In February and March 2017, three Main Steam Safety Relief Valve ( SRV) body assemblies (main body and pilot assembly) and the remaining five SRV pilot assemblies were tested at National Technical Systems Laboratories (formerly Wyle Laboratories). These SRVs had been removed from Cooper Nuclear Station during Refueling Outage 29 in the Fall of 2016. One SRV pilot assembly failed the as-found lift pressure testing; another SRV pilot assembly was conservatively considered a failure due to lack of as-found lift pressure test data since it was inadvertently disassembled prior to performing the as-found lift pressure test.
There were two causes for the failures. One of the SRV pilot assemblies failed due to corrosion bonding; the other SRV pilot assembly failed due to a lack of a barrier to prevent inadvertent disassembly of the SRV pilot prior to testing.
Although the Technical Specifications limits related to the set point lift pressures of the SRV pilot valve assemblies were exceeded, an analysis indicates that the design basis pressures to ensure safety of the reactor vessel and its pressure related appurtenances were not challenged. Public safety was not at risk. Safety to plant personnel and plant equipment was not at risk. |
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Category:Letter
MONTHYEARML23334A2012024-01-0303 January 2024 Issuance of Amendment No. 274 Revision to Technical Specifications to Adopt TSTF-551, Revision 3, Revise Secondary Containment Surveillance Requirements ML23311A1122023-11-0909 November 2023 Project Manager Assignment 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 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 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 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 ML23102A0282023-04-19019 April 2023 U.S. Nuclear Regulatory Commission Presentation at the May 8, 2023, Brownville Village Meeting IR 05000298/20230012023-04-17017 April 2023 Integrated Inspection Report 05000298/2023001 ML23060A1582023-03-0808 March 2023 Design Basis Assurance Inspection (Programs) Inspection Report 05000298/2023001 IR 05000298/20220062023-03-0101 March 2023 Annual Assessment Letter for Cooper Nuclear Station Report 05000298/2022006 ML23041A1622023-02-10010 February 2023 Licensed Operator Positive Fitness-for-Duty Test Request for Additional Information IR 05000298/20220042023-01-30030 January 2023 Integrated Inspection Report 05000298/2022004 IR 05000298/20220112022-12-23023 December 2022 License Renewal Phase 4 Inspection Report 05000298/2022011 ML22286A2072022-11-30030 November 2022 Issuance of Amendment No. 272 Revision to Technical Specifications to Adopt TSTF-554, Revision 1, Revise Reactor Coolant Leakage Requirements IR 05000298/20220032022-10-27027 October 2022 Integrated Inspection Report 05000298/2022003 ML22304A0052022-10-26026 October 2022 Surveillance Capsule Location (Re-insertion Into the Reactor Vessel) IR 05000298/20223022022-10-20020 October 2022 NRC Initial Operator Licensing Examination Approval 05000298/2022302 ML22276A1562022-10-0505 October 2022 Notification of Commercial Grade Dedication Inspection 05000298/2023011 and Request for Information IR 05000298/20224022022-09-29029 September 2022 NRC Security Inspection Report 05000298/2022402 (Full Report) IR 05000298/20220052022-08-18018 August 2022 Updated Inspection Plan for Cooper Nuclear Station (Report 05000298 2022005) IR 05000298/20223012022-08-10010 August 2022 NRC Examination Report 05000298/2022301 IR 05000298/20220022022-07-28028 July 2022 Integrated Inspection Report 05000298/2022002 ML22200A2772022-07-21021 July 2022 Correction to Proposed Inservice Testing Alternative RS-01, Revision of Error in Safety Evaluation ML22152A1232022-07-18018 July 2022 Issuance of Amendment No. 271 Request for Exception from Certain Primary Containment Leak Rate Testing Requirements IR 05000298/20224012022-06-29029 June 2022 Security Baseline Inspection Report 05000298/2022401 IR 05000298/20224032022-06-28028 June 2022 Security Baseline Inspection Report 05000298/2022403 IR 05000298/20220102022-06-16016 June 2022 Triennial Fire Protection Inspection Report 05000298/2022010 ML22140A1612022-06-0808 June 2022 Proposed Inservice Inspection Alternative RR5-01 Revision 1 ML22147A1122022-06-0101 June 2022 NRC Initial Operator Licensing Examination Approval 05000298/2022301 ML22111A1382022-05-13013 May 2022 Proposed Inservice Testing Alternative RS-01, Revision 0 IR 05000298/20220012022-04-28028 April 2022 Integrated Inspection Report 05000298/2022001 IR 05000298/20224042022-04-13013 April 2022 Material Control and Accounting Program Inspection Report 05000298/2022404 - (Public) ML22084A6032022-04-0404 April 2022 Notification of NRC Evaluations of Changes, Tests and Experiments Inspection 05000298/2022002 and Request for Information ML22090A2892022-04-0101 April 2022 John Larson'S Invitation to Participate in the 8th Nuclear Regulatory Commission'S Workshop on Vendor Oversight ML22045A0012022-03-31031 March 2022 Proposed Inservice Inspection Alternative RI5- 02 Revision 3 IR 05000298/20210062022-03-0202 March 2022 Annual Assessment Letter for Cooper Nuclear Station (Report 05000298/2021006) IR 05000298/20210042022-01-24024 January 2022 Integrated Inspection Report 05000298/2021004 ML21350A0582021-12-21021 December 2021 Withdrawal of an Amendment Request ML21340A2362021-12-20020 December 2021 Issuance of Amendment No. 270 Adoption of Technical Specifications Task Force Traveler TSTF-582, Revision 0, RPV WIC Enhancements 2024-01-03
[Table view] Category:Licensee Event Report (LER)
MONTHYEAR05000298/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-2017-0042017-08-17017 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-2017-0052017-08-17017 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-2017-0032017-07-24024 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-2016-0072016-12-19019 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-2016-0062016-12-19019 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-2016-0042016-11-22022 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 2017-09-27
[Table view] |
Reported lessons learned are incorporated into the licensing process and fed back to industry Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U S Infocollects Resource@nrc gov, and to the Desk Officer, Office of Information and Regulatory 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.
