ENS 41692

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v t e ENS Event
08:11 May 12, 2005
Title	Technical Specification Required Shutdown Due to Loss of Emergency Bus E1
Event Description	On May 12, 2005, at 0411 hours0.00476 days <br />0.114 hours <br />6.795635e-4 weeks <br />1.563855e-4 months <br />, electrical power was lost to the 4160 VAC Emergency Bus E1. Emergency Diesel Generator 1 was inoperable for maintenance at the time of the electrical power loss. This power loss to Emergency Bus E1 affected both Units 1 and 2. Unit 1 The loss of power to E1 resulted in Division 1 Primary Containment Isolation Valve (PCIV) actuations. The actuations included the Primary Containment Isolation System (PCIS) Group 2 (i.e., Drywell Equipment and Floor Drain, Traversing In-core Probe, Residual Heat Removal (RHR) Discharge to Radwaste, and RHR Process Sample), Group 3 (i.e., Reactor Water Cleanup), and Group 6 (i.e., Containment Atmosphere Control/Dilution, Containment Atmosphere Monitoring, and Post Accident Sampling Systems) valves, as well as the Reactor Building Ventilation System isolation (i.e., Secondary Containment isolation) and the automatic start of Standby Gas Treatment (SGT) System train B. The actuations of PCIVs and Reactor Building Ventilation System isolation were complete and the affected equipment responded as designed to the invalid signal (i.e., the valves and dampers that were open, at the time of the event, closed). Additionally, SGT System train B started and functioned successfully. Loss of power to E1 also resulted in entry into LCO 3.0.3 (i.e., be in Mode 2 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />, Mode 3 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />, and Mode 4 within 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />) due to all required reactor coolant leakage detection instrumentation/systems being inoperable. At 0440 hours0.00509 days <br />0.122 hours <br />7.275132e-4 weeks <br />1.6742e-4 months <br />, it was discovered that all three Control Room Air Conditioning (AC) subsystems became inoperable due to failure of the control building air compressors and Technical Specification LCO 3.0.3 was entered. At 0515 hours0.00596 days <br />0.143 hours <br />8.515212e-4 weeks <br />1.959575e-4 months <br />, it was determined that both Control Room Emergency Ventilation (CREV) subsystems became inoperable when the dampers drifted shut. At 0546 hours0.00632 days <br />0.152 hours <br />9.027778e-4 weeks <br />2.07753e-4 months <br />, a control building air compressor was started and the control room air conditioning and CREV subsystems were returned to operable status. Operators initiated a plant shutdown for Unit 1, as required by Technical Specifications at 0948 hours0.011 days <br />0.263 hours <br />0.00157 weeks <br />3.60714e-4 months <br />. Unit 2 Conditions and activities associated with the Control Room AC and CREV systems apply to Unit 2 as well as Unit 1. Reporting Requirements Met by this Notification 10 CFR 50.72(b)(2)(1), the initiation of any nuclear plant shutdown required by the plant's Technical Specifications, applies to Unit 1. 10 CFR 50.72(b)(3)(v)(D), a condition that, at the time of discovery, could have prevented the fulfillment of the safety function of systems that are needed to mitigate the consequences of an accident (i.e., Control Room AC and CREV), applies to both Units 1 and 2. 10 CFR 50.73(a)(i), invalid actuation of general containment isolation signals affecting containment isolation valves in more than one system, applies to Unit 1. INITIAL SAFETY SIGNIFICANCE EVALUATION Currently Unit 2 is operating at steady state with Unit 1 being shut down. Specified systems actuated as designed. No adverse impact to the control room environment occurred during the period (i.e., one hour and 35 minutes) the affected ventilation system was inoperable. The other redundant emergency busses are operable. Prior to the event reactor coolant leakage level for Unit 1 was well within operating limits. The actions as required by the