On October 28, 2016, during replacement of relay PCIS-REL-K27 at Cooper Nuclear Station ( CNS), the action of installing a new relay onto the shared plastic DIN rail disturbed the mounting rail in a manner that caused contacts of the adjacent relay, PCIS-REL-K30, to open. This caused Shutdown Cooling ( SDC) isolation valve RHR-MO-17 to close, which actuated the logic to trip the running 'A' Residual Heat Removal ( RHR) pump.
Operations declared 'A' RHR SDC subsystem inoperable at 09:24 hours and entered Limiting Condition for Operation (LCO) 3.9.7, Condition A, and Condition C. Alternate Decay Heat Removal remained in service throughout the event.
Event Notification 52327 was made to the Nuclear Regulatory Commission Operations Center.
While SDC was out of service, PCIS-REL-K27 work was completed. SDC was declared operable at 05:30 hours on October 29, 2016, and was placed in service at 18:30 hours, and the LCO was exited.
The root cause of the event is that CNS did not identify the risk from mechanical agitation during Primary Containment Isolation System (PCIS) relay installation; therefore, the risk was not adequately evaluated or mitigated.
To prevent recurrence, CNS will revise Procedure 0.50.5 to list the relays or other devices which could impact SDC when in service.
This is a Safety System Functional Failure. |
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Category:Letter
MONTHYEARIR 05000298/20240032024-11-0505 November 2024 Integrated Inspection Report 05000298/2024003 ML24250A2052024-10-0808 October 2024 Issuance of Amendment No. 278 Regarding Revision to Technical Specification Table 3.3.2.1-1 and Transfer of Minimum Critical Power Ratio Values to Core Operating Limit Report ML24227A0822024-09-0303 September 2024 Summary of Regulatory Audit in Support of License Amendment Request to Modify the High Pressure Coolant Injection Low Flow Value IR 05000298/20240052024-08-22022 August 2024 Updated Inspection Plan for Cooper Nuclear Station (Report 05000298/2024005) IR 05000298/20240022024-07-25025 July 2024 Integrated Inspection Report 05000298/2024002 ML24183A1722024-07-17017 July 2024 Issuance of Amendment No. 277 to Adopt TSTF-374, Revision to TS 5.5.13 and Associated TS Bases for Diesel Fuel Oil ML24197A1462024-07-15015 July 2024 NRC Region IV Ltr to Cooper Nuclear Station Re FEMA Level 1 Finding ML24134A1782024-07-0303 July 2024 Issuance of Amendment No. 276 Revision to Technical Specification 3.8.3, Diesel Fuel Oil, Lube Oil and Starting Air, to Allow for Cleaning, Inspection and Any Needed Repairs During Refuel Outage 33 ML24197A0682024-06-24024 June 2024 FEMA Ltr to Missouri State Emergency Management Agency - Level 1 Finding, 24 June 2024 ML24192A0112024-06-13013 June 2024 2024-06-Post Exam Comments 05000298/LER-2023-002-01, Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications2024-06-0606 June 2024 Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications IR 05000298/20244012024-06-0404 June 2024 Security Baseline Inspection Report 05000298/2024401 ML24151A1082024-05-30030 May 2024 NRC Initial Operator Licensing Examination Approval 05000298/2024301 ML24137A0942024-05-17017 May 2024 Regulatory Audit Plan in Support of License Amendment Request to Modify Allowable Value Regarding Technical Specification for High Pressure Coolant Injection Pump Discharge Low Flow 05000298/LER-2024-005, High Pressure Coolant Injection Pressure Switch Installation Causes Condition That Could Have Prevented Fulfillment of a Safety Function and a Condition Prohibited B Technical2024-05-13013 May 2024 High Pressure Coolant Injection Pressure Switch Installation Causes Condition That Could Have Prevented Fulfillment of a Safety Function and a Condition Prohibited B Technical. 