|Entered date||Site||Region||Scram||Reactor type||Event description|
|ENS 53576||31 August 2018 23:26:00||LaSalle||NRC Region 3||Manual Scram||This notification is being provided in accordance with 10 CFR 50.72(b)(2)(iv)(B). On August 31, 2018 at 2105 CDT, Unit 2 Reactor Manual Scram signal was inserted due to Main Condenser vacuum degrading. The turbine was tripped following the scram. Main Condenser vacuum is at 6 inches of backpressure slowly improving following the scram and turbine trip. During the scram, one Control Rod (30-31) did not fully insert. Control Rod 30-31 has been manually inserted to position 00 with the first position identified as position 24. Plant is in a stable condition with reactor pressure being maintained by the Turbine Bypass valves. Reactor water level is being controlled with feedwater. Investigation into the cause of the elevated condenser in leakage is in progress. The Senior NRC Resident has been notified.|
|ENS 52564||18 February 2017 02:58:00||LaSalle||NRC Region 3||Manual Scram|
This notification is being provided in accordance with 10CFR 50.72(b)(2)(iv)(B). On February 17, 2017 at 2353 CST, Unit 1 Reactor Automatic Scram signal was received due to Turbine Control Valves Fast Closure. The turbine trip was due to receipt of Level 8 Trip due to a failure of the Feedwater Regulating Valve to Full open. Plant is in a stable condition with reactor pressure being maintained by the Turbine Bypass valves. Reactor water level is being controlled with Feedwater thru the Low Flow Feedwater Regulating Valve. Further investigation into the cause of the event is in progress. All control rods fully inserted, and decay heat is being removed via steam to the main condenser using bypass valves. The licensee has notified the NRC Resident Inspector.
Upon further review of the event data, it was determined that the Nuclear Station Operator (NSO) had initiated a manual scram, which was followed by a Turbine Control Valve (TCV) fast closure automatic scram when the turbine tripped. The licensee has notified the NRC Resident Inspector. Notified R3DO (Jeffers).
|ENS 52547||14 February 2017 02:40:00||LaSalle||NRC Region 3||Automatic Scram||GE-5||This notification is being provided in accordance with 10 CFR 50.72(b)(2)(iv)(B). On February 13, 2017 at 2309 CST, a Unit 1 Reactor Automatic Scram signal was received due to Turbine Control Valve Fast Closure. The turbine trip was due to the main generator trip on Differential Current. The 'U' safety relief valve actuated in the relief mode on the turbine trip, and has subsequently reset with tailpipe temperature returning to normal. The plant is in a stable condition with reactor pressure being maintained by the Turbine Bypass valves. Reactor water level is being controlled with feedwater. Investigation into the cause of the event is in progress. All control rods fully inserted on the scram. Unit 1 is in a normal shutdown electric plant alignment. Unit 2 was not affected. The licensee notified the NRC Resident Inspector.|
|ENS 52505||23 January 2017 10:34:00||LaSalle||NRC Region 3||Manual Scram||GE-5||This notification is being provided pursuant with 10 CFR 50.72 (b)(2)(iv)(B). (On January 23, 2017) at 0806 (CST), Unit 2 Manual Scram was inserted due to a Stator Water Cooling runback signal and a Turbine Bypass Valve opening. The Plant is stable, reactor pressure is being maintained with Bypass valves. Reactor water level is being controlled with feedwater. Investigation into the cause of the event is in progress. All control rods fully inserted. The licensee has notified the NRC Resident Inspector.|
|ENS 48969||25 April 2013 22:23:00||LaSalle||NRC Region 3||Manual Scram||GE-5||This report is being made pursuant to 10CFR50.72(b)(2)(iv)(B), RPS Actuation (scram). At 2019 CDT on April 25, 2013, LaSalle Unit 2 was manually scrammed due to a loss of Condenser Circulating Water. The Unit was manually scrammed after the condenser circulating water pumps tripped due to high level in the turbine building condenser pit. The high level in the condenser pit was caused by a leak on the upper manway of the condenser water box during a maintenance activity. MSIV's were isolated due to loss of heat sink. The safety relief valves were used in pressure control mode. Current plant status: reactor level is stable and reactor pressure is stable. The condenser water box manway leak has been isolated. The plant will remain in hot shutdown pending investigation and repairs. Reactor Core Isolation Cooling (RCIC) is being used in the pressure control mode. The licensee has notified the NRC Resident Inspector.|
|ENS 48939||17 April 2013 16:59:00||LaSalle||NRC Region 3||Automatic Scram||GE-5|
LaSalle Unit 1 and LaSalle Unit 2 have both experienced an automatic reactor scram, in conjunction with a loss of offsite power. This was caused by an apparent lightning strike in the main 345kV/138kV switchyard during a thunderstorm. 138kV line 0112 has been inspected in the field, and heavy damage has been noted on the insulators on two of the three phases on a line lightning arrestor line side. The plant systems have all responded as expected. All five diesel generators started, and have loaded on to their respective buses as designed. All rods went full in on both units during the respective scrams. HPCS (High Pressure Core Spray) system was started on each unit and automatically aligned for injection for initial level control. The MSIVs (Main Steam Isolation Valves) are shut on both units with decay heat being removed via the safety relief valves. Suppression pool cooling is in progress. The licensee will notify the NRC Resident Inspector and has notified the State. Notified DHS, FEMA, USDA, HHS, DOE, NICC, EPA, and Nuclear SSA via email.
