06-13-2017 | On April 15, 2017 at approximately 10:56 am, with the plant at 0% power in Mode 4 (Shutdown), while performing a plant shutdown procedure the "D" outboard Main Steam Isolation Valve ( MSIV), AO-2- 86D was functionally tested. The Monticello Nuclear Generating Plant ( MNGP) Technical Specifications (TS) Surveillance Requirement (SR) 3.6.1.3.6 requires that the isolation time of each MSIV is > 3 seconds and ime was measured at approximately 40.7 seconds. The valve was declared inoperable and subsequently repaired. The failure was attributed to the air pack pilot valves.
This component failure is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS 3.6.1.3 " Primary Containment Isolation Valves," since AO-2-86D may have been inoperable for greater than the TS 3.6.1.3, Required Action A.1, Completion Time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to isolate a main steam line, and the Completion Time for TS 3.6.1.3, Required Action F, to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> when the completion time of A.1 is not met. There were minimal safety consequences associated with the condition since the primary containment isolation function was maintained. |
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Category:Letter
MONTHYEARML24025A9362024-01-31031 January 2024 Exemption from Select Requirements of 10 CFR Part 73 (EPID L-2023-LLE-0055 (Security Notifications, Reports, and Recordkeeping and Suspicious Activity Reporting)) IR 05000263/20230042024-01-31031 January 2024 Integrated Inspection Report 05000263/2023004 ML24024A0722024-01-24024 January 2024 Independent Spent Fuel Storage Installation, Onticello, Supplement to Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation IR 05000263/20244012024-01-22022 January 2024 Information Request for the Cyber-Security Baseline Inspection, Notification to Perform Inspection 05000263/2024401 L-MT-23-054, Subsequent License Renewal Application Supplement 82024-01-11011 January 2024 Subsequent License Renewal Application Supplement 8 L-MT-23-047, License Amendment Request: Revision to the MNGP Pressure Temperature Limits Report to Change the Neutron Fluence Methodology and Incorporate New Surveillance Capsule Data2023-12-29029 December 2023 License Amendment Request: Revision to the MNGP Pressure Temperature Limits Report to Change the Neutron Fluence Methodology and Incorporate New Surveillance Capsule Data L-MT-23-056, Subsequent License Renewal Application Response to Request for Additional Information and Request for Confirmation of Information - Set 1 Part 22023-12-18018 December 2023 Subsequent License Renewal Application Response to Request for Additional Information and Request for Confirmation of Information - Set 1 Part 2 ML23349A0572023-12-15015 December 2023 and Independent Spent Fuel Storage Installation, Revision to Correspondence Service List for Northern States Power - Minnesota IR 05000263/20234022023-12-13013 December 2023 Security Baseline Inspection Report 05000263/2023402 L-MT-23-042, 2023 Annual Report of Changes in Emergency Core Cooling System Evaluation Models Pursuant to 10 CFR 50.462023-12-11011 December 2023 2023 Annual Report of Changes in Emergency Core Cooling System Evaluation Models Pursuant to 10 CFR 50.46 L-MT-23-052, Subsequent License Renewal Application Supplement 72023-11-30030 November 2023 Subsequent License Renewal Application Supplement 7 L-MT-23-051, Update to the Technical Specification Bases2023-11-28028 November 2023 Update to the Technical Specification Bases L-MT-23-049, Subsequent License Renewal Application Response to Request for Additional Information and Request for Confirmation of Information - Set 12023-11-21021 November 2023 Subsequent License Renewal Application Response to Request for Additional Information and Request for Confirmation of Information - Set 1 ML23319A3182023-11-15015 November 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation IR 05000263/20230032023-11-13013 November 2023 Integrated Inspection