Semantic search

Jump to: navigation, search
Search

Edit query Show embed code

The query [[Category:Licensee Event Report]] [[Site::Summer]] was answered by the SMWSQLStore3 in 0.0899 seconds.


Results 1 – 23    (Previous 50 | Next 50)   (20 | 50 | 100 | 250 | 500)   (JSON | CSV | RSS | RDF)
 Report dateSiteEvent description
05000395/LER-2017-00231 January 2018Summer

1.0 ABSTRACT On June 29, 2017 at 0857. VCSNS Unit 1 automatically tripped due to low Feedwater (FW) flow to the 'B' Steam Generator (SG). The trip was the result of a spurious closure of the Main FW to 'B' Steam Generator Flow Control Valve, IFV00488-FW. The Flow Control Valve's closure resulted in low SG level coincident with the low FW now, which caused an automatic reactor trip. The plant trip response was normal.

The cause of this event was determined to be the inadvertent closure of IFV00488-1'W due to solenoid valve failure. The solenoid valve failure appears to be a result of an inadequate solder applied to the solenoid coil during the manufacturing process.

NIRO FORM 366 (04 2017)

05000395/LER-2017-00522 December 2017Summer

At 1957 on November 07, 2017, VCSNS Unit 1 was operating. in Mode 1 at 100% reactor power when a turb'ne trip caused an automatic reactor trip. All systems responded as expected, with the exception of 'B' Steani Generator Feedwater Isolation Valve (FW1V) XVG1611B-FW. This valve did not appear to automatically close and was slow to indicate closed from the Main Control Board, however this did not complicate the response. All Control Rods fully inserted and all Emergency Feedwater (Mk') pumps started as required. The Operating crew stabilized the plant, which remained in Mode 3 with decay heat removal via the Steam Dump system to the Main Condenser.

The cause of the turbine trip has been determined to be a loss of Digital Control System (DCS) power to all three Main Feedwater Pumps (FWP), which was caused by the failure of Non-Safety Related Inverter XIT5905.

05000395/LER-2017-00615 December 2017Vc Summer - Unit 1
Summer

At 0230 on October 30, 2017, VCSNS Unit 1 entered Technical Specification (TS) 3.3.3.9, Explosive Gas Monitoring Instrumentation, Action b. Entry into the TS action was a result of having one less than the minimum number of operable oxygen monitoring channels on the Waste Gas Holdup System Explosive Gas Monitoring System. TS Table 3.3-13, Line Item la requires a minimum of two operable channels for oxygen monitoring. When the number of operable monitoring channels is one less than required, the system can remain in operation, provided that grab samples are taken and analyzed at least once per 24 hours.

Upon entry into the TS action statement, the Control Room initiated station procedure GTP 702, General Test Procedure for Surveillance Activity Tracking and Triggering, and notified Chemistry of the grab sample requirements. The TS requirements were not adequately communicated to the oncoming personnel the following shift. As a result, the grab sample and analysis was not performed until 0405 on October 31, 2017 (after the 0230 requirement). The analysis was found to be satisfactory.

At the time of the event, Virgil C. Summer Nuclear Station (VCSNS) Unit I was operating in Mode I at 100% rated thermal power.

05000395/LER-2017-00312 December 2017Vc Summer - Unit 1
Summer

On August 28, 2017, at 0837, VCSNS Unit 1 automatically tripped due to a turbine trip. The turbine trip was caused by the Main Generator Differential Lockout due to a fault on the center phase, 230 kV lightning arrester, on the Main Transformer (XTF-1).

The plant trip response was normal. All control rods fully inserted. Balance of Plant (BOP) buses automatically transferred to their alternate power source, Emergency Auxiliary Transformers (XTF-31/32). Both Motor Driven (MD) Emergency Feedwater (EF) pumps and the Turbine Driven EF Pump started as designed.