05000298/LER-2024-004, Main Turbine Stop Valve Position Switches Do Not Meet Channel Independence Criteria Results in Two Channels Being Declared Inoperable and a Condition Prohibited by Technical Specifications2024-05-0909 May 2024 Main Turbine Stop Valve Position Switches Do Not Meet Channel Independence Criteria Results in Two Channels Being Declared Inoperable and a Condition Prohibited by Technical Specifications IR 05000298/20240012024-05-0303 May 2024 Integrated Inspection Report 05000298/2024001 ML24129A0952024-04-25025 April 2024 Preparation and Scheduling of Operator Licensing Examinations IR 05000298/20240102024-04-24024 April 2024 Comprehensive Engineering Team Inspection Report 05000298/2024010 05000298/LER-2024-003, High Pressure Coolant Injection Steam Leak Causes Condition That Could Have Prevented Fulfillment of a Safety Function and a Condition Prohibited by Technical Specifications2024-04-22022 April 2024 High Pressure Coolant Injection Steam Leak Causes Condition That Could Have Prevented Fulfillment of a Safety Function and a Condition Prohibited by Technical Specifications ML24096A1202024-04-0505 April 2024 Issuance of Amendment No. 275 Revision to Technical Specification 3.3.1.1 (Emergency Circumstances) ML24093A2282024-04-0202 April 2024 Notice of Enforcement Discretion for Cooper Nuclear Station IR 05000298/20240902024-04-0101 April 2024 – Notice of Violation, NRC Inspection Report 05000298/2024090 05000298/LER-2024-001, Inoperable Turbine Stop Valve Limit Switch Causes Condition Prohibited by Technical Specifications2024-03-0404 March 2024 Inoperable Turbine Stop Valve Limit Switch Causes Condition Prohibited by Technical Specifications 05000298/LER-2024-002, Technical Specifications Prohibited Condition for Inoperable Service Water Booster Pump2024-03-0404 March 2024 Technical Specifications Prohibited Condition for Inoperable Service Water Booster Pump IR 05000298/20230062024-02-28028 February 2024 Annual Assessment Letter for Cooper Nuclear Station - Report 05000298/2023006 IR 05000298/20230042024-02-12012 February 2024 Integrated Inspection Report 05000298/2023004 ML24033A3092024-02-12012 February 2024 Summary of Regulatory Audit Regarding the Relief Request RC3-02 Regarding Drywell Head Bolting IR 05000298/20230122024-02-12012 February 2024 NRC Inspection Report 05000298/2023012 ML23334A2012024-01-0303 January 2024 Issuance of Amendment No. 274 Revision to Technical Specifications to Adopt TSTF-551, Revision 3, Revise Secondary Containment Surveillance Requirements 05000298/LER-2023-002, Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications2023-12-20020 December 2023 Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications ML23311A2082023-11-0909 November 2023 Reassignment of U.S. Nuclear Regulatory Commission Branch Chief in the Division of Operating Reactor Licensing for Plant Licensing Branch IV ML23311A1122023-11-0909 November 2023 Project Manager Assignment IR 05000298/20230032023-11-0202 November 2023 Integrated Inspection Report 05000298/2023003 IR 05000298/20234012023-11-0101 November 2023 Cyber Security Report 05000298/2023401 Public ML23264A8052023-10-11011 October 2023 Issuance of Amendment No. 273 Revision to Technical Specifications to Adopt TSTF-580, Revision 1, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling ML23233A1882023-09-0505 September 2023 Regulatory Audit Plan in Support of Relief Request RC3-02 Regarding Drywell Head Bolting IR 05000298/20243012023-09-0101 September 2023 Notification of NRC Initial Operator Licensing Examination 05000298/2024301 IR 05000298/20230052023-08-21021 August 2023 Updated Inspection Plan for Cooper Nuclear Station (Report 05000298/2023005)- Mid Cycle Letter IR 05000298/20230022023-08-0808 August 2023 Integrated Inspection Report 05000298/2023002 IR 05000298/20234022023-08-0303 August 2023 NRC Security Inspection Report 05000298/2023402 ML23214A2742023-08-0303 August 2023 Nuclear Station - Notification of Inspection (NRC Inspection Report 05000298/2023004) and Request for Information IR 05000298/20234202023-08-0101 