10-04-2017 | On August 5, 2017, at approximately 2235, the Nine Mile Point Unit 2 (NMP2) reactor scrammed on an automatic scram signal during performance of quarterly turbine stop valve surveillance testing. The automatic Reactor Protection System ( RPS) actuation and reactor scram is reportable per 10 CFR 50.73(a)(2)(iv)(A). The definitive root cause of the equipment failure was not located but was bound to spurious actuation of load limit relays KL186 and KL187. The spurious action was caused by an intermittent ground and/or an induced voltage within the load limit circuit. This is a result of the non-fault tolerant original design of the Electro-hydraulic Control ( EHC) system. The corrective action planned is replacement of the current single point vulnerable NMP2 Turbine EHC system with a fault tolerant Digital EHC system. Interim actions have also been developed to mitigate risk associated with testing of the current system until replacement can be accomplished during the 2018 refueling outage. |
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Category:Letter
MONTHYEARNMP1L3570, Supplemental Information Letter - Revision to the Technical Specifications Design Features Sections to Remove the Nine Mile 3 Nuclear Project, LLC, Designation2024-02-0101 February 2024 Supplemental Information Letter - Revision to the Technical Specifications Design Features Sections to Remove the Nine Mile 3 Nuclear Project, LLC, Designation IR 05000220/20230042024-02-0101 February 2024 Integrated Inspection Report 05000220/2023004 and 05000410/2023004 NMP1L3569, CFR 50.46 Annual Report2024-01-26026 January 2024 CFR 50.46 Annual Report ML24004A2122024-01-0808 January 2024 Senior Reactor and Reactor Operator Initial License Examinations ML23354A0012024-01-0404 January 2024 Exemption from Select Requirements of 10 CFR Part 73 (EPID L-2023-LLE-0059 (Security Notifications, Reports, and Recordkeeping and Suspicious Activity Reporting)) 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 NMP1L3566, Radiological Emergency Plan Document Revision. Includes EP-AA-1013, Revision 10, Radiological Emergency Plan Annex for Nine Mile Point Station2023-12-14014 December 2023 Radiological Emergency Plan Document Revision. Includes EP-AA-1013, Revision 10, Radiological Emergency Plan Annex for Nine Mile Point Station IR 05000410/20243012023-12-14014 December 2023 Initial Operator Licensing Examination Report 05000410/2024301 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 NMP1L3564, Supplemental Response to Part 73 Exemption Request - Withdrawal of Request for Exemption from 10 CFR 73, Subpart B, Preemption Authority Requirements2023-12-0707 December 2023 Supplemental Response to Part 73 Exemption Request - Withdrawal of Request for Exemption from 10 CFR 73, Subpart B, Preemption Authority Requirements ML23291A4642023-12-0707 December 2023 Issuance of Amendment No. 251 Regarding the Adoption of Title 10 the Code of Federal Regulations Section 50.69, Risk-Informed Categorization and Treatment of SSC for Nuclear Power Plants ML23289A0122023-12-0606 December 2023 Issuance of Amendment No. 250 Regarding the Revision to Technical Specifications to Adopt TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b NMP1L3563, Submittal of Relief Request I5R-12, Revision 0, Concerning the Installation of a Full Structural Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-to-Nozzle Dissimilar Metal Weld (32-WD-208)2023-12-0404 December 2023 Submittal of Relief Request I5R-12, Revision 0, Concerning the Installation of a Full Structural Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-to-Nozzle Dissimilar Metal Weld (32-WD-208) IR 05000220/20234022023-11-28028 November 2023 Security Baseline Inspection Report 05000220/2023402 and 05000410/2023402 NMP1L3557, Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-11-22022 November 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation ML23317A1192023-11-10010 November 2023 Constellation Energy Generation, LLC - 2023 Annual Report - Guarantees of Payment of Deferred Premiums IR 05000220/20234202023-11-0101 November 2023 Security Baseline Inspection Report 05000220/2023420 and 05000410/2023420 ML23305A0052023-11-0101 November 2023 Operator Licensing Examination Approval IR 05000220/20230032023-10-25025 October 2023 Integrated Inspection Report 05000220/2023003 and 05000410/2023003 IR 05000220/20235012023-10-17017 October 2023 Emergency Preparedness Biennial Exercise Inspection Report 05000220/2023501 and 05000410/2023501 IR 05000220/20230112023-10-16016 October 2023 Comprehensive Engineering Team Inspection Report 05000220/2023011 and 05000410/2023011 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 NMP1L3554, Submittal of Revision 28 to the Final Safety Analysis Report (Updated), Fire Protection Design Criteria Document, 10CFR50.59 Evaluation Summary Report, 10CFR54.37(b) Aging Management Review, and Technical Specifications with Revised Bases2023-10-0606 October 2023 Submittal of Revision 28 to the Final Safety Analysis Report (Updated), Fire Protection Design Criteria Document, 10CFR50.59 Evaluation Summary Report, 10CFR54.37(b) Aging Management Review, and Technical Specifications with Revised Bases C IR 05000220/20233032023-09-20020 September 2023 Retake Operator Licensing Examination Report 05000220/2023303 ML23250A0822023-09-19019 September 2023 Regulatory Audit Summary Regarding LARs to Adopt TSTF-505, Rev. 2, and 10 CFR 50.69 ML23257A1732023-09-14014 September 2023 Requalification Program Inspection IR 05000220/20230052023-08-31031 August 2023 Updated Inspection Plan for Nine Mile Point Nuclear Station, Units 1 and 2 (Report 05000220/2023005 and 05000410/2023005) 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 NMP2L2851, Relief Request Associated with Successive Inspections for Generic Letter 88-01 / BWRVIP-75-A Augmented Examinations2023-08-25025 August 2023 Relief Request Associated with Successive Inspections for Generic Letter 88-01 / BWRVIP-75-A Augmented Examinations ML23151A3472023-08-21021 August 2023 Issuance of Amendments to Adopt TSTF-295-A, Modify Note 2 to Actions of PAM Table to Allow Separate Condition Entry for Each Penetration NMP1L3534, License Amendment Request - Revision to the Technical Specifications Design Features Sections to Remove the Nine Mile 3 Nuclear Project, LLC, Designation2023-08-18018 August 2023 License Amendment Request - Revision to the Technical Specifications Design Features Sections to Remove the Nine Mile 3 Nuclear Project, LLC, Designation ML23220A0262023-08-0808 August 2023 Licensed Operator Positive Fitness-for-Duty Test IR 05000220/20234012023-08-0808 August 2023 Cyber Security Inspection Report 05000220/2023401 and 05000410/2023401 (Cover Letter Only) NMP1L3545, Supplemental Information Letter to Adopt TSTF-505, Provide Risk- Informed Extended Completion Times - RITSTF Initiative 4b, Revision 2 and 10 CFR 50.69, Risk-informed Categorization and Treatment of Structures, Systems .2023-08-0404 August 2023 Supplemental Information Letter to Adopt TSTF-505, Provide Risk- Informed Extended Completion Times - RITSTF Initiative 4b, Revision 2 and 10 CFR 50.69, Risk-informed Categorization and Treatment of Structures, Systems . 