03-23-2016 | Unit 1 reactor enclosure secondary containment integrity was briefly declared inoperable when both doors on a reactor enclosure 201' elevation pipe tunnel airlock were simultaneously opened. The cause of the event was a degraded closing mechanism on the airlock inboard door. The airlock doors were closed to restore reactor enclosure secondary containment integrity. The degraded inboard door closing mechanism was repaired. |
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Category:Letter
MONTHYEARIR 05000352/20243012024-02-0202 February 2024 Initial Operator Licensing Examination Report 05000352/2024301 and 05000353/2024301 IR 05000352/20230042024-01-31031 January 2024 Integrated Inspection Report 05000352/2023004 and 05000353/2023004 IR 05000352/20240112024-01-31031 January 2024 Information Request to Support Post-Approval Site Inspection for License Renewal; Inspection Report 05000352/2024011 ML24026A2962024-01-26026 January 2024 Supplement to License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System (PPS)- Syrs, . ML24004A0342024-01-17017 January 2024 Exemption from Select Requirements of 10 CFR Part 73 (EPID L-2023-LLE-0026 (Security Notifications, Reports, and Recordkeeping and Suspicious Activity Reporting)) IR 05000352/20230102024-01-11011 January 2024 Age-Related Degradation Report 05000352/2023010 and 05000353/2023010 IR 05000352/20234012023-12-21021 December 2023 Cybersecurity Inspection Report 05000352/2023401 and 05000353/2023401 ML23321A2362023-12-14014 December 2023 Issuance of Amendment Nos. 262 and 224 Adoption of TSTF-477, Revision 3 and Associated Technical Specification Changes 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 ML23333A2182023-11-29029 November 2023 Operator Licensing Examination Approval ML23325A2062023-11-21021 November 2023 Supplement to License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System ML23313A0432023-11-13013 November 2023 Summary of Regulatory Audit in Support of Amendment Request for Control Room Air Conditioning Technical Specifications ML23317A1192023-11-10010 November 2023 Constellation Energy Generation, LLC - 2023 Annual Report - Guarantees of Payment of Deferred Premiums IR 05000352/20230032023-10-27027 October 2023 Integrated Inspection Report 05000352/2023003 and 05000353/2023003 and Independent Spent Fuel Storage Installation Inspection 07200065/2023001 ML23297A1722023-10-24024 October 2023 Request for Information for a Biennial Problem Identification and Resolution Inspection; Inspection Report 05000352/2024010 and 05000353/2024010 IR 05000352/20235012023-10-17017 October 2023 Emergency Preparedness Biennial Exercise Inspection Report 05000352/2023501 and 05000353/2023501 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 ML23279A0612023-10-0505 October 2023 Paragon Energy Solutions LLC, Part 21 Final Report Re Potential Defect with Eaton Jd and Hjd Series Molded Case Circuit Breakers (Mccbs) ML23276A5162023-10-0303 October 2023 Federal Emergency Management Agency Level 1 Finding from 2023 Evaluated Emergency Preparedness Exercise ML23275A1082023-09-29029 September 2023 FEMA Level 1 Findings Limerick NPP- Boyertown/Colebrookdale ML23241A9452023-09-27027 September 2023 Generation Station, Units 1 and 2 Regulatory Audit Plan Supporting Review of the Equipment Qualification Portion of Limerick Digital Instrumentation and Controls License Amendment Request ML23269A0522023-09-26026 September 2023 Request for Information and Notification of Conduct of IP 71111.21.N.04, Age-Related Degradation, Reference Inspection Report 05000352/2023010 and 05000353/2023010 ML23255A0952023-09-12012 September 2023 Resubmittal of License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System (PPS) to Address ML23254A0242023-09-0606 September 2023 Paragon Energy Solutions LLC, Potential Defect with Eaton Jd and Hjd Series Molded Case Circuit Breakers (Mccbs) ML23249A1002023-09-0606 September 2023 Requalification Program Inspection IR 05000352/20230052023-08-31031 August 2023 Updated Inspection Plan for Limerick Generating Station, Units 1 and 2 (Report 05000352/2023005 and 05000353/2023005) ML23248A2082023-08-31031 August 2023 UFSAR Cover Page ML23242A2172023-08-30030 August 2023 Response to Request for Additional Information for Application to Adopt TSTF-477, Revision 3, Add Action for Two Inoperable Control Room AC Subsystems and Associated Technical Specification Changes 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 ML23228A0942023-08-16016 August 2023 Response to Request for Additional Information for Supplemental License Amendment Request to Revise Technical Specifications and Exemption Request from Requirements of 10CFR50.62 ATWS Rule to Support the . IR 05000352/20230022023-08-14014 August 2023 Integrated Inspection Report 05000352/2023002 and 05000353/2023002 ML23220A0182023-08-0808 August 2023 Information Request for the Cybersecurity Baseline Inspection, Notification to Perform Inspection 05000352/2023401 