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PLANT STATUS
Cooper Nuclear Station (CNS) was in Mode 1, Power Operations, 100 percent power, at the time of discovery i.e., February 28, 2017.
BACKGROUND
The pressure relief system includes three American Society of Mechanical Engineers code safety valves (SV) [EllS:SB] and eight safety relief valves (SRV) [El IS:RV], all of which are located on the main steam lines [EIIS:SB] within the drywell [EllS:NH], between the reactor vessel [EIIS:RPV] and the first main steam isolation valve [EllS:ISV]. The SVs provide protection against over pressurization of the nuclear system and discharge directly into the interior space of the drywell. The SRVs discharge to the suppression pool and provide three main functions: overpressure relief operation to limit the pressure rise and prevent safety valve opening, overpressure safety operation to prevent nuclear system over pressurization, and depressurization operation (opened automatically or manually) as part of the emergency core cooling system [EllS:BJ, BM, BO].
Technical Specifications (TS) Limiting Condition for Operation 3.4.3 requires the safety function of seven SRVs and three SVs to be operable. The nominal set pressure and tolerances for these valves are established in CNS TS Surveillance Requirement (SR) 3.4.3.1.
The SRVs installed at CNS are Target Rock Model 7567F, two-stage, pilot-actuated valves with pilot assemblies comprised of Stellite 21 pilot discs and Stellite 6B pilot body seats. The pilot assemblies had been in continuous service since the Fall of 2014.
In 2015, five of eight SRV pilot valve assemblies removed in the Fall of 2014 failed to lift within the TS lift setpoint requirements. The cause of these failures was determined to be corrosion bonding. Corrective actions included submitting a TS change to the Nuclear Regulatory Commission requesting setpoint changes as noted in EE 10-053, "Margin Evaluation for SRVs Out-of-Service," and reducing the number of operable SRVs from seven to five. This action has not been completed.
EVENT DESCRIPTION
Three Main Steam SRV body assemblies (main body and pilot assembly) and the remaining five SRV pilot assemblies, removed during Refueling Outage (RE) 29 in the Fall of 2016, were tested at National Technical Systems Laboratories (NTS; formerly Wyle Laboratories). One SRV pilot assembly failed the as-found lift pressure testing; another SRV pilot assembly was conservatively considered a failure due to lack of as-found lift pressure test data since it was disassembled prior to performing the as-found lift pressure test.
The pressure setpoint for SRV pilot assembly serial number 377 is 1090 psig. The TS SR 3.4.3.1 as- found limit of acceptance is 1090 +1- 3%. The first actual lift pressure of this SRV pilot assembly was recorded as 1127 psig. Second and third lifts were performed with the results being 1113 psig and 1106 psig respectively.
Cooper Nuclear Station 05000- 298 2017
3. LER NUMBER
Reported lessons learned are incorporated into the licensing process and fed back to industry Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U S Infocollects Resource@nrc gov, and to the Desk Officer, Office of Information and Regulatory 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 -00 2017 - 002 SRV pilot assembly serial number 382 was inadvertently disassembled by Target Rock technicians prior to the performance of the as-found lift test, thus due to the absence of as-found test data, the results were conservatively considered a failure of the ±3% setpoint criteria.
BASIS FOR REPORT
CNS is reporting this event as an operation or condition prohibited by plant TS per 10 CFR 50.73(a)(2)(i)(B), and also as a condition that could have prevented the fulfillment of the safety function of structures or systems as defined under 10 CFR 50.73(a)(2)(v).
