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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)

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.

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.

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.

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).

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.

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.

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

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.

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).

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.