Report 05000263/2023003 and 07200058/2023001 L-MT-23-043, 10 CFR 50.55a(z)(1) Request Regarding OMN-17, Revision 1. VR-092023-11-13013 November 2023 10 CFR 50.55a(z)(1) Request Regarding OMN-17, Revision 1. VR-09 L-MT-23-038, License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.62023-11-10010 November 2023 License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6 L-MT-23-046, Subsequent License Renewal Application Response to Request for Additional Information Round 2 - Set 12023-11-0909 November 2023 Subsequent License Renewal Application Response to Request for Additional Information Round 2 - Set 1 ML23291A1102023-10-23023 October 2023 Environmental Audit Summary and RCIs and RAIs ML23285A3062023-10-12012 October 2023 Implementation of the Fleet Standard Emergency Plan for the Monticello Nuclear Generating Plant and the Prairie Island Nuclear Generating Plant L-MT-23-041, Subsequent License Renewal Application Response to Request for Confirmation of Information Set 22023-10-0303 October 2023 Subsequent License Renewal Application Response to Request for Confirmation of Information Set 2 L-MT-23-037, Subsequent License Renewal Application Response to Request for Additional Information Set 32023-09-22022 September 2023 Subsequent License Renewal Application Response to Request for Additional Information Set 3 ML23262B0372023-09-19019 September 2023 Response to NRC Request for Additional Information Regarding the 2023 Monticello and Prairie Island Plant Decommissioning Funding Status Reports ML23248A2092023-09-18018 September 2023 Proposed Alternative VR-11 to the Requirements of the ASME OM Code Associated with Periodic Verification Testing of MO-2397, Reactor Water Cleanup Inboard Isolation Valve ML23256A1682023-09-13013 September 2023 Independent Spent Fuel Storage Installation and Monticello Nuclear Generating Plant - Voluntary Security Clearance Program 2023 Insider Threat Program Self-Inspection IR 05000263/20230102023-09-0707 September 2023 Commercial Grade Dedication Inspection Report 05000263/2023010 L-MT-23-036, Subsequent License Renewal Application Response to Request for Additional Information Set 2 and Supplement 62023-09-0505 September 2023 Subsequent License Renewal Application Response to Request for Additional Information Set 2 and Supplement 6 ML23214A2412023-08-31031 August 2023 Letter: Aging Management Audit - Monticello Unit 1 - Subsequent License Renewal Application IR 05000263/20230052023-08-30030 August 2023 Updated Inspection Plan for Monticello Nuclear Generating Plant (Report 05000263/2023005) L-MT-23-035, Subsequent License Renewal Application Supplement 52023-08-28028 August 2023 Subsequent License Renewal Application Supplement 5 ML23241A9732023-08-21021 August 2023 Request for Scoping Comments Concerning the Environmental Review of Monticello Nuclear Generating Plant, Unit 1, Subsequent License Renewal Application (Docket No. 50-263) L-MT-23-034, Subsequent License Renewal Application Response to Request for Additional Information Set 12023-08-15015 August 2023 Subsequent License Renewal Application Response to Request for Additional Information Set 1 ML23222A0122023-08-10010 August 2023 Independent Spent Fuel Storage Installation and Monticello Nuclear Generating Plant - Changes in Foreign Ownership, Control or Influence ML23215A1312023-08-0909 August 2023 License Renewal Regulatory Audit Regarding the Environmental Review of the Subsequent License Renewal Application IR 05000263/20230022023-08-0707 August 2023 Plantintegrated Inspection Report 05000263/2023002 L-MT-23-028, 2023 Refueling Outage 90-Day Inservice Inspection (ISI) Summary Report2023-07-31031 July 2023 2023 Refueling Outage 90-Day Inservice Inspection (ISI) Summary Report L-MT-23-032, 10 CFR 50.55a(z)(2) Request Regarding MO-2397, VR-112023-07-31031 July 2023 10 CFR 50.55a(z)(2) Request Regarding MO-2397, VR-11 ML23198A0412023-07-28028 July 2023 LRA Availability Letter ML23206A2342023-07-25025 July 2023 Independent Spent Fuel Storage Installation, and