The cause of this event was the failure of the center phase lightning arrester on XTF-1. The failed arrester, along with the other two lightning arresters that were in service on XTF-1 during the reactor trip, was replaced. The lightning arresters were sent to an independent lab, NEETRAC - Georgia Tech, for testing and evaluation.

The examination results indicate that the most probable cause of the arrester failure was an internal flashover of the metal oxide varistor blocks. The cause of the internal flashover is likely moisture ingress from the upper end seal.

05000395/LER-2017-00124 July 2017Vc Summer.- Unit 1
Summer

On June 16, 2017, the station completed a past operability review and determined that an IsAnergency Feedwater Auto Start Actuation Signal was inoperable from November 12. 2016 until April 7. 2017. Technical Specification (TS) 3.3.2 Limiting Conditions for Operation (J,C.0) was entered due to having less than the minimum number of channels operable for Motor Driven Emergency Feedwater Pump (NIDE:MVP) actuation per TS Table 3.3-3 Functional IJnit 6.g.

'Ibis event was caused by the Low Pressure (LP) and High Pressure (HP) steam inlet valves not closing because the Secondary Operating Cylinder and associated Pilot Valve were corroded. Water intrusion into the 'C' Main Feedwater Punip (MFP) oil system had caused the corrosion of the carbon steel components within '1.1)P0022C such that the Secondary Operating Cylinder and Pilot Valve were not functional.

This condition is reportable under 10CFR50.73(a.)(2)(i)(B), an operation or condition which was prohibited by the plant's Technical Specifications.

05000395/LER-2015-0028 June 2015Summer

A past operability review determined that HVAC System Mechanical Water Chiller (X11X0001A) had been non-functional during the month of July 2013 due to a vulnerability with component operation resulting in a low oil level condition. The event impacts the operability requirements of the Chilled Water (VU) System and the area room coolers the system supports per TS 3/4.7.9, "Area Temperature Monitoring.

On September 25, 2013, XHX0001A tripped on low oil level following surveillance testing. The "Circuit 2 Low Oil Level" fault occurred due to the compressor oil level dropping below the low oil level indicator switch set point for 60 seconds which initiates shutdown of the component. The cause was low superheat, causing liquid floodback to the compressor and a low evaporator heat load that was insufficient to promote proper oil return in the evaporator. The chiller unit was intermittently operated as the only chiller on the "A" VU train in July 2013. Due to this vulnerable condition the non-functional chiller impacted the operability of the "A" train components served by the "A" train VU system.

On April 9, 2015, the station determined this event was reportable and is being submitted in accordance with 10 CFR 50.73(a)(2)(i)(B).

05000395/LER-2015-00112 May 2015Summer

On March 17, 2015 a past operability review determined that XVG03005A-SP, Outside Reactor Containment (ORC) Reactor Building (RB) Spray Sump Isolation Valve A, was inoperable due to failure to fully stroke open during a surveillance test. XVG03004A-SP, Inside Reactor Containment RB Spray Sump Isolation Valve A, and XVG03005A-SP automatically open on receipt of RWST Lo-Lo Level coincident with a SI signal to transfer XPP0038A, Reactor Building Spray Pump A, suction from the RWST to the RB Sumps.

XVG03004A-SP and XVG03005A-SP are also logically tied to XVG03001A-SP, RB Spray Pump A RWST Suction Header Valve.

The full-open limit switches on XVG03004A-SP and XVG03005A-SP initiate automatic closure of XVG03001A-SP. Since XVG03005A-SP did not stroke fully open, the automatic swapover sequence could not have been completed, rendering the "A" train of RB Spray inoperable.

The cause of XVG03005A-SP to fully stroke open was due to spring pack relaxation and associated torque switch setting tolerances which resulted in the torque switch opening prior to the valve reaching the 100% open limit switch.

The torque switch setting was adjusted from 1 to 1.5 to allow higher developed torque before the switch opens to trip the motor. This adjustment will also reduce the effects from spring pack relaxation.

