03-15-2016 | building. The alarms occurred during an entry to the Unit 2 Reactor Water Cleanup ( RWCU) pump room. A negative reactor building pressure was restored within two minutes (approximately 20:40 hours) without operator action.
Since both Units 1 and 2 share a common reactor building (RB), the loss of differential pressure impacted both Units 1 and 2 secondary containments.
The cause was a sheared air line inside the Unit 1 RB ventilation exhaust plenum which depressurized the air header supplying operating air to all three Unit 1 reactor building exhaust fan isolation dampers, causing the dampers to fail open, including the one on the standby fan.
Corrective actions included replacing the sheared air line, and the addition of a preventive maintenance task for replacement of equivalent air lines on all RB supply and exhaust fan dampers.
The safety significance of this event was minimal. Given the impact on the secondary containment, this report is submitted (for Units 1 and 2) in accordance with the requirements of 10CFR 50.73(a)(2)(v)(C), which requires the reporting of any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material. |
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Category:Letter
MONTHYEARIR 05000254/20230042024-02-0505 February 2024 Integrated Inspection Report 05000254/2023004 and 05000265/2023004 ML24004A0052024-01-17017 January 2024 Exemption from Select Requirements of 10 CFR Part 73 (EPID L-2023-LLE-0042 (Security Notifications, Reports, and Recordkeeping and Suspicious Activity Reporting)) RS-24-001, Response to Request for Additional Information Regarding Relief Request I5R-26, Inservice Inspection Program Relief Request Regarding Examination Coverage for the Fifth Inservice Inspection Interval2024-01-0303 January 2024 Response to Request for Additional Information Regarding Relief Request I5R-26, Inservice Inspection Program Relief Request Regarding Examination Coverage for the Fifth Inservice Inspection Interval IR 05000254/20234032023-12-22022 December 2023 Public- Quad Cities Nuclear Power Station Security Baseline Inspection Report 05000254/2023403 and 05000265/2023403 IR 05000254/20230102023-12-20020 December 2023 Comprehensive Engineering Team Inspection Report 05000254/2023010 and 05000265/2023010 ML23349A1622023-12-17017 December 2023 Issuance of Amendment Nos. 298 and 294 Increase Completion Time in Technical Specification 3.8.1.B.4 (Emergency Circumstances) RS-23-128, Response to Request for Additional Information for the Emergency License Amendment Request Increase Technical Specifications Completion Time in TS 3.8.1.B.4 from 7 Days to 30 Days2023-12-15015 December 2023 Response to Request for Additional Information for the Emergency License Amendment Request Increase Technical Specifications Completion Time in TS 3.8.1.B.4 from 7 Days to 30 Days 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 RS-23-123, Emergency License Amendment Request - Increase Technical Specifications Completion Time in TS 3.8.1.B.4 from 7 Days to 30 Days2023-12-13013 December 2023 Emergency License Amendment Request - Increase Technical Specifications Completion Time in TS 3.8.1.B.4 from 7 Days to 30 Days ML23339A1762023-12-0505 December 2023 Notification of NRC Baseline Inspection and Request for Information (05000265/2024001) ML23319A3342023-11-20020 November 2023 Regulatory Audit in Support of License Amendment Requests to Adopt TSTF 505, Revision 2 and 10 CFR 50.69 RS-23-104, Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-11-17017 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 05000254/20230032023-11-0909 November 2023 Integrated Inspection Report 05000254/2023003 and 05000265/2023003 RS-23-113, Submittal of Updated Final Safety Analysis Report (Ufsar), Revision 17 and Fire Protection Report (Fpr), Revision 262023-10-20020 October 2023 Submittal of Updated Final Safety Analysis Report (Ufsar), Revision 17 and Fire Protection Report (Fpr), Revision 26 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 ML23206A0382023-09-21021 September 2023 Proposed Alternative to the Requirements of the ASME Code IR 05000254/20230112023-09-20020 September 2023 Safety-Conscious Work Environment Issue of Concern Team Inspection Report 05000254/2023011 and 05000265/2023011 RS-23-089, Sixth Ten-Year Interval Inservice Testing Program2023-09-0505 September 2023 Sixth Ten-Year Interval Inservice Testing Program 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 RS-23-086, Relief Request I5R-26, Inservice Inspection Program Relief Request Regarding Examination Coverage for the