03-24-2017 | On January 23, 2017, operators initiated a manual scram of the LaSalle County Station Unit 2 reactor as a result of observing a generator run-back due to a generator stator winding cooling (GC) system malfunction. Initial troubleshooting identified the most likely cause was plugging in the 'A' GC heat exchanger, based on inspection of the GC system flow-path components. The GC system was realigned to the 'B' heat exchanger until inspections could be performed in the upcoming refueling outage, and the unit was re-started on January 24, 2017.
Further inspections of the GC components were performed while the unit was shut down for a planned refueling outage. These inspections determined the cause of the GC system failure was stem-disc separation in the 'A' GC heat exchanger inlet valve. The valve was repaired during the refueling outage.
This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event or condition that resulted in manual or automatic actuation of the Reactor Protection System ( RPS). There were no safety consequences associated with the event since there was no loss of safety function, and the RPS functioned as designed. |
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Category:Letter
MONTHYEARIR 05000373/20230042024-01-24024 January 2024 County Station - Integrated Inspection Report 05000373/2023004 and 05000374/2023004 ML24024A1332024-01-24024 January 2024 Confirmation of Initial License Examination IR 05000373/20230122024-01-18018 January 2024 County Station - Biennial Problem Identification and Resolution Inspection Report 05000373/2023012 and 05000374/2023012 ML23354A2902024-01-0505 January 2024 Exemption from Select Requirements of 10 CFR Part 73 (EPID L-2023-LLE-0028 (Security Notifications, Reports, and Recordkeeping and Suspicious Activity Reporting)) ML23360A6082023-12-27027 December 2023 County Station Request for Information for NRC Commercial Grade Dedication Inspection: Inspection Report 05000373/2024010 and 05000374/2024010 ML23278A1292023-12-14014 December 2023 Units 1 & 2; Limerick, Units 1 & 2; Nine Mile Point, Units 1 & 2; and Peach Bottom, Units 2 & 3 -Revision to Approved Alternatives to Use Boiling Water Reactor Vessel and Internals Project Guidelines ML23305A1402023-12-13013 December 2023 Units 1 & 2; Nine Mile Point, Unit 2; Peach Bottom, Units 2 & 3; and Quad Cities, Units 1 and 2 - Issuance of Amendments to Adopt Traveler TSTF-580 ML23317A1192023-11-10010 November 2023 Constellation Energy Generation, LLC - 2023 Annual Report - Guarantees of Payment of Deferred Premiums RS-23-120, Supplemental Information Letter for Part 73 Exemption Request - Responses to Request for Confirmatory Information2023-11-10010 November 2023 Supplemental Information Letter for Part 73 Exemption Request - Responses to Request for Confirmatory Information IR 05000373/20230032023-11-0909 November 2023 County Station Integrated Inspection Report 05000373/2023003, 05000374/2023003, and 07200070/2023001 ML23286A2602023-11-0808 November 2023 Issuance of Amendment Nos. 260 and 245 to Renewed Facility Operating Licenses Relocation of Pressure and Temperature Limit Curves to the Pressure Temperature Report IR 05000373/20234012023-11-0707 November 2023 County Station Security Baseline Inspection Report 05000373/2023401 and 05000374/2023401 RS-23-103, Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-10-13013 October 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation RS-23-097, Constellation Energy Generation, LLC, Advisement of Leadership Changes and Submittal of Updated Standard Practice Procedures Plans2023-10-12012 October 2023 Constellation Energy Generation, LLC, Advisement of Leadership Changes and Submittal of Updated Standard Practice Procedures Plans IR 05000374/20230102023-10-11011 October 2023 NRC Inspection Report 05000374/2023010 IR 05000373/20233012023-09-15015 September 2023 Errata to NRC Initial License Examination Report 05000373/2023301; 05000374/2023301 RS-23-080, Constellation Energy Generation, LLC, Application to Revise Technical Specifications to Adopt TSTF-264-A, Revision 0, 3.3.9 and 3.3.10 - Delete Flux Monitors Specific Overlap Requirement SRs2023-08-30030 August 2023 Constellation Energy