Semantic search
Jump to navigation
Jump to search
| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 52556 | 16 February 2017 14:35:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Inoperable Due to Interlock Failure | This report is being made in accordance with 10 CFR 50.72(b)(3)(v)(C), for an event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material and 10 CFR 50.72(b)(3)(v)(D) for an event or condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident. An employee entered a secondary containment airlock and identified that both doors of the airlock opened simultaneously when the door on the reactor building side was opened. The employee immediately secured both doors in the airlock and notified the Main Control Room Supervisor. Both doors in the airlock were open for approximately 5 seconds. With both doors open, Technical Specifications (TS) Surveillance Requirement (SR) 3.6.4.1.2 was not met. This rendered secondary containment inoperable in accordance with TS 3.6.4.1. Reactor Building differential pressure, as observed in the Main Control Room, has remained more negative than -0.25 inches of vacuum water gauge at all times. Initial investigation determined that the interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the interlock. The licensee informed the NRC Resident Inspector. | Secondary containment | |
| ENS 52496 | 19 January 2017 02:56:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Both Secondary Containment Airlock Doors Open Simultaneously | This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(C), event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material and 10 CFR 50.72(b)(3)(v)(D), event or condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident. An employee entered a secondary containment interlock (airlock) and identified that both doors of the interlock opened simultaneously when the door on the reactor building side was opened. The employee immediately secured both doors in the interlock and notified the Main Control Room Supervisor. Both doors in the interlock were open for approximately five seconds. With both doors open, TS SR 3.6.4.1.2 was not met. This rendered secondary containment inoperable per TS 3.6.4.1. Reactor Building differential pressure, as observed in the Main Control Room has remained less than -0.25 in. H2O at all times. Initial investigation determined that the interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the interlock. The licensee notified the NRC Resident Inspector. Notified R3DO (McCraw). | Secondary containment | |
| ENS 51741 | 17 February 2016 16:35:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Inoperable Due to Door Interlock Malfunction | This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(C), event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material and 10 CFR 50.72(b)(3)(v)(D), an event or condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident. An employee entered a secondary containment interlock and identified that both doors of the interlock opened simultaneously when the door on the reactor building side was opened. The employee immediately secured both doors in the interlock and notified the Main Control Room Supervisor. Both doors in the interlock were open for approximately 5 seconds. With both doors open, TS SR 3.6.4.1.2 was not met. This rendered secondary containment inoperable per TS 3.6.4.1. Reactor Building differential pressure, as observed in the Main Control Room, has remained less than -0.25 inches H20 at all times. Initial investigation determined that a mechanical interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the interlock. The licensee has notified the NRC Resident Inspector. | Secondary containment | 05000374/LER-2016-001 |
| ENS 51725 | 11 February 2016 04:07:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Inoperable | This report is being made pursuant to 10CFR50.72(b)(3)(v)(C), event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material and 10CFR50.72(b)(3)(v)(D), event or condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident. LaSalle Station's Unit 1 and Unit 2 were in Mode 1. At 2207 (CST) (on 2/10/16), Secondary Containment Differential Pressure dropped below the Technical Specification (TS) 3.6.4.1 minimum of 0.25 inches water vacuum. The initial indications are a failure of one Unit 1 Reactor Building Exhaust Isolation Damper, which resulted in a trip of the Unit 1 Reactor Building Exhaust Fans. At 2245, Secondary Containment Differential Pressure was restored to within the TS 3.6.4.1 limits by securing and isolating the Unit 1 Reactor Building Ventilation System. Troubleshooting plans are being developed to determine cause of the damper failure and to correct the deficient condition. The licensee has notified the NRC Resident Inspector. | Secondary containment Reactor Building Ventilation | 05000373/LER-2016-001 |