Monticello Nuclear Generating Plant, Changes in Foreign Ownership, Control or Influence ML23201A0352023-07-24024 July 2023 Notification of an NRC Biennial Licensed Operator Requalification Program Inspection and Request for Information ML23202A0032023-07-21021 July 2023 Independent Spent Fuel and Independent Spent Fuel Storage Installation, Monticello Nuclear Generating Plant, Submittal of Quality Assurance Topical Report (NSPM-1) L-MT-23-031, Subsequent License Renewal Application Supplement 4 and Responses to Request for Confirmation of Information - Set 12023-07-18018 July 2023 Subsequent License Renewal Application Supplement 4 and Responses to Request for Confirmation of Information - Set 1 ML23195A1732023-07-14014 July 2023 Revision of Standard Practice Procedures Plan IR 05000263/20235012023-07-13013 July 2023 Emergency Preparedness Inspection Report 05000263/2023501 2024-01-31
[Table view] Category:Licensee Event Report (LER)
MONTHYEAR05000263/LER-2017-0062018-01-12012 January 2018 Loss of Reactor Protection System Scram Function During Main Steam Isolation Valve and Turbine Stop Valve Channel Functional Tests due to Use of a Test Fixture, LER 17-006-00 for Monticello Regarding Loss of Reactor Protection System Scram Function During Main Steam Isolation Valve and Turbine Stop Valve Channel Functional Tests Due to Use of a Test Fixture 05000263/LER-2017-0052017-09-20020 September 2017 Diesel Generator Emergency Service Water System Automatic Transfer to Alternate Shutdown Panel, LER 17-005-00 for Monticello Nuclear Generating Plant Regarding Diesel Generator Emergency Service Water System Automatic Transfer to Alternate Shutdown Panel 05000263/LER-2015-0042017-08-22022 August 2017 Past Inoperability of Turbine Stop Valve Scram Function Exceeded Technical Specification Requirements, LER 15-004-01 for Monticello Regarding Past Inoperability of Turbine Stop Valve Scram Function Exceeded Technical Specification Requirements 05000263/LER-2017-0042017-08-16016 August 2017 High Pressure Coolant Injection Steam Stop Valve Failed to Open During Test, LER 17-004-00 for Monticello Regarding High Pressure Coolant Injection Steam Stop Valve Failed to Open During Test 05000263/LER-2017-0032017-06-14014 June 2017 Main Steam Isolation Valve Leakage Exceeds Technical Specification Limits, LER 17-003-00 for Monticello Regarding Main Steam Isolation Valve Leakage Exceeds Technical Specification Limits 05000263/LER-2017-0012017-06-13013 June 2017 Reactor Scram and Group II Isolation Due to 11 Reactor Feed Pump (RFP) Removal from Service with 12 RFP Isolated, LER 17-001-00 for Monticello Regarding Reactor Scram and Group II Isolation Due to 11 Reactor Feed Pump (RFP) Removal from Service with 12 RFP Isolated 05000263/LER-2017-0022017-06-13013 June 2017 Main Steam Isolation Valve Closure Time Outside of Technical Specification Requirements, LER 17-002-00 for Monticello Nuclear Generating Plant Regarding Main Steam Isolation Valve Closure Time Outside of Technical Specification Requirements 05000263/LER-2016-0032017-05-25025 May 2017 HPCI Declared Inoperable Due to Excessive Water Level in Turbine, LER 16-003-01 for Monticello Regarding HPCI Declared Inoperable Due to Excessive Water Level in Turbine 05000263/LER-2016-0012017-05-25025 May 2017 High Pressure Coolant Injection System Cracked Pipe Nipple Caused Oil Leak, LER 16-001-02 for Monticello Regarding High Pressure Coolant Injection System Cracked Pipe Nipple Caused Oil Leak 05000263/LER-2016-0022016-09-30030 September 2016 Inadequate Appendix R Fire Barrier Impacts Safe Shutdown Capability, LER 16-002-00 for Monticello Regarding Inadequate Appendix R Fire Barrier Impacts Safe Shutdown Capability 05000263/LER-2014-0032016-07-13013 July 2016 Torus to Drywell Vacuum Breaker Dual Indication During Testing, LER 14-003-01 for Monticello Nuclear Generating Plant RE: Torus to Drywell Vacuum Breaker Dual Indication During Testing 05000263/LER-2014-0022016-07-13013 July 2016 Torus to Drywell Vacuum Breaker Did Not