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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 57046 | 23 March 2024 04:04:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Trip | The following information was provided by the licensee via email: At 0004 EDT on March 23, 2024, with the unit in Mode 1 at 23 percent power, the reactor automatically scrammed due to high reactor pressure vessel pressure when the turbine bypass valves unexpectedly closed while attempting to lower generator MW to 55 MWe to support shutdown for a refueling outage. The scram was not complex, with systems responding normally post-scram, with the exception of the pressure control system. The transient occurred while lowering on turbine speed/load demand which caused a rise in pressure and power until the reactor protection system setpoint for reactor pressure high was exceeded and resulted in an automatic reactor scram. The plant was preparing to shut down for a refueling outage when the trip occurred. Operations responded and stabilized the plant. Reactor water level is being maintained at normal level. Decay heat is being removed by the main steam system to the main condenser using manual operation of the turbine bypass valves. All control rods inserted into the core. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CPR 50.72(b)(2)(iv)(B). Additionally, received expected (primary containment) isolations for Level 3: Group 13 drywell sumps, Group 15 (traverse in-core probe) TlPs (which was already isolated) and Group 4 (residual heat removal - shutdown cooling) RHR-SDC (which was already isolated). The primary containment isolation event is being reported under 10 CFR 50.72(b)(3)(iv)(A). Also, due to the main turbine bypass valves unexpectedly closing, this is also being reported under 10 CFR 50.72(b)(3)(v)(D). There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
The purpose of this notification is to retract the 10 CFR 50.72(b)(3)(v)(D) reporting criteria of event notification 57046 reported on March 23,2024. Based on further evaluation, Fermi 2 has concluded that there was no event or condition that could have prevented fulfillment of a safety function that was needed to mitigate the consequence of an accident. Although discussed in Chapter 15 of the UFSAR, the turbine bypass valves do not provide a safety related function and are not credited safety related components for accident mitigation. Therefore, Fermi 2 is retracting the 10 CFR 50.72(b)(3)(v)(D) reporting criteria that was included on the March 23, 2024 event notification. Notified R3DO (Betancourt-Roldan) | Reactor Protection System Primary containment Reactor Pressure Vessel Main Condenser Control Rod Main Steam | |
| ENS 55964 | 25 June 2022 03:38:00 | 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 Main Turbine Trip | The following information was provided by the licensee via email: At 2338 EDT, on June 24, 2022, with the unit in Mode 1 at 100 percent power, the reactor automatically scrammed due to an RPS actuation following a Main Turbine Trip. The cause of the turbine trip is not known at this time. The scram was not complex, with systems responding normally post-scram. Operations responded and stabilized the plant. Reactor water level has been recovered and maintained at the normal level. Decay Heat is being removed by the Main Steam system to the main condenser using the Turbine Bypass Valves. All Control Rods inserted into the core. The transient occurred with no surveillances or activities in progress. Investigation into the cause of the Turbine Trip is in progress. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The low reactor water level caused an isolation of Primary Containment (Groups 4/13/15) as expected. The Primary Containment Isolation Event is being reported under 10 CFR 50.72(b)(3)(iv)(A). There was no impact to the health and safety of the public or plant personnel. The NRC resident has been notified. | Reactor Protection System Primary containment Main Condenser Control Rod Main Steam | |
| ENS 55732 | 4 February 2022 22:00:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram | The following information was provided by the licensee via email: At 1700 EST, on February 4, 2022 with the unit in Mode 1 at 58 percent power, the reactor automatically scrammed due to low Reactor water level due to a transient on the Feedwater System while preparing to shutdown for a refueling outage. The scram was not complex, with systems responding normally post-scram. Operations responded and stabilized the plant. Reactor water level has been recovered and maintained at normal level. Decay Heat is being removed by the Main Steam system to the main condenser using the Turbine Bypass Valves. All Control Rods inserted into the core. The transient occurred while in the process of removing the South Reactor Feed Pump from service. While reducing speed on the South, the North Reactor Feed Pump increased in speed and tripped on low suction. The plant was preparing to shut down for a refueling outage when the trip occurred. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Additionally, in preparation of plant shutdown, Primary Containment De-Inerting was in progress. The low Reactor water level caused an isolation of Primary Containment (Groups 4/13/15). The Primary Containment Isolation Event is being reported under 10 CFR 50.72(b)(3)(iv)(A). There was no impact to the health and safety of the public or plant personnel. The NRC resident has been notified. | Feedwater Reactor Protection System Primary containment Main Condenser Control Rod Main Steam | |
| ENS 53336 | 14 April 2018 14:40:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 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 and Emergency Core Cooling System Injection | At 1040 EDT, Fermi 2 automatically scrammed on RPV (Reactor Pressure Vessel) Level 3 following a loss of the Division 1 Station System Transformer (SST) #64. All control rods fully inserted. HPCI (High Pressure Coolant Injection) and RCIC (Reactor Core Isolation Cooling) automatically started as designed on Reactor Water Level (RWL) 2 and restored RWL. The lowest RWL reached was 101.8 inches (above Top of Active Fuel). HPCI injected for approximately 35 seconds. RWL is currently being maintained in the normal level band with RCIC. No Safety Relief Valves (SRVs) actuated. All isolations and actuations for RWL 3 and 2 occurred as expected. Investigation into loss of SST #64 continues. At the time of the scram, all Emergency Core Cooling Systems (ECCS) and Emergency Diesel Generators (EDGs) were operable, and no safety related equipment was out of service. This report is being made in accordance with 10CFR50.72(b)(2)(iv)(A), any event that results in ECCS discharge into the reactor coolant system as a result of a valid signal and 10CFR50.72(b)(2)(iv)(B), any event that results in the actuation of the Reactor Protection System (RPS) when the reactor is critical. Following the loss of power and reactor scram, the Division 2 EECW (Emergency Equipment Cooling Water) Temperature Control Valve (TCV) controller was in Emergency Manual and maintaining max cooling. Operators placed the controller in Auto and the TCV is controlling normally. The NRC Senior Resident has been notified. Decay heat is being removed via Division 2 steam dumps to the condenser. The plant is in a modified shutdown electric lineup with offsite power available and stable. Emergency diesel generators did automatically start and load.
