04-18-2017 | On February 18, 2017, at 3:37 p.m. CST, while a refueling outage was in progress, the operators were shifting subsystems of the main control building ventilation system. The Division 2 "B" chiller had been in service, and it was intended to start the Division 1 "C" chiller to facilitate the outage work schedule. After the swap, operators noted that the air flow was abnormally low, and within approximately four minutes, the "C" chiller tripped. The operators were unsuccessful in attempts to restore the Division 2 subsystem to service;and the abnormal operating procedures for the loss of control building ventilation were then implemented. The electrical distribution subsystems in the control building were declared inoperable due to the loss of the ventilation system. This condition is being reported in accordance with 10 CFR 50.73(a)(2)(v)(A). As described in the causal analysis, a circuit breaker manufacturing defect that violated the single failure requirements of 10 CFR 50 Appendix A, General Design Criteria, was discovered. This is being reported in accordance with 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition. During the restoration of the ventilation system, main control room temperature increased from approximately 73F to 81F as recorded in the operator's logs. No high temperature alarms from the electrical equipment rooms actuated. Thus, this event was of minimal significance to the health and safety of the public. |
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Category:Letter
MONTHYEARIR 05000458/20230402024-01-18018 January 2024 95001 Supplemental Inspection Supplemental Report 05000458/2023040 and Follow-Up Assessment Letter RBG-48271, Supplement to License Amendment Request to Adopt Risk Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times RITSTF Initiative 4b and Application to Adopt 10 CFR 50.69, Risk2024-01-12012 January 2024 Supplement to License Amendment Request to Adopt Risk Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times RITSTF Initiative 4b and Application to Adopt 10 CFR 50.69, Risk ML24012A1962024-01-12012 January 2024 Response to 2nd Round Request for Additional Information Concerning Relief Request Number EN-RR-22-001 Proposed Alternative to Use ASME Code Case N-752, Risk-Informed Categorization and ML24011A1742024-01-11011 January 2024 Security Baseline Inspection Report (Cover Letter) ML23349A1672023-12-21021 December 2023 Request for Withholding Information from Public Disclosure ML23348A3572023-12-14014 December 2023 Application to Revise Technical Specifications to Use Online Monitoring Methodology Slides and Affidavit for Pre-Submittal Meeting ML23340A1592023-12-13013 December 2023 Entergy Operations, Inc. - Entergy Fleet Project Manager Assignment ML23352A0292023-12-13013 December 2023 Entergy - 2024 Nuclear Energy Liability Evidence of Financial Protection IR 05000458/20230102023-12-12012 December 2023 Biennial Problem Identification and Resolution Inspection Report 05000458/2023010 RBG-48267, Reply to a Notice of Violation, NRC Inspection Report 05000458/20230032023-12-0707 December 2023 Reply to a Notice of Violation, NRC Inspection Report 05000458/2023003 ML23333A1362023-11-29029 November 2023 Supplement to Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation ML23325A1432023-11-21021 November 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation ML23310A0322023-11-13013 November 2023 Integrated Inspection Report 05000458/2023003 IR 05000458/20230032023-11-13013 November 2023 Integrated Inspection Report 05000458/2023003 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 ML23311A4322023-11-0909 November 2023 Notification of NRC Supplemental Inspection (95001) and Request for Information RBG-48264, Core Operating Limits Report (COLR) - Cycle 23, Revision 12023-11-0606 November 2023 Core Operating Limits Report (COLR) - Cycle 23, Revision 1 RBG-48260, Notification of Readiness for Supplemental Inspection2023-10-12012 October 2023 Notification of Readiness for Supplemental Inspection ML23278A2402023-10-0606 October 2023 Regulatory Audit Plan in Support of License Amendment Requests to Revise TSs to Adopt Risk-Informed Completion Times and Implement the Provisions of 10 CFR 50.69 RBG-48258, Notification of Readiness for Supplemental Inspection2023-10-0505 October 2023 Notification of Readiness for Supplemental Inspection RBG-48259, Revision to Reply to Notice of Violation; EA-23-0552023-10-0303 October 2023 Revision to Reply to Notice of Violation; EA-23-055 ML23270B9932023-09-29029 September 2023 Request to Update ASME Boiler & Pressure Vessel Code Relief Request SE with NRC-Approved Revision