenser vacuum. Unit 2 reactor was being shutdown for a refueling outage. At approximately 37 percent power, turbine steam seals were lost resulting in a degrading vacuum. The vacuum degraded quickly, resulting in a main turbine trip before the reactor operator could insert a manual scram. At 37 percent power, the turbine trip caused an automatic scram. This occurred during a transfer from normal steam seal supply to the auxiliary boiler supply. All control rods (fully) inserted. Reactor water level lowered to +2 inches causing Level 3 (+13 inches) isolation. No ECCS actuations occurred. The Operations crew subsequently maintained reactor water level at the normal operating band using RCIC (Reactor Core Isolation Cooling). No steam relief valves opened. The reactor recirculation pumps tripped on EOC-RPT due to the turbine trip at power. The reactor is currently stable in Mode 3. Investigation into the cause of the loss of turbine steam seals is underway. The NRC Resident Inspector was notified. A voluntary notification to PEMA (Pennsylvania Emergency Management Agency) and press release will occur. Unit 2 is in a normal shutdown electrical lineup. Turbine steam seals were restored to the normal steam supply and condenser vacuum was restored. Decay heat is being removed via the steam bypass valves to the condenser. Unit 2 is proceeding with their cooldown to support the scheduled refueling outage. | Reactor Recirculation Pump Main Condenser Control Rod | 05000388/LER-2015-003 |
| ENS 49342 | 14 September 2013 07:30:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Scram Due to Feedwater Transient During Shutdown | At approximately 0330 hours on September 14, 2013, Susquehanna Steam Electric Station Unit 2 reactor was manually scrammed while transitioning the 'A' reactor feed pump from flow control mode to discharge pressure mode. Reactor water level rose to +54 inches causing a trip of reactor feedpumps. Subsequently the mode switch was taken to shutdown to manually scram the Unit 2 reactor. All control rods inserted. Reactor water level lowered to approximately +18 inches. There were no automatic emergency core cooling system initiations. No steam relief valves opened during the event. No containment isolations occurred. All safety systems operated as expected. RCIC system was manually initiated for level control until a reactor feedpump was recovered, then RCIC was manually shutdown. The cause of the feedwater flow transient and trip of the reactor feedwater pumps is under investigation. This report is being made per 10CFR50.72(b)(2)(iv)(B) for a 4 hour report, and 10CFR50.72(b)(3)(iv)(A) for an 8 hour report. Decay heat is being removed via the turbine bypass valve to the condenser. Offsite power remains stable, and there was no impact on Unit 1. The licensee has notified the NRC Resident Inspector. The Pennsylvania Emergency Management Agency will be notified, and the licensee will be making a press release. | Feedwater Emergency Core Cooling System Control Rod | 05000388/LER-2013-003 |
| ENS 49099 | 7 June 2013 16:03:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Scram Due to a Reactor Water Level Transient During Startup | At approximately 1203 (EDT) on June 7, 2013, Susquehanna Steam Electric Station Unit One reactor was manually scrammed during reactor startup. Pressure setpoint was being adjusted to the normal operating setpoint, from 750 psig to 934 psig, when all turbine bypass valves unexpectedly opened. Reactor Feed Pumps, Main Turbine, HPCI and RCIC tripped on the high level setpoint Level 8 (+54 inches) due to the resultant reactor level swell. The reactor operator then inserted a manual scram. All control rods inserted. Reactor water level lowered to approximately -10 inches causing Level 3 (+13 inches) isolations. There were no automatic emergency core cooling system initiations. No steam relief valves opened during the event. All safety systems operated as expected. The cause of the Turbine Bypass valve opening is under investigation. Unit 2 was unaffected. The licensee notified the NRC Resident Inspector and will notify the Pennsylvania Emergency Management Agency. | Main Turbine Control Rod | |