| ENS 50827 | 17 February 2015 17:45:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Containment Inoperable Due to Interlock Doors Open Simultaneously | This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(C), event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material and 10 CFR 50.72(b)(3)(v)(D), event or condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident. LaSalle's Station Unit 1 was in Mode 1 and Unit 2 was in Mode 5 for its scheduled refuel outage. There was no movement of irradiated fuel or CORE ALTERATIONS at the time. OPDRVs (Operations with Potential to Drain the Reactor Vessel) were in progress in the secondary containment on Unit 2. An employee entered a secondary containment interlock and identified that both doors of the interlock opened simultaneously when the door on the reactor building side was opened. The employee immediately secured both doors in the interlock and notified the main control room supervisor. Both doors in the interlock were open for somewhere between 5-10 seconds. With both doors open, TS SR 3.6.4.1.2 was not met and this rendered secondary containment inoperable per TS 3.6.4.1. Reactor building differential pressure, in the main control room, was never observed to be less than -0.25 inches of water column. Initial investigation determined that the interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the interlock. The NRC Resident Inspector has been notified. | Secondary containment | 05000373/LER-2015-003 |
| ENS 50674 | 12 December 2014 19:24:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Both Secondary Containment Airlock Doors Opened Simultaneously | This report is being made pursuant to 10CFR50.72(b)(3)(v)(C), 'Event or Condition that could have prevented fulfillment of a Safety Function needed to Control the Release of Radioactive Material' and 10CFR50.72(b)(3)(v)(D), 'Event or Condition that could have prevented fulfillment of a Safety Function needed to Mitigate the Consequences of an Accident.' Unit 1 and Unit 2 were in Mode 1 and no movement of irradiated fuel, core alterations, or OPDRVs (Operations with the Potential to Drain the Reactor Vessel) were in progress in the secondary containment. An employee entered a secondary containment interlock and identified that both doors of the interlock opened simultaneously when the door on the reactor building side was opened. The employee immediately secured both doors in the interlock and notified the Main Control Room Supervisor. Both doors in the interlock were open for approximately 10 seconds. With both doors open, TS SR 3.6.4.1.2 was not met. This rendered secondary containment inoperable per TS 3.6.4.1. Reactor building differential pressure, as observed in the Main Control Room, has remained less than -0.25 inches of water column at all times. Initial investigation determined that the interlock for the doors was malfunctioning. Administrative controls (barricades and signs) have been put in place to ensure the doors remain closed pending repairs to the interlock. The licensee notified the NRC Resident Inspector. | Secondary containment | 05000373/LER-2015-001 |
| ENS 50076 | 30 April 2014 15:37:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Momentary Loss of Secondary Containment Due to Airlock Interlock Malfunction | This report is being made pursuant to 10CFR50.72(b)(3)(v)(C), Event or Condition that could have prevented fulfillment of a Safety Function needed to Control the Release of Radioactive Material and 10CFR50.72(b)(3)(v)(D), Event or Condition that could have prevented fulfillment of a Safety Function needed to Mitigate the Consequences of an Accident. Unit 1 was in mode 1 and in a condition of moving irradiated fuel in the secondary containment. Unit 2 was in mode 5 and in the condition of moving irradiated fuel in the secondary containment, core alterations, and operations with the potential to drain the reactor vessel. An employee entered a secondary containment interlock (Unit 2) and identified that both doors of the interlock opened simultaneously when the door on the auxiliary building side was opened. The employee immediately secured both doors in the interlock and notified the Main Control Room Supervisor. Both doors in the interlock were open for approximately 5 seconds. With both doors open, TS SR 3.6.4.1.2 (Technical Specification Surveillance Requirement) was not met. This rendered secondary containment inoperable per TS 3.6.4.1. Reactor Building differential pressure, as observed in the Main Control Room, has remained less that -0.25 inches of water column at all times. Initial investigation determined that the interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the interlock. The licensee has notified the NRC Resident Inspector. | Secondary containment | 05000373/LER-2014-003 |