of Bwrip Guidelines (GG-ISI-020 & RBS-ISI-019) (EPID L-2022-LLR-0090) - Non-Proprietary ML23269A1242023-09-27027 September 2023 Request for Withholding Information from Public Disclosure IR 05000458/20234012023-09-26026 September 2023 Cyber Security Inspection Report 05000458/2023401 IR 05000458/20230012023-09-21021 September 2023 NRC Inspection Report 05000458/2023001, Disputed Non-Cited Violation Rescinded RBG-48254, Report of Changes and Errors to 10CFR50.462023-09-21021 September 2023 Report of Changes and Errors to 10CFR50.46 IR 05000458/20234032023-09-21021 September 2023 NRC Security Inspection Report 05000458/2023403 (Cover Letter) RBG-48249, Reply to a Notice of Violation, EA-23-0712023-09-14014 September 2023 Reply to a Notice of Violation, EA-23-071 RBG-48253, Submittal of Owner'S Activity Report Form for Cycle 222023-09-12012 September 2023 Submittal of Owner'S Activity Report Form for Cycle 22 IR 05000458/20230122023-09-0101 September 2023 Comprehensive Engineering Team Inspection Report 05000458/2023012 IR 05000458/20230052023-08-21021 August 2023 Updated Inspection Plan for River Bend Station (Report 05000458/2023005) - Mid Cycle Letter RBG-48247, Reply to Notice of Violation; EA-23-0552023-08-21021 August 2023 Reply to Notice of Violation; EA-23-055 IR 05000458/20230922023-08-15015 August 2023 Final Significance Determination of a White Finding, Notice of Violation, and Follow-Up Assessment Letter; NRC Inspection Report 05000458/2023092 IR 05000458/20230022023-08-0909 August 2023 Integrated Inspection Report 05000458/2023002 ML23208A2112023-07-27027 July 2023 Entergy Operations Inc., Application to Revise Technical Specifications to Adopt TSTF-205, Revision of Channel Calibration, Channel Functional Test, and Related Definitions ML23195A0692023-07-24024 July 2023 2023 River Bend Station Notification of Biennial Problem Identification and Resolution Inspection and Request for Information IR 05000458/20230912023-07-20020 July 2023 Final Significance Determination of a White Finding, Notice of Violation, and Follow-Up Assessment Letter; NRC Inspection Report 05000458/2023091 ML23207A0762023-07-14014 July 2023 EN 56557 - Update to Part 21 Report Re Potential Defect with Trane External Auto/Stop Emergency Stop Relay Card Pn: XI2650728-06 ML23195A0222023-07-11011 July 2023 4-2022-012 Letter - OI Closure to Licensee IR 05000458/20234042023-07-11011 July 2023 NRC Security Inspection Report 05000458/2023404 (Cover Letter Only) IR 05000458/20230902023-06-26026 June 2023 NRC Inspection Report 05000458/2023090 and Preliminary White Finding ML23159A2302023-06-0808 June 2023 Response to Request for Additional Information Concerning Request to Update ASME Code Relief Request Safety Evaluations with NRC-Approved Revision of BWRVIP Guidelines (GG-ISI-020, and RBS-ISI-019) ML23159A0052023-06-0505 June 2023 56557-EN 56557 - Paragon - Redlined RBG-48226, Core Operating Limits Report (COLR) - Cycle 23, Revision 02023-05-31031 May 2023 Core Operating Limits Report (COLR) - Cycle 23, Revision 0 RBG-48237, Response to NRC Integrated Inspection Report 05000458/20230012023-05-25025 May 2023 Response to NRC Integrated Inspection Report 05000458/2023001 ML23130A2732023-05-10010 May 2023 and Waterford 3 Steam Electric Station - Response to Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations ML23117A2172023-05-0101 May 2023 Safety Evaluation for Quality Assurance Program Manual Reduction in Commitment ML23116A2352023-05-0101 May 2023 Integrated Inspection Report 05000458/2023001 RBG-48220, Submittal of 2022 Annual Radioactive Effluent Release Report2023-04-25025 April 2023 Submittal of 2022 Annual Radioactive Effluent Release Report 2024-01-18
[Table view] Category:Licensee Event Report (LER)
MONTHYEAR05000458/LER-2017-0092017-11-13013 November 2017 Potential Loss of Safety Function of Secondary Containment due to Unsecured Personnel Door, LER 17-009-00 for River Bend, Unit 1 Regarding Potential Loss of Safety Function of Secondary Containment due to Unsecured Personnel Door 05000458/LER-2017-0072017-08-21021 August 2017 Automatic Reactor Scram due to Failure of Main Generator Voltage Regulator Mode Transfer Relay, LER 17-007-00 for River Bend Station - Unit 1 Regarding Automatic Reactor Scram due to Failure of Main Generator Voltage Regulator Mode Transfer Relay 05000458/LER-2017-0062017-07-13013 July 2017 Potential Loss of Safety Function of Onsite Power Sources due to Inadvertent Inoperability of Control Building Chiller, LER 17-006-00 for River Bend, Unit 1 re Potential Loss of Safety Function of Onsite Power Sources due to Inoperability of Control Building Chiller 05000458/LER-2016-0032017-06-0808 