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 Entered dateSiteRegionReactor typeEvent description
ENS 5427713 September 2019 12:21:00Watts BarNRC Region 2

EN Revision Text: EMERGENCY OPERATING FACILITY UNAVAILABLE DUE TO ACCESS ISSUES This is an eight-hour, non-emergency notification for a loss of Emergency Assessment Capability. A condition impacting access to the Emergency Operating Facility, Central Emergency Control Center (CECC), located in the TVA Chattanooga Office Complex occurred on September 13, 2019 at 0527 EDT. Fire suppression capabilities for the TVA Chattanooga Office Complex are currently impacted by a water main failure rendering access to the facility unsafe for personnel. If an emergency is declared requiring CECC activation during this period, other emergency response centers will be activated and staffed using existing emergency planning procedures and have the capability to perform the functions normally performed by the CECC. This is an eight-hour, non-emergency notification for a loss of Emergency Assessment Capability. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii) because the condition affects the functionality of an emergency response facility. The condition does not affect the health and safety of the public. The NRC Resident Inspector has been notified.

  • * * UPDATE ON 9/19/2019 AT 1341 EDT FROM DEAN BAKER TO ANDREW WAUGH * * *

Water lines impacting the Chattanooga Office Complex were repaired, and as of time 0734 EDT on 9/16/19, the CECC was returned to a functional status. The NRC Resident Inspector has been informed of this event update. Notified R2DO (Ehrhardt).