August 2023 Security Baseline Inspection Report 05000298/2023420 05000298/LER-2022-002-01, Manual Core Spray Injection to Restore Skimmer Surge Tank Level2023-06-29029 June 2023 Manual Core Spray Injection to Restore Skimmer Surge Tank Level ML23173A0862023-06-26026 June 2023 Information Request for the Cybersecurity Baseline Inspection, Notification to Perform Inspection 05000298/2023401 IR 05000298/20230102023-05-17017 May 2023 Biennial Problem Identification and Resolution Inspection Report 05000298/2023010 05000298/LER-2022-004-01, 1 for Cooper Nuclear Station, Manual Reactor Scram and Group I Isolation Due to Main Turbine Bypass Valve Failing Open2023-05-11011 May 2023 1 for Cooper Nuclear Station, Manual Reactor Scram and Group I Isolation Due to Main Turbine Bypass Valve Failing Open 05000298/LER-2023-001, Valve Test Failures Result in Condition Prohibited by Technical Specifications2023-05-0808 May 2023 Valve Test Failures Result in Condition Prohibited by Technical Specifications IR 05000298/20234032023-05-0404 May 2023 Security Baseline Inspection Report 05000298/2023403 ML23129A2822023-04-20020 April 2023 Submittal of Revision 31 to Updated Safety Analysis Report 2024-09-03
[Table view] Category:Licensee Event Report (LER)
MONTHYEAR05000298/LER-2023-002-01, Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications2024-06-0606 June 2024 Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications 05000298/LER-2024-005, High Pressure Coolant Injection Pressure Switch Installation Causes Condition That Could Have Prevented Fulfillment of a Safety Function and a Condition Prohibited B Technical2024-05-13013 May 2024 High Pressure Coolant Injection Pressure Switch Installation Causes Condition That Could Have Prevented Fulfillment of a Safety Function and a Condition Prohibited B Technical. 05000298/LER-2024-004, Main Turbine Stop Valve Position Switches Do Not Meet Channel Independence Criteria Results in Two Channels Being Declared Inoperable and a Condition Prohibited by Technical Specifications2024-05-0909 May 2024 Main Turbine Stop Valve Position Switches Do Not Meet Channel Independence Criteria Results in Two Channels Being Declared Inoperable and a Condition Prohibited by Technical Specifications NLS2024035, Main Turbine Stop Valve Position Switches Do Not Meet Channel Independence Criteria Results in Two Channels Being Declared Inoperable and a Condition Prohibited by Technical Specifications2024-05-0909 May 2024 Main Turbine Stop Valve Position Switches Do Not Meet Channel Independence Criteria Results in Two Channels Being Declared Inoperable and a Condition Prohibited by Technical Specifications 05000298/LER-2024-003, High Pressure Coolant Injection Steam Leak Causes Condition That Could Have Prevented Fulfillment of a Safety Function and a Condition Prohibited by Technical Specifications2024-04-22022 April 2024 High Pressure Coolant Injection Steam Leak Causes Condition That Could Have Prevented Fulfillment of a Safety Function and a Condition Prohibited by Technical Specifications 05000298/LER-2024-002, Technical Specifications Prohibited Condition for Inoperable Service Water Booster Pump2024-03-0404 March 2024 Technical Specifications Prohibited Condition for Inoperable Service Water Booster Pump 05000298/LER-2024-001, Inoperable Turbine Stop Valve Limit Switch Causes Condition Prohibited by Technical Specifications2024-03-0404 March 2024 Inoperable Turbine Stop Valve Limit Switch Causes Condition Prohibited by Technical Specifications 05000298/LER-2023-002, Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications2023-12-20020 December 2023 Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications 05000298/LER-2022-002-01, Manual Core Spray Injection to Restore Skimmer Surge Tank Level2023-06-29029 June 2023 Manual Core Spray Injection to Restore Skimmer Surge Tank Level 05000298/LER-2022-004-01, 1 for Cooper Nuclear