June 2017 Operations Prohibited by Technical Specifications Due to Reactor Control Rod Drift During Core Alterations, LER 16-003-01 for River Bend Station, Unit 1, Regarding Operations Prohibited by Technical Specifications Due to Control Blade Drift During Core Alterations 05000458/LER-2017-0052017-06-0505 June 2017 1 OF 3, LER 17-005-00 for River Bend Station, Unit 1, Regarding Operations Prohibited by Technical Specifications Due to Inoperable Main Control Room Filter Train 05000458/LER-2017-0042017-05-22022 May 2017 Loss of High Pressure Core Spray Safety Function During Surveillance Due to Malfunction of Test Return Valve, LER 17-004-00 for River Bend Station, Unit 1, Regarding Loss of High Pressure Core Spray Safety Function During Surveillance Due to Malfunction of Test Return Valve 05000458/LER-2017-0032017-05-0909 May 2017 Manual Reactor Scram Initiated in Response to Increase in Steam Pressure During Steam Leak Troubleshooting, LER 17-003-00 for River Bend Station, Unit 1, Regarding Manual Reactor Scram Initiated in Response to Increase in Steam Pressure During Steam Leak Troubleshooting 05000458/LER-2017-0022017-04-18018 April 2017 Loss of Safety Function of Onsite Electrical Distribution Due to Malfunction of Control Building HVAC System, LER 17-002-00 for River Bend Station, Unit 1, Regarding Loss of Safety Function of Onsite Electrical Distribution Due to Malfunction of Control Building HVAC System 05000458/LER-2017-0012017-04-0303 April 2017 Operations Prohibited by Technical Specifications (Conduct of Operations With a Potential to Drain the Reactor Vessel With Primary Containment Open), LER 17-001-00 for River Bend Station, Unit 1, Regarding Operations Prohibited by Technical Specifications (Conduct of Operations With a Potential to Drain the Reactor Vessel With Primary Containment Open) 05000458/LER-2016-0072016-07-25025 July 2016 1 Operations Prohibited by Technical Specifications Due to Failure to Implement Required Actions Within Completion Time, LER 16-007-00 for River Bend Station, Unit 1, Regarding Operations Prohibited by Technical Specifications Due to Failure to Implement Required Actions Within Completion Time 05000458/LER-2016-0062016-07-12012 July 2016 Potential Loss of Safety Function of Multiple Systems Due to Design Deficiency in 480-volt Circuit Breakers, LER 16-006-00 for River Bend Station re: Potential Loss of Safety Function of Multiple Systems Due to Design Deficiency in 480-volt Circuit Breakers 05000458/LER-2016-0042016-03-29029 March 2016 Actuation of the Division 1 Emergency Diesel Generator and Primary Containment Isolation Logic Due to Partial Loss of Offsite Power, LER 16-004-00 for River Bend, Unit 1, Regarding Actuation of the Division 1 Emergency Diesel Generator and Primary Containment Isolation Logic Due to Partial Loss of Offsite Power 05000458/LER-2016-0022016-03-0707 March 2016 Automatic Reactor Scram and Division 2 Primary Containment Isolation Due to Offsite Grid Electrical Transient, LER 16-002-00 for River Bend, Unit 1, Regarding Automatic Reactor Scram and Division 2 Primary Containment Isolation Due to Offsite Grid Electrical Transient 05000458/LER-2016-0012016-03-0707 March 2016 Potential Loss of Secondary Containment Safety Function Due to Failure of Auxiliary Building Ventilation System, LER 16-001-00 for River Bend, Unit 1, Regarding Potential Loss of Secondary Containment Safety Function Due to Failure of Auxiliary Building Ventilation System 05000458/LER-2015-0102016-02-0808 February 2016 Potential Loss of Safety Function of High Pressure Core Spray Due to Failure of Main Control Building Ventilation Chiller, LER 15-010-00 for River Bend Station, Unit 1, Regarding Potential Loss of Safety Function of High Pressure Core Spray Due to Failure of Main Control Building Ventilation Chiller 05000458/LER-2015-0092016-01-26026 January 2016 1 OF 3, LER 15-009-00 for River Bend Station, Unit 1 Regarding Automatic Reactor Scram Due to Partial Loss of Offsite Power Caused by Fault in Local 230K Switchyard 05000458/LER-2015-0082016-01-18018 January 2016 Potential Loss of Safety Function of High Pressure Core Spray Due to Failure of Main Control Building Ventilation Chiller, LER 15-008-00 of River Bend Station, Unit 1, Regarding Loss of Safety Function of High Pressure Core Spray Due to Failure of Main Control Building Ventilation Chiller 05000458/LER-2015-0072016-01-18018 January 2016 Potential Loss of Safety Function of High Pressure Core Spray Due to Failure of Main Control Building Ventilation Chiller, LER 15-007-00 for River Bend Station - Unit 1 Regarding Potential Loss of Safety Function of High Pressure Core Spray Due to Failure of Main Control Building Ventilation Chiller RBG-47473, Special Report for NEI 07-07 Notification2014-06-0404 June 2014 Special Report for NEI 07-07 Notification ML0627100382006-05-16016 May 2006 Final Precursor Analysis - River Bend Station, LER-458/04-005-01, Automatic Reactor Trip Due to Loss of Non-Vital 120V Instrument Bus 2017-08-21