ENS 542521 September 2019 00:09:00Watts BarNRC Region 2While operating at 100 percent power, the Watts Bar Unit 1 reactor was manually tripped at 2055 EDT on August 31, 2019 due to loss of steam generator #2 level control. The trip was not complex. All control and shutdown bank rods inserted properly in response to the manual reactor trip. All safety systems, including Auxiliary Feedwater, actuated as designed. Operations responded and stabilized the plant. Decay heat is being removed by the Auxiliary Feedwater and the Steam Dump System. Unit 2 is not affected. The cause of the loss of steam generator water level control is being investigated. The manual actuation of the Reactor Protection System (RPS) is being reported as a four hour report under 10 CFR 50.72 (b)(2)(iv)(B). The automatic actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector was notified."
ENS 5422014 August 2019 20:00:00Watts BarNRC Region 2This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an invalid Containment Ventilation Isolation (CVI) actuation at Watts Bar Nuclear Plant (WBN) Unit 2. On July 26, 2019, at 1003 Eastern Daylight Time (EDT), the Train A CVI actuated due to an invalid High Radiation signal from 2-RM-90-130, Containment Purge Air Exhaust Monitor. Prior to and following the invalid High Radiation alarm, all radiation monitors except 2-RM-90-130 were stable at their normal values. All required automatic actuations occurred as designed. Upon investigation, the cause of the invalid High Radiation alarm was due to a failed ratemeter for 2-RM-90-130. Control room operators performed appropriate checks and confirmed that the subject indication was an invalid high radiation signal. The ratemeter for 2-RM-90-130 was replaced and the monitor returned to service. At the time of the event, plant conditions for a High Radiation alarm did not exist; therefore, the CVI was invalid. The NRC Resident Inspector was notified."
ENS 5412720 June 2019 17:59:00Watts BarNRC Region 2At 1340 EDT on June 20, 2019, a breach in excess of allowable margin in the Unit 2 Shield Building annulus was identified. T.S. LCO 3.6.15, Condition A was entered. The breach is expected to be repaired within the 24 hours allowed LCO time. No other equipment issues were identified. The Shield Building ensures that the release of radioactive material from the containment atmosphere is restricted to those leakage paths and associated leakage rates assumed in the accident analysis during a Loss of Coolant Accident (LOCA). This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(C). NRC Resident Inspector has been notified. The breach consists of a tear in a flexible boot seal for a penetration associated with the suction path for gas treatment fans. There is no release of radioactive material associated with this event.
ENS 5411212 June 2019 11:55:00Watts BarNRC Region 2At 0849 (EDT), a significant air leak on an inline air filter was identified. At 0908, the leak on the filter was isolated. A subsequent review of this situation determined that this air leak impacted operation of the A Train of the Control Room Emergency Air Temperature Control System (CREATCS) which is required to be operable in accordance with Technical Specification 3.7.10. At the time of this event, the B Train of CREATCS was out of service for planned maintenance. With both trains of CREATCS out of service, both Watts Bar Units entered a condition that could have prevented fulfillment of a safety function. This condition was terminated when the leaking air filter was isolated. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). NRC Resident Inspector has been notified."
ENS 5407722 May 2019 05:45:00Watts BarNRC Region 2On May 22, 2019, at 0233 EDT, Watts Bar Nuclear Plant (WBN) Unit 2 reactor was manually tripped due to a failure of the #2 Main Feedwater Regulating Valve during power ascension following a refueling outage. Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed. All Control and Shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and Steam Dumps. Unit 2 is in a normal shutdown electrical alignment. This reactor trip and system actuation is being reported under 10 CFR 50.72(b)(3)(iv)(A) and 10 CFR 50.72(b)(2)(iv)(B). There was no impact to WBN Unit 1. The NRC Senior Resident has been notified."
ENS 5402123 April 2019 09:44:00Watts BarNRC Region 2At 0232 EDT on April 23, 2019, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 0233 EDT, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10 Control Room Emergency Ventilation System (CREVS) was declared not met for both trains. Watts Bar Unit 1 entered Condition B. Watts Bar Unit 2 was not performing movement of irradiated fuel assemblies and did not meet the APPLICABILITY for CREVS per LCO 3.7.10. At 0233 EDT on April 23, 2019, the alarm cleared, CREVS was declared operable and LCO 3.7.10 Condition B was exited. The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. From 0232 EDT to 0233 EDT, (Watts Bar Nuclear) WBN was unable to validate that CREVS could fulfill its required Safety Function. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified."