| ENS 48607 | 19 December 2012 22:31:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram Due to Low Reactor Pressure Vessel Level | At approximately 17:31 hours on December 19, 2012, Susquehanna Steam Electric Station Unit Two reactor automatically scrammed on low RPV level (Level 3, +13 inches) while transitioning the 'A' reactor feed pump from discharge pressure mode to flow control mode. All control rods inserted and both reactor recirculation pumps tripped. Reactor water level lowered to approximately -29 inches causing Level 3 (+13 inches) isolations. An automatic trip of the reactor recirculation pumps occurred, but is not expected at this RPV level. There were no automatic emergency core cooling system initiations. No steam relief valves opened during the event. All safety systems operated as expected. The cause of the loss of feed water flow and trip of the reactor recirculation pumps is under investigation. This report is being made per 10CFR50.72(b)(2)(iv)(B) for a 4 hour report, and 10CFR50.72(b)(3)(iv)(A) for an 8 hour report. Decay heat is removed via steam to the main condenser using the bypass valves . On-site electrical power is in the normal configuration. The Unit 2 reactor is currently stable in Mode 3. Unit 1 was not affected and operates at 99% power. The licensee will inform the Commonwealth of Pennsylvania and make a press release. The NRC Resident Inspector was notified. | Reactor Recirculation Pump Reactor Pressure Vessel Emergency Core Cooling System Main Condenser Control Rod | 05000388/LER-2012-004 |
| ENS 48598 | 16 December 2012 06:56:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Reactor Scram from 98% Power During Turbine Control Valve Testing | 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 hour reports, and 10 CFR 50.72(b)(3)(iv)(A) for an 8 hour 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. | Reactor Protection System Reactor Recirculation Pump Control Rod | 05000388/LER-2012-003 |
| ENS 48496 | 9 November 2012 06:18:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Unit 2 Manual Scram Due to Loss of the Integrated Control System | At approximately 0118 hours (EST) on November 9, 2012, Susquehanna Steam Electric Station Unit Two reactor was scrammed by plant operators due to a loss of ICS (Integrated Control System; which controls the reactor feed and reactor recirculation systems). The reactor operator placed the mode switch in shutdown when reactor water level reached +25 inches and lowering. All control rods inserted and both reactor recirculation pumps tripped at -38 inches. Reactor water level lowered to -52 inches causing Level 3 (+13 inches) and level 2 (-38 inches) isolations. HPCI and RCIC both automatically initiated. HPCI was overridden prior to injection and RCIC was utilized to restore reactor water level to the normal band. 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. The (Unit 2) reactor is currently stable in Mode 3. An investigation into the cause of the loss of ICS is underway. Unit One continued power operation (at 78% power). The NRC Resident Inspectors were notified. A press release will occur. The licensee will inform the State of Pennsylvania. Decay heat removal is being maintained through the main condenser. On-site electrical power is in the normal configuration. | Reactor Recirculation Pump Decay Heat Removal Main Condenser Control Rod | 05000388/LER-2012-002 |
| ENS 47172 | 19 August 2011 14:46:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Reactor Scram During Quarterly Surveillance Test | At 1046 hours on August 19, 2011, Susquehanna Steam Electric Station Unit 2 reactor scrammed while (operators were) performing a quarterly functional test of reactor water high level trip channels for feedwater / main turbine. The main turbine tripped when a single channel high reactor water level signal was inserted, which was unexpected. Actual water level was within the normal band when the main turbine tripped. The main turbine trip resulted in a reactor scram. Reactor recirculation pump trips as designed and all control rods inserted. Reactor water level lowered to +2 inches causing Level 3 (+ 13 inches) isolations. Reactor water level was restored to the normal operating band using the feedwater system. Six main steam relief valves opened for a short duration, as expected, due to the turbine trip transient. Subsequently, reactor pressure was controlled via turbine bypass valve operation. All safety systems operated as expected. No ECCS or RCIC initiations occurred or were required. The reactor recirculation pumps were subsequently restarted to re-establish forced core circulation. The reactor is currently stable in Mode 3. An investigation into the cause of the scram is underway. Unit 1 was unaffected and continued power operation. The NRC Resident Inspector was notified. A press release will occur. | Feedwater Main Turbine Reactor Recirculation Pump Control Rod Main Steam | |