Station, Manual Reactor Scram and Group I Isolation Due to Main Turbine Bypass Valve Failing Open2023-05-11011 May 2023 1 for Cooper Nuclear Station, Manual Reactor Scram and Group I Isolation Due to Main Turbine Bypass Valve Failing Open 05000298/LER-2023-001, Valve Test Failures Result in Condition Prohibited by Technical Specifications2023-05-0808 May 2023 Valve Test Failures Result in Condition Prohibited by Technical Specifications 05000298/LER-2022-004, Manual Reactor Scram and Group I Isolation Due to Main Turbine Bypass Valve Failing Open2023-02-14014 February 2023 Manual Reactor Scram and Group I Isolation Due to Main Turbine Bypass Valve Failing Open 05000298/LER-2022-003, Actuation of Reactor Protection System Initiates a Full Reactor Scram2023-01-11011 January 2023 Actuation of Reactor Protection System Initiates a Full Reactor Scram 05000298/LER-2022-002, Manual Core Spray Injection to Restore Skimmer Surge Tank Level2022-12-19019 December 2022 Manual Core Spray Injection to Restore Skimmer Surge Tank Level 05000298/LER-2022-001, Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications Limit2022-07-20020 July 2022 Secondary Containment Differential Pressure Perturbation Exceeds Technical Specifications Limit 05000298/LER-2021-003, Re Failure of High Pressure Coolant Injection Flow Indicating Switch Results in Condition Prohibited by Technical Specifications2021-12-27027 December 2021 Re Failure of High Pressure Coolant Injection Flow Indicating Switch Results in Condition Prohibited by Technical Specifications 05000298/LER-2016-0012017-09-27027 September 2017 De-Energized High Pressure Coolant Injection Auxiliary Lube Oil Pump Caused by Relay Failure Results in Loss of Safety Function and a Condition Prohibited by Technical Specifications, LER 16-001-01 for Cooper Nuclear Station Regarding De-Energized High Pressure Coolant Injection Auxiliary Lube Oil Pump Caused by Relay Failure Results in Loss of Safety Function, a Condition Prohibited by Tech Specs, and a 10 CFR Part 21 Report 05000298/LER-2017-0052017-08-17017 August 2017 Traversing In-core Probe In-shield Limit Switch Mounting Failure Results in Common Cause Inoperability of Independent Trains or Channels and Condition Prohibited by Technical Specifications, LER 17-005-00 for Cooper Nuclear Station Regarding Traversing In-core Probe In-shield Limit Switch Mounting Failure Results in Common Cause lnoperability of Independent Trains or Channels and Condition Prohibited by Technical Specifications 05000298/LER-2017-0042017-08-17017 August 2017 Torus to Drywell Vacuum Breaker Failure to Indicate Full Closed Causes Loss of Safety Function, LER 17-004-00 for Cooper Nuclear Station Regarding Torus to Drywall Vacuum Breaker Failure to Indicate Full Closed Causes Loss of Safety Function 05000298/LER-2017-0032017-07-24024 July 2017 Mispositioned Control Room Emergency Filter System Supply Fan Damper Causes Loss of Safety Function, LER 17-003-00 for Cooper Nuclear Station re Mispositioned Control Room Emergency Filter System Supply Fan Damper Causes Loss of Safety Function 05000298/LER-2017-0022017-04-27027 April 2017 Valve Test Failures Result in Condition Prohibited by Technical Specifications and a Loss of Safety Function, LER 17-002-00 for Cooper Nuclear Station Regarding Valve Test Failures Result in Condition Prohibited by Technical Specifications and a Loss of Safety Function 05000298/LER-2017-0012017-04-0505 April 2017 Residual Heat Removal Minimum Flow Valves OUt of Position Results in Loss of Safety Function and Condition Prohibited by Technical Specifications, LER 17-001-00 for Cooper Regarding Residual Heat Removal Minimum Flow Valves Out of Position Results in Loss of Safety Function and Condition Prohibited by Technical Specifications 05000298/LER-2016-0082017-01-0505 January 2017 Purchase and Installation of Incorrect Actuator Results in a Condition Prohibited by Technical