Indicate Closed During Testing, LER 14-002-01 for Monticello Regarding Torus to Drywell Vacuum Breaker Did Not Indicate Closed During Testing 05000263/LER-2015-0072016-01-21021 January 2016 Loss of Residual Heat Removal Capability, LER 15-007-00 for Monticello Regarding Loss of Residual Heat Removal Capability 05000263/LER-2015-0062016-01-21021 January 2016 - Reactor Scram due to Group 1 Isolation from Foreign Material in the Main Steam Flow Instrument Line, LER 15-006-00 for Monticello Regarding Reactor Scram due to Group 1 Isolation from Foreign Material in the Main Steam Flow Instrument Line ML1015505712009-09-12012 September 2009 Event Notification for Monticello on State Offsite Notification Due to Not Meeting Permit Requirements L-MT-05-035, LER 50-004-00 for Monticello Nuclear Generating Plant Regarding Voluntary LER for Control Rod Drive Insert Line Leakage2005-05-12012 May 2005 LER 50-004-00 for Monticello Nuclear Generating Plant Regarding Voluntary LER for Control Rod Drive Insert Line Leakage ML0216100952002-05-15015 May 2002 LERs 02-001-01 & 02-002-01 for Monticello Nuclear Generating Plant Re Mechanical Pressure Regulator Failure Causes Reactor Scram & Application of Instrument Deviation Acceptance Criteria Allowed As-Found Settings to Be Outside Tech Spec Val 2018-01-12
[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 internet e-mail to Infocollects.Resource@nrc.gov, arid 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.
EVENT DESCRIPTION
On April 15, 2017 at approximately 10:56 AM, with the plant at 0% power in Mode 4 (Shutdown), while performing a plant shutdown procedure the "D" outboard Main Steam [SB] Isolation Valve (MSIV) [ISV] AO-2-86D was functionally tested. The Monticello Nuclear Generating Plant (MNGP) Technical Specifications (TS) Surveillance Requirement (SR) 3.6.1.3.6 requires that the isolation time of each MSIV is > 3 seconds and MSIV closing time was measured at approximately 40.7 seconds. The valve was declared inoperable and repaired during the refueling outage.
During the test AO-2-86D was given a close signal via the control room hand switch [HS]. The valve delayed to start of closing by approximately 35 seconds and then proceeded to close normally in about 5 seconds.
On site troubleshooting activities commenced and determined that the Hiller Co. air pack pilot valves (Model No. C10010A — called V1 and V3) were the cause of the closure delay. The V1 pilot valve was found to be stuck in a closed position. The air pack was sent to the vendor to perform more inspection, testing and repair. The vendor discovered scoring on the piston rod and mounting plate of the booster assembly on the V1 pilot valve. This is evidence of binding and misalignment that caused the valve to not shuttle when called upon. The V3 pilot valve was shown through data analysis to have delayed movement during the event. The air pack was repaired by the vendor replacing the solenoid cluster and the pilot valves, and the boosters were rebuilt.
The air pack was returned to MNGP, reinstalled and AO-2-86D completed satisfactory testing on 5/5/2017.
A previous similar failure occurred on November 23, 2015 when AO-2-86D closed in 130 seconds after delaying start of closure. The troubleshooting of that failure indicated the plunger sticking or binding of an in-series solenoid valve was the cause of the failure to close in the required TS limits. Upon further review, this MSIV closure time failure is now attributed to the AO-2-86D air pack pilot valves failing to function as designed.
EVENT ANALYSIS
The event was determined to be reportable in accordance with 10 CFR 50.73 (a)(2)(i)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications." Specifically, this component failure is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (F-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 205550001, or by Internet e-mail to 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, arid a person is not required to respond to, the information collection.