applicable Technical Specifications have been established. CORRECTIVE ACTIONS Activities are currently under way to determine the cause of the E1 power loss and restore electrical power to Emergency Bus E1. Causes and actions to preclude recurrence will be addressed in accordance with the corrective action program and provided to the NRC in the associated licensee event report. The licensee notified the NRC Resident Inspector. * * UPDATE ON 05/13/05 @ 0952 BY LEONARD BELLER TO CHAUNCEY GOULD * * * On May 12, 2005, at 0411 hours0.00476 days <br />0.114 hours <br />6.795635e-4 weeks <br />1.563855e-4 months <br />, electrical power was lost to the 4160 VAC Emergency Bus E1. Emergency Diesel Generator 1 was inoperable for maintenance at the time of the electrical power loss. This power loss to Emergency Bus E1 affected both Units 1 and 2. A non-emergency notification (Event Number 41692) was made to the NRC Operations Center at 112:2 hours. This follow-up notification discusses plant recovery from the Emergency Bus E1 power loss. Unit 1 Loss of power to E1 resulted in entry, into LCO 3.0.3 (i.e., be in Mode 2 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />, Mode 3 within 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />, and Mode 4 within 39 hours4.513889e-4 days <br />0.0108 hours <br />6.448413e-5 weeks <br />1.48395e-5 months <br />) due to all required reactor coolant system (RCS) leakage detection instrumentation being inoperable. Operators initiated a plant shutdown for Unit 1, as required by Technical Specifications at 0948 hours0.011 days <br />0.263 hours <br />0.00157 weeks <br />3.60714e-4 months <br />. A Notice of Enforcement Discretion (NOED) was requested from the NRC to waive compliance with the shutdown requirements associated with RCS leakage detection instrumentation in order to provide more time for an orderly plant shutdown. In lieu of the RCS leakage detection shutdown requirements (i.e., be in Mode 2 by 1111 hours0.0129 days <br />0.309 hours <br />0.00184 weeks <br />4.227355e-4 months <br />), Unit 1 would adhere to the shutdown requirements associated with loss of Emergency Bus E1 (i.e.,, be in Mode 3 by May 13, 2005, at 0011 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br />). The requested NOED was verbally granted by the NRC on May 12, 2005 at 1050 hours0.0122 days <br />0.292 hours <br />0.00174 weeks <br />3.99525e-4 months <br />, so shutdown activities for Unit 1 continued versus the insertion of a manual reactor scram, with the unit at approximately 65 percent of rated thermal power. Power was restored to Emergency Bus E1 and the LCO associated with RCS leakage detection instrumentation was exited on May 12, 2005 at 1740 hours0.0201 days <br />0.483 hours <br />0.00288 weeks <br />6.6207e-4 months <br />. The LCO associated with loss of power to Emergency Bus E1 was exited at 2015 hours0.0233 days <br />0.56 hours <br />0.00333 weeks <br />7.667075e-4 months <br />. Unit 2 The LCO associated with loss of power to Emergency Bus E1 also applied to Unit 2, and was exited at 2015 hours0.0233 days <br />0.56 hours <br />0.00333 weeks <br />7.667075e-4 months <br />, CORRECTIVE ACTIONS Emergency Diesel Generator 1 was made available, but not operable, on May 13, 2005, at 0117 hours0.00135 days <br />0.0325 hours <br />1.934524e-4 weeks <br />4.45185e-5 months <br />. The licensee notified the NRC Resident Inspector. Reg 2 RDO (Moorman) was notified.

ENS 41692 +/-
Where
Brunswick North Carolina (NRC Region 2)
Reporting

10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation
LER:	05000325/LER-2005-004
Time - Person (Reporting Time:+3.18 h0.133 days <br />0.0189 weeks <br />0.00436 months <br />)
Opened:	Dave Jester 11:22 May 12, 2005
NRC Officer:	Wesley Held
Last Updated:	May 13, 2005
41692 - NRC Website
v • d • e

v t e Emergency Notification System
Brunswick with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown, 10 CFR 50.73(a)(1), Submit an LER
WEEKMONTHYEAR2024-01-02T04:33:00 [Table view]
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