This update provides additional clarification of the applicable reporting criteria for this event associated with Primary Containment Isolation Actuations. All isolations and actuations for RWL (Groups 4, 13, and 15) and RWL 2 (Groups 2, 10, 11, 12, 14, 16, 17, and 18) occurred as expected. This report is also being made in accordance with 10CFR50.72(b)(3)(iv)(A), any event or condition that results in valid actuation of any systems listed in paragraph (b)(3)(iv)(B): RPS, HPCI, and RCIC. RPV pressure is being maintained by the bypass valves to the main condenser. All actuations that occurred were fully completed and restored. The licensee notified the NRC Resident Inspector. Notified R3DO (Stone).
This update provides additional information regarding the specified system actuations and an additional applicable reporting criteria. The loss of Division 1 Station System Transformer (SST) #64 at 1040 EDT on 4/14/2018 resulted in the automatic initiation of Emergency Diesel Generators (EDG) 11 and 12. The EDGs started as expected and continue to supply their associated busses. This is reportable pursuant to 10CFR50.72(b)(3)(iv)(A), as an event or condition that resulted in a valid actuation of any system listed in paragraph (b)(3)(iv)(B), including EDGs. In addition, the loss of the Division 1 SST #64 resulted in the expected transfer from the normal to alternate power source for the Low Pressure Coolant Injection (LPCI) swing bus, rendering LPCI loop select inoperable. The alternate power source continued to energize the LPCI swing bus throughout the event until the system was realigned to the normal power source at 1239 EDT on 4/14/2018. This condition is reportable pursuant to 10CFR50.72(b)(3)(v)(D). The licensee notified the NRC Resident Inspector. Notified R3DO (Stone). | Reactor Coolant System Reactor Protection System Emergency Diesel Generator Primary containment Emergency Core Cooling System Safety Relief Valve Main Condenser Control Rod Low Pressure Coolant Injection | |
| ENS 51391 | 14 September 2015 03:05:00 | 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)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Manual Scram Due to Loss of Turbine Building Closed Cooling Water | At 2305 EDT on September 13, 2015, a manual scram was initiated in response to a loss of all Turbine Building Closed Cooling Water (TBCCW). All control rods fully inserted. The lowest Reactor Water Level (RWL) reached was 137 inches. All isolations and actuations for RWL 3 occurred as expected. Decay heat was initially being removed through the Main Turbine Bypass System to the Main Condenser, however, as a result of the loss of TBCCW, the Main Feed Pumps lost cooling and had to be secured. At 2310, Standby Feedwater was initiated and Main Feedwater was secured. The loss of TBCCW also caused all Station Air Compressors (SACs) to trip on loss of cooling. The loss of SACs caused the Instrument Air header pressure to degrade to the point at which the Secondary Containment isolation dampers drifted closed. This resulted in the Reactor Building vacuum exceeding the Technical Specification limit. At 2325, operators started the Standby Gas Treatment system and manually initiated a Secondary Containment isolation signal. Secondary Containment vacuum was promptly restored to within Technical Specification limits. Additionally, Operators were monitoring for expected MSIV drift due to the degraded Instrument Air header pressure. When outboard MSIVs were observed to be drifting, Operators closed the outboard and inboard MSIVs at 2345. At 2352, Safety Relief Valves (SRVs) reached the Low-Low Setpoint and began cycling to control reactor pressure. RWL is currently being maintained in the normal level band with the Standby Feedwater and Control Rod Drive systems. Reactor Pressure is being controlled with Safety Relief Valves. Operators are currently in the Emergency Operating Procedure for Reactor Pressure Vessel control. Investigation into the loss of TBCCW continues. No safety-related equipment was out of service at the time of the event. All offsite power sources were adequate and available throughout the duration of the event. The NRC resident inspector has been notified.