Fifth Inservice Inspection Interval2023-08-28028 August 2023 Relief Request I5R-26, Inservice Inspection Program Relief Request Regarding Examination Coverage for the Fifth Inservice Inspection Interval SVP-23-038, Owner'S Activity Report Submittal Fifth 10-Year Interval 2023 Refueling Outage Activities2023-08-14014 August 2023 Owner'S Activity Report Submittal Fifth 10-Year Interval 2023 Refueling Outage Activities IR 05000254/20230022023-08-0808 August 2023 Integrated Inspection Report 05000254/2023002 and 05000265/2023002 ML23178A0742023-08-0707 August 2023 Issuance of Amendment Nos. 296 and 292 Adoption of TSTF-416 Low Pressure Coolant Injection (LPCI) Valve Alignment Verification Note Location ML23216A0362023-08-0707 August 2023 Notification of an NRC Biennial Licensed Operator Requalification Program Inspection and RFI ML23216A0562023-08-0404 August 2023 Information Meeting (Open House) with a Question and Answer Session to Discuss NRC 2022 End-Of-Cycle Plant Performance Assessment of Quad Cities Nuclear Power Station, Units 1 and 2 SVP-23-031, Regulatory Commitment Change Summary Report2023-07-14014 July 2023 Regulatory Commitment Change Summary Report ML23181A1062023-06-30030 June 2023 Postponement- Information Meeting (Open House) with a Question-And-Answer Session to Discuss NRC 2022 End-Of-Cycle Plant Performance Assessment of Quad Cities Nuclear Power Station ML23178A2422023-06-28028 June 2023 Reassignment of the U.S. Nuclear Regulatory Commission Branch Chief in the Division of Operating Reactor Licensing for Plant Licensing Branch III ML23179A1932023-06-28028 June 2023 07122023 Letter-Significant Public Meeting to Discuss NRC End-of-Cycle Performance Assessment of Quad Cities Nuclear Plant for Performance for 2022 Calendar Year IR 05000254/20234012023-06-26026 June 2023 Cyber Security Inspection Report 05000254/2023401 and 05000265/2023401 IR 05000265/20230402023-06-22022 June 2023 Reissue Quad Cities Nuclear Power Station 95001 Supplemental Inspection Supplemental Report 05000265/2023040 and Follow Up Assessment Letter 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 ML23167B1722023-06-16016 June 2023 95001 Supplemental Inspection Report 05000265/2023040 and Follow-Up Assessment Letter RS-23-060, Application to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems, and Components for Nuclear Power Reactors2023-06-0808 June 2023 Application to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems, and Components for Nuclear Power Reactors RS-23-059, License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b2023-06-0808 June 2023 License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b ML23144A3632023-05-26026 May 2023 Information Meeting (Open House) with a Question and Answer Session to Discuss NRC 2022 End-of-Cycle Plant Performance Assessment of Quad Cities Nuclear Power Station, Units 1 and 2 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 ML23033A4042023-05-15015 May 2023 Exemption from the Requirements of 10 CFR Part 2, Section 2.109(B) Related to Submission of Subsequent License Renewal Application Letter IR 05000254/20234022023-05-15015 May 2023 Security Baseline and ISFSI Inspection Reports 05000254/2023402, 05000265/2023402, 07200053/2023401 ML23132A2022023-05-12012 May 2023 Annual Radiological Environmental Operating Report ML23125A0612023-05-0808 May 2023 Proposed Alternative to the Requirements of the ASME Code IR 05000254/20230012023-05-0808 May 2023 Integrated Report 05000254/2023001 and 05000265/2023001 RS-22-067, 10 CFR 50.46 Annual Report2023-05-0404 May 2023 10 CFR 50.46 Annual Report ML23118A3472023-05-0101 May 2023 County, 1 & 2; Nine Mile Point, 2; and Quad Cities, 1 & 2 - Correction of Amendment No. 193 Adoption of TSTF-306, Revision 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration EPID L-2022-LLA-0143 RS-23-068, Response to Request for Additional Information for Quad Cities Relief Request I6R-11, Proposed Alternatives for a Temper Bead Weld Repair of the Mating Surfaces of the Reactor Pressure Vessel Head and Shell2023-04-28028 April 2023 Response to Request for Additional Information for Quad Cities Relief Request I6R-11, Proposed Alternatives for a Temper Bead Weld Repair of the Mating Surfaces of the Reactor Pressure Vessel Head and Shell SVP-23-018, Radioactive Effluent Release Report for 20222023-04-28028 April 2023 Radioactive Effluent Release Report for 2022 ML23114A2522023-04-28028 April 2023 Request to Use a Provision of a Later Edition of the ASME Boiler & Pressure Vessel Code, Section XI ML23110A0622023-04-25025 April 2023 Transmittal of Final Quad Cities Nuclear Power Plant, Unit 1 Accident Sequence Precursor Report (Licensee Event Report 254-2022-001) ML23081A0382023-04-25025 April 2023 County, 1 & 2; Nine Mile Point, 2; and Quad Cities, 1 & 2 - Issuance of Amendments to Adopt TSTF-306, Rev. 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration 2024-02-05