Generation, LLC, Application to Revise Technical Specifications to Adopt TSTF-264-A, Revision 0, 3.3.9 and 3.3.10 - Delete Flux Monitors Specific Overlap Requirement SRs RS-23-087, Revision to Approved Alternatives Associated with the Use of the BWRVIP Guidelines in Lieu of Specific ASME Code Requirements on Reactor2023-08-0404 August 2023 Revision to Approved Alternatives Associated with the Use of the BWRVIP Guidelines in Lieu of Specific ASME Code Requirements on Reactor ML23212A9012023-08-0303 August 2023 Regulatory Audit Report to Support the Review of the Amendments to Relocation of the Pressure Temperature Limit Curves to the Pressure and Temperature Limits Report IR 05000373/20230022023-08-0101 August 2023 County Station - Integrated Inspection Report 05000373/2023002 and 05000374/2023002 ML23208A3182023-07-27027 July 2023 Notification of an NRC Biennial Licensed Operator Requalification Program Inspection and RFI RS-23-084, Response to Request for Additional Information Regarding the Application to Revise Design Basis to Allow Use of Plastic Section Properties in Lower Downcomer Braces Analysis2023-07-24024 July 2023 Response to Request for Additional Information Regarding the Application to Revise Design Basis to Allow Use of Plastic Section Properties in Lower Downcomer Braces Analysis ML23192A5272023-07-12012 July 2023 NRC Initial License Examination Report 05000373/2023301; 05000374/2023301 ML23186A2062023-07-0606 July 2023 Information Request for a NRC Post-Approval Site Inspection for License Renewal 05000374/2023010 ML23181A1502023-06-30030 June 2023 Combined Response to Request for Additional Information and Supplemental Information in Support of LAR to Relocate Pressure and Temperature Limit Curves to the Pressure and Temperature Limits Report ML23178A2422023-06-28028 June 2023 Reassignment of the U.S. Nuclear Regulatory Commission Branch Chief in the Division of Operating Reactor Licensing for Plant Licensing Branch III IR 05000373/20230112023-06-26026 June 2023 County Station - Quadrennial Fire Protection Team Inspection Report 05000373/2023011 and 05000374/2023011 RS-23-077, Response to NRC Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations2023-06-16016 June 2023 Response to NRC Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations ML23167A0352023-06-16016 June 2023 Registration of Use of Cask to Store Spent Fuel ML23171A9562023-06-12012 June 2023 Post Exam Ltr RS-23-042, Application to Revise Technical Specifications to Adopt TSTF-580, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling2023-05-25025 May 2023 Application to Revise Technical Specifications to Adopt TSTF-580, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling IR 05000373/20230012023-05-10010 May 2023 County Station - Integrated Inspection Report 05000373/2023001 and 05000374/2023001 ML23123A2202023-05-0303 May 2023 Relief Request I4R-14 for Alternative Frequency to Containment Unbonded Post-Tensioning System Inservice Inspection ML23118A3472023-05-0101 May 2023 County, 1 & 2; Nine Mile Point, 2; and Quad Cities, 1 & 2 - Correction of Amendment No. 193 Adoption of TSTF-306, Revision 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration EPID L-2022-LLA-0143 ML23121A1612023-05-0101 May 2023 Information Meeting (Open House) with a Question-and-Answer Session to Discuss NRC 2022 End-of-Cycle Plant Performance Assessment of LaSalle County Station, Units 1 and 2 ML23114A2522023-04-28028 April 2023 Request to Use a Provision of a Later Edition of the ASME Boiler & Pressure Vessel Code, Section XI ML23081A0382023-04-25025 April 2023 County, 1 & 2; Nine Mile Point, 2; and Quad Cities, 1 & 2 - Issuance of Amendments to Adopt TSTF-306, Rev. 