| ENS 46569 | 25 January 2011 11:10:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Scram Due to an Unisolable Extraction Steam System Leak | At 0610 EST hours on January 25, 2011, Susquehanna Steam Electric Station Unit 1 reactor was manually scrammed due to an unisolable extraction steam system leak in the 1C Feed Water Heater Bay area. At 0517 EST reactor operators commenced lowering reactor power from 98.4% to 65%. Attempts to isolate the source of the leakage were unsuccessful. Based on continued indications of unisolated steam leakage, operations decided to shut down the plant. The reactor operator placed the mode switch in shutdown. All control rods inserted. Reactor water level lowered to -31 inches causing Level 3 (+ 13 inches) isolation and RCIC initiation. The operations crew subsequently maintained reactor water level at the normal operating band using FW (feedwater). No steam relief valves opened. All safety systems operated as expected. RCIC automatically initiated on a -30 inch level signal and was manually secured. The reactor is currently stable in Mode 3. Investigation into the cause of the extraction steam system leakage is underway. The NRC Resident Inspector was notified. A voluntary notification to PEMA and press release will occur. The steam leak was isolated after the turbine was tripped. The plant is stable at normal temperature and pressure. Decay heat is being removed via the condenser steam dumps to the main condenser. The electrical lineup is in a normal configuration. Estimated time to restart is not known. | Main Condenser Control Rod | |
| ENS 46103 | 16 July 2010 20:41:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Scram Due to Unisolable Circulating Water System Leak | At approximately 1641 EDT on July 16, 2010, Susquehanna Steam Electric Station Unit 1 reactor was manually scrammed due to a large unisolable circulating water system leak in the main condenser area. Attempts to isolate the source of the leakage were unsuccessful. During these attempts, reactor operators lowered reactor power from approximately 90% to about 39%. Based on rising water level in the condenser area and unsuccessful isolation of the source of the leakage, Operations decided to shut down the plant. The reactor operator placed the mode switch in shutdown. All control rods (fully) inserted. Reactor water level lowered to -28 inches causing Level 3 (+13 inches) isolations. The Operations crew subsequently maintained reactor water level at the normal operating band using RCIC. No steam relief valves opened. The main steam isolation valves were manually closed and the circulating water system was shut down. Pressure control was initiated using HPCI in the pressure control mode. All safety systems operated as expected. The reactor is currently stable in Mode 3. Actions to isolate and investigate the cause of the circulating water system leakage are underway. Unit 2 continued power operation. The licensee has notified the NRC Resident Inspector, and will be issuing a press release. | Main Steam Isolation Valve Circulating Water System Main Condenser Control Rod | 05000387/LER-2010-003 |
| ENS 45930 | 15 May 2010 03:01:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Scram Due to Increasing Reactor Water Level | At approximately 2301 hours EDT on May 14, 2010, Susquehanna Steam Electric Station Unit One reactor scrammed while performing a condensate pump trip test. The reactor operator placed the mode switch in shutdown when reactor water level reached +51 inches and rising. The main turbine tripped due to high reactor water level. All control rods inserted and both reactor recirculation pumps tripped. Reactor water level lowered to -30 inches causing Level 3 (+13 inches) isolations. The Operations crew restored reactor water level to the normal operating band using RCIC (Reactor Core Isolation Cooling) and subsequently the feedwater system. All isolations 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. The reactor is currently stable in Mode 3. An investigation into the cause of the shutdown is underway. Unit Two continued power operation. The NRC Resident Inspectors were notified. A press release will occur. The licensee was performing testing on the digital feedwater control system which was installed during their recent refueling outage when the loss of level control occurred. It appears that the control system did not respond fast enough to control water level. This resulted in the reactor operator inserting a manual scram at +51 inches prior to reaching the reactor automatic scram setpoint of +54 inches for water level. Currently, the plant is removing decay heat via main steam line drains to the condenser. The plant is in its normal shutdown electrical lineup with all safety equipment available. The licensee has notified the Pennsylvania Emergency Management Agency. | Feedwater Main Turbine Reactor Recirculation Pump Main Steam Line Control Rod | 05000387/LER-2010-002 |