[Table view] Category:Licensee Event Report (LER)
MONTHYEARSVP-22-072, Manual Scram Due to Feedwater Regulator Valve Failure Increasing Reactor Water Level2022-12-30030 December 2022 Manual Scram Due to Feedwater Regulator Valve Failure Increasing Reactor Water Level 05000254/LER-2017-0042018-01-0505 January 2018 Unit 1 HPCI Did Not Trip Due to Wear Debris in the Turbine Stop Valve Oil Resetting Solenoid, LER 17-004-00 For Quad Cities Nuclear Power Station, Unit 1 re: Unit 1 HPCI Did Not Trip Due to Wear Debris in the Turbine Stop Valve Oil Resetting Solenoid 05000254/LER-2017-0032017-11-17017 November 2017 Control Room Emergency Ventilation Air Conditioning Piping Refrigerant Leak Due to High Cycle Fatigue, LER 17-003-00 for Quad Cities, Unit 1, Regarding Control Room Emergency Ventilation Air Conditioning Piping Refrigerant Leak Due to High Cycle Fatigue 05000265/LER-2017-0012017-07-13013 July 2017 High Pressure Coolant Injection Minimum Flow Valve Failed to Open, LER 17-001-00 for Quad Cities, Unit 2, Regarding High Pressure Coolant Injection Minimum Flow Valve Failed to Open 05000254/LER-2017-0022017-05-26026 May 2017 Four Main Steam Isolation Valves (MSIVs) Closure Times Exceeded, LER 17-002-00 for Quad Cities, Unit 1, Regarding Four Main Steam Isolation Valves (MSIVs) Closure Times Exceeded 05000254/LER-2017-0012017-03-22022 March 2017 Secondary Containment Interlock Doors Opened Simultaneously, LER 17-001-00 for Quad Cities, Unit 1, Regarding Secondary Containment Interlock Doors Opened Simultaneously 05000265/LER-2016-0022016-06-24024 June 2016 High Pressure Coolant Injection System Declared Inoperable Due to Valve Packing Leak, LER 16-002-00 for Quad Cities Nuclear Power Station Unit 2 - RE: High Pressure Coolant Injection System Declared Inoperable Due to Valve Packing Leak 05000265/LER-2016-0012016-05-19019 May 2016 Main Steam Isolation Valve Local Leak Rate Tests Exceed Technical Specification Limits, LER 2016-001-00 for Quad Cities Nuclear Power Station, Unit 2 Regarding Main Steam Isolation Valve Local Leak Rate Tests Exceed Technical Specification Limits 05000254/LER-2016-0022016-03-14014 March 2016 Secondary Containment Differential Pressure Momentarily Lost Due to Air Line Failure (RWCU Pump Rm), LER 16-002-00 for Quad Cities Units 1 and 2, Regarding Secondary Containment Different Pressure Momentarily Lost due to Air Failure (RWCU pump Rm) 05000254/LER-2016-0012016-03-10010 March 2016 Secondary Containment Differential Pressure Momentarily Lost Due to Air Line Failure (RWCU Hx Rm), LER 16-001-00 for Quad Cities, Unit 1, Regarding Secondary Containment Differential Pressure Momentarily Lost Due to Air Line Failure (RWCU Hx Rm) 05000254/LER-2015-0102016-02-0505 February 2016 Loss of Control Room Emergency Ventilation System Due to Differential Pressure Switch Failure, LER 15-010-00 for Quad Cities, Unit 1, Regarding Loss of Control Room Emergency Ventilation System Due to Differential Pressure Switch Failure SVP-03-036, LER 03-S01-00, Security Event Report for Quad Cities, Unescorted Protected Area Access Granted Based on Falsified Information and Inadequate Screening Caused by a Failure of Administrative Controls.2003-03-0303 March 2003 LER 03-S01-00, Security Event Report for Quad Cities, Unescorted Protected Area Access Granted Based on Falsified Information and Inadequate Screening Caused by a Failure of Administrative Controls. ML17252B4771976-09-15015 September 1976 LER 76-059-00 for Dresden, Units 2 and 3 Re Review of Quad-Cities Unusual Event Letter Led to Discovery That Dresden'S Standby Gas Treatment System Deviated from Single Failure Criteria That Disabled the SBGT System ML18348A2401976-08-0606 August 1976 LER 1976-027-00, Reportable Occurrence of Control Rods for Quad-Cities, Unit 1 ML18348A2391976-08-0404 August 1976 LER 1976-026-00, Reportable Occurrence of Control Rods for Quad-Cities, Unit 1 2022-12-30
[Table view] |
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor, 2957 Megawatts Thermal Rated Core Power Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
EVENT IDENTIFICATION
Momentary Loss of Secondary Containment Differential Pressure due to High Cycle Fatigue Failure of an air line in the Unit 1 Reactor Building Exhaust fan plenum.