| ENS 49840 | 19 February 2014 00:20:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Momentary Loss of Secondary Containment | This report is being made pursuant to 10CFR50.72(b)(3)(v)(C), Event or Condition that could have prevented fulfillment of a Safety Function needed to Control the Release of Radioactive Material. An employee entered a secondary containment (airlock) interlock and identified that both doors of the interlock opened simultaneously when the door on the reactor building side was opened. The employee immediately secured both doors in the interlock and notified the Main Control Room Supervisor. Both doors in the interlock were open for approximately 3 seconds. With both doors open, TS SR 3.6.4.1.2 was not met. This rendered secondary containment inoperable per TS 3.6.4.1. Reactor Building differential pressure, as observed in the Main Control Room, has remained less than -0.25 inches H2O at all times. Initial investigation determined that a mechanical interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the mechanical interlock. The licensee notified the NRC Resident Inspector. | Secondary containment | 05000373/LER-2014-001 |
| ENS 49615 | 8 December 2013 05:55:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | Average Power Range Monitors Declared Inoperable Due to Non-Conservative Power Value | This report is being made pursuant to 10CFR50.72(b)(3)(v)(A), event or condition that at the time of discovery could have prevented the fulfillment of a safety function of systems that are needed to shutdown the reactor and maintain it in a safe shutdown condition. A scheduled load reduction for surveillance testing and control rod sequence exchange was in progress. During the control rod sequence exchange, the core monitoring software system (3DMonicore) was used to obtain a 'case' which records various calculated and actual core parameters (i.e. core thermal power, Power Range Monitor indication). The 'case' data is used to evaluate the Technical Specification (TS) Surveillance Requirement (SR) acceptance criteria for SR 3.3.1.1.2 to verify the absolute difference between the average power range monitor (APRM) channels and the calculated power is less than or equal to 2% rated thermal power (RTP) while operating at greater than or equal to 25% RTP. The 'case' showed that all 3 A RPS Trip System APRM channels exceeded the allowable 2% difference threshold in the non-conservative direction (i.e. APRM power reading less than calculated thermal power, difference of 2.9, 3.1, and 2.5% respectively). TS 3.3.1.1 requires at least 2 operable APRM channels per trip system (there are 2 RPS trip systems, A and B). At least 1 of 2 TS required APRM channels are required to maintain the Safety Function (i.e. SCRAM). In this situation, none of the A RPS TS required APRM channels met their SR and were declared inoperable. TS 3.3.1.1 allows delaying entry into the associated Condition and Required Action for this inoperability for up to 2 hours when the inoperability is solely due to APRM indication not within the 2% limit; therefore no TS Required Action tracking timeclocks were entered. A confirmatory 'case' was performed that validated that the subject SR was not met. Prompt action was taken to restore the APRM indications to within limits (this action took approximately 22 minutes to complete) and the subject APRMs were declared operable, restoring the A RPS Safety Function. The licensee notified the NRC Resident Inspector and the Illinois Emergency Management Agency. | Control Rod | 05000374/LER-2013-003 |
| ENS 49462 | 22 October 2013 16:29:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Personnel Air Lock Door Interlock Failure | This report is being made pursuant to 10CFR50.72(b)(3)(v)(C), 'Event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material.' An employee entered a secondary containment interlock and while the door was closing, another employee opened the other secondary containment interlock door thereby having two doors open. The employee immediately secured both doors in the interlock and notified the main control room supervisor. Both doors in the interlock were open for approximately 10 seconds. With both doors open, TS SR 3.6.4.1.2 was not met. This rendered secondary containment inoperable per TS 3.6.4.1. Reactor Building differential pressure, as observed in the main control room, has remained satisfactory and less than -0.25 inches of H20 at all times. Initial investigation determined that a mechanical interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the mechanical interlock. The licensee has notified the NRC Resident Inspector. | Secondary containment | 05000373/LER-2013-001 05000373/LER-2013-007 |