[Table view] |
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05000-458 2017 002 00
REPORTED CONDITION
On February 18, 2017, at 3:37 p.m. CST, while a refueling outage was in progress, the operators were shifting subsystems of the main control building ventilation system [VI]. The Division 2 "B" chiller (**CHU**) had been in service, and it was intended to start the Division 1 "C" chiller to facilitate the outage work schedule. After the swap, operators noted that the air flow was abnormally low, and within approximately four minutes, the "C" chiller tripped. The operators attempted to restore the Division 2 subsystem to service, but they were unsuccessful, and the abnormal operating procedures for the loss of control building ventilation were then implemented. The electrical distribution subsystems [ED] in the control building were declared inoperable due to the loss of the ventilation system. This condition is being reported in accordancewith 10 CFR 50.73(a)(2)(v).
As described in the causal analysis below, a circuit breaker (**BKR**) manufacturing defect that violated the single failure requirements of 10 CFR 50 Appendix A, General Design Criteria, was discovered. This is being reported in accordance with 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition.
BACKGROUND
Two 100-percent capacity chillers provide cooling to each ventilation system sub-loop, each of which provides cooling, heating, ventilation, pressurization, and smoke removal for several areas within the building. The ventilation system comprises two independent, redundant trains of components and subsystems either of which supports the safety function of providing a controlled environment in the main control room (MCR) and the environmental requirements of the safety-related electrical equipment in the building. Each control building ventilation subsystem is supported by the respective safety-related emergency diesel generator.
The control building chilled water system (HVK) provides chilled water to the cooling coils in three separate air handlers within each division. The air handling system (HVC) removes the heat generated within the MCR and electrical equipment rooms. Air handlers serve the MCR, standby switchgear rooms, battery charger rooms, inverter rooms, and chiller rooms. Each air handler serves both trains of their assigned areas (i.e., both the Division 1 and 2 standby switchgear rooms cooling may be fully served by the air handler in either train). In the event of a total ventilation system failure, the current Technical Specification action to restore the ventilation system is bounded by the 2-hour completion times for DC sources
IMMEDIATE ACTIONS
In troubleshooting the abnormally low air flow with the Division 1 subsystem in service, it was discovered that air flow control dampers in the system had not operated correctly, which diverted air flow from the operating air handler.
Operators implemented abnormal operating procedures to provide alternate means of cooling to the affected areas and monitored the areas for temperature rise.
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05000-458 2017 002 00 Under temporary configuration controls, operators closed the air dampers by removing their control power fuses, and restored the normal air flow path. The Division 1 "C" HVK chiller was successfully started at 5:37 p.m. CST. At the onset of the event, MCR temperatures were approximately 73F. The highest temperature recorded before the restoration of the cooling system was approximately 81F.
CAUSAL ANALYSIS
The failure of the air handler dampers to close correctly was traced to an internal failure in the 480-volt circuit breaker for the Division 2 switchgear room air handling unit. It was found that a mechanism operated cell (MOC) switch positioner linkage screw had fallen out, causing the logic circuit for the damper controls to fail to actuate. The screw in the MOC linkage failed because it was shorter than required by the circuit breaker design (i.e., one-quarter inch in length versus three-eighths inch).
"Single failure" is defined by 10 CFR 50 Appendix A, General Design Criteria for Nuclear Power Plants. A single failure means an occurrence which results in the loss of capability of a component to perform its intended safety functions.