| ENS 45866 | 22 April 2010 14:51:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Reactor Scram on Low Reactor Vessel Water Level During Feedwater Integrated Control System Testing | At 10:51 on 4/22/10, Susquehanna Unit 1 experienced an automatic reactor SCRAM on reactor low level, +13", during the initial testing of the Feedwater Integrated Control System. Following the SCRAM, reactor water level dropped to approx. -30", and the Reactor Core Isolation Cooling system initiated and injected into the vessel. Level was recovered by the Feedwater System and the RCIC system. Division 2 Alternate Rod Insertion unexpectedly initiated during the level transient. Due to scheduled maintenance activities, the 11B Aux Bus did not transfer to the off site power supply post SCRAM. The 11B Aux bus was restored at 12:17. There were no ECCS initiations and no challenges to containment. This event is a Reactor Protection System (RPS) actuation when the reactor is critical, and is reportable as a four hour ENS Notification under 10 CFR 50.72(b)(2)(iv)(B). This event is also an unplanned actuation of a system used to mitigate the consequences of a significant event and is reportable as an eight hour ENS notification under 10CFR50.72(b)(3)(iv)(A). The scram was described as uncomplicated. All rods fully inserted and all systems functioned as required. The initiation of the alternative rod insertion should not occur unless level drops below -38" but the initiation did not result in any complications. The offsite supply breaker to Aux bus 11B was under maintenance when the scram occurred and so the loss of power was expected. This bus supplies some balance of plant loads which were lost (recirculation pump, condensate pump, and circulating water pump) but the loss of these components had no impact on the transient. The NRC Resident Inspector has been notified. The licensee will notify State authorities and also plans a press release. | Feedwater Reactor Protection System Reactor Core Isolation Cooling | 05000387/LER-2010-002 |
| ENS 43011 | 26 November 2006 01:42:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Reactor Scram from Full Power Due to Generator Load Reject | At 2042 on 11/25/06, Susquehanna Unit 1 reactor automatically scrammed due to an apparent generator load reject. All rods fully inserted, and both reactor recirculation pumps tripped. Reactor water level lowered to approximately +13" inches causing level 3 (+13") isolations, and was restored to normal level (+35") by the feedwater system. All isolations at this level occurred as expected. Five steam safety relief valves opened then reclosed. Pressure was subsequently controlled via turbine bypass valve operation. All safety systems operated as expected. The 'A' reactor recirculation pump was restarted to re-establish forced core recirculation. Reactor water cleanup (RWCU) system has been restarted and placed in service. The reactor is currently stable in Mode 3. An investigation is underway. Unit Two continued power operation. The NRC resident inspector was notified. A press release will occur. Decay heat is being removed by normal feedwater to the reactor vessel and steaming through the steam bypass valves to the condenser. The licensee intends to notify the State of Pennsylvania EOC. | Feedwater Reactor Recirculation Pump Reactor Water Cleanup Safety Relief Valve | |
| ENS 42642 | 15 June 2006 07:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Reactor Scram While Shifting Power Supplies | At approximately 0300 hours on 15 June, the Susquehanna Unit One reactor automatically scrammed due to an apparent neutron monitoring trip while transferring Reactor Protection System power supplies. All rods (fully) inserted, and both reactor recirculation pumps tripped. Reactor water level lowered to -38" causing level 3 (+13") and level 2 (-38")isolations, and was restored to normal level (+35") by RCIC and subsequently the feedwater system. All isolations 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. A reactor recirculation pump was restarted to re-establish forced core circulation. The reactor is currently stable in condition 3. An investigation into the cause of the shutdown is underway. Unit Two continued power operation. The NRC resident inspectors were notified. A press release will occur. After the scram, HPCI automatically started but was manually shut down with RCIC maintaining vessel level. Decay heat removal is being maintained with main feedwater and the turbine steam dumps. The electrical grid is stable. No major LCOs were in affect at the time of the event. | Feedwater Reactor Protection System Reactor Recirculation Pump Decay Heat Removal | 05000387/LER-2006-004 |
| ENS 41746 | 6 June 2005 16:33:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram Due to Apparent Generator Load Rejection | At approximately 1233 hours, the Susquehanna Unit Two reactor automatically scrammed due to an apparent generator load reject. All rods inserted, and both reactor recirculation pumps tripped. Reactor water level lowered to -6" causing level 3 (setpoint +13") isolations, and was restored to normal level (+35") by the feedwater system. All isolations at this level occurred as expected. Two steam relief valves opened, then reclosed. Pressure was subsequently controlled via turbine bypass valve operation. All safety systems operated as expected. Some balance of plant loads shutdown apparently due to a voltage perturbation. A reactor recirculation pump was restarted to re-establish forced core circulation. The reactor is currently stable in condition 3. An investigation into the cause of the shutdown is underway. Unit One continued power operation. The NRC resident inspectors were notified. A press release will occur. The licensee will be notifying the State of Pennsylvania. | Feedwater Reactor Recirculation Pump | 05000388/LER-2005-005 |