A. CONDITION PRIOR TO EVENT
Unit: 1 / 2 Reactor Mode: 1 / 1 Event Date: January 15, 2016 Event Time: 20:38 hours Mode Name: Power Operation / Power Operation Power Level: 100% / 100%
B. DESCRIPTION OF EVENT
On January 15, 2016, at 20:38 hours, unexpected Main Control Room Reactor Building (RB) low differential pressure (DP) alarms were received due to loss of negative DP in the RB. At approximately the same time, Operations had entered the Unit 2 RWCU Pump room.
Reactor building DP was observed rising to 0 inches water column (WC) and peaked at +0.2 inch WC. Technical Specification (TS) 3.6.4.1 Condition A, and QGA 300, Secondary Containment Control was entered for both Units Secondary Containment being inoperable. With no operator action, a negative reactor building DP was restored at approximately 20:40 hours. TS 3.6.4.1 Condition A and QGA 300 were exited at 20:42 hours.
On January 16, 2016 at 01:42 hours, ENS #51659 was made to the NRC under 10 CFR 50.72 (b)(3)(v)(C), to report this event as an event or condition that could have prevented the fulfillment of a safety function of structures or systems that are needed to control the release of radioactive material.
An investigation of this event was performed which determined that a sheared air line to the 1C RB exhaust fan isolation damper depressurized a common air header to all three Unit 1 RB exhaust fan isolation dampers, causing them to fail open. This air line was internal to the exhaust ductwork, therefore it could not be identified through normal Operator rounds. With a normal fan lineup of two supply and two exhaust fans operating per unit, the isolation damper for the standby Unit 1 exhaust fan remained open. This created a recirculation path which was compensated by the RB DP control dampers throttling nearly full open. This significantly degraded the margin available for the system to respond to changes in building DP. When an entry was made into the Unit 2 RWCU HX room, the area DP control system responded as expected by throttling closed all area DP control dampers which decreased total building exhaust flow. With reduced margin available in the building DP control, this caused a positive pressure condition in the RB.
C. CAUSE OF EVENT
The cause was a sheared air line inside the Unit 1 RB ventilation exhaust plenum which depressurized the air header supplying operating air to all three Unit 1 RB exhaust fan isolation dampers, causing the dampers to fail open, including the one on the standby fan.
The cause of the sheared air line was high cycle fatigue failure as a result of an inadequate piping support for the vibration environment. The specific routing and support of this line is not detailed in design specifications and therefore was attributed to deficient worker practices during original installation. The failed component is original plant equipment and therefore this is considered a historical cause.
The building and area DP control systems are not interconnected, but can have substantial effects on each other.
Specifically, when a RWCU area room is opened, the sensed area pressure increases. This causes the area DP control system to reposition the area DP control dampers in the closed direction in an attempt to restore area DP.
This reduces building exhaust flow, which will cause building pressure to increase and the DP control dampers to further open to restore building DP.
D. SAFETY ANALYSIS
System Design The function of the secondary containment is to contain, dilute, and hold up fission products that may leak from primary containment following a Design Basis Accident (DBA). In conjunction with operation of the Standby Gas Treatment System (SBGTS) and closure of certain valves [V] whose lines penetrate the secondary containment, the secondary containment is designed to reduce the activity level of the fission products prior to release to the environment, and to isolate and contain fission products that are released during certain operations that take place inside primary containment, when primary containment is not required to be operable, or that take place outside primary containment.
Updated Final Safety Analysis Report (UFSAR) Section 6.2.3.1 provides that the safety objective of the secondary containment system, in conjunction with other engineered safeguards and nuclear safety systems, is to limit the release of radioactive materials so that offsite doses resulting from a postulated DBA will remain below 10 CFR 100 guideline values.