ENS 5384022 January 2019 09:41:00Watts BarNRC Region 2This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an invalid Containment Ventilation Isolation (CVI) actuation at Watts Bar Nuclear Plant (WBN) Unit 1. On December 2, 2018 at 0028 Eastern Standard Time (EST), the Train A CVI actuated due to an invalid High Radiation signal from 1-RM-90-130, Containment Purge Exhaust Radiation Monitor. In addition to the Train A CVI, instrument malfunction alarms were received for 1-RM-90-106, Lower Containment Radiation Monitor and 1-RM-90-112, Upper Containment Radiation Monitor as the associated valves isolated for the CVI. A common instrument malfunction alarm was also received for 1-RM-90-130 and 1-RM-90-131, Containment Purge Exhaust Radiation Monitors. Prior to and following the invalid High Radiation alarm, all radiation monitors except 1-RM-90-130 were stable at their normal values. All required automatic actuations occurred as designed. Upon investigation, the cause of the invalid High Radiation alarm was due to a failed ratemeter for 1-RM-90-130. Control room operators performed appropriate checks and confirmed that the subject indication was an invalid high radiation signal. The ratemeter for 1-RM-90-130 was replaced and the monitor returned to service. At the time of the event, plant conditions for a High Radiation alarm did not exist; therefore, the CVI was invalid. The NRC Resident Inspector was notified."
ENS 5380121 December 2018 00:02:00Watts BarNRC Region 2At 1642 Eastern Standard Time (EST) on December 20, 2018, it was determined that both trains of Containment Air Return Fan (CARF) were simultaneously INOPERABLE from 0817 (EST) to 1129 (EST) on November 20, 2018. This condition is not bounded by existing design and licensing documents; however, it poses no impact to the health and safety of the public or plant personnel. Therefore, this event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified."
ENS 5369727 October 2018 16:52:00Watts BarNRC Region 2On October 27, 2018, at 1533 EDT, Watts Bar Nuclear (WBN) Plant Unit 1 reactor was manually tripped due to a failure of the #3 Reactor Coolant Pump normal feeder breaker to close during the planned power transfer to unit power following startup. Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed. All Control and Shutdown rods fully inserted. (Main Steam Isolation Valves) MSIVs were required to be isolated due to cooldown. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and Steam Generator Atmospheric Dump Valves. Unit 1 is in a normal shutdown electrical alignment. This reactor trip and system actuation is being reported under 10CFR 50.72(b)(3)(iv)(A) and 10CFR 50.72 (b)(2)(iv)(B). There was no effect on WBN Unit 2. The NRC Senior Resident has been notified."
ENS 5359311 September 2018 05:17:00Watts BarNRC Region 2At 0113 EDT on September 11, 2018, it was discovered both trains of CREVS (control room emergency ventilation system) were simultaneously inoperable; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. The door to the main control room habitability zone from the turbine building was left open and unattended for about a minute, breaking the pressure boundary in the room, resulting in an alarm. The door was closed, clearing the alarm and the CREVS was considered operable.
ENS 5355722 August 2018 11:23:00Watts BarNRC Region 2At 0943 EDT on August 22, 2018, the Watts Bar Unit 2 reactor automatically tripped while operating at 100 percent power. All control and shutdown bank rods inserted properly in response to the automatic reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. The reactor automatically tripped due to a main turbine trip signal. An investigation is in progress. The automatic actuation of the Reactor Protection System (RPS) is being reported as a four-hour report under 10 CFR 50.72 (b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event."
ENS 5346722 June 2018 12:14:00Watts BarNRC Region 2At 0841 EDT on June 22, 2018, the Watts Bar Unit 2 reactor automatically tripped while operating at 95% power. All control and shutdown bank rods inserted properly in response to the automatic reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. The reactor automatically tripped due to a main turbine trip. The turbine trip was caused by main generator electrical trip. An investigation is in progress. The automatic actuation of the Reactor Protection System (RPS) is being reported as a four hour report under 10 CFR 50.72 (b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event. The plant is currently stable at normal operating temperature and pressure. The grid is stable and the plant is in its normal shutdown electrical lineup. Unit 1 was unaffected by the Unit 2 trip.
ENS 5339811 May 2018 15:19:00Watts BarNRC Region 2Westinghouse PWR 4-LoopAt 1011 EDT on May 11, 2018, Containment Shield Building Annulus differential pressure exceeded the required limit. The Shield Building was declared inoperable requiring entry into Technical Specification (TS) 3.6.15 Conditions A and B. The event was initiated by failure of the operating annulus vacuum fan. Main Control Room Operators manually started the stand-by annulus vacuum fan to recover pressure. Shield Building Annulus differential pressure was restored to the required value at 1016 EDT and TS 3.6.15 Condition A and B were exited on May 11, 2018 at 1016 EDT. The failure mechanism for the annulus vacuum fan is being investigated. The Containment Shield Building ensures the release of radioactive material from the containment atmosphere is restricted to those leakage paths and associated leakage rates assumed in the accident analysis during a Loss of Coolant Accident (LOCA). The Emergency Gas Treatment System (EGTS) would have automatically started and performed its design function to maintain the Shield Building Annulus differential pressure within required limits. The event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.72(b)(3)(v)(D). The NRC Resident has been notified.
ENS 5335622 April 2018 04:28:00Watts BarNRC Region 2Westinghouse PWR 4-Loop