Multiple failures resulting from a single occurrence are considered to be a single failure. The control building ventilation system is required to be designed against an assumed single failure. Failure of the screw caused the failure of both the Division 1 and Division 2 ventilation subsystems.
It is possible that the MOC screw may have been loose since the last time the breaker was successfully closed on January 31. However, its actual failure can be pinpointed only to the opening of the breaker the on date of the event.
CORRECTIVE ACTIONS TO PREVENT RECURRENCE
All safety-related, electrically operated Masterpact NT breakers were categorized with regard to the design of their MOC logic circuit switches. Those breakers with the potential to cause the mis-operation of other components by the same failure mechanism of the February 18 event were inspected to verify that correct screws and lock washers were installed.
The remaining population of Masterpact NT breakers will be inspected.
Design changes were implemented to alter the damper logic circuits for the main control room and electrical equipment area air handlers to eliminate the cause of this event as a potential failure mode for damper actuation.
Technical and quality requirements for receipt inspections of Masterpact circuit breakers will be revised to specifically examine the MOC hardware. Similar breakers already in the warehouse will be inspected. These actions are being tracked in the corrective action program.
EVALUATION OF PRIOR OCCURRENCES
No events reported in the last three years by RBS have occurred as a result of the breaker failure mode discovered in this evaluation.
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- respond to, the information collection.
05000-458 2017 002 00
SAFETY SIGNIFICANCE
The normal operating upper temperature limit for the main control room and electrical equipment rooms served by the HVC system is 104F. During the restoration of the ventilation system, main control room temperature increased from approximately 73F to 81F as recorded in the operator's logs. The electrical distribution equipment rooms are served by remote temperature monitors, and none of those associated alarms actuated in the MCR during the time that the ventilation system was out of service. Thus, this event was of minimal significance to the health and safety of the public.
(NOTE: Energy Industry Identification System component function identifier and system name of each component or system referred to in the LER are annotated as (**XX**) and [XX], respectively.)
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05000458/LER-2017-001 | Operations Prohibited by Technical Specifications (Conduct of Operations With a Potential to Drain the Reactor Vessel With Primary Containment Open) LER 17-001-00 for River Bend Station, Unit 1, Regarding Operations Prohibited by Technical Specifications (Conduct of Operations With a Potential to Drain the Reactor Vessel With Primary Containment Open) | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | 05000458/LER-2017-002 | Loss of Safety Function of Onsite Electrical Distribution Due to Malfunction of Control Building HVAC System LER 17-002-00 for River Bend Station, Unit 1, Regarding Loss of Safety Function of Onsite Electrical Distribution Due to Malfunction of Control Building HVAC System | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v), Loss of Safety Function | 05000458/LER-2017-003 | Manual Reactor Scram Initiated in Response to Increase in Steam Pressure During Steam Leak Troubleshooting LER 17-003-00 for River Bend Station, Unit 1, Regarding Manual Reactor Scram Initiated in Response to Increase in Steam Pressure During Steam Leak Troubleshooting | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | 05000458/LER-2017-004 | Loss of High Pressure Core Spray Safety Function During Surveillance Due to Malfunction of Test Return Valve LER 17-004-00 for River Bend Station, Unit 1, Regarding Loss of High Pressure Core Spray Safety Function During Surveillance Due to Malfunction of Test Return Valve | 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material | 05000458/LER-2017-005 | 1 OF 3 LER 17-005-00 for River Bend Station, Unit 1, Regarding Operations Prohibited by Technical Specifications Due to Inoperable Main Control Room Filter Train | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications | 05000458/LER-2017-006 | Potential Loss of Safety Function of Onsite Power Sources due to Inadvertent Inoperability of Control Building Chiller LER 17-006-00 for River Bend, Unit 1 re Potential Loss of Safety Function of Onsite Power Sources due to Inoperability of Control Building Chiller | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | 05000458/LER-2017-007 | Automatic Reactor Scram due to Failure of Main Generator Voltage Regulator Mode Transfer Relay LER 17-007-00 for River Bend Station - Unit 1 Regarding Automatic Reactor Scram due to Failure of Main Generator Voltage Regulator Mode Transfer Relay | 10 CFR 50.73(a)(2)(iv)(A), System Actuation | 05000458/LER-2017-009 | Potential Loss of Safety Function of Secondary Containment due to Unsecured Personnel Door LER 17-009-00 for River Bend, Unit 1 Regarding Potential Loss of Safety Function of Secondary Containment due to Unsecured Personnel Door | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material |
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