At 0409 EDT the Reactor Core Isolation Cooling (RCIC) system was placed in service due to identification of an unisolable leak in the Standby Feedwater System. Reactor water level and pressure is now being controlled though the RCIC system and Safety Relief Valves. This event update is reportable as a valid manual initiation of a specified safety system under 10CFR50.72(b)(3)(iv)(A). The NRC resident inspector has been notified. The leak rate was reported as approximately 5-10 gallons per minute from a weld on the standby feedwater pump header drain valve F326. The licensee reported the leak stopped once RCIC was placed into service. The licensee is still investigating the issue. Notified the R3DO (Pelke), IRD Manager (Grant), NRR EO (Morris).
At 1847 EDT on September 14, 2015, a valid automatic Reactor Protection System (RPS) actuation occurred due to Reactor Water Level 3 while shutdown in MODE 3. Operators were manually controlling Reactor Pressure Vessel (RPV) level and pressure with Reactor Core Isolation Cooling (RCIC) and Safety Relief Valves (SRV). While operators were cycling SRVs, the RPV level went below the Level 3 setpoint. Operators promptly restored RPV level by manual operation of RCIC. The Level 3 actuation and associated isolations were verified to operate properly. The scram signal has been reset. Fermi 2 remains in MODE 3 controlling RPV Level and Pressure through manual operation of RCIC and SRVs. This is the second occurrence of a valid specified safety system actuation reportable under 10CFR50.72(b)(3)(iv)(A) for this ongoing event. The NRC Resident Inspector has been notified. Notified R3DO (Riemer), IRD Manager (Grant), and NRR EO (Morris)
This update provides clarification of the applicable reporting criteria for this Event associated with primary containment isolation actuations. Upon the manual reactor scram at 2305 EDT on September 13, 2015, Reactor Protection System (RPS) Level 3 actuated and Primary Containment Isolation System (PCIS) Groups 4, 13 and 15 actuated as expected. The applicable reporting criterion for these actuations is 10 CFR 50.72(b)(3)(iv)(A). The applicable reporting criterion for the manual closure of the inboard and outboard main steam isolation valves at 2345 EDT on September 13, 2015, is also 10 CFR 50.72(b)(3)(iv)(A). In addition, the manual closures of all MSIV lead to a loss of condenser vacuum which resulted in the actuation of PCIS Group 1 at 0001 EDT on September 14, 2015, as expected. The applicable reporting criterion for this actuation is also 10 CFR 50.72(b)(3)(iv)(A). Upon reaching Level 3 at 1847 EDT on September 14, 2015, PCIS Groups 4, 13 and 15 actuated as expected. The applicable reporting criterion for this actuation is 10 CFR 50.72(b)(3)(iv)(A). The licensee informed the NRC Resident Inspector. Notified the R3DO (Stone). | Feedwater Secondary containment Reactor Protection System Main Steam Isolation Valve Primary Containment Isolation System Reactor Core Isolation Cooling Primary containment Main Turbine Reactor Pressure Vessel Standby Gas Treatment System Safety Relief Valve Main Condenser Control Rod | |
| ENS 50903 | 19 March 2015 11:02:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Scram Due to an Oscillation Power Range Monitor Upscale Actuation | At 0702 EDT on March 19, 2015, Fermi 2 received an automatic scram due to actuation of the Reactor Protection System (RPS) function of Oscillation Power Range Monitor (OPRM) Upscale. The plant had recently transitioned to Single Loop Operation after securing the 'A' Reactor Recirculation Pump due to loss of normal and emergency cooling water supply. The lowest reactor water level was 134 inches above top of active fuel. Reactor water level is being maintained in the normal band by the Feedwater and Control Rod Drive Systems. No Safety Relief Valves (SRV) actuated. Reactor pressure is being maintained via the Main Turbine Bypass Valves and Main Condenser. Reactor Pressure Vessel Level 3 isolation occurred. No additional safety system actuations occurred. All off-site power sources were available throughout the event. The plant is currently in Mode 3 and in a stable condition. Investigation into the cause of the event is ongoing. This event is being reported under the four hour Non-Emergency reporting criteria of 10CFR50.72(b)(2)(iv)(B). The NRC Resident Inspector has been notified. | Feedwater Reactor Protection System Reactor Recirculation Pump Reactor Pressure Vessel Safety Relief Valve Main Condenser Control Rod | |
| ENS 48487 | 7 November 2012 14:21:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Shutdown Due to Hydrogen In-Leakage to Stator Water Cooling System | At 09:21 EST 11/7/12, the reactor mode switch was taken to shutdown and the main turbine generator was manually tripped in response to hydrogen gas in-leakage into the stator water cooling system from the main turbine generator. The scram was uncomplicated, and all control rods, except one, fully inserted into the core. One control rod stopped at position 02 and was manually inserted. The lowest reactor vessel water level reached was 125 inches, and as expected, HPCI & RCIC did not actuate. No safety relief valves (SRV) actuated. Reactor water level is being controlled in the normal band using the control rod drive and reactor feedwater systems. All isolations and actuations for reactor water level 3 occurred as expected. The cause of the increased hydrogen gas in-leakage into stator water cooling is under investigation. At the time of the manual scram, all Emergency Diesel Generators were operable. All Emergency Core Cooling Systems were available and no significant safety related equipment was out of service. This report is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), as an event that results in actuation of the reactor protection system (RPS) when the reactor is critical. The MSIVs are open with decay heat being removed via steam to the main condenser using the bypass valves. The plant is in a normal shutdown electrical lineup. The licensee has notified the NRC Resident Inspector. | Feedwater Reactor Protection System Emergency Diesel Generator Main Turbine Stator Water Cooling Emergency Core Cooling System Safety Relief Valve Main Condenser Control Rod | 05000341/LER-2012-006 |