On April 22, 2018 at 0222 EDT, Watts Bar Nuclear Plant (WBN) Unit 2 entered TS (Technical Specifications) LCO (Limiting Condition for Operation) 3.0.3 due to both trains of the Residual Heat Removal System (RHRS) becoming inoperable. During surveillance testing, the gas void values on Emergency Core Cooling System (ECCS) piping common to both trains did not meet acceptance criteria. This caused both RHRS trains to become inoperable. Operations subsequently vented the RHRS to meet the acceptance criteria and exited TS LCO 3.0.3 at 0227 EDT. More frequent surveillances will be conducted to monitor gas void volumes while additional analysis is being performed to determine corrective actions. The NRC Resident Inspector has been notified.

  • * * RETRACTION FROM TONY PATE TO HOWIE CROUCH ON 5/4/18 AT 1455 EDT * * *

This event is being retracted. The initial report was based on a conservative acceptance criteria for gas accumulation adopted on April 19, 2018 when it was determined that the previously used acceptance criteria for gas accumulation in the ECCS was non-conservative. Additional analysis has subsequently been performed and determined that a higher gas accumulation acceptance criteria does not challenge operability. With a void of less than the acceptance criteria, in the event of ECCS actuation, the system piping support loads will remain within structural limits and the piping system will remain operable. Therefore, both trains of Unit 2 RHRS were operable and the previously reported 10 CFR 50.72(b)(3)(v)(B) event is being retracted. The NRC Resident Inspector staff has been informed of this event retraction. Notified R2DO (Desai) of this retraction.

ENS 5335522 April 2018 02:34:00Watts BarNRC Region 2Westinghouse PWR 4-Loop

On April 21, 2018 at 2152 EDT, Watts Bar Nuclear Plant (WBN) Unit 1 entered TS (Technical Specifications) LCO (Limiting Condition for Operation) 3.0.3 due to both trains of the Residual Heat Removal System (RHRS) becoming inoperable. During surveillance testing, the gas void values on Emergency Core Cooling System (ECCS) piping common to both trains did not meet acceptance criteria. This caused both RHRS trains to become inoperable. Operations subsequently vented the RHRS to meet the acceptance criteria and exited TS LCO 3.0.3 at 2222 EDT. More frequent surveillances will be conducted to monitor gas void volumes while additional analysis is being performed to determine corrective actions. The NRC Resident Inspector has been notified.

  • * * RETRACTION FROM ANTHONY PATE TO DONALD NORWOOD AT 1310 EDT ON 5/9/2018 * * *

This event is being retracted. The initial report was based on a conservative acceptance criteria for gas accumulation adopted on April 19, 2018 when it was determined that the previously used acceptance criteria for gas accumulation in the ECCS was non-conservative. Additional analysis has subsequently been performed and determined that a higher gas accumulation acceptance criteria does not challenge operability. With a void of less than the acceptance criteria, in the event of ECCS actuation, the system piping support loads will remain within structural limits and the piping system will remain operable. Therefore, both trains of Unit 1 RHRS were operable and the previously reported 10 CFR 50.72(b)(3)(v)(B) event is being retracted. The NRC Resident Inspector has been informed of this event retraction. Notified R2DO (Ehrhardt).