| ENS 48791 | 28 February 2013 10:00:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Secondary Containment Door Interlock Malfunction | This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(C), event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material. An employee entered a secondary containment interlock and identified that both doors of the interlock opened simultaneously when the door on the reactor building side was opened. The employee immediately secured both doors in the interlock and notified the main control room supervisor. Both doors in the interlock were open for approximately 10 seconds. With both doors open, TS SR 3.6.4.1.2 was not met. This rendered secondary containment inoperable per TS 3.6.4.1. Reactor building differential pressure, as observed in the main control room, has remained less than -0.25" H2O at all times. Initial investigation determined that a mechanical interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the mechanical interlock. The licensee has notified the NRC Resident Inspector. | Secondary containment | 05000373/LER-2013-001 |
| ENS 48317 | 18 September 2012 06:15:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Malfunction of the Secondary Containment Door Interlock | This report is being made pursuant to 10CFR50.72(b)(3)(v)(C), Event or Condition that could have prevented fulfillment of a Safety Function needed to Control the Release of Radioactive Material. An employee entered a secondary containment interlock and identified that both doors of the interlock opened simultaneously when the door on the reactor building side was opened. The employee immediately secured both doors in the interlock and notified the Main Control Room Supervisor. Both doors in the interlock were open for approximately 10 seconds. With both doors open, TS SR 3.6.4.1.2 was not met. This rendered secondary containment inoperable per TS 3.6.4.1. Reactor Building differential pressure, as observed in the Main Control Room, has remained less than -0.25" H20 at all times. Initial investigation determined that a mechanical interlock for the doors was malfunctioning. Administrative controls have been put in place to ensure the doors remain closed pending repairs to the mechanical interlock. The licensee notified the NRC Resident Inspector. | Secondary containment | 05000373/LER-2012-001 |
| ENS 47509 | 7 December 2011 20:58:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Reactor Building Ventilation Differential Pressure Above Technical Specifications | This report is being made pursuant to 10CFR50.72(b)(3)(v)(C) and (D), event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material and mitigate the consequences of an accident. Following initial troubleshooting of the reactor building ventilation (VR) differential pressure (DP) control loop, the Unit 1 VR DP controller was left in manual per the troubleshooting steps. It was noted at 1458 CST, on 12/7/11, that building DP was above the TS SR 3.6.4.1.1 required value of -0.25" H20. This rendered the secondary containment inoperable. Reactor building DP was returned to within the TS requirements within 14 minutes, and following system walkdowns, secondary containment was declared operable at 1615 (CST, on) 12/7/11. Troubleshooting will continue with other excursions above -0.25" H2O possible until repairs are complete (anticipated being complete week of 12/12/11). This condition requires the licensee to comply with technical specifications values within 4 hours or be in Mode 3 within 12 hours. The licensee has notified the NRC Resident Inspector. * * * RETRACTION FROM R. DRAPER TO P. SNYDER ON 12/22/11 AT 1440 EST * * * On December 7, 2011, following initial troubleshooting of the reactor building ventilation (VR) differential pressure (DP) control loop, the building DP was above the TS SR 3.6.4.1.1 value of -0.25 inch of vacuum water gauge. The secondary containment was declared inoperable and determined to be a loss of safety function. During the investigation it was determined that the event occurred due to a failure in the non-safety reactor building ventilation differential pressure control loop. The safety related function of the secondary containment and the non-safely reactor building ventilation differential pressure control loop are completely independent from one another. It is recognized that reactor building DP may exceed the TS SR (Technical Specification Surveillance Requirement) 3.6.4.1.1 value due to non-safety related component failures such as system fan trips, pressure controller malfunctions, rapid air