| ENS 48309 | 14 September 2012 20:03:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Automatic Reactor Scram Due to the Loss of the 120 Kv Switchyard | At 1603 EDT, Fermi 2 automatically scrammed due to onsite loss of 120 kV switchyard. All control rods fully inserted. The lowest Reactor Water Level (RWL) reached was 98 inches. Division I diesels, EDG-11 and EDG-12, automatically started and loaded. HPCI and RCIC automatically started and restored RWL. RWL is currently being maintained in the normal level band with Condensate/Feed and Control Rod Drive (CRD) systems. No Safety Relief Valves (SRV) actuated. All isolations and actuations for RWL 3 and 2 occurred as expected. Investigation into loss of 120 kV switchyard continues. At the time of the scram, all Emergency Core Cooling (ECCS) and Emergency Diesel Generators (EDG) were operable with the exception of EDG-11 which was available vice operable due to ventilation work, and no other safety related equipment was out of service. This report is being made in accordance with 10CFR50.72(b)(2)(iv)(A), any event that results in ECCS discharge into the reactor coolant system as a result of a valid signal and 10CFR50.72(b)(2)(iv)(B), any event that results in actuation of the reactor protection system (RPS) when the reactor is critical. EDG-11 and EDG-12 are performing all of their functions and providing power to the Division I AC buses. Temperatures are being monitored in the room containing EDG-11 and the room is not approaching any temperature limits. The MSIVs are open with decay heat being removed via steam to the main condenser using the bypass valves. The licensee has notified the NRC Resident Inspector. | Reactor Coolant System Reactor Protection System Emergency Diesel Generator Safety Relief Valve Main Condenser Control Rod | 05000341/LER-2012-005 |
| ENS 48047 | 25 June 2012 17:30:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Reactor Feed Pump Trip Results in Manual Reactor Scram | At 1330 EDT on June 25, 2012, while restoring the Main Turbine Generator (MTG) to service after repairs to Main Unit Transformer 2B (MUT2B), Main Control Room (MCR) staff manually initiated a reactor scram in response to trip of both Reactor Feed Pumps (RFP). All control rods fully inserted. The lowest Reactor Water Level (RWL) reached was 154 inches and, as expected, HPCI and RCIC did not actuate. RWL was restored to normal using the Standby Feedwater (SBFW) system. RWL is currently being maintained in the normal level band with SBFW and Control Rod Drive (CRD) systems. No Safety Relief Valves (SRV) actuated. All isolations and actuations for RWL 3 occurred as expected. Investigation into the trip of RFPs continues. At the time of the scram, all Emergency Core Cooling Systems (ECCS) and Emergency Diesel Generators (EDG) were operable and no safety related equipment was out of service. This report is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B) as an event that results in actuation of the reactor protection system (RPS) when the reactor is critical. The plant is in a normal shutdown electrical lineup with decay heat being removed via steam to the main condenser using the bypass valves. The licensee notified the NRC Resident Inspector. | Feedwater Reactor Protection System Emergency Diesel Generator Main Turbine Emergency Core Cooling System Safety Relief Valve Main Condenser Control Rod | 05000341/LER-2012-003 |
| ENS 46359 | 24 October 2010 20:41:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Scram Due to a Turbine Trip Resulting from a Low Condenser Vacuum | At 1641 EDT 10/24/10, the reactor mode switch was taken to shutdown following an automatic scram due to a main turbine trip, caused by a loss of (condenser) vacuum. The scram was uncomplicated, Control Rod 10-35 did not fully insert on scram and was manually inserted from position 38. The lowest reactor vessel water level reached was 137 inches, and as expected, HPCI, RCIC. & SRVs did not actuate. Reactor water level is being controlled in the normal band using the CRD (Control Rod Drive) and reactor feedwater systems. All isolations and actuations for reactor water level 3 occurred as expected. The loss of condenser vacuum is under investigation. All Emergency Core Cooling Systems and EDG's (Emergency Diesel Generators) were operable, and no safety related equipment was out of service. This report is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), as an event that results in actuation of the reactor protection system (RPS) when the reactor is critical. Decay heat is being removed through the main turbine bypass valves to the main condenser. Electrical offsite power lineups are normal. Reactor pressure is 882 psig and reactor temperature is 515 degrees F (NOP and NOT). The reactor is stable in mode 3. The licensee notified the NRC Resident Inspector. | Feedwater Reactor Protection System Emergency Core Cooling System Main Condenser | 05000341/LER-2010-003 |