ENS 5334920 April 2018 00:55:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn April 19, 2018 at 1944 EDT, Watts Bar Nuclear Plant (WBN) determined that a preliminary analysis shows current acceptance criteria for gas accumulation in the WBN Unit 1 and Unit 2 Safety Injection System (SIS) and Residual Heat Removal System (RHRS) discharge piping may be non-conservative. The surveillances that check void values and allow venting of the systems are to be performed utilizing conservative criteria at more frequent intervals to ensure gas void volumes remain under acceptable limits. Additional analysis is being performed to determine final actions. The NRC Resident Inspector has been notified.
ENS 5332712 April 2018 12:14:00Watts BarNRC Region 2Westinghouse PWR 4-LoopAt 0920 EDT on April 12, 2018, the Watts Bar Unit 2 reactor automatically tripped while operating at 100 percent power. All control and shutdown bank rods inserted properly in response to the automatic reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. The cause of the automatic reactor trip is being investigated. The automatic actuation of the Reactor Protection System (RPS) is being reported as a four-hour report under 10 CFR 50.72 (b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight-hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event. The plant is currently stable at normal operating temperature and pressure. The grid is stable and the plant is in its normal shutdown electrical lineup. Unit 1 was unaffected by the Unit 2 trip.
ENS 5329126 March 2018 20:07:00Watts BarNRC Region 2Westinghouse PWR 4-LoopAt 1839 Eastern Daylight Time (EDT) on March 26, 2018, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 1840 EDT, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10, Control Room Emergency Ventilation System (CREVS), was declared not met for both trains and Condition B entered. At 1840 EDT on March 26, 2018, the alarm cleared, CREVS was declared operable and LCO (Limiting Condition for Operation) 3.7.10, Condition B was exited. The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. From 1839 EDT to 1840 EDT, WBN (Watts Bar Nuclear) was unable to validate that CREVS could fulfill its required Safety Function. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). A watch has been posted at the door to prevent recurrence. The NRC Resident Inspector has been notified.
ENS 5328826 March 2018 11:51:00Watts BarNRC Region 2Westinghouse PWR 4-LoopAt 1058 Eastern Daylight Time (EDT) on March 26, 2018, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 1100 EDT, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10, Control Room Emergency Ventilation System (CREVS), was declared not met for both trains and Condition B entered. At 1100 EDT on March 26, 2018, the alarm cleared, CREVS was declared operable and LCO (Limiting Condition for Operation) 3.7.10, Condition B was exited. The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. From 1058 EDT to 1100 EDT, WBN (Watts Bar Nuclear) was unable to validate that CREVS could fulfill its required Safety Function. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified.
ENS 531964 February 2018 12:00:00Watts BarNRC Region 2Westinghouse PWR 4-Loop

At 0445 (EST) on February 4, 2018, Watts Bar Unit 1 entered Technical Specification 3.6.1 condition A and 3.6.3 condition A.1 and A.2 due to inoperable containment penetration thermal relief check valves 1-CKV-31-3407 and 1-CKV-31-3421 associated with one train of the Containment Incore Instrument Room Chiller system. During surveillance testing, the thermal relief check valves failed to open and pass flow as required by acceptance criteria. The two penetrations were subsequently drained and isolated in accordance with the surveillance procedure to remove any thermal expansion concerns. Technical Specification 3.6.1 was exited February 4, 2018 at 0512 once the two penetrations were drained and isolated. The purpose of the thermal relief check valves is to allow flow from an isolated penetration back into the upstream containment piping to prevent over-pressurization due to thermal expansion. Over-pressurization of an isolated containment penetration could potentially cause the penetration or both of the isolation valves to fail and provide a direct flow path to the environment from the potentially contaminated containment atmosphere under certain Design Basis Accidents. Therefore, failure of the thermal relief check valves to open could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(C). NRC Resident Inspector has been notified.