05000-263 2017 prohibited by TS 3.6.1.3 "Primary Containment Isolation Valves," since AO-2-86D was inoperable for greater than the TS 3.6.1.3, Required Action A.1, Completion Time of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to isolate a main steam line, and the Completion Time for TS 3.6.1.3, Required Action F, to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> when the completion time of A.1 is not met.
This event is not classified as a safety system functional failure as the inboard valve was fully operational.
SAFETY SIGNIFICANCE
There were minimal safety consequences associated with the condition. The inboard MSIV on Main Steam line "D" (AO-2-80D) was tested for both leak rate and closing time over the past cycle and each test was completed satisfactorily. Additionally, the inboard MSIVs are a different design and do not utilize Hiller Co. air pack pilot valves. Therefore, the primary containment isolation capability of the main steam lines remained operable which ensured the required isolation safety function was maintained.
CAUSE
The air pack assembly for AO-2-86D was sent to the vendor to perform an inspection, teardown and functional testing of the air pack. In addition to minor leaking at several fittings and around the solenoid valves and manifolds, the vendor discovered scoring on the V1 piston rod and mounting plate of the booster assembly, metallic pieces in the pilot valve body and fretting on the edges of the elastomeric valve seat. Some small black particles (foreign material) were also noted in the V3 pilot valve body and the solenoid manifold ports. Both the V1 and V3 valves must function correctly for the MSIV to close within the TS required time.
The cause of the event was attributed to a failure of both of the pilot valves. As described above the V1 pilot valve was found to be stuck in a closed position and score marks were found on the stem and bottom of the valve shaft. This is evidence of binding and misalignment that caused the valve to not shuttle when called upon.
Regarding pilot valve V3, NSPM performed a more detailed review of data from the April 15, 2017 event and previous operations of AO-2-86D. The review indicated that the MSIV Air supply pressure during the "D" MSIV delayed closure event on November 23, 2015 shows a pressure dip that corresponds to a partial opening of V3 prior to full close. The April 15, 2017 event does not show the same pressure dip, indicating that the V3 valve had delayed movement (sticking) prior to opening.
002 - 00 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 Internet e-mail to used to impose an information collection does riot display a currently valid OMB control number, the NRC may riot conduct or sponsor, arid a person is not required to respond to, the information collection.
7 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
Monticello Nuclear Generating Plant 05000-263 2017 - 00 AO-2-86D was fully functional (closure time and leak rate) from April 14, 2014 to 1R27 as demonstrated by 1R26 As-left testing, cycle 27 On-line testing and 1R27 As-found testing. During 1R27, the AO-2-86D air pack for the AO-2-86D valve actuator was replaced thus introducing the failure mechanism (delay to close) observed twice, once on November 23, 2015 (two minute closure time) and again on April 15, 2017 (forty second closure time).
CORRECTIVE ACTION
The air pack assembly for AO-2-86D was sent to the vendor for repair. The vendor replaced the solenoid cluster, the pilot valves and the boosters were rebuilt. After the air pack was returned to MNGP, the air pack was bench tested to verify proper cycling of the assembly. The air pack was returned to MNGP, reinstalled and AO-2-86D completed satisfactory testing on May 5, 2017.
To reduce the risk of future failures NSPM is planning to develop a bench testing procedure for air pack assemblies prior to their installation in an MSIV.
PREVIOUS SIMILAR EVENTS
In LER 2015-006-00, NSPM reported that a previous similar failure occurred on November 23, 2015 when AO-2-86D closed after delaying by approximately 130 seconds. The troubleshooting from that event indicated that an in-series solenoid valve plunger sticking or binding was the cause of the failure to close within the required TS limits. Upon further review, as discussed above, this MSIV closure time failure is now attributed to the AO-2-86D air pack pilot valves failing to function as designed.
ADDITIONAL INFORMATION
The Institute of Electrical and Electronics Engineer codes for equipment are denoted by [XX].
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