Specifications, LER 16-008-00 for Cooper Nuclear Station Regarding Purchase and Installation of Incorrect Actuator Results in a Condition Prohibited by Technical Specifications 05000298/LER-2016-0062016-12-19019 December 2016 High Vibration on Control Room Emergency Filter System Fan Results in Inoperability and Loss of Safety Function, LER-16-006-00 for Cooper Nuclear Station Regarding High Vibration on Control Room Emergency Filter System Fan Results in Inoperability and Loss of Safety Function 05000298/LER-2016-0072016-12-19019 December 2016 Isolation of Shutdown Cooling due to Relay Maintenance Results in a Loss of Safety Function, LER 16-007-00 for Cooper Nuclear Station Regarding Isolation of Shutdown Cooling due to Relay Maintenance Results in a Loss of Safety Function 05000298/LER-2016-0042016-11-22022 November 2016 Closure of Multiple Main Steam Isolation Valves due to High Flow Signal, LER 16-004-00 for Cooper Nuclear Station Regarding Closure of Multiple Main Steam Isolation Valves due to High Flow Signal 05000298/LER-2016-0032016-11-0909 November 2016 Scaffold Construction Places Plant in a Condition Prohibited by Technical Specifications, LER 16-003-00 for Cooper Nuclear Station RE: Scaffold Construction Places Plant in a Condition Prohibited by Technical Specifications 05000298/LER-2016-0022016-06-27027 June 2016 De-Energized High Pressure Coolant Injection Auxiliary Lube Oil Pump Caused By Light Bulb Failure Results in Loss of Safety Function, LER 16-002-00 for Cooper Regarding De-Energized High Pressure Coolant Injection Auxiliary Lube Oil Pump Caused By Light Bulb Failure Results in Loss of Safety Function NLS2015063, Retraction of Licensee Event Report 2014-005-00, Lube Oil Leak Results in a Potential Condition Prohibited by Technical Specifications and a Potential Loss of Safety Function.2015-06-0909 June 2015 Retraction of Licensee Event Report 2014-005-00, Lube Oil Leak Results in a Potential Condition Prohibited by Technical Specifications and a Potential Loss of Safety Function. ML13149A1722013-05-26026 May 2013 E-mail from Micheal Mulligan to R.Guzman, Pilgrim Evacuation Plan Broken During Blizzard Nemo and Unenforced by the Nrc. NLS2013015, Special Report, Offgas Treatment System Charcoal Adsorbers Out of Service2013-01-29029 January 2013 Special Report, Offgas Treatment System Charcoal Adsorbers Out of Service NLS2008058, LER 08-S01-00 for Cooper Regarding Temporary Suspension of Security Measures Due to Tornado Warning2008-08-0505 August 2008 LER 08-S01-00 for Cooper Regarding Temporary Suspension of Security Measures Due to Tornado Warning 2024-06-06
[Table view] |
Reported lessons learned are incorporated into the licensing process and fed back to industry. Send 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 Affairs, NEOB-10202, (3150-0104), Office of Management and 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.
PLANT STATUS
Cooper Nuclear Station (CNS) was in Mode 5, Refueling, at 0 percent power, at the time of the event.
BACKGROUND
The safety objective of the Residual Heat Removal (RHR) system [EllS:BO] is to provide core cooling, in conjunction with other Emergency Core Cooling Systems, and to provide containment cooling as required during abnormal operational transients and postulated accidents. The RHR system consists of two heat exchangers [EllS:HX], four main system pumps [EIIS:P], and associated piping, valves [EIIS:V], controls and instrumentation. Irradiated fuel in the shutdown reactor core generates heat during the decay of fission products and increases the temperature of the reactor coolant. The decay heat must be removed to reduce the temperature of the reactor coolant to less than or equal to 212 degreeS Fahrenheit (F) in preparation for performing Refueling or Cold Shutdown maintenance operations, or the decay heat must be removed for maintaining the reactor in Hot Shutdown condition.