  • * * RETRACTION AT 1336 EST ON 03/29/2018 FROM TONY PATE TO TOM KENDZIA * * *

The purpose of this notification is to retract ENS notification 53196 made on 2/4/2018 for Watts Bar Nuclear Plant. The previous notification reported a surveillance failure of two containment penetration thermal relief check valves that, at the time of discovery, could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material. After Engineering evaluation, it has been determined there is reasonable assurance the two thermal relief check valves (1-CKV-31-3407 and 1-CKV-31-3421) were capable of performing their specified safety function to isolate containment and act as a thermal relief device during a design basis accident. The basis of the evaluation included: 1. No maintenance activities or interactions with the check valves had occurred since last tested. 2. All surveillance testing for the valves was within required frequency. 3. The opening force for a new check valve of the same size and similar to 1-CKV-31-3407 and 1-CKV-31-3421 is 0.38 pounds. Engineering analysis has determined the minimum failure pressure of the piping systems associated with the containment penetration in question is 450 psig. If it is assumed the force applied on the check valve seat reaches 450 psig, the force applied on the seat would reach 111 pounds or 300 times the force required to open a new, clean check valve. Based on engineering judgement of previous operating experience where the pressure required to open the same stuck check valve was within a safety factor of 6 to potential equipment damage, the thermal relief check valves would have opened prior to equipment damage and thus the identified condition would not have resulted in adversely affecting the containment isolation boundary. Entry into Technical Specification (TS) 3.6.1 condition A on 2/4/2018 at 0445 has been retracted. Although not a loss of safety function, the containment penetrations associated with 1-CKV-31-3407 and 1-CKV-31-3421 remain inoperable and are being tracked by TS 3.6.3 condition A.1 and A.2. The NRC Resident Inspector has been notified. Notified the R2DO (Rose).