| ENS 41646 | 28 April 2005 11:19:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unit 2 Manual Reactor Scram Due to Loss of Main Transformer Cooling | At approximately 0700 U2 B Main Transformer cooling was lost. Unit 2 reactor power was reduced from 100% to 75%. Attempts to restore the 2B Main Transformer cooling were unsuccessful, and Unit 2 was manually scrammed from 75% reactor power. RPV water level decreased to -30" due to the SCRAM and was restored by normal Feedwater and RCIC injection. The Main Condenser remained available as a heat sink and there were no SRV lifts. The low water level did result in receiving the Level 2 Division 2 containment isolation signal (-38"), and all expected isolations and initiations did occur. This event requires a 4 hour ENS notification in accordance with 10CFR50.72(b)(2)(iv)(B) for an RPS actuation when critical, and an 8 hour ENS notification per 10CFR50.72(b)(3)(iv)(A) for the injection from RCIC and receipt of the level 2 Containment Isolation signal. Additionally, a press release to the public will be issued, and requires a 4 hour ENS notification in accordance with 10CFR50.72(b)(2)(xi). All rods fully inserted during the manual scram. The electrical system is in a normal shutdown lineup. Secondary containment ventilation was momentarily disrupted in unit-1 and successfully restored. The licensee notified the NRC Resident Inspector and will be notifying the state and media concerning this event. | Feedwater Secondary containment Main Transformer Main Condenser | 05000388/LER-2005-003 |
| ENS 40695 | 21 April 2004 20:35:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Scram in Response to High Main Turbine Vibration During Startup | At 1635 on 04/21/2004, Susquehanna Unit 1 was returning to service from its 13th Refueling and Inspection Outage which included main turbine replacement. During start-up turbine testing with the generator off line, several main turbine bearings experienced high vibration. In response to these high vibrations, the reactor was manually scrammed from approximately 17% power. The main steam line isolation valves were manually closed and main condenser vacuum was broken in order to more rapidly slow the main turbine speed. All control rods fully inserted on the SCRAM, a level 3 containment isolation signal was received as expected. RCIC was manually initiated to control reactor water level. Lowest reactor water level reached was approximately 3" narrow range. There were no radioactive releases. This RPS actuation is reportable under 10CFR50.72(b)(2)(iv)(B) as an 'Unplanned RPS Actuation with the Reactor Critical.' The RPS Actuation and the RCIC injection are reportable per 10CFR50.72(b)(3)(iv)(A) 'Unplanned Actuations of Systems that Mitigate the Consequences of Significant Events.' Investigation into the high main turbine bearing vibrations is ongoing. The main turbine was tripped prior to the manual scram and no SRVs have lifted due to low decay heat level. The electric plant is in a normal lineup. The licensee notified the NRC Resident Inspector and the PEMA representative. | Main Turbine Main Steam Line Main Condenser Control Rod | |
| ENS 40196 | 24 September 2003 04:53:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Automatic Scram at Susquehanna on Low Water Level | At 0053 hours on September 24, 2003 with Susquehanna Unit 1 operating at 100% power an automatic reactor scram occurred due to low water level. At the time of the scram, reactor feed pump testing was in progress and the 'C' reactor feed pump tripped. The reactor recirc pumps runback initiated as expected when water level reached 30" with the feed pump tripped. Level continued to drop and reached the Level 3 auto scram setpoint. Level continued to drop and reached a low level of approximately -48" wide range. Reactor Core Isolation Cooling and High Pressure Coolant Injection auto started at their initiation setpoints and injected to the vessel to recover level. All level 2 and 3 containment isolations occurred as expected. The reactor recirc pumps tripped as expected when level 2 was reached. Reactor Pressure was controlled with bypass valves, there were no Safety Relief Valve lifts. There are no challenges to containment. Unit 1 is currently stable in Mode 3 with both reactor recirc pumps restarted. A human performance error was the cause of the reactor feed pump trip. Investigation is continuing into the plant response to the reactor feed pump trip. The NRC Resident Inspector was notified of this event. | High Pressure Coolant Injection Reactor Core Isolation Cooling Safety Relief Valve |