05000395/LER-2014-00419 September 2014Summer

1.0 ABSTRACT On 7/22/2014 at 0414, VC Summer Nuclear Station automatically tripped due to low Steam Generator water level in "C" Steam Generator. The trip was the result of the Condensate Bypass Valve, XVB09210-WI, failing to open as required while removing the Condensate Demineralization (WI) System from service during plant startup. With flow removed from the WI system and bypass valve XVB09210-W1 closed, condensate flow to the Deaerator Storage Tank (DAST) was isolated. All operating main Feedwater pumps tripped on DAST Low-Low level setpoint. The water level in the Steam Generators decreased and resulted in a reactor trip.

The cause of this event was failure of XVB09210-WI to stroke open due to a failed solenoid actuator and a procedure deficiency in manipulating the WI System. For corrective actions, the solenoid actuator for XVB09210-W1 was replaced and the system operating procedure for the WI system has been revised to direct the operator to verify that XVB09210-WI is has actuated open before reducing the flow through the Condensate Polishing Demineralizers.

This report is submitted in accordance with 10CFR50.73(a)(2)(iv)(A).

05000395/LER-2013-00228 August 2014Summer

1.0 ABSTRACT On April 22, 2013 the past operability determination identified that valve XVG09627B-CC was inoperable for a period of time greater than allowed by Technical Specification 3.7.3 for the Component Cooling Water System. On October 31, 2012, while performing a surveillance test, the normally closed Component Cooling (CC) System emergency makeup valve (XVG09627B-CC) failed to stroke open. The valve stroked open successfully on a subsequent test and was returned to service. On April 14, 2014, XVG09627B-CC failed to stroke open while performing the same surveillance test. The emergency makeup supply to the CC System is provided by the Service Water (SW) System. The SW System functions in the event of a complete loss of the normal makeup capability provided by the Demineralized Water System or if leakage exceeds the normal makeup capacity. The safety related function of XVG09627B-CC is to open to allow SW from the B Train to makeup to the B train CC system. By failing to open, this valve was unable to perform its design function without additional operator action.

The causes of this event are attributed to a low valve manipulation frequency, added frictional forces and possible spring degradation.

XVG09627B-CC has been rebuilt with new closure and trip springs and new packing that has a lower friction resistance. The valve supports were adjusted to enhance the alignment of the operator and the pressure regulator closing force was reduced. The valve was stroke tested satisfactorily after being rebuilt. This report is submitted in accordance with 10CFR50.73(a)(2)(i)(13).

05000395/LER-2014-00324 June 2014Summer1.0 ABSTRACT On April 26, 2014, while performing a surveillance test, the normally closed Component Cooling (CC) System emergency makeup valve (XVG09627A-CC) failed to stroke open. During the second attempt XVG09627A-CC opened in 11.29 seconds, which exceeded the maximum allowed stroke time of ten (10) seconds. This surveillance test is performed each refueling outage and was last successfully tested during the fall 2012 refueling outage (RF20). The emergency makeup supply to the CC System is provided by the Service Water (SW) System. The SW System functions as a source of emergency makeup in the event of a complete loss of the normal makeup capability provided by the Demineralized Water System or if leakage exceeds the normal makeup capacity. The safety related function Of XVG09627A-CC is to open to allow SW from the "A" Train to provide makeup to the "A" train CC system. By failing to open, this valve was unable to perform its design function without additional operator action. Since the valve did not stroke open on April 26, 2014, the station has concluded the valve may not have operated if required during the operating cycle. While XVG09627A-CC was unavailable, it was determined that XVG09627B-CC was also inoperable. A PRA risk evaluation determined the event of both valves being inoperable is of low safety significance. The cause of this event is believed to be low valve manipulation frequency, added frictional forces, and possible spring degradation. XVG09627A-CC has been rebuilt with new closure and trip springs and new packing that has a lower friction resistance. The pressure regulator closing force was also reduced. This report is submitted in accordance with 10CFR50.73(a)(2)(i )(B).
05000395/LER-2014-00216 June 2014Summer