In addition to information (previously provided), LaSalle Unit 2 received a high drywell pressure signal (1.77 psig) due to loss of containment cooling from the loss of power. At the time of this high drywell pressure signal, high pressure core spray pump and 2B residual heat removal (RHR) pump was already in operation, the low pressure core spray system and 2A residual heat removal system was secured and (placed) in pull to lock. When the signal was satisfied the ECCS (Emergency Core Cooling Systems) signal was processed but only the 2C RHR pump would have started. In this case, the 2C RHR pump tripped when the signal was received. There is no evidence of reactor coolant leakage. There was no additional ECCS systems discharging into the RCS (Reactor Coolant System). As (initially stated), level was controlled using High Pressure Core Spray and level control is now being maintained using the Reactor Core Isolation Cooling (RCIC) systems. The 2C RHR pump trip is under investigation. Due to the initial loss of offsite power for both Unit 1 and Unit 2 reported at 1511 (CDT), multiple containment isolation valves isolated and closed as expected. Once initial containment isolations were verified, two Unit 2 primary containment vent and purge valves were opened to vent the Unit 2 containment. Once Unit Two containment pressure reached 1.77 (psig), these two vent valves isolated as expected. Due to the loss of offsite power, the Station Vent Stack Wide Range Gas Monitor (WRGM) and the Standby Gas Treatment Wide Range Gas Monitor (VGWRGM) also lost power. Manual sampling has been implemented and power is restored to the VGWRGM, however the VGWRGM has not been declared operable yet. Normal radiation levels have been reported from the manual sampling. (This is being reported in accordance with 10CFR50.72(b)(3)(xiii).) The licensee notified the NRC Resident Inspector and the State of Illinois. Notified the R3 IRC, NRR EO(Skeen), IRD MOC (Grant).
After the Unit 2 primary containment vent and purge system isolated on the Unit 2 containment High Pressure signal, Venting of the Unit 1 primary containment was commenced. At 2005 CDT, Unit 1 primary containment pressure reached the Group 2 primary containment isolation system setpoint (1.77 PSIG) causing the primary containment vent and purge valves being used to vent the Unit 1 containment to isolate. Unit 1 primary containment venting was being performed through the Standby Gas Treatment system which is a filtered system. In addition to the primary containment isolation signal on high drywell pressure, an ECCS initiation on high drywell pressure also occurred. The ECCS signal resulted in an auto start of the 1C RHR system. The 1B RHR system was already running in suppression pool cooling mode. 1A RHR and LPCS had been secured to prevent overloading the common diesel generator for division 1. The common diesel generator supplies both Unit 1 and Unit 2 division 1 ESF busses. The licensee informed the NRC Resident Inspector. Notified NRR EO (Skeen), IRD MOC (Grant) and R3IRC (Louden).
LaSalle has terminated the unusual event which was initiated at 1511 on 4/17/13 and reported under EN 48939. This unusual event has been terminated based on meeting the following established criteria. This report is being made in accordance with 10CFR50.72.(c)(1)(iii). 1) Off-site power has been restored to all ESF busses 2) Fuel Pool Cooling has been restored on both units 3) Primary Containment Chillers have been restored on both units 4) Drywell pressure is less than ECCS initiation setpoint 5) ECCS signals cleared to allow diesels to be placed in stand by Recovery of remaining plant systems will be managed through the Outage Control Center (OCC)." The licensee informed the NRC Resident Inspector. Notified R3DO (Orth), NRR EO (Chernoff), IRD (Grant), DHS, FEMA, USDA, HHS, DOE, NICC, EPA, and Nuclear SSA via email.
In addition to the 10 CFR 50.72 Sections initially identified, the Loss of Offsite Power was also reportable under 10 CFR 50.72(b)(3)(v)(D) as an event or condition that could have prevented the fulfillment of the safety function of systems needed mitigate the consequences of an accident. This event is considered a safety system functional failure for both Units 1 and 2. The licensee will notify the NRC Resident Inspector. Notified the R3DO (Orth).