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration ML23110A3202023-04-21021 April 2023 Information Request to Support the NRC Annual Baseline Emergency Action Level and Emergency Plan Changes Inspection ML23107A1822023-04-18018 April 2023 Operator Licensing Examination Approval Lasalle County Station, May 2023 RS-23-049, Constellation Energy Generation, LLC, Report on Status of Decommissioning Funding for Reactors and Independent Spent Fuel Storage Installations2023-03-23023 March 2023 Constellation Energy Generation, LLC, Report on Status of Decommissioning Funding for Reactors and Independent Spent Fuel Storage Installations ML23073A2182023-03-22022 March 2023 Issuance of Amendment No. 258 to Renewed Facility Operating Licenses Exigent Amendment to Revise Design Basis Related to Seismic Requirements RS-23-048, Exigent Amendment Request to Revise Design Basis Related to Seismic Requirements2023-03-0707 March 2023 Exigent Amendment Request to Revise Design Basis Related to Seismic Requirements ML23061A1632023-03-0303 March 2023 Reassignment of the U.S. Nuclear Regulatory Commission Branch Chief in the Division of Operating Reactor Licensing for Plant Licensing Branch 3 IR 05000373/20220062023-03-0101 March 2023 Annual Assessment Letter for LaSalle County Station, Units 1 and 2 (Report 05000373/2022006 and 05000374/2022006) RS-23-045, Constellation Energy Generation, LLC Submittal of Fitness for Duty Performance Data Reports for 2022 Per 10 CFR 26.717(c) & 10 CFR 26.2032023-02-28028 February 2023 Constellation Energy Generation, LLC Submittal of Fitness for Duty Performance Data Reports for 2022 Per 10 CFR 26.717(c) & 10 CFR 26.203 RS-23-037, Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station2023-02-22022 February 2023 Annual 10 CFR 50.46 Report of Emergency Core Cooling System Evaluation Model Changes and Errors for LaSalle County Station ML23024A1372023-02-0303 February 2023 Request for Withholding Information from Public Disclosure for LaSalle County Station, Unit Nos. 1 and 2 ML23031A1972023-01-31031 January 2023 Notification of NRC Fire Protection Team Inspection Request for Information, Inspection Report Nos. 05000373/2023011 and 05000374/2023011 IR 05000373/20220042023-01-31031 January 2023 County Station - Integrated Inspection Report 05000373/2022004 and 05000374/2022004 RS-23-003, Constellation Energy Generation, LLC, Summary of Changes to Quality Assurance Topical Report, NO-AA-10, and Decommissioning Quality Assurance Program, NO-DC-102023-01-31031 January 2023 Constellation Energy Generation, LLC, Summary of Changes to Quality Assurance Topical Report, NO-AA-10, and Decommissioning Quality Assurance Program, NO-DC-10 2024-01-05
[Table view] Category:Licensee Event Report (LER)
MONTHYEAR05000373/LER-2017-0072017-08-18018 August 2017 Low Pressure Core Spray System Inoperable due to Loss of Cooling, LER 17-007-00 for LaSalle County Station, Unit 1, Regarding Low Pressure Core Spray System Inoperable due to Loss of Cooling 05000374/LER-2017-0032017-08-0909 August 2017 High Pressure Core Spray System Inoperable due to Injection Valve Stem-Disc Separation, LER 17-003-01 for LaSalle County Station, Unit 2 Regarding High Pressure Core Spray System Inoperable due to Injection Valve Stem-Disc Separation 05000374/LER-2017-0042017-07-14014 July 2017 Two Main Steam Safety Relief Valves Failed Inservice Lift Inspection Pressure Test, LER 17-004-01 for LaSalle, Unit 2, Regarding Two Main Steam Safety Relief Valves Failed Inservice Lift Inspection Pressure Test 05000373/LER-2017-0062017-07-14014 July 2017 Low Pressure Core Spray Inoperable due to Minimum Flow Valve Failure in Closed Position, LER 17-006-00 for LaSalle, Unit 1, Regarding Low Pressure Core Spray Inoperable due to Minimum Flow Valve Failure in Closed Position 05000373/LER-2017-0052017-04-18018 April 2017 Manual Reactor Scram Resulting From Feedwater Regulating Valve Failure Causing High Reactor Water Level, LER 17-005-00 for LaSalle County, Unit 1, Regarding Manual Reactor Scram Resulting From Feedwater Regulating Valve Failure Causing High Reactor Water Level 05000373/LER-2017-0042017-04-17017 April 2017 Secondary Containment Inoperable Due to Interlock Doors Open, LER 17-004-00 for LaSalle County, Unit 1, Regarding Secondary Containment Inoperable Due to Interlock Doors Open 05000373/LER-2017-0032017-04-14014 April 2017 Automatic Reactor Scram due to Main Generator Trip on Differential Current During Back-Feed Operations, LER 17-003-00 for LaSalle County Station, Unit 1, Regarding Automatic Reactor Scram due to Main Generator Trip on Differential Current During Back-Feed Operations 05000374/LER-2017-0022017-03-30030 March 2017 High Pressure Core Spray System Declared