| ENS 45979 | 6 June 2010 06:38:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Automatic Reactor Scram Due to Partial Loss of Offsite Power | Reactor shutdown. All control rods inserted. Maintaining reactor vessel level with reactor core isolation cooling. Maintaining reactor vessel pressure with reactor core isolation cooling. (Automatic) Reactor scram due to loss of division 2 offsite power. Classification code: Unusual Event (HU1) Natural Destruction Phenomena Affecting the Protected Area. The licensee declared a Notification of Unusual Event at 0253 EDT. All rods fully inserted and decay heat is being removed by the main condensers. Division 1 buses are being powered by 1 of 3 offsite feeds and division 2 buses are being powered by the Emergency Diesel Generators. The licensee has notified the NRC Resident Inspector.
Division 2 power provided by Emergency Diesel Generators number 13 and 14. Classification Alert Code: (HA1) Natural Destruction Phenomena Affecting the Plant Vital Area. Main condenser is the heat sink. The licensee declared an Alert at 0417 EDT. The reactor remains stable in Mode 3. Physical damage to the auxiliary and the turbine buildings were noticed after an initial inspection. The licensee has notified the NRC Resident Inspector. Notified R3RA (Satorius), NRR (Grobe), IRD (Morris), R3DO (Pelke), NRR EO (Galloway), DHS (Doyle), FEMA (Guy), DOE(Morrone), USDA (Ussery), HHS (Standifer), and CNSC (Gdesnryxrs).
At 0238 (EDT), severe weather caused a loss of 345KV (switchyard power). Reactor scrammed from a turbine trip. Plant is stabilized with RPV (Reactor Pressure Vessel) water level in normal band and RPV pressure at 820 psig. RPV Pressure is being controlled on turbine BPV (By Pass Valve). Division 2 EDG's (Emergency Diesel Generator) are supplying power to division 2 buses. Plant is currently in Alert due to physical damage to plant due to severe weather. The NRC Senior Resident Inspector is on-site. Notified IRD (Morris), R3DO (Pelke), NRR EO (Galloway).
There is no release of radiological materials. No further potential exists for uncontrolled release of radioactive materials to the environment. The Reactor is shut down. Reactor pressure and temperature are within normal bands. Offsite electrical feeds to the site have been restored. An overall damage assessment has been prepared and reviewed to ensure no conditions exist that would create an entry condition to the Emergency Plan. Plant repairs will be accomplished through site processes. At 0220 EDT on 6/7/10, the licensee has terminated from the Alert classification. The licensee has notified the NRC Resident Inspector. Notified R3RA (Satorius), NRR (Grobe), IRD (Grant), R3DO (Pelke), NRR EO (Galloway), DHS (Doyle), FEMA (Blankenship), DOE(Bailey), USDA (Ussery), HHS (Peagler), and CNSC (Gdesnryxrs). | Emergency Diesel Generator Reactor Core Isolation Cooling Main Condenser Control Rod | 05000341/LER-2010-002 |
| ENS 45789 | 25 March 2010 20:27:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Shutdown Due to Main Turbine Trip | At 1627 EDT on 3/25/10, the reactor mode switch was taken to shutdown following an automatic scram due to a main turbine trip. The scram was uncomplicated, and all control rods fully inserted into the core. The lowest reactor vessel water level reached was 136 inches, and as expected, HPCI & RCIC did not actuate. No safety relief valves (SRV) actuated. Reactor water level is being controlled in the normal band using the control rod drive and reactor feedwater systems. All isolations and actuations for reactor water level 3 occurred as expected. The cause of the Main Turbine Trip is under investigation. At the time of the scram all Emergency Core Cooling Systems and (Emergency Diesel Generators) EDGs were operable, and no safety related equipment was out of service. The licensee notified the NRC Resident Inspector. | Feedwater Emergency Core Cooling System Safety Relief Valve Control Rod | 05000341/LER-2010-001 |
| ENS 45394 | 30 September 2009 15:09:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Shutdown Due to Hydrogen In-Leakage to Stator Water Cooling System | At 11:09 EDT 09/30/09, the reactor mode switch was taken to shutdown and the main turbine generator was manually tripped in response to hydrogen gas in-leakage into the stator water cooling system from the main turbine generator. The scram was uncomplicated, and all control rods fully inserted into the core. The lowest reactor vessel water level reached was 122 inches, and as expected, HPCI & RCIC did not actuate. No safety relief valves (SRV) actuated. Reactor water level is being controlled in the normal band using the control rod drive and reactor feedwater systems. All isolations and actuations for reactor water level 3 occurred as expected. The cause of the increased hydrogen gas in-leakage into the stator water cooling is under investigation. At the time of the manual scram all Emergency Core Cooling Systems and Emergency Diesel Generators were operable, and no significant safety related equipment was out of service. This report is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), as an event that results in actuation of the reactor protection system (RPS) when the reactor is critical. The licensee has notified the NRC Resident Inspector. | Feedwater Reactor Protection System Emergency Diesel Generator Main Turbine Stator Water Cooling Emergency Core Cooling System Safety Relief Valve Control Rod | 05000341/LER-2009-002 |