An engineering analysis demonstrated that the reactor vessel would not be challenged during an overpressure event. In addition, an analysis determined that the existing Minimum Critical Power Ratio (MCPR) operating limit would have protected the MCPR safety limit in the event of an anticipated operational occurrence. As such, this event will not be counted as a Safety System Functional Failure to the Nuclear Regulatory Commission performance indicator since no loss of safety function occurred.
SAFETY SIGNIFICANCE
Although the TS SR related to the set point lift pressures of the SRV pilot valve assemblies was exceeded, an analysis of this event indicates that the design basis pressures to ensure safety of the reactor vessel and its pressure related appurtenances were not challenged. Public safety was not at risk. Safety to plant personnel and plant equipment was not at risk.
CAUSE
Corrosion bonding was determined to be the cause of SRV pilot serial number 377 failing its lift test.
The lack of a barrier to prevent inadvertent disassembly of SRV pilot serial number 382 prior to the as found testing resulted in the conservative failure of the ±3% setpoint criteria. The conservative failure of serial number 382 eliminated margin for the remaining SRV pilots.
CORRECTIVE ACTIONS
As reported in LER 2015-001-01, presuming that no technical reason is discovered to prevent the following, submit a TS change to the Nuclear Regulatory Commission requesting setpoint changes as noted in EE 10-053; NEDC-33 543P, Revision 0, Class III, DRF 0000-0103-4647, dated February 2010; GE-H NEDC-33620P, Revision 0, May 2011; and GE-H, report 002N5242.R0, entitled, Cooper Cycle 28 SRV Set Point Study. This action has not been completed.
In addition, CNS will ensure that Target Rock's procurement documentation includes a mechanism to prevent the inadvertent disassembly of a CNS SRV pilot valve prior to performance of the as-found setpoint testing.
Reported lessons learned are incorporated into the licensing process and fed back to industry Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U S 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 -00 2017 - 002
PREVIOUS EVENTS
Licensee Event Report (LER) 2015-001-01 — On January 26 and February 11, 2015, five of eight Target Rock SRV pilot valves assemblies failed to lift within TS lift setpoint requirements. National Technical Systems, formerly Wyle Laboratories, performed this testing. The pressure setpoint for SRV pilot assembly serial number 385 was 1090 +/-3%; it lifted at 1124 psig. The pressure setpoint for SRV pilot assembly serial number 386 was 1100 +/-3%; it lifted at 1192 psig. The pressure setpoint for SRV pilot assembly serial number 1242 was 1090 +/- 3%; it lifted at 1267.7 psig. The pressure setpoint for SRV pilot assembly serial number 1243 was 1100 +/- 3%; it lifted at 1139 psig. The pressure setpoint for SRV pilot assembly serial number 1241 was 1090 psig +/-3%; it lifted at 1138 psig. Subsequent informational lifts were performed for all of the failed assemblies and were within TS pressure setpoint tolerances. The direct cause of the failures was corrosion bonding.
within TS lift setpoint requirements. Wyle Laboratories performed this testing. The pressure setpoint of the failed pilot assembly was 1090 +/- 32.7 psig; it lifted at 1199 psig. Two subsequent informational lifts were performed for the SRV pilot assembly and were within the TS pressure setpoint tolerances. The mechanistic cause was the same as reported in previous LERs, pilot disc-to-seat corrosion bonding.
lift within TS lift setpoint requirements. Wyle Laboratories performed this testing. The pressure setpoint for the first pilot assembly is 1100 +/- 33.0 psig; the SRV pilot assembly lifted at 1166 psig. The pressure setpoint for the second pilot assembly is 1090 +/- 32.7 psig; it lifted at 1139 psig. Two subsequent informational lifts were performed for both SRV pilot assemblies and were within the TS pressure setpoint tolerances. The mechanistic cause was the same as reported in previous LERs, pilot disc-to-seat corrosion bounding.
Wyle Laboratories identified that one of eight SRV pilot assemblies failed as-found pressure setpoint testing. The SRV pilot assembly lifted at 1165 psig, outside its TS setpoint tolerance of 1100 +/- 33.0 psig. The mechanistic cause was pilot disc-to-seat corrosion bounding between the Stellite 21 pilot disc and Stellite 6B pilot body seat to cause the SRV pilot assembly to lift outside its TS setpoint tolerance.
performed at Wyle Laboratories identified that one of eight SRV pilot valve assemblies failed to lift within its TS lift setpoint of 1090 +/- 32.7 psig. The failure was a result of sufficient corrosion bonding between the SRV pilot valve assembly Stellite 21 disc and the pilot valve Stellite 6B body seat to cause the SRV pilot valve to lift outside its TS setpoint tolerance.