ENS 5317317 January 2018 22:41:00Watts BarNRC Region 2Westinghouse PWR 4-LoopAt 2002 EST on January 17, 2018, annulus differential pressure exceeded its pressure limit. At that time, the Shield Building was declared inoperable requiring entry into Technical Specification 3.6.15, Conditions A and B. Action was taken by field operators to swap annulus vacuum control dampers to restore annulus differential pressure. At 2024 EST, annulus differential pressure was restored to required limits, the Shield Building was declared operable, and LCO 3.6.15, Conditions A and B were exited. The temporary loss of the Shield Building resulted from a failure of the annulus vacuum control system to maintain the required differential pressure. Manual swap-over of pressure control to the backup damper restored differential pressure to required limits allowing exit from TS LCO 3.6.15 and restoration of the Shield Building safety function. The Shield Building ensures that the release of radioactive material from the containment atmosphere is restricted to those leakage paths and associated leakage rates assumed in the accident analysis during a Loss of Coolant Accident (LOCA). The Emergency Gas Treatment System (EGTS) would have automatically started and performed its design function to maintain annulus vacuum within required limits. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified.
ENS 5313220 December 2017 18:18:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn December 20, 2017, at 1040 Eastern Standard Time (EST), the Watts Bar Nuclear Plant (WBN) 1B-B 6.9kV Shutdown Board (SDBD) normal feeder breaker opened. The loss of voltage to the 1B-B SDBD resulted in the start of the 1B-B Motor Driven Auxiliary Feedwater (MDAFW) pump, the Unit 1 Turbine Driven Auxiliary Feedwater (TDAFW) pump, and the start of all four Emergency Diesel Generators (EDGs). Power was restored to the 1B-B 6.9 kV SDBD when it loaded on to its associated EDG. Following initial investigation, the 1B-B 6.9 kV SDBD was transferred to its alternate offsite power source, Common Station Service Transformer (CSST) C at 1217 EST. At 1230 EST, the 1B-B 6.9 kV SDBD alternate feeder breaker opened. The loss of voltage to the 1B-B SDBD did not result in the restart of the 1B MDAFW pump, the Unit 1 TDAFW pump, or EDGs; this equipment remained running from the earlier event. Power was restored to the 1B-B 6.9 kV SDBD when it loaded on to its associated EDG. Restoration of normal offsite power to the 1B-B SDBD was completed at 1654. Other than several common Unit Technical Specifications having not been met, Unit 2 was not operationally impacted by the transfer of the 1B-B Shutdown Board to onsite power and remains in Mode 1 at 100% power. This report is made per 10 CFR 50.72(b)(3)(iv)(A). NRC Resident Inspector has been notified. The licensee investigation continues for the cause of the event.
ENS 5311211 December 2017 11:06:00Watts BarNRC Region 2Westinghouse PWR 4-LoopWhile operating at 97% power, the Watts Bar Unit 2 reactor was manually tripped at 0857 EST on December 11, 2017 due to multiple dropped control rods. All control and shutdown bank rods inserted properly in response to the manual reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and the Steam Dump System. The cause of the dropped rods is being investigated. The manual actuation of the Reactor Protection System (RPS) is being reported as a four hour report under 10 CFR 50.72 (b)(2)(iv)(B). The actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event. No safety or relief valves lifted during this event.
ENS 5309226 November 2017 16:16:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn November 26, 2017, at 1225 Eastern Standard Time (EST), the Watts Bar Nuclear Plant (WBN) Unit 2 experienced an unplanned ECCS discharge to the Unit 2 Reactor Coolant System (RCS) while de-pressurized, in Mode 5, with the Pressurizer vented to the Pressurizer Relief Tank. ECCS injection via the Boron Injection flow path occurred during planned Safety Injection system Engineered Safety Features Actuation System (ESFAS) testing. The Boron Injection flow path should have been isolated and should not have resulted in any injection flow to the Unit 2 RCS. Since the injection was not a part of the pre-planned test this is reportable under 10 CFR 50.72(b)(2)(iv), System Actuation. All other systems responded as expected in accordance with the ESFAS testing procedure. The unintended ECCS injection flow was isolated and flow through the Boron Injection path was verified to be stopped at 1232 EST. The Unit 2 Pressurizer level and pressure remained below any limits and no safety limits were challenged. NRC Resident Inspector has been notified.
ENS 5304430 October 2017 15:50:00Watts BarNRC Region 2Westinghouse PWR 4-LoopAt 0942 Eastern Daylight Time (EDT) on October 30, 2017, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 0943 EDT, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification 3.7.10 Control Room Emergency Ventilation System (CREVS) was declared not met for both trains and Condition B entered. At 0945 EDT the alarm cleared, CREVS was declared operable and LCO 3.7.10, Condition B was exited. The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. From 0942 EDT to 0943 EDT WBN (Watts Bar Nuclear) was unable to validate that CREVS could fulfill its required Safety Function. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). NRC Resident Inspector has been notified.
ENS 5291217 August 2017 17:24:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn August 17, 2017, at 1205 Eastern Daylight Time (EDT), the Watts Bar Nuclear Plant (WBN) lost power to the 1B-B 6.9kV Shutdown Board. The loss of power to this safety related bus resulted in an automatic start of the Unit 1 Turbine Driven Auxiliary Feedwater Pump (TDAFWP). The motor driven AFW pumps did not start and were not expected to start for this event. No other system actuations occurred as a result of loss of power to the 1B-B 6.9kV Shutdown Board. Power to the 1B-B Shutdown Board was restored at 1505 EDT on August 17, 2017. During the loss of power to the 1B-B Shutdown Board, a reduction in containment and control rod drive mechanism cooling occurred. At 1233 EDT, lower containment average temperature exceeded the procedural limitations specified, and Technical Specification 3.6.5 Condition A was entered for containment average air temperature not within limits. Lower containment average temperature was restored to within limits at 1525 EDT on August 17, 2017. This is reportable as a potential loss of safety function. Other than several common Unit Technical Specifications having not been met, Unit 2 was not operationally impacted by the loss of power to the 1B-B Shutdown Board and remains in Mode 1 at 100% power. The NRC Resident Inspector has been notified. The loss of power occurred during restoration from Emergency Diesel Generator maintenance.
ENS 5287225 July 2017 11:07:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn July 25, 2017, at 0428 Eastern Daylight Time (EDT) Watts Bar Nuclear Plant (WBN) Unit 2 was in Mode 3, beginning a Reactor Startup. While in the initial phase of withdrawing the first of four Control Rod banks, the two associated group demand position indicators deviated greater than 2 steps from each other. In accordance with Technical Requirement 3.1.7, Position Indication System, Shutdown, with one or more group demand position indicators inoperable, the reactor trip breakers are to be opened immediately. Operations personnel opened the reactor trip breakers immediately by initiating a manual trip of the