and 05000353/2023401 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 ML23212B2362023-07-31031 July 2023 Supplement to License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System - WEC Documents ML23212B1052023-07-31031 July 2023 Supplement to License Amendment Request to Revise Technical Specifications and Exemption Request from Requirements of 10CFR50.62 ATWS Rule to Support the Digital Modernization Project Installation - Revise ML23202A2192023-07-21021 July 2023 Response to Request for Additional Information for Supplemental License Amendment Request to Revise Technical Specifications and Exemption Request from Requirements of 10CFR50.62 ATWS Rule to Support the . ML23193B0122023-07-20020 July 2023 Audit Plan in Support of Review of License Amendment Request and Exemption Request for Digital Instrumentation and Controls Installation Support (Epids L-2023-LLA-0025 and L-2023-LLE-0005) ML23187A0962023-07-19019 July 2023 Generation Station, Unit Nos. 1 and 2 - Revised Estimated Review Completion Date Concerning License Amendment Request to Replace Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System ML23208A1522023-07-0606 July 2023 PEMA Letter Dated 7-6-23 Re Limerick Exercise 9-26-23 ML23177A2242023-06-26026 June 2023 Supplement to License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection . ML23145A1972023-06-23023 June 2023 Correction to the Renewed Facility Operating License Pages in Amendment Nos. 255, 256, 257, 258, 259, and 260 2024-02-02
[Table view] Category:Licensee Event Report (LER)
MONTHYEAR05000352/LER-2017-0012017-01-27027 January 2017 Condition Prohibited by TS due to Parts Quality Issue, LER 17-001-00 for Limerick Generating Station, Units 1 and 2 Regarding Condition Prohibited by TS due to Parts Quality Issue 05000353/LER-2016-0012016-07-27027 July 2016 Manual Actuation of the Reactor Protection System When Critical Due to Wiring Design Error, LER 16-001-00 for Limerick, Unit 2 Regarding Manual Actuation of the Reactor Protection System When Critical Due to Wiring Design Error 05000352/LER-2016-0032016-05-18018 May 2016 Plant Shutdown Required by Technical Specification Due to a Pressure Boundary Leak, LER 16-003-00 for Limerick, Unit 1, Regarding Plant Shutdown Required by Technical Specification Due to a Pressure Boundary Leak 05000352/LER-2016-0022016-04-11011 April 2016 Condition Prohibited by Technical Specifications Due to Inoperable Safeguard Batteries During Cell Replacements, LER 16-002-00 for Limerick, Unit 1 & 2, Regarding Condition Prohibited by Technical Specifications Due to Inoperable Safeguard Batteries During Cell Replacements 05000352/LER-2016-0012016-03-23023 March 2016 Inoperable Reactor Enclosure Secondary Containment Integrity Due to Open Airlock, LER 16-001-00 for Limerick, Unit 1, Regarding Condition That Could Have Prevented Fulfillment of the Reactor Enclosure Secondary Containment Integrity Safety Function 2017-01-27
[Table view] |
Reported lessons learned are incorporated into the licensing process and fed back to industry.
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Unit Conditions Prior to the Event Unit 1 was in Operational Condition (OPCON) 1 (Power Operation) at 100 percent power.
There were no structures, systems or components out of service that contributed to this event.
Description of the Event
On Monday, January 25, 2016, Limerick Unit 1 was operating at 100 percent power with maintenance ongoing in the residual heat removal service water (RHRSW) / emergency service water (ESW) pipe tunnel. At approximately 1819 hours0.0211 days <br />0.505 hours <br />0.00301 weeks <br />6.921295e-4 months <br />, the main control room supervisor (CRS) was notified that the local airlock open door alarm (EIIS:ALM) was activated when a worker in the pipe tunnel opened the airlock outboard (pipe tunnel side) door (El IS:DR). The alarm indicated that both air lock doors were briefly opened for one reactor enclosure airlock. The reactor enclosure low pressure alarm setpoint is 0.20 inches of vacuum water gauge (WG) and the reactor enclosure low pressure alarm did not actuate during the event. The airlock was open for less than 10 seconds; therefore, the main control room airlock open alarm did not actuate. The reactor enclosure secondary containment integrity (El IS:NH) was declared inoperable for the period when both doors were open.
An investigation determined that a worker using the airlock properly verified that the door open blue light indication was not lit and then opened the outboard airlock door which activated the local airlock open alarm. The most likely cause of the alarm was a degraded inboard door closing mechanism that resulted in the inboard door opening far enough to activate the alarm when the outboard door was opened. The worker immediately reclosed the open outboard door when the local alarm actuated and the breach of secondary containment was terminated. The airlock was open for a period of less than 10 seconds.