Shutdown Cooling (SDC) is a subsystem of RHR and is placed in operation during a normal reactor shutdown and cooldown. Reactor Coolant is pumped by the RHR main system pumps from recirculation loop 'A' through the RHR heat exchangers prior to returning to the reactor vessel through connections to their respective recirculation loop.
The relays used in the Primary Containment Isolation System (PCIS) logic are model CR120A industrial relays [EllS:RLY] manufactured by General Electric. The CR120A relay has a max voltage rating of 300 volts and is a small multi-circuit AC control relay. The relays are popular due to their small size and long mechanical life. CNS currently performs predictive maintenance plans on the relays to replace the coils on a 10-year frequency.
EVENT DESCRIPTION
On October 28, 2016, SDC isolation valves RHR-MO-17 and RHR-MO-18 were open with RHR Loop A in RHR SDC flush lineup, with an intention of placing RHR Loop A in SDC. The Alternate Decay Heat Removal (ADHR) system was maintaining Reactor Pressure Vessel (RPV) and Spent Fuel Pool temperature.
Work orders were created to replace twenty-seven PCIS relay coils, including relay coil for PCIS-REL-K27, in Refueling Outage (RE29). During testing after completion of the work order, it was identified that the PCIS-REL-K27 relay did not actuate as expected (delayed response). This led to a revision of the work order to replace the entire relay instead of just a coil replacement. This required more wires to be lifted and the relay to be removed from the DIN rail and replaced.
SDC was placed in service at 08:49 hours on October 28, 2016. Subsequently, during replacement of the PCIS-REL-K27 relay, the action of installing a new relay onto the shared plastic DIN rail disturbed the mounting rail in a manner that caused the 1-2 contact of the adjacent relay, PCIS-REL-K30, to open. This caused RHR-MO-17 to close, which actuated the logic to trip the running 'A' RHR pump. Operations declared A RHR SDC subsystems inoperable at 09:24 hours and entered Technical Specification (TS) Cooper Nuclear Station 05000- 298 2016
3. LER NUMBER
-007 -00 Reported lessons learned are incorporated into the licensing process and fed back to industry. Send 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 Affairs, NEOB-10202, (3150-0104), Office of Management and 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.
05000- 298 Cooper Nuclear Station -007 -00 2016 Limiting Condition for Operation (LCO) 3.9.7, Condition A, Required Action A.1, "Verify an alternate method of decay heat removal is available within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter;" entered TS LCO 3.9.7, Condition C, Required Action C.1, "Verify reactor coolant circulation by an alternate method within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of no reactor coolant circulation and once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter;" and also entered TS LCO 3.9.7, Condition C, Required Action C.2, "Monitor reactor coolant temperature hourly.
ADHR remained in service throughout the event and the plant remained aligned for natural circulation.
Spent fuel pool weir temperature monitoring was commenced to verify natural circulation. No increase in RPV temperature was observed and there was no impact to plant operations.
While SDC was out of service, PCIS relay K27 work was completed. SDC was declared operable at 05:30 hours on October 29, 2016, and TS LCO 3.9.7, Condition A was exited. The plant remained in TS LCO 3.9.7, Condition C, and aligned for Natural Recirculation, until SDC was placed in service-at 18:30 hours on October 29, 2016, at which time TS LCO 3.9.7, Condition C was exited.
BASIS FOR REPORT
This event is reportable in accordance with 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat. Event Notification 52327 was made to the Nuclear Regulatory Commission Operations Center per 10 CFR 50.72(b)(3)(v).
SAFETY SIGNIFICANCE
This is a Safety System Functional Failure because of the loss of the shutdown cooling function of the RHR system. The plant was in MODE 5 performing refueling activities and conducting an Operations with a Potential for Draining the Reactor Vessel activity. The shutdown cooling function of RHR was required to be operable per TS. The Division 1 RHR system was fully functional except for the isolation of RHR-17MV. During the loss of SDC, decay heat removal was being provided by the ADHR system.
The reactor coolant temperature did not change during the event. There were no actual safety consequences associated with this event. The potential safety consequences of this event were minimal due to the limited duration the condition existed and the redundant decay heat removal equipment which remained available.