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 IR 05000220/20230022023-08-0101 August 2023 Integrated Inspection Report 05000220/2023002 and 05000410/2023002 ML23207A0762023-07-14014 July 2023 EN 56557 - Update to Part 21 Report Re Potential Defect with Trane External Auto/Stop Emergency Stop Relay Card Pn: XI2650728-06 NMP1L3544, Fifth Inservice Inspection Interval, First Inservice Inspection Period 2023 Owner'S Activity Report for RFO-27 Inservice Examinations2023-07-14014 July 2023 Fifth Inservice Inspection Interval, First Inservice Inspection Period 2023 Owner'S Activity Report for RFO-27 Inservice Examinations ML23186A1642023-07-0606 July 2023 Operator Licensing Retake Examination Approval NMP2L2846, Nine Mire Point Nuclear Station, Units 1 and 2, General License 30-day Cask Registration Notifications2023-07-0505 July 2023 Nine Mire Point Nuclear Station, Units 1 and 2, General License 30-day Cask Registration Notifications ML23192A0622023-06-30030 June 2023 Engine Systems, Inc., 10CFR21 Reporting of Defects and Non-Compliance, Report No. 10CFR21-0136, Rev. 0 IR 05000220/20230102023-06-29029 June 2023 Biennial Problem Identification and Resolution Inspection Report 05000220/2023010 and 05000410/2023010 ML23131A4242023-06-23023 June 2023 Issuance of Amendment No. 249 Regarding the Revision to Technical Specification 3.3.1 to Adopt Technical Specifications Task Force Traveler TSTF-568 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 NMP1L3539, Day Commitment Response - Relief Request I5R-11 Concerning the Installation of a Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-to-Nozzle Dissimilar Metal Weld (32-WD-208)2023-06-0909 June 2023 Day Commitment Response - Relief Request I5R-11 Concerning the Installation of a Weld Overlay on Reactor Pressure Vessel Recirculation Inlet Nozzle N2E Safe End-to-Nozzle Dissimilar Metal Weld (32-WD-208) ML23159A0052023-06-0505 June 2023 56557-EN 56557 - Paragon - Redlined 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 05000410/20233022023-05-15015 May 2023 Initial Operator Licensing Examination Report 05000410/2023302 2024-02-01
[Table view] Category:Licensee Event Report (LER)
MONTHYEARML18018B1152018-01-18018 January 2018 Scram Summary 91-01 Relating to a Turbine Trip and Automatic Reactor Scram When the Main Transformer Phase B Developed an Internal Fault on August 13, 1991 ML18018B1122018-01-18018 January 2018 Scram Summary 91-01 Relating to an Event on August 13, 1991 Concerning a Turbine Trip and Automatic Reactor Scram When the Main Transformer Phase B Developed an Internal Fault 05000410/LER-2017-0022017-11-28028 November 2017 Secondary Containment Inoperable Due to Wind Conditions, LER 17-002-00 for Nine Mile Point Nuclear Station, Unit 2 Regarding Secondary Containment Inoperable Due to Wind Conditions 05000220/LER-2017-0032017-11-0202 November 2017 Automatic Reactor Scram due to Reactor Vessel Low Water Level, LER 17-003-00 for Nine Mile Point, Unit 1, Regarding Automatic Reactor Scram due to Reactor Vessel Low Water Level 05000410/LER-2017-0012017-10-0404 October 2017 1 OF 5, LER 17-001-00 for Nine Mile Point Nuclear Station, Unit 2, Regarding Automatic Reactor Scram due to High Reactor Pressure 05000220/LER-2017-0022017-05-18018 May 2017 Manual Reactor Scram Due to Pressure Oscillations, LER 17-002-00 for Nine Mile Point Nuclear Station, Unit 1 Regarding Manual Reactor Scram Due to Pressure Oscillations 05000220/LER-2017-0012017-02-0808 February 2017 Manual Reactor Scram Due to Hiah Turbine Vibration, LER 17-01-00 for Nine Mile Point Unit 1 RE: Manual Reactor Scram Due to High Turbine Vibration NMP1L3129, LER 17-01-00 for Nine Mile Point Unit 1 Manual Reactor Scram Due to High Turbine Vibration2017-02-0808 February 2017 LER 17-01-00 for Nine Mile Point Unit 1 Manual Reactor Scram Due to High Turbine Vibration 05000220/LER-2016-0022016-09-26026 September 2016 Isolation of both Emergency Condensers due to loss of UPS 162B, LER 16-002-00 for Nine Mile Point, Unit 1, Regarding Isolation of Both Emergency Condensers due to Loss of UPS 1628 05000220/LER-2016-0012016-07-12012 July 2016 Secondary Containment Inoperable Due to Simultaneous Opening of Airlock Doors, LER 16-001-00 for Nine Mile Point Nuclear Station Unit 1 Regarding Secondary Containment Inoperable Due to Simultaneous Opening of Airlock Doors 05000410/LER-2016-0012016-06-0606 June 2016 Secondary Containment Inoperable Due to Simultaneous Opening of Airlock Doors, LER 16-001-00 for