The worker notified Operations shift management of the containment breach.
TS 3.6.5.1.1 Reactor Enclosure Secondary Containment Integrity surveillance requirement 4.6.5.1.1.a requires verification that reactor enclosure pressure is greater than or equal to 0.25 inches of vacuum water gauge on a 24-hour frequency. The TS surveillance requirement 4.6.5.1.1.b.2 requires at least one door in each access to the reactor enclosure be verified closed on a 31-day frequency. TS 3.6.5.1.1 is applicable in operational conditions (OPCON) 1, 2, and 3.
This LER is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(v)(C) for a condition that could have prevented the fulfillment of the safety function of structures or systems needed to control the release of radioactive material.
NEI 99-02 (Revision 7), Regulatory Assessment Performance Indicator Guideline, section 2.2 Mitigating Systems Cornerstone, Safety System Functional Failures, Clarifying Notes, states the following:
Engineering analyses: events in which the licensee declared a system inoperable but an engineering analysis later determined that the system was capable of performing its safety function are not counted, even if the system was removed from service to perform the analysis.
This event will not be reported in the NRC performance indicator (PI) for safety system functional failures (SSFF) since an engineering analysis (technical evaluation) was performed which determined that the system was capable of performing its safety function during events when the airlock was open for less than 10 seconds. The post-LOCA dose calculation does not credit reactor enclosure secondary containment integrity for mitigation of on-site and off- site doses for the first 15.5 minutes of the event. Therefore, this event is bounded by the existing dose calculation.
Analysis of the Event
There was no actual safety consequence associated with this event. The potential safety consequences of this event were minimal. Both doors on the airlock were open simultaneously for less than 10 seconds.
To prevent a breach of secondary containment each reactor enclosure airlock is equipped with door open indicating lights that are used to locally verify the door status. If both doors are opened simultaneously a local alarm is actuated. If both doors remain open for greater than 10 seconds, an alarm is actuated in the main control room and operators are dispatched to verify that the airlock doors are closed.
UFSAR 6.2.3.2.1 describes the secondary containment design. The reactor enclosure secondary containment (Zones I and II) is designed to limit the inleakage to 200% of their zone free volume per day, and the refueling area secondary containment (Zone III) is designed to limit the inleakage to 50% of its zone free volume per day. These inleakage rates are based on a negative interior pressure of 0.25 inches wg, while operating the standby gas treatment system (SGTS). Following a LOCA the affected zone is maintained at this negative pressure by operation of the SGTS.
Cause of the Event
The cause of the event was a degraded closing mechanism on the airlock inboard door. This event was not prevented by the design of the reactor enclosure airlocks since there is no mechanical interlock and the door open indicating light does not prevent simultaneous opening of both airlock doors.
Corrective Action Completed The airlock doors were closed to restore reactor enclosure secondary containment integrity.
The degraded inboard door closing mechanism was adjusted.
Previous Similar Occurrences Unit 2 LER 2015-006, Unit 2 LER 2014-007, Unit 2 LER 2014-004, Unit 2 LER 2014-003, Unit 1 LER 2014-003, Unit 2 LER 2014-002, Unit 2 LER 2014-001, Unit 1 LER 2014-002, Unit 1 LER 2014-001, and Unit 2 LER 2013-003 were submitted due to reactor enclosure airlock breaches allowed by the airlock design. Unit 2 LER 2013-002 was submitted due to a reactor enclosure airlock breach caused by a non-functional airlock door open indicating light not providing the correct door status. Unit 2 LER 2014-006 was submitted due to a reactor enclosure airlock breach caused by a door improperly latched closed.
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05000353/LER-2016-001 | Manual Actuation of the Reactor Protection System When Critical Due to Wiring Design Error LER 16-001-00 for Limerick, Unit 2 Regarding Manual Actuation of the Reactor Protection System When Critical Due to Wiring Design Error | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | 05000352/LER-2016-001 | Inoperable Reactor Enclosure Secondary Containment Integrity Due to Open Airlock LER 16-001-00 for Limerick, Unit 1, Regarding Condition That Could Have Prevented Fulfillment of the Reactor Enclosure Secondary Containment Integrity Safety Function | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material | 05000352/LER-2016-002 | Condition Prohibited by Technical Specifications Due to Inoperable Safeguard Batteries During Cell Replacements LER 16-002-00 for Limerick, Unit 1 & 2, Regarding Condition Prohibited by Technical Specifications Due to Inoperable Safeguard Batteries During Cell Replacements | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | 05000352/LER-2016-003 | Plant Shutdown Required by Technical Specification Due to a Pressure Boundary Leak LER 16-003-00 for Limerick, Unit 1, Regarding Plant Shutdown Required by Technical Specification Due to a Pressure Boundary Leak | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
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