CAUSE
The root cause is that CNS did not identify the risk from mechanical agitation during PCIS relay installation; therefore, the risk was not adequately evaluated or mitigated.
CORRECTIVE ACTIONS
To prevent recurrence, CNS will revise Procedure 0.50.5 to list the relays or other devices which could impact SDC when in service.
Reported lessons learned are incorporated into the licensing process and fed back to industry. Send 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 Affairs, NEOB-10202, (3150-0104), Office of Management and 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.
05000- 298 Cooper Nuclear Station - 007 - 00 2016
3. LER NUMBER
PREVIOUS EVENTS
On May 30, 2015, steam flashing in the SDC line occurred, creating pressure transients that caused RHR-MO-17 and RHR-MO-18 to close. The steam flashing occurred due to temperature in the SDC line being at or near saturation temperature causing localized boiling then void collapse with coolant being drawn from the reactor vessel thru the reactor recirculation system. This event was reported under LER 2015-004-00, Isolation of Shutdown Cooling Results in a Loss of Safety Function, dated July 29, 2015.
On October 14, 2012, flashing of the hot reactor coolant to steam occurred, causing a pressure spike that exceeded 72 psig. Consequently, RHR-MO-17 and RHR-MO-18 clbsed, isolating the RHR SDC loop. This event was reported under LER 2012-004-00, Isolation of Shutdown Cooling Results in Loss of Safety Function, dated December 6, 2012.
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05000298/LER-2016-001 | De-Energized High Pressure Coolant Injection Auxiliary Lube Oil Pump Caused by Relay Failure Results in Loss of Safety Function and a Condition Prohibited by Technical Specifications LER 16-001-01 for Cooper Nuclear Station Regarding De-Energized High Pressure Coolant Injection Auxiliary Lube Oil Pump Caused by Relay Failure Results in Loss of Safety Function, a Condition Prohibited by Tech Specs, and a 10 CFR Part 21 Report | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | 05000298/LER-2016-002 | De-Energized High Pressure Coolant Injection Auxiliary Lube Oil Pump Caused By Light Bulb Failure Results in Loss of Safety Function LER 16-002-00 for Cooper Regarding De-Energized High Pressure Coolant Injection Auxiliary Lube Oil Pump Caused By Light Bulb Failure Results in Loss of Safety Function | 10 CFR 50.73(a)(2)(v), Loss of Safety Function | 05000298/LER-2016-003 | Scaffold Construction Places Plant in a Condition Prohibited by Technical Specifications LER 16-003-00 for Cooper Nuclear Station RE: Scaffold Construction Places Plant in a Condition Prohibited by Technical Specifications | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | 05000298/LER-2016-004 | Closure of Multiple Main Steam Isolation Valves due to High Flow Signal LER 16-004-00 for Cooper Nuclear Station Regarding Closure of Multiple Main Steam Isolation Valves due to High Flow Signal | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | 05000298/LER-2016-005 | Implementation of Enforcement Guidance Memorandum 11-003, Revision 3, Causes Conditions Prohibited by Technical Specifications | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | 05000298/LER-2016-006 | High Vibration on Control Room Emergency Filter System Fan Results in Inoperability and Loss of Safety Function LER-16-006-00 for Cooper Nuclear Station Regarding High Vibration on Control Room Emergency Filter System Fan Results in Inoperability and Loss of Safety Function | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | 05000298/LER-2016-007 | Isolation of Shutdown Cooling due to Relay Maintenance Results in a Loss of Safety Function LER 16-007-00 for Cooper Nuclear Station Regarding Isolation of Shutdown Cooling due to Relay Maintenance Results in a Loss of Safety Function | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | 05000298/LER-2016-008 | Purchase and Installation of Incorrect Actuator Results in a Condition Prohibited by Technical Specifications LER 16-008-00 for Cooper Nuclear Station Regarding Purchase and Installation of Incorrect Actuator Results in a Condition Prohibited by Technical Specifications | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
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