temperature changes due to blast heater trips, or station heat recovery coil issues. A failure of a non-safety component does not result in a loss of safety function. The safely function of the secondary containment is maintained by adequate leak tightness and the operable ventilation equipment required to maintain the negative pressure requirements of TS SR 3.6.4.1.1. The safety related Stand-By Gas Treatment (SGT) ventilation system performs the negative pressure safety function. The secondary containment isolation safety function, isolation dampers and SGT systems remained operable throughout the event. Therefore this event did not constitute a loss of safety function of secondary containment and this event is not reportable. The licensee notified the NRC Resident Inspector. Notified R3DO (Pelke). | Secondary containment Reactor Building Ventilation | |
| ENS 46372 | 28 October 2010 15:45:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Standby Liquid Control System Test Tank Seismic Analysis Faulty | This report is being made pursuant to 10CFR50.72(b)(3)(v), Event or Condition that could have prevented fulfillment of a Safety Function. As part of a recent NRC Component Design Basis Inspection (CDBI), the seismic analysis of the Unit One and Unit Two Standby Liquid Control (SBLC) system test tanks was questioned. During the formal operability determination process initiated on 10/27/10, Engineering was verifying design data and calculations. During this review, on 10/28/10, Engineering determined that the historical calculation used the wrong formula in determining the test tank's natural frequency. The consequence is that if the test tank is filled with water, the possibility exists that the test tank could fall over or collapse during a seismic event and adversely affect adjacent safety-related items (i.e. SBLC). Calculations confirm that empty test tanks are seismically qualified. The SBLC test tanks on both units had been drained of water on 10/27/10 and thus both Unit One and Unit Two SBLC systems are fully operable at this time. The licensee has notified the NRC Resident Inspector. | Standby Liquid Control | 05000373/LER-2010-003 05000331/LER-2010-006 |
| ENS 40476 | 25 January 2004 17:10:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Inoperable Refueling Interlock | This report is being made pursuant to 10CFR50.72(b)(3)(v)(A) and 10CFR50.72(b)(3)(v)(D), Event or Condition that could have prevented fulfillment of a Safety Function needed to Maintain Safe Shutdown and Mitigate the Consequences of an Accident. During Unit 1 refueling operations, it was discovered at 1110 hours 1/25/04 CST that the Refuel Position One-Rod-Out Interlock was inoperable. Because this interlock is credited for mitigating the 'Control Rod Removal Error During Refueling' event evaluated in the UFSAR, this is reportable as an 8 hour ENS notification. With the Unit 1 Mode Switch in REFUEL, the one-rod-out interlock function was tested per LaSalle Operating Surveillance LOS-RD-SR4. Since the acceptance criterion of this surveillance was not met, the interlock was declared inoperable and the required actions of Technical Specification 3.9.2 entered. Currently all control rod withdrawals are suspended and all control rods are fully inserted in core cells containing fuel assemblies. The Unit 1 Mode Switch is in Shutdown. Actions are in progress to restore the One-Rod-Out Interlock to an operable status. The licensee notified the NRC Resident Inspector.
During further investigation, it was determined that the system design is such that whenever the Mode Switch is placed in the REFUEL position with a rod withdrawn, no select block is received but a rod withdrawal block is generated. This design feature allows control rods to be inserted should the Mode Switch be placed in REFUEL with any rod out. The LaSalle Operating Surveillance (LOS-RD-SR4) used to demonstrate operability of the Refuel Position One-Rod-Out Block does not currently recognize this design feature and its acceptance criteria is based solely on receipt of the select block. The subject procedure will be revised to ensure all rods are fully inserted prior to performing the surveillance thereby ensuring the logic initial conditions are met to satisfactorily demonstrate the select block function. With these initial conditions satisfied, the Refuel Position One-Rod-Out Interlock was satisfactorily tested on 1/25/04 at 1935 hours CST. Therefore, the Refuel Position One-Rod-Out interlock performed as designed and was capable of performing its safety function. Thus, this occurrence was not reportable under 10CFR50.72(b)(3)(v)(A) and 10CFR50.72(b)(3)(v)(D)." The licensee notified the NRC Resident Inspector. Notified R3DO (Louden). | Control Rod |