1.0 ABSTRACT On April 18, 2014. V.C. Summer Nuclear Station (VCSNS) Unit I identified three reactor vessel head (RVH) penetrations (9, 43, and 51) that did not meet the requirements of 10 CFR 50.55a(g)(6)(ii)(D) and American Society of Mechanical Engineers (ASME) Section XI Code Case N-729-1. On April 26, 2014, the RVH penetration inspections were finalized and two additional penetrations (15 and 22) were identified for repair. The station was in a refueling outage (RF21) and the plant was defueled. The indications were not through wall as indicated by volumetric and bare metal visuals. The inspection results are reportable in accordance with 10 CFR 50.73(a)(2)(ii)(A).

The flaws were repaired using the embedded flaw repair process in accordance with NRC approved WCAP-15987-P, Revision 2-P-A and Relief Request RR-4-05. The apparent cause of the flaws is attributed to primary water stress corrosion cracking.

05000395/LER-2014-00112 June 2014Summer

1.0 ABSTRACT On April 14, 2014, while performing a surveillance test, the normally closed Component Cooling (CC) System emergency makeup valve (XVG09627B-CC) failed to stroke open. This surveillance test is performed each refueling outage and was last successfully tested during a mid cycle outage on March 30, 2013. The emergency makeup supply to the CC System is provided by the Service Water (SW) System. The SW System functions as a source of emergency makeup in the event of a complete loss of the normal makeup capability provided by the Demineralized Water System or if leakage exceeds the normal makeup capacity. The safety related function of XVG09627B-CC is to open to allow SW from the B Train to provide makeup to the B train CC system. By failing to open, this valve was unable to perform its design function without additional operator action.

Since the valve did not stroke open on April 14, 2014, the station has concluded the valve may not have operated if required during the remaining operating cycle after the successful test on March 30, 2013. While XVG09627B-CC was unavailable, it was discovered that XVG09627A-CC was also inoperable. A PRA risk evaluation determined the event of both valves being inoperable is of low safety significance. The cause of this event is believed to be low valve manipulation frequency, added frictional forces and possible spring degradation. XVG09627B-CC has been rebuilt with new closure and trip springs and new packing that has a lower friction resistance. The valve supports were adjusted to enhance the alignment of the operator and the pressure regulator closing force was reduced. This report is submitted in accordance with 10CFR50.73(a)(2)(i)(B) and 10CFR50.73(a)(2)(v)(D).

05000395/LER-2013-00631 January 2014Summer

On December 4, 2013, at approximately 1027 EST, 'B' train Control Room (CR) ventilation was in the emergency recirculation mode of operation as required by Technical Specification (TS) 3.3.3.1, Action 29. This Technical Specification action requires that the CR ventilation be in the emergency recirculation mode of operation when the Control Room Supply Air monitor is out of service.

An Instrument and Controls (I&C) technician was calibrating the Control Room Supply Air Atmospheric Radiation Monitor using station procedures. An operator was assisting using the system operating procedure for the Control Building Ventilation System. The (I&C) technician could not complete the test because the relay room recirculation damper position could not be verified. The technician communicated to the operator he needed to back out of the procedure. The operator mistakenly proceeded to a step in the system operating procedure to return the system to normal which resulted in securing Control Room Emergency Ventilation. The Control Room Emergency Ventilation was out of TS Action requirements for approximately 30 seconds, thus violating TS 3.3.3.1, Table 3.3-6 Action 29.

05000395/LER-2013-00511 December 2013Summer

As a result of recent industry operating experience (OE 305419, EN 49411, EN 49419) regarding the impact of unfused Direct Current (DC) ammeter circuits in the Control Room, Virgil C. Summer Nuclear Station (VCSNS) performed a review of ammeter circuitry. On October 16, 2013, the review determined the described condition to be applicable to VCSNS resulting in an unanalyzed condition with respect to 10CFR50 Appendix R analysis requirements.