Nine Mile Point, Unit 2, Regarding Secondary Containment Inoperable Due to Simultaneous Opening of Airlock Doors 05000410/LER-2015-0032016-03-31031 March 2016 Primary Containment Isolation Function for some valves not maintained during Surveillance Testing, LER 15-003-01 for Nine Mile Point, Unit 2, Regarding Primary Containment Isolation Function For Some Valves Not Maintained During Surveillance Testing ML1005504842010-02-15015 February 2010 Special Report: Inoperable Suppression Chamber Water Level Instrumentation ML0903605172009-01-21021 January 2009 Special Report: Inoperable Channel of Suppression Chamber Water Level Instrumentation ML0534802052005-12-0202 December 2005 Special Report for Nine Mile Point Unit 1 Re Channel #12 of the Containment Hydrogen Monitoring System Inoperable ML0515400362005-05-24024 May 2005 Special Report, Channel #11 of the Containment Hydrogen Monitoring Inoperable for Scheduled Preventive Maintenance ML0509602422004-12-17017 December 2004 Final Precursor Analysis - NMP-1 Grid Loop ML0509602522004-12-17017 December 2004 Final Precursor Analysis - NMP-2 Grid Loop ML0434304492004-11-22022 November 2004 Special Report for Nine Mile Point, Unit 1 Regarding Channel #12 of the Containment Hydrogen Monitoring System Removed from Service for Planned Maintenance ML0425300732004-08-27027 August 2004 Special Report for Nine Mile Point Unit 1 Re Channel #11 of the Containment Hydrogen Monitoring System Inoperable for Scheduled Preventive Maintenance ML0418105152004-06-18018 June 2004 Revised Special Report for Nine Mile Point, Unit 1 Re Channel #12 of the Containment Hydrogen Monitoring System Inoperable ML0413204992004-05-0404 May 2004 Special Report for Nine Mile Point Unit 1 Regarding Inoperability of Channel #12 of the Containment Hydrogen Monitoring System ML0410603992004-04-0707 April 2004 Special Report, Channel #11 of the Containment Hydrogen Monitoring System Inoperable for Scheduled Corrective Maintenance ML0336404932003-12-19019 December 2003 Special Report Regarding Channel #11 Containment Hydrogen Monitoring System Being Inoperable for Scheduled Preventive Maintenance ML0221303572002-07-23023 July 2002 Special Report for Nine Mile Point Unit 2 Re Noble Gas Activity Monitoring Instrumentation Inoperable for Greater than 72 Hours ML18018B1112000-03-0707 March 2000 LER 99-019-01 Supplement 1, for Nine Mile Point, Unit 2, Regarding Two Standby Liquid Control Valves Not Tested as Required by Technical Specification 4.0.5 and LER 99-010-01, Supplement 1, Unit 2 Reactor Trip Due to a Feedwater Master .. ML18018B0771997-12-29029 December 1997 Letter Replying to Notice of Violation as Contained in NRC Inspection Report 50-220/97-07 and 50-410/97-07 ML18018B1171991-09-0404 September 1991 NRC UPS Meeting ML18018B2511978-09-29029 September 1978 LER 78-034-00 for Nine Mile Point, Unit 2, Regarding an Environmental Contractor Obtaining 22 Hourly Fish Impingement Samples, and One Two-Hour Sample, Which Is Contrary to the Technical Specification Requiring 24 Hourly Samples ML18018B2521978-08-24024 August 1978 LER 78-030-00, 78-031-00, and 78-032-00 for Nine Mile Point Unit 1 Regarding, Respectively, Unavailability of Feedwater Pump 29-03 While Its Pump Seals Were Replaced, Unavailability of Liquid Poison Pump NP02A While a Frozen Valve .. ML18018B2531978-07-28028 July 1978 LER 78-029-00 for Nine Mile Point, Unit 2, Regarding Discovery of High Drywell Pressure Switches RE04A, RE04B, and RE04C with Setpoints Less Conservative than the Technical Specifications ML18018B2541978-07-25025 July 1978 LER 78-028-00 for Nine Mile Point Unit 1 Regarding Discovery of the Allowable Test Interval of TS 4.1.4c for the Core Spray Power-Operated Valves Had Been Exceeded ML18018B2551978-07-13013 July 1978 LERs 78-025-00, 78-026-00, and 78-027-00 for Nine Mile Point Unit 1 Regarding, Respectively, Discovery of RE04D with a Setpoint of 3.70 