|ENS 45265||15 August 2009 20:06:00||LaSalle||NRC Region 3||Automatic Scram||GE-5||At 1606 CDT on August 15, 2009, LaSalle Unit 2 automatically scrammed due to a turbine trip. The turbine trip occurred during weekly turbine trip testing. Two safety relief valves actuated (and reseated) in the relief mode on the turbine trip. The reactor water cleanup system isolated during the transient (not being reported as there was no isolation in multiple systems). The plant is stable with reactor pressure control to the main condenser via the main steam isolation valves. The plant is planning to remain in hot shutdown pending (turbine) electro-hydraulic (EHC) system troubleshooting and repair. All control rods fully inserted during the scram. The site is aligning the ring bus for the normal shutdown electrical lineup. Reactor water level is being maintained using the main feedwater system and decay heat is being removed via the turbine bypass valves. The licensee notified the NRC Resident Inspector.|
|ENS 42348||20 February 2006 02:14:00||LaSalle||NRC Region 3||Automatic Scram||GE-5|
While shutting down Unit 1 IAW LGP-2-1 with the main turbine off line the plant experienced a turbine control system (EHC) malfunction. This resulted in opening all main turbine bypass valves and subsequent reactor low pressure condition. The low pressure condition resulted in a closure of all main steam isolation valves (MSIV's) and automatic reactor scram. Three rods failed to indicate fully inserted on the scram. Plant emergency operating procedures were entered. All ECCS and plant systems operated as expected. All control rods are fully inserted and the ATWS emergency operating procedure has been exited. The main turbine had been taken off line prior to this event and shutdown was being conducted with heat removal on the bypass valves. Pressure control is currently by using the steam line drains with the Safety Relief Valves in manual. Level is being maintained using normal feedwater. The electrical grid is stable though the plant is not yet on backfeed. Diesel generators are operable. The licensee will notify the NRC Resident Inspector. The NRC entered Monitoring Mode at 0243. Notified R4DO (Graves), DHS (SWO), FEMA (J Kanupp), DOE (S. Morrone), EPA(NRC) (Nowak), USDA (Amanda), HHS (Kleiman).
In addition to the initial notification, La Salle is reporting a group 1 isolation in accordance with 10CFR50.72(b)(3)(iv)(a).
The site exited the Site Area Emergency and entered the recovery phase.
At the time of the scram @ 0023 hours rod 38-43 showed position 24 and rods 26-15 and 34-47 showed unknown. Based on more than one rod out condition, it is unanalyzed until shutdown margin can be verified.
NRC exited Monitoring Mode. Notified IRD (Wilson), NRR EO (J. Lyons), R3DO (Lara), R4DO (Graves), NRR (Dyer), DHS (SWO), FEMA (Eerwin), DOE (Joe Stambaugh), NRC (does not take updates), USDA (Jim Brzostek), HHS (SOC) (Lt Hrynyshen).
Post trip evaluations have confirmed that all control rods were fully inserted within four minutes of the reactor scram. A review of the post-trip data suggests that there were only control rod indication problems on the three subject rods and all control rods were fully inserted immediately at the time of the reactor scram. Follow-up evaluations also demonstrated that even if the three subject control rods remained fully withdrawn in a cold shutdown condition, the reactor would have remained adequately shutdown. Additional confirmatory evaluations are continuing. The licensee issued a press release on this event. The licensee notified the NRC Resident Inspector. R3DO(Hills) has been notified.
|ENS 41560||4 April 2005 13:19:00||LaSalle||NRC Region 3||Manual Scram||GE-5||The following information was obtained from the licensee via facsimile (licensee text in quotes): This telephone notification is provided in accordance with 10 CFR 50.73(a)(1), to report an invalid actuation reportable under 10 CFR 50.73(a)(2)(iv)(A). On February 7, 2005, at 0756 (CST), with Unit 2 in Mode 3 'Hot Shutdown' in preparation for the 2005 refueling outage, the 2A Reactor Protection System (RPS) bus unexpectedly de-energized during performance of LOS-RP-W1, 'Manual Scram Instrumentation.' As a result, an RPS Bus A half scram and Division 1 Primary Containment Isolation System (PCIS) isolations were received, including the isolation of shutdown cooling. All affected containment isolation valves closed as designed. An inspection found that the 2A RPS MG set output breaker had opened. RPS Bus A was transferred to its alternate feed, and the associated containment isolations were reset. Shutdown cooling was restored at 0845 hours on February 7, 2005. Troubleshooting found that the 2A RPS MG set voltage regulator had failed. The voltage regulator was replaced and successfully tested, and the 2A RPS MG set was returned to service. Laboratory testing of the failed voltage regulator circuit board found that a solder joint had failed on load-dropping resistor R8, which caused the excitation output voltage to decrease sharply. This resulted in a trip of the 2A RPS MG set output breaker on low voltage. The apparent cause of the failed solder joint was a manufacturing defect. Corrective actions include visual inspections of RPS MG set voltage regulatory circuit boards in the field and in the storeroom, and the development of enhanced receipt inspection requirements. This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an invalid actuation of containment isolation valves in more than one system. The licensee has notified the NRC Resident Inspector.|
|ENS 40357||27 November 2003 03:24:00||LaSalle||NRC Region 3||Manual Scram||GE-5||A manual reactor scram was initiated due to a decreasing reactor vessel water level. The decreasing water level occurred during a feedwater transient while performing a power reduction in preparation for taking the main generator off line for maintenance. The licensee is investigating the cause of the feedwater transient, but it occurred while one turbine driven reactor feed pump was being taken off line. All rods fully inserted following the scram and no ECCS or safety relief valves actuated. Residual heat is being rejected to the condenser. The licensee notified NRC Resident Inspector.|