| ENS 44942 | 28 March 2009 05:46:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Reactor Scram Due to Mode Switch Being Placed in Shutdown Following High Vibration on Main Turbine #1 Bearing | At 0146 EDT 3/28/09, the reactor mode switch was taken to shutdown in response to high vibration levels on the Main Turbine #1 bearing. Reactor power was at its reduced level in preparation for entry into Refueling Outage #13 which was scheduled to begin at 0300 EDT. All control rods fully inserted into the core. The lowest reactor vessel water level reached was 162 inches. HPCI & RCIC did not initiate. No safety relief valves (SRV) actuated. Reactor water level is being controlled in the normal band using the Control Rod Drive (CRD) system. All isolations and actuations for reactor vessel water level 3 occurred. The cause of the high main turbine vibrations is currently under investigation. There was no maintenance or testing in progress that would explain the high turbine vibration levels. At the time of the scram all ECCS systems and Emergency Diesel Generators were operable. This report is being made in accordance with 10CFR50.72(b)(2)(iv)(B), any event that results in actuation of the reactor protection system (RPS) when the reactor is critical. The Licensee notified the NRC Resident Inspector. | Reactor Protection System Emergency Diesel Generator Main Turbine Safety Relief Valve Control Rod | 05000341/LER-2009-001 |
| ENS 43948 | 31 January 2008 20:44:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Scram in Response to Trip of Both Reactor Recirc Pumps | At 1544 EST 01/31/2008, the reactor mode switch was taken to shutdown in response to the trip of both reactor recirc pumps. All control rods fully inserted into the core. The lowest reactor vessel water level reached was 157 inches. Reactor water level is being controlled in the normal band using CRD. The cause of the reactor recirc pump trips are under investigation at this time. There was no maintenance or testing in progress that would explain the pump trips. At the time of the scram all ECCS systems and Emergency Diesel Generators were operable with the exception of Division 1 RHR. Division 1 RHR Surveillance testing was in progress. Surveillance testing is complete. Division 1 RHR is available with administrative activities remaining before it will be declared operable. Isolations and actuations occurred as expected. This report is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), Any event that results in actuation of the reactor protection system (RPS) when the reactor is critical." Decay heat is being removed to the main condenser via the turbine bypass valves. The electric plant is a normal shutdown lineup. No SRVs lifted during the reactor scram. The licensee notified the NRC Resident Inspector. | Reactor Protection System Emergency Diesel Generator Main Condenser Control Rod | 05000341/LER-2008-001 |
| ENS 43784 | 15 November 2007 08:13:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Reactor Scram - Initiation of Ari Caused by Level 2 Signal | At 03:13 EST 11/15/2007, a reactor scram occurred due to initiation of ARI caused by a Level 2 signal from Div 1 level instrumentation. The reactor mode switch was taken to shutdown in response to the trip of the recirc pumps initiated by ARI as directed by our Abnormal Operating procedures. All control rods fully inserted into the core. The lowest reactor vessel water level reached was 183 inches. The MSIV's were manually closed to control cooldown rate. Reactor water level is being controlled by CRD and reactor water cleanup blowdown. At the time of the scram, protective tagging was being hung on the Division I Reference Leg Backfill system. At the time of the scram all ECCS systems and Emergency Diesel Generators were operable. This report is being made in accordance with 10 CFR 50.72(b)(2)(iv)(B), any event that results in actuation of the reactor protection system (RPS) when the reactor is critical. The licensee is investigating the cause of the scram. There was no ECCS injection. Primary plant pressure is 400 psig, and primary plant temperature is 335 degrees Fahrenheit. The scram is uncomplicated. The licensee notified the NRC Resident Inspector. | Reactor Protection System Emergency Diesel Generator Reactor Water Cleanup Control Rod | 05000341/LER-2007-002 |
| ENS 42738 | 29 July 2006 19:50:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Reactor Scram and Eccs Injection Due to Loss of Feedwater | At 15:50 EDT on 7/29/06, a Level 3 reactor scram occurred due to a loss of feedwater. The loss of feedwater was caused by a loss of Division 1 electrical power. All control rods fully inserted into the core. The lowest reactor vessel water level reached was 110 inches. HPCI and RCIC auto initiated on Level 2 and injected into the reactor pressure vessel. The Division 1 Emergency Diesel Generators auto initiated and supplied the Division 1 ESF buses. Level 3 and Level 2 isolations occurred as expected. Reactor water level is now being controlled in the normal water level band using Standby Feedwater. No SRVs lifted and RPV pressure is being controlled by the Turbine Pressure Regulator with the main condenser available as the heat sink. At the time of the scram, work was being performed on the 120kV mat which resulted in a loss of Bus 101. Group 13 (Drywell Sumps) isolated on Reactor Water Level 3. Group 10 (Reactor Water Cleanup Inboard), Group 11 (Reactor Water Cleanup Outboard), Group 12 (Torus Water Management System), Group 17 ( Reactor Recirc Pump Seals and Primary Containment Radiation Monitoring), and Group 18 (Primary Containment Pneumatic Supply) isolated on Reactor Water Level 2. The licensee notified the NRC Resident Inspector. The licensee stated that HPCI injected for 2 minutes and was then secured as Standby Feedwater was started. At the time of the notification, Bus 101 had been re-energized, and preparations were being made to restore normal power to the Division 1 buses and return the Emergency Diesel Generators to standby. The licensee is investigating the exact cause of the loss of power.