PSIG, Discovery of Numerous Small Leaks in Small Sample and Instrument Pipes, and Discovery of RE22D wit ML18018B2561978-06-21021 June 1978 LER 78-024-00 for Nine Mile Point Unit 1 Regarding Discovery That Test N1-St-Q2,4,5,7,8,9, and 10 Had Not Been Performed During a Review of Quarterly Surveillance Test Results ML18018B2571978-06-12012 June 1978 LERs 78-020-00, 78-021-00, 78-022-00, and 78-023-00 for Nine Mile Point Unit 1 Regarding, Respectively, Discovery of RE18A with a Setpoint of 135 Inches Wc, Discovery of RE04A and RE04B with a Setpoint of 3.65 PSIG, Discovery of Turbine ... ML18018B2591978-06-0101 June 1978 LER 78-019-00 for Nine Mile Point Unit 1 Regarding Discovery That Hydraulic Snubber 31-HS-1 Had Failed and Was Empty of Hydraulic Fluid and Disconnected from Its Anchor at the Feedwater Pipe ML18018B2581978-05-26026 May 1978 LER 78-009-01 for Nine Mile Point Unit 1 Regarding Replacement of Explosive Charges in the TIP Shear Valves with New Charges and the Resulting Unsatisfactory Ohmmeter Continuity Test for Acceptable Electric Contact ML18018B2601978-04-24024 April 1978 LER 78-018-00 for Nine Mile Point Unit 1 Regarding Discovery of Main Steam High Flow Switch with a Setpoint of 106.2 PSI, Which Is Above the Technical Specification ML18018B2611978-04-0707 April 1978 LERs 78-014,00, 78-016-00, and 78-016-00 for Nine Mile Point Unit 1 Regarding, Respectively, Discovery That the Fuel Transfer Pump on 102 D/G Would Not Fill the Day Tank, Discovery of RE18C with a Setpoint of 129 Inches Wc, and RE04B .. ML18018B2621978-03-28028 March 1978 LER 78-014-00 and LER 78-015-00 for Nine Mile Point Unit 1 Regarding, Respectively, Discovery That the Fuel Transfer Pump in 102 D/G Would Not Fill the Day Tank and Discovery That #12 Control Room Air Treatment Fan Would Not Run ML18018B2631978-03-16016 March 1978 LER 78-011-00, LER 78-012-00 and LER 78-013-00 for Nine Mile Point, Unit 1 Re Technical Specification Violations of Section 3.6.2 ML18018B2641978-03-0101 March 1978 LER 78-007-00, LER 78-008-00, LER 78-009-00 and LER 78-010-00 for Nine Mile Point, Unit 1 Re Technical Specification Violations of Listed Sections ML18018B2651978-02-24024 February 1978 LER 78-006-00 for Nine Mile Point, Unit 1 Re During Steady State Operation, Performance of Surveillance Test IC-75 Found a Trip Setpoint of 22.5 Inches Water on One Vacuum Switch in the Vacuum Relief System from the Pressure Suppression Cha ML18018B2661978-02-0707 February 1978 LER 78-004-00 and LER 78-005-00 for Nine Mile Point, Unit 1 Re During Unit Shutdown, Reserve Power Breaker on Power Board II Failed to Close in After Loss of Normal Power and During Plant Outage While Marking Up Outside MSIV 01-03 Discovere ML18094A0301978-01-31031 January 1978 LER 1978-003-03 for Nine Mile Point Unit 1 Re Surveillance Test Found Main Steam High Flow Switch with Setpoint of 107.5 PSI ML18018B1221978-01-31031 January 1978 LER 78-002-00 for Nine Mile Point 1 Regarding Drywell High Pressure Switch RE04A Setpoint Drift and LER 78-003-00 ML18018B2701978-01-13013 January 1978 Submittal of Licensee Event Report LER 78-01 Concerning Delta Temperature of the Discharge Water Exceeded Environmental Tech. Spec ML18094A0291978-01-13013 January 1978 LER 1978-001-00 for Nine Mile Point Station Unit 1 Re Delta Temperature of Discharge Water Exceeded Specification 2.1.5 of Environmental Tech Specs ML18018B1361977-07-21021 July 1977 LER 77-032-00 for Nine Mile Point Unit 1 Regarding a Water Phase Material Sample in the Reactor Vessel Inspection Lapse During Refueling ML18018B1421977-07-14014 July 1977 LER 77-029-00, 77-030-00, 77-031-00, 77-034-00, & 77-035-00 for Nine Mile Point Unit 1 Low-Low-Low Level Set Point Out of Specs on RE-18A, Vacuum Switch Trip & Reset Point on Torus Relief Valves Out of Specs, Weld Leak in Emergency Condense 2018-01-18
[Table view] |
comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear.