The RB Ventilation is designed to maintain the RB (RB is common to both Units 1 and 2) at a negative pressure during normal operation.
Safety Impact Since both Units 1 and 2 share a common RB (secondary containment), the momentary loss of secondary containment differential pressure effects both units.
TS 3.6.4.1, Condition A, requires restoration of secondary containment to operable status within four hours. This four hour completion time provides a period of time to correct the problem that is commensurate with the importance of maintaining secondary containment during Modes 1, 2, and 3, since the probability of an accident occurring during this short period where secondary containment is inoperable is minimal.
The primary purpose of the secondary containment is to minimize the ground level release of airborne radioactive materials and to provide a controlled, elevated release of the building atmosphere under accident conditions. An engineering analysis was performed to demonstrate that during the time that secondary containment differential pressure increased to positive for approximately two (2) minutes, there would be a negligible effect on the resulting dose calculations. Secondary containment would have sufficiently contained radioactive materials during a LOCA such that all current dose limits would remain met. Secondary containment would have been able to perform its safety function. Therefore, the dose consequence from postulated releases from the RB during this short duration would be bounded by the existing design basis LOCA analysis. The safety significance of this event was minimal.
The engineering analysis that was performed demonstrated this event did not constitute a Safety System Functional Failure (SSFF). (Reference NEI 99-02, Revision 7, Regulatory Assessment Performance Indicator Guideline, Section 2.2, Mitigating Systems Cornerstone, Safety System Functional Failures, Clarifying Notes, Engineering analyses.) As such, this event will not be reported in the NRC Performance Indicator (PI) for SSFF since an engineering analysis was performed which determined that the system was capable of performing its safety function during this event when the secondary containment differential pressure increased to positive for approximately two (2) minutes.
Risk Insights The plant Probabilistic Risk Assessment (PRA) model gives no credit to secondary containment or RB Ventilation and does not include it in the model, hence the as-found conditions did not contribute to an increase in risk. In addition, overall RB negative DP was restored in approximately two minutes, so the physical integrity of the secondary containment structure was never compromised and the primary containment function was never lost.
In conclusion, the overall safety significance and impact on risk of this event were minimal.
E. CORRECTIVE ACTIONS
Immediate:
1. The sheared air line was replaced and a full system post maintenance test (PMT) was performed to verify that RWCU pump room.
Follow-up:
1. Establish additional trending for RB ventilation DP control dampers to identify potential decreases in system margin.
and 2 RB ventilation exhaust fan dampers.
F. PREVIOUS OCCURRENCES
The station events database, LERs, and INPO Consolidated Event System (ICES) were reviewed for similar events at the Quad Cities Nuclear Power Station. This event was attributed to an inadequate support installation of an air line during original plant construction. Based on the nature of this failure, the events listed below, although similar in topic, are not considered significant station experience that would have directly contributed to preventing this event.
- Station Issue Report (IR) 1412296: Low RB to Atmosphere DP Condition During Fan Starts, September 13, 2012 — Numerous issues were identified in 2012 with maintaining RB DP during fan starts and entries to RWCU rooms. The apparent cause that was identified during this troubleshooting was exhaust fan isolation dampers and area DP control dampers not operating properly due to numerous small air leaks. The air leaks were cuased by aged rubber gaskets and not vibration induced like the current event. System DP control improved significantly following these repairs.
- LER 254/2014-001-00, 5/5/14, Secondary Containment Differential Pressure Momentarily Lost Due to Fuel Pool Monitor Radiation Monitor Spike (3/4/14) — A Fuel Pool Channel 1B High Radiation spiked high causing the Unit 1 and Unit 2 RB Ventilation and Control Room Ventilation to isolate as designed. The SBGTS was already in operation for a scheduled surveillance. The previous event caused a momentary positive differential pressure until the RB Ventilation isolation dampers closed within 60 seconds and draw down the building within a 2-3 minute period. This event was caused while operating the RB Ventilation system and caused by a sheared air line on the exhaust fan isolation damper system.
This event and the current event occurred three (3) days apart. Troubleshooting was still in progress from the 1/12/16 event when the current 1/15/16 event occurred. Ongoing troubleshooting activities had not yet identified and corrected the deficient condition before the second event occurred.
G. COMPONENT FAILURE DATA
Failed Equipment: Male threaded brass pipe fitting Component Manufacturer: Unknown Component Model Number: N/A Component Part Number: N/A This event has been reported to ICES under Failure report No. 321170.