The purpose of this report is to update the information provided at 19:19 ET on 7/29/2006. This event was originally reported under reporting criteria 50.72(b)(2)(iv)(A) as an ECCS injection. It has subsequently been determined that both the HPCI and RCIC systems auto-started in response to a reactor low water level 2 (Level 2) injection signal, however, only the RCIC system injected into the vessel. The Level 2 signal was only present for about 2.7 seconds until reactor water level recovered above Level 2. The HPCI injection logic is such that the Level 2 signal must be present until HPCI startup has completed. This includes time for the hydraulic pressure from the HPCI Auxiliary Oil Pump to develop enough pressure to open the HPCI turbine steam isolation valve (E4100F067) and time to stroke open the motor operated HPCI turbine steam isolation valve (E4100F001). It took about 12 seconds before steam was admitted to the HPCI turbine. Thus, the HPCI main pump outlet valve (E4150F006) did not open due to the short duration of the Level 2 signal. This is consistent with the HPCI system design. Therefore the event was not reportable as an event that resulted in or should have resulted in an ECCS injection into the reactor vessel. The event remains reportable under criteria 50.72(b)(2)(iv)(B) and 50.72(b)(3)(iv)(A). Additional clarification of the cause of the scram is also provided. The loss of bus 101 resulted in the loss of power to the operating south reactor feed pump (SRFP) turbine lube oil pump resulting in a loss of feedwater flow from the SRFP. The north reactor feed pump continued to operate. The plant is designed with an automatic runback of the recirculation system to allow continued operation following the loss of a single feed pump. However, the loss of bus 101 also resulted in the locking of the reactor recirculation pump speeds (scoop tube lock), disabling the runback feature. This led to a reactor scram on reactor low water level 3 (Level 3) since a single feed pump is not able to maintain reactor water level at 100% power operation. When south reactor feed pump lubrication pressure recovered, feedwater flow from the SRFP recovered. Recovering feedwater injection from the SRFP following the scram caused a rapid increase in reactor water level and a high reactor water level 8 (Level 8) shutdown of the HPCI, RCIC and reactor feedwater pumps. The standby feedwater system was subsequently started and used to maintain reactor level. The plant is restarting, and is in Mode 2 with reactor temperature at approximately 508�F and reactor pressure at approximately 817 psi at the time of this report. Based on this update, ECCS injection was removed from CFR Section of the report. The licensee notified the NRC Resident Inspector. Notified R3 DO (K. O'Brien) | Feedwater | 05000341/LER-2006-003 |
| ENS 42643 | 15 June 2006 14:53:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Scram Due to Turbine Trip | At 10:53 on 6/15/06, a reactor scram, occurred due to a Turbine/Generator Trip. All control rods fully inserted into core. The lowest vessel water level reached was 134 inches. Water level is now being controlled in the normal water level band using Condensate/Feedwater system. No SRVs lifted. RPV pressure is being controlled by the Turbine Pressure Regulator. At the time of the scram, 2B Main Transformer cleaning was taking place. The initial alarm was 'Main Transformer 2B Oil Temp Hi' followed by Generator Differential Relaying and a Turbine Trip. Transformer Deluge also initiated. An investigation is in progress to determine the specific cause for the initiating event. Group 13 'Drywell Sumps' isolated on Level 3 as expected. At the time of the scram, all ECCS systems and Emergency Diesel Generators were Operable. The licensee notified the NRC Resident Inspector. | Emergency Diesel Generator Main Transformer Control Rod | 05000341/LER-2006-002 |
| ENS 41354 | 24 January 2005 21:10:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Due to Unidentified Leakage Greater than 10 Gpm | The licensee reported that it had indications of unidentified reactor coolant leakage greater than 10 gpm which placed the licensee into an unusual event emergency action level (EAL). Indication of drywell sump level increase and pump out rate gave an approximate leak rate of 30 gpm. The licensee also indicated that drywell pressure was above the normal range. The unusual event declaration was made at 1610 EST. At 1619 EST, the licensee manually scrammed the reactor. The scram was uncomplicated with all rods fully inserting and all systems functioning as required. Decay heat is being rejected to the main condenser. There has been no ECCS injection actuation and reactor water level is being maintained by feed pumps. The licensee has no significant safety related equipment out of service. The licensee stated that there is no indication of further degradation of the leak rate and the source of the leak is still under investigation The licensee has notified the NRC Resident Inspector along with State, Local, and other government agencies.