Regulatory Commission, Washington, DC 20555-0001, or by e-mail to 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.
3. LER NUMBER
2017 001 - 00
I. DESCRIPTION OF EVENT
A. PRE-EVENT PLANT CONDITIONS:
Prior to the event, Nine Mile Point Unit 2 (NMP2) was in Mode 1 and operating at 84% reactor power. Turbine controls troubleshooting and overspeed trip system repairs had been completed, followed by power ascension from 20% power to 84% power. The plant was stabilized at 84% power to support quarterly turbine valve testing.
B. EVENT:
On August 5, 2017, at approximately 2235, during performance of quarterly turbine valve testing, an automatic Reactor scram occurred. The RPS system actuation was due to high reactor pressure. The pressure increase occurred when the turbine control valves (TCV) began closing while stroking turbine stop valves (TSV) 1 and 2. All systems responded as expected to the reactor scram signal.
Based on the turbine bypass valves (TBV) fast opening and TCVs ramping closed, a loss of control valve demand was determined to be the initiator of the event. The TSV limit switch circuit was tested for grounds or stuck limit switches after the scram but none could be found.
Troubleshooting identified an erroneous control valve demand signal resulting in fast closure of the control valves and subsequent increase in reactor pressure. After instrumenting the load control circuit, an anomaly on the load limit amplifier card was identified. The card was replaced and sent out for failure analysis. To further protect against latent failures, a temporary modification to lift the leads on the stop valve load limit switches was implemented. Lifting the leads minimizes the risk of fast closure of the TCVs in the event of a stuck load limit switch during future turbine valve testing.
The failure analysis of the load limit amplifier card determined the card was functioning properly and was not the cause of the event. This further supports that the spurious actuation of load limit relays KL186 and KL187 was caused by an intermittent ground and/or an induced voltage within the load limit circuit.
Nine Mile Point Unit 1 (NMP1) was unaffected by the scram at NMP2.
The event has been entered into the plant's corrective action program as IR 4039435.
C. INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED TO
THE EVENT:
No other systems, structures, or components contributed to this event.
comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by . e-mail to 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 - 00 Nine Mile Point Unit 2 05000410 2017
D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES AND OPERATOR
ACTIONS:
The dates, times, and major occurrences and operator actions for this event are as follows. All dates are 2017.
August 5 1500 Began power ascension from 20% after completion of turbine controls troubleshooting and overspeed trip repairs.
2040 Power ascension placed on hold at 84% power and started TSV and TCV testing per N2-OSP-RPS-0001.
2235 During step 8.8.3, when testing the last set of TSVs, the TCVs started closing, the TBVs opened and the reactor scrammed on high reactor pressure. EOP-RPV was entered due to low reactor water level, as well as high reactor pressure. N2- SOP-101C was entered due to the reactor scram.
2323 Exited EOP-RPV and N2-SOP-101C.
E. METHOD OF DISCOVERY:
This event was self-revealing during the performance of the surveillance test when relays were heard actuating unexpectedly and a reactor scram occurred.
F. SAFETY SYSTEM RESPONSES:
All systems operated as expected. After the scram, there were no safety system actuations.
II. CAUSE OF EVENT:
The definitive root cause of the equipment failure was not located but was bound to spurious actuation of load limit relays KL186 and KL187. The spurious action was caused by an intermittent ground and/or an induced voltage within the load limit circuit. This is a result of the non-fault tolerant original design of the Electro-hydraulic Control (EHC) system.