Inoperable due to Cooling Water Strainer Backwash Valve Stem-Disc Separation, LER 17-002-00 for LaSalle, Unit 2, Regarding High Pressure Core Spray System Declared Inoperable due to Cooling Water Strainer Backwash Valve Stem-Disc Separation 05000374/LER-2017-0012017-03-24024 March 2017 Manual Reactor Scram due to Turbine-Generator Run-Back Caused by Stem-Disc Separation in Stator Water Cooling Heat Exchanger Inlet Valve, LER 17-001-00 for LaSalle County, Unit 2 Regarding Manual Reactor Scram due to Turbine-Generator Run-Back Caused by Stem-Disc Separation in Stator Water Cooling Heat Exchanger Inlet Valve 05000373/LER-2017-0012017-02-0808 February 2017 Reactor Core Isolation Cooling System Inoperable Longer than Allowed by the Technical Specifications due to Low Suction Pressure Trips, LER 17-001-00 for LaSalle County, Unit 1, Regarding Reactor Core Isolation Cooling System Inoperable Longer than Allowed by the Technical Specifications due to Low Suction Pressure Trips 05000374/LER-2016-0012016-04-18018 April 2016 Secondary Containment Inoperable Due to Interlock Doors Open, LER 16-001-00 for LaSalle County, Unit 2, Regarding Secondary Containment Inoperable Due to Door Interlock Doors Open 05000373/LER-2016-0012016-04-11011 April 2016 Secondary Containment Inoperable due to Reactor Building Ventilation Damper Failure, LER 16-001-00 for LaSalle County, Unit 1 & 2, Regarding Secondary Containment Inoperable Due to Reactor Building Ventilation Damper Failure 2017-08-09
[Table view] |
comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects,Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Off ce of Management ani Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
001 2017 . REV - 00
PLANT AND SYSTEM IDENTIFICATION
LaSalle County Station Unit 2 is a General Electric Boiling Water Reactor with 3546 Megawatts Thermal Rated Core Power.
The affected system was the generator stator winding cooling (GC) system, which supports main generator reliability by removing heat from the generator field rectifiers and generator terminal bushings. The GC system supplies cooling water from one of two pumps in combination with one of two heat exchangers.
CONDITION PRIOR TO EVENT
Unit(s): 2 Reactor Mode(s): 1
DESCRIPTION OF EVENT
Event Date: January 23, 2017 Event Time: 0806 CST Mode(s) Name: Power Operation Power Level: 99 percent On January 23, 2017, LaSalle County Station Unit 2 was in Mode 1 at 99 percent, while in coast-down for a scheduled refueling outage. At 0806 hours0.00933 days <br />0.224 hours <br />0.00133 weeks <br />3.06683e-4 months <br /> CST, operators inserted a manual scram, in accordance with station procedures, in response to a GC system malfunction and generator load run-back. The unit was placed in a stable condition with all control rods fully inserted.
Reactor pressure was maintained with the turbine bypass valves, and reactor water level was controlled using the main feedwater system.
At the time of the event, stator water cooling was being provided by the 'B' GC pump aligned to the 'A' GC heat exchanger. The event was preceded by unexpected alarms with the GC and electro-hydraulic control (EHC) systems. Field operators reported that local alarms were observed for stator inlet flow, stator inlet pressure, and stator outlet temperature.
CAUSE OF EVENT
Initial investigation found the 'B' GC pump had been running with a higher than normal discharge pressure as indicated on a local gauge between the pump and the discharge check valve. Further investigation found evidence that limited cooling water flow to the generator existed, suggesting that blockage or a stem-to-disc separation of an upstream valve had occurred. Thermography, visual inspection, borescope inspection, and testing of all valves in the normal flow-path from the 'B' GC pump and the 'A' heat exchanger to the pressure control valve indicated that the most likely cause was plugging in the 'A' heat exchanger. Additional inspections of the GC system were performed during the scheduled refueling outage in order to ascertain a more definitive cause.
These inspections determined the cause of the GC system failure was stem-disc separation in the 'A' GC heat exchanger inlet valve 2GC-Y08.