At 1640 EST, the licensee upgraded to an ALERT following additional leak rate calculations that indicated the leak rate was approximately 75 - 80 gpm based on drywell sump pump out rate. The licensee's EAL for an alert is RCS leakage greater than 50 gpm. The NRC entered the monitoring mode at 1653 EST. The licensee stated that there has been no increase in drywell radiation levels and that sump water chemistry analysis is in progress. In addition to the normal government agencies notified, the NRC also notified the Canadian Nuclear Safety Commission Duty Officer (R. Chamberlaine).
The licensee has indications that the leakage may not be reactor coolant leakage. Chemistry results show that the sump water radiation levels are at a level less than would be expected for RCS leakage. In addition, a secondary cooling system was found in a lineup configuration that could have masked leakage from the system. The licensee is waiting to get additional chemistry results on the presence of corrosion inhibitors in the sump water to provide additional confirmation that the leakage is not from the RCS.
The licensee confirmed the presence of corrosion inhibitors in the drywell sump. In addition, based on manipulations of the Reactor Building Closed Cooling Water system and the Emergency Equipment Cooling Water system the licensee believes that the leakage is from the Reactor Building Closed Cooling Water system and not RCS leakage. The plant is stable and the licensee is continuing to cool down with pressure now at 180 psi and decreasing.
The licensee terminated its Alert and Unusual Event at 22:28 EST based on sump water chemistry, activity, and Reactor Building Closed Cooling Water System manipulations that indicate the leakage is secondary cooling water and not from the RCS. The NRC secured from the monitoring mode at 22:36 EST. Notified DHS (Belt), FEMA (Caldwell), DOE (Dasilva), EPA (Baumgartner) USDA (Sykes), and HHS( Pyles). The Canadian Nuclear Safety Commission Duty Officer (R. Chamberlaine) was also notified. | Emergency Equipment Cooling Water Main Condenser | 05000341/LER-2005-001 |
| ENS 41243 | 4 December 2004 09:17:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Scram Due to an Auto Voltage Regulator Trip | On December 4, 2004 at 0417 (EST), the Reactor Scrammed as the result of an AVR (Automatic Voltage Regulator) trip. AVR Channels A and B were both operating at the time. The AVR trip caused a Main Generator trip which caused a Main Turbine trip. The Main Turbine trip causes a direct Reactor SCRAM on Turbine Valve position. RPS functioned properly and all rods inserted (fully). MSIVs remain open with Reactor Level being maintained in the normal band of 173 to 214 inches. Reactor Pressure is being maintained with the Main Turbine Bypass valves. Isolations expected for Reactor Level 3 occurred and have been reset. Previous to the reactor scram, the AVR alarm was being monitored. All other safety systems functioned as required. Similar event occurred 09/04/04 (EN#41017). The licensee notified the NRC Resident Inspector. | 05000341/LER-2004-004 | |
| ENS 41017 | 4 September 2004 03:45:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Rps Actuation | On September 3, 2004, at 2345, the Reactor Scrammed as the result of an (Automatic Voltage Regulator) AVR trip relay. AVR Channel A was not operating at the time due to an earlier fault (0541, 9/3/04). The AVR trip relay caused a Main Generator trip which caused a Main Turbine trip. The Main Turbine trip causes a direct Reactor SCRAM on Turbine Valve position. RPS functioned properly and all rods inserted. MSIVs remain open with Reactor Level maintained in the normal band of 173 to 214 inches. Reactor Pressure is being controlled with the Main Turbine Bypass valves at 600 to 1050 psig. Isolations occurred as expected for Reactor Level 3. The Licensee notified the NRC Resident Inspector. | 05000341/LER-2004-002 |