The wiring design for the ammeters contains a shunt in the current flow from each DC battery or charger. The ammeter wiring attached to the shunt does not contain fuses. It is postulated that a fire could cause one of the ammeter wires to hot short to ground. Concurrently, the fire could cause another DC wire from the opposite polarity on the same battery or the same battery charger to also short to ground. This would cause a ground loop through the unfused ammeter cable. The potential exists that the cable could heat up causing a secondary fire in the ammeter raceway. The secondary fire could adversely affect safe shutdown equipment and potentially cause the loss of the ability to safely shutdown per 10CFR50 Appendix R.

The apparent cause of this event is double short to ground faults of opposite polarity were not considered during the design process of the Battery System. A corrective action has been added to the National Fire Protection Association (NFPA) 805 implementation to provide a permanent solution to address this unanalyzed Appendix R condition. As an interim action, roving fire watches have been established for the affected areas.

05000395/LER-2013-00119 November 2013Summer1.0 ABSTRACT On 3/24/2013 at 0458, a grid disturbance caused an undervoltage relay actuation on the "A" train 7200 Volt Switchgear Bus and the automatic start of the standby "A" Emergency Diesel Generator (EDG). At the time of the event, the "A" train Switchgear Bus was aligned to its normal offsite 115 kV power source. The grid disturbance was longer in duration than the associated undervoltage relay delay time. However the undervoltage event did not exist long enough to trip open the normal incoming breaker or initiate the Engineered Safety Features Load Sequencer (ESFLS). The EDG came up to the rated frequency and voltage, but the output breaker did not close, which was as expected. At 0520 the EDG was secured and restored to standby. The station was in Mode 5 for a mid cycle outage. All station equipment and all transmission system equipment operated as designed. Corrective actions to minimize the probability of reoccurrence have been added to the station's corrective action program. The event is reportable per 10CFR50.73(a)(2)(iv)(A), and 10CFR50.73(a)(2)(iv)(B)(8).
05000395/LER-2013-00321 August 2013Summer

On June 25, 2013 with the plant in Mode 1, the "A" Chiller (XHX0001A) shut down during a fast bus transfer of its 7.2 kV bus power supply due to the tripping of two molded case circuit breakers (MCCBs) located on the "A" Chiller skid. The "A" Chiller was running prior to a planned fast transfer of its 7.2 kV bus power supply from the normal power source (115kV) to the alternate source (230kV). Troubleshooting found both compressor motor MCCBs in the tripped condition.

The instantaneous trip calibration of the MCCBs was designed to trip the breakers with an incoming current greater than the nominal value of 2000A, and a current greater than this magnitude was experienced during this event. Trips of the MCCBs require local operator action to restart the chiller. A subsequent restart attempt resulted in both compressor motors not starting. The "A" Chiller has peen considered to be inoperable since being placed into service August 5, 2011 due to the inability of the chiller to respond to Engineered Safety Features (ESF) sequencer demand following a grid perturbation similar to the bus voltage transient that occurred with a "fast transfer" scenario. The Chilled Water System is an attendant cooling water system that supports the Control Room Emergency Filtration System (CREFS). VCSNS Technical Specifications (TS) 3.7.6 requires two trains of CREFS to be operable while in Mode one through four.

The MCCBs on the Chiller skid have been adjusted to trip at higher amperage. The instantaneous trip setting for the MCCBs has been changed from 2000A to an instantaneous trip range of 3063A to 3938A.