III. ANALYSIS OF THE EVENT:
The automatic reactor scram is reportable under 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.73(a)(2)(iv)(A). It is defined under paragraph 10 CFR 50.73(a)(2)(iv)(A) as any event or condition that resulted in manual or automatic action of any of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). The RPS system actuation, including reactor scram, is listed in 10 CFR 50.73(a)(2)(iv)(B).
comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to NE08-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. It 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.
3. LER NUMBER 1. FACILITY NAME 2017 001 - 00 The definitive root cause of the equipment failure was not located but was bound to spurious actuation of load limit relays KL186 and KL187. The spurious action was caused by an intermittent ground and/or an induced voltage within the load limit circuit. The relay actuation resulted in the TCVs closing, the TBVs opening and a reactor scram on high reactor pressure.
All control rods fully inserted and there were no safety system actuations.
Based on the above discussion, it is concluded that the safety significance of this event is low and the event did not pose a threat to the health and safety of the public or plant personnel.
Troubleshooting identified an erroneous control valve demand signal resulting in fast closure of the TCVs and subsequent increase in reactor pressure. After instrumenting the load control circuit, an anomaly on the load limit amplifier card was identified. The load limit amplifier card was replaced. Failure analysis did not identify any anomalies with the card.
To further protect against latent failures, leads have been lifted on the stop valve load limit switches to prevent fast closure of the TCVs in the event of a stuck load limit switch during future valve testing.
This event does affect the NRC Regulatory Oversight Process Indicator for unplanned scrams per 7000 hours0.081 days <br />1.944 hours <br />0.0116 weeks <br />0.00266 months <br /> of critical operation.
IV. CORRECTIVE ACTIONS:
A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL
STATUS:
The load limit amplifier card was replaced.
B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:
To prevent recurrence, replacement of the current obsolete and single point vulnerable NMP2 Turbine EHC system with a fault tolerant Digital EHC system is scheduled for the next refueling outage.
To further protect against latent failures, a temporary modification to lift the leads on the stop valve load limit switches was implemented. Lifting the leads minimizes the risk of fast closure of the control valves in the event of a stuck load limit switch during future turbine valve testing. Additionally, to minimize risk prior to replacement of the system, the testing method for TSVs is being revised prior to the next performance.
comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to 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.
3. LER NUMBER 1. FACILITY NAME 2017 001 - 00
V. ADDITIONAL INFORMATION:
A. FAILED COMPONENTS:
The definitive root cause of the equipment failure was not located but was bound to spurious actuation of load limit relays KL186 and KL187. The spurious action was caused by an intermittent ground and/or an induced voltage within the load limit circuit.
The load limit amplifier card was replaced, but troubleshooting determined it was not the single cause of the event. Potentially stuck limit switches have been disabled.
B. PREVIOUS LERs ON SIMILAR EVENTS:
None C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION
IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM REFERRED TO
IN THIS LER:
COMPONENT
Electro Hydraulic Control System Load Limit Amplifier Card Load Limit Relay Limit Switch Turbine Stop Valve Turbine Control Valve Turbine Bypass Valve Main Turbine Reactor Protection System
None
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05000410/LER-2017-001 | 1 OF 5 LER 17-001-00 for Nine Mile Point Nuclear Station, Unit 2, Regarding Automatic Reactor Scram due to High Reactor Pressure | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | 05000220/LER-2017-001 | Manual Reactor Scram Due to Hiah Turbine Vibration LER 17-01-00 for Nine Mile Point Unit 1 RE: Manual Reactor Scram Due to High Turbine Vibration | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | 05000410/LER-2017-002 | Secondary Containment Inoperable Due to Wind Conditions LER 17-002-00 for Nine Mile Point Nuclear Station, Unit 2 Regarding Secondary Containment Inoperable Due to Wind Conditions | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material | 05000220/LER-2017-002 | Manual Reactor Scram Due to Pressure Oscillations LER 17-002-00 for Nine Mile Point Nuclear Station, Unit 1 Regarding Manual Reactor Scram Due to Pressure Oscillations | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | 05000220/LER-2017-003 | Automatic Reactor Scram due to Reactor Vessel Low Water Level LER 17-003-00 for Nine Mile Point, Unit 1, Regarding Automatic Reactor Scram due to Reactor Vessel Low Water Level | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
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