The preliminary results from the root cause investigation indicate the likely cause of the stem-disc separation was due to maintenance activities from a valve disassembly performed in 2003 for a suspected leak-by. If the investigation reveals insights or cause different than described in this LEA, a supplement will be provided.
REPORTABILITY AND SAFETY ANALYSIS
This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event or condition that resulted in a manual or automatic actuation of the Reactor Protection System (RPS). There was no safety consequences associated with the event since all equipment functioned as designed to shut down the reactor and operational and safety limits were maintained within margin to place the unit into safe shutdown condition.
The main generator provides electrical power from the motive force supplied by the main turbine. The main generator consists of a rotor, bearings, stator, collector rings, brushes, and high-voltage bushings. One of the support systems for the main generator is the GC system. Since the turbine and generator are used together, the main turbine is designed with several trip signals, including a loss of GC.
3. LER NUMBER
comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.goy, and to the Desk Officer, Office of Information and Regulatory Affairs, used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
LICENSEE EVENT REPORT (LEI)
CONTINUATION SHEET
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.00v/reading-rm/doc-collections/nureas/staff/sr1022/r3/) 3. LER NUMBER 2. DOCKET NUMBER - 00 In this event, the digital EHC (DEHC) system detected the conditions for generator run-back (two-of-two low pressure switches closed) and initiated a run-back. During a run-back, after a 15-second delay the DEHC system is designed to reduce the load reference at 30 percent per minute from the normal full power load reference of 105 percent. This caused the control valves to close, which caused the reactor pressure to rise and the bypass valves to open. Approximately 54 seconds after the run-back was initiated, a manual scram was inserted, which reduced reactor pressure and allowed the bypass valves to close. The DEHC system functioned as expected.
CORRECTIVE ACTIONS
Initial investigation found evidence that limited cooling water flow to the generator existed, and testing of all valves in the normal flow-path from the B' GC pump and the 'A' heat exchanger to the pressure control valve indicated that the most likely cause was plugging in the 'A' heat exchanger. An extent of condition review was performed for the opposite unit's GC system and associated valves and controllers. A review of GC heat exchanger preventative maintenance for both units indicated all tasks were current, with no outstanding corrective work orders. Additionally, a review of corrective work orders on the GC valves at LaSalle indicated they were related to leak-by issues and not tube plugging.
Additional inspections of the GC system were performed during the scheduled refueling outage in order to ascertain a more definitive cause. These inspections determined the cause of the GC system failure was stem-disc separation in the 'A' GC heat exchanger inlet valve 2GC-Y08. The valve was repaired during the refueling outage, which restored the system. The extent of condition applied to the 'B' train GC heat exchanger inlet valve 2GC-Y09, which was disassembled and inspected as part of the troubleshooting plan, due to its operation under similar conditions. Similarly, the GC heat exchanger outlet valves were inspected (2GC-Y11) or replaced (2GC-Y10). Unit 1 GC heat exchanger inlet and outlet valves are scheduled for the next Unit 1 refueling outage for stem-disc replacements.
PREVIOUS OCCURRENCES
A review of LaSalle Station Licensee Event Reports for the past three years, related to reactor trips, identified instances where a reactor manual or automatic scram was inserted; however, no previous occurrences related directly to turbine controls or the GC system operation at LaSalle Station were identified. Valve stem-disc separation issues have occurred at LaSalle Station, including the following event.
On August 5, 2014, Unit 2 automatically scrammed from 100 percent power on high neutron flux, followed by a Group I containment isolation. Troubleshooting of the 2C Main Steam Isolation Valve (MSIV) determined that the valve stem-disc had separated from the stem, which allowed the main disc to drop into the main steam's flow-path. The cause of the stem- disc separation on the 2C MSIV was fretting wear attributable to marginal design. The root cause of the event was a legacy decision made in 2008 deferring installation of a manufacturer upgrade that would have prevented the failure. Corrective actions included installing the upgrade on all MSIVs on both units, and reviewing previous deferral decisions made using the same decision-making process.
COMPONENT FAILURE DATA
Manufacturer: Crane [C665] / Aloyco [A200] Device: 90-Degree Angle, Globe, 6-Inch [Model 336-B-SP] Component ID: Crane Part Number PN 31196 2017 001