El

05000395/LER-2012-00231 July 2013Summer

On 06/14/2012, with the plant in Mode 1 at 100% power, it was determined that opening the code boundary valve between the safety related and seismically qualified Refueling Water Storage Tank (RWST) and the non-safety related and non-seismically qualified Spent Fuel Pool (SFP) Purification Loop in Modes 1-4 renders the RWST inoperable. This alignment was utilized for RWST water mixing in support of weekly surveillance sampling and for filtration of the RWST water prior to refueling outages. As a result, on multiple occasions the RWST was inoperable for a period longer than allowed by Technical Specifications (TS) 3.5.4, Emergency Core Cooling Systems - Refueling Water Storage Tank, Limiting Conditions for Operation (LCO).

The cause of this event is a result of regulatory requirements for the separation of seismically qualified and non-qualified systems, structures and components not being adequately incorporated into the Design Basis Document (DBD) and Updated Final Safety Analysis Report (UFSAR).

Immediate actions consisted of implementation of a Station Order (11-22), which indefinitely suspended this alignment, and submittal of a license amendment request (LAR) to revise TS 3.5.4 such that the non-seismically qualified piping of the SFP Purification System may be aligned to the RWST by operation of a seismically qualified manual ASME code boundary valve under administrative controls for performance of RWST surveillance requirements and pre-outage filtration. This change will only be applicable through the next two fuel cycles.

I

05000395/LER-2011-00327 September 2011Summer

At 1201 hours on 05/27/2011 with the plant in Mode 3 at normal operating temperature and pressure, a Safety Injection (SI) occurred due to opening the 'C' Main Steam Isolation Valve (MSIV), with the downstream steam header depressurized.

The resulting steam flow depressurized the 'C' Steam Line to greater than 97 psid below the 'A' and 'B' Steam Lines, which caused an SI on both Engineered Safety Feature (ESF) trains. Following the Safety Injection actuation, all plant systems functioned as designed.

Immediate actions consisted of securing the SI and stabilizing the plant in Mode 3 via Emergency Operating Procedures (EOP5). In addition, the MSIVs and Bypass valves were tagged closed to ensure proper controls were in place prior to operating the valves. Oncoming Operating Crews were briefed prior to taking the shift on the importance of maintaining cognizance of changing plant conditions and providing thorough turnover when relieving other crew members during the shift.

The root cause of this event was determined to be failure to follow procedures while manipulating a plant system.

05000395/LER-2011-0011 July 2011Summer

On May 3, 2011 at 0514 hours, V.C. Summer Nuclear Station (VCSNS) determined the following:

During circuit analysis review for transitioning the Fire Protection Program to NFPA 805, VCSNS identified a violation of the Appendix R requirement to maintain one train of systems free of fire damage, which are necessary to achieve and maintain Hot Shutdown conditions. VCSNS determined that a fire in the Main Control Room (MCR), the Cable Spreading Room (CSR), or the Control Building (CB) 412 North Chase could result in a hot short that could actuate a relay and trip and lock out all incoming breakers to the B-train essential electrical bus (XSW1DB).

A root cause analysis was conducted and determined the cause was human error in the Appendix R analysis performed for VCSNS by a vendor.

Immediate corrective actions consisted of establishing roving fire watches in the affected areas and revising the Fire Emergency Procedures (FEPs) to ensure the ability to achieve/maintain Hot Shutdown conditions.

This report also provides a 10 CFR Part 21 written notification.

05000395/LER-2011-0021 July 2011Summer

On May 3, 2011 at 0514 hours, V.C. Summer Nuclear Station (VCSNS) determined the following:

During circuit analysis review for transitioning the Fire Protection Program to NFPA 805, VCSNS identified a violation of the Appendix R requirement to maintain one train of systems free of fire damage , which are necessary to achieve and maintain Hot Shutdown conditions. This violation applies to postulated fires in the Main Control Room (MCR) or Cable Spreading Room (CSR). Circuits were identified in the MCR and the CSR that impact a control power circuit that could result in the loss of ability to start the B Emergency Diesel Generator (EDG) using local controls.

A root cause analysis was conducted and determined that the root cause was a less than adequate design change/configuration management process. Specifically, a design modification caused the subject vulnerability and the associated Appendix R review (both performed by a vendor for VCSNS) did not ensure the issue was corrected.

Immediate corrective actions consisted of establishing roving fire watches and installing jumpers to defeat the subject control power start permissive contacts.

05000395/LER-2003-00327 February 2004Summer

On September 8, 2003, at 1530 hours maintenance personnel opened the "A" train Control Room charcoal filter plenum to replace a charcoal filter that failed surveillance testing. On September 9, at 0730 hours, the shift supervisor asked if the system could perform its design function during an accident in the current configuration. At approximately the same time (0805 hours), maintenance was directed to close up the system (reinstall the plenum covers and gag the isolation dampers closed).

Engineering stated that the tag-out of the "A" train ventilation system inadvertently repositioned the isolation dampers for the emergency charcoal filter plenum and fan XFN 0030A open. The configuration would not allow maintaining the required positive 0.125 inch water column as specified in TS (3.7.6) and as verified by the intermittent control room low pressure alarms. This maintenance activity effectively breached the control room boundary and rendered the two emergency trains inoperable. This activity unknowingly placed the plant into Technical Specification Limiting Condition for Operability (LCO) 3.0.3, which requires 1 hour to prepare for plant shutdown and 6 hours to Hot Standby. This is being reported under 50.73(a)(2)(i)(B), a condition prohibited by Technical Specifications as the condition was undetected for 16 hours. Additionally, the event is reportable under 50.73 (a)(2)(v)(D) and 50.73(a)(2)(vii).

Replacement of the charcoal was suspended and the filter plenum was closed and isolated by manually gagging the isolation dampers while a plan was developed that would not degrade the ventilation system (charcoal replacement was completed on September 10, 2003). The NRC Emergency Operations Center was notified at approximately 1130 hours; event number EN# 40142.

A root cause evaluation has been completed and is attached to the corrective action document (CER 03-2819).

05000395/LER-2003-0022 July 2003Summer

A reactor trip on Over Temperature Delta Temperature (OTDT) occurred from 100 percent power on May 12, 2003, at 0102 hours, due to the main generator breaker opening. A root cause team was assembled to investigate the cause of the trip. Troubleshooting identified that the main generator field breaker position sensing circuit had degraded contacts that caused the digital voltage regulator to sense a loss of excitation and open the main generator breaker. Immediate corrective action involved replacing degraded contacts, removing suspect breaker position switch contacts, and adding a redundant circuit for this voltage regulator anticipatory trip function.

This was a programmed anticipatory trip function. The main generator never actually lost excitation until the trip and was fully protected.

Notification of this event was reported under Event Notification EN# 39838 at 0328 hours on May 12, 2003 in accordance with 10 CFR 50.72(bX1).

Following the plant trip, all major systems functioned as expected. The plant was stabilized in Mode 3.

NRC EOM 366 (7-2001)

05000395/LER-2003-00113 June 2003Summer

On April 22-23, 2003, steam propagation barrier door DRIB/107 was first discovered chained and strapped open and later found blocked open.

This event was caused by a lack of specific training for the Security Officers assigned to continuously monitor materials stored in the room behind the door. The door was being opened to provide cooling to the Security Officer on duty in the area. Upon first discovery, the chains and straps were removed and the door was secured.

Approximately 10 hours later, the door was found blocked open by the Security Officer on duty by physically standing with his back against the door. At this time the door was secured again.

Investigation revealed the event was reportable under 10 CFR 50.73(a)(2Xi)(B).

Opening door DRIB/107 beyond normal ingress and egress impacted both trains of control room ventilation as a result of breaching the pressure boundary encompassing all three Heating, Ventilation, and Cooling Water (HVAC) rooms. Loss of both trains of Control Room Ventilation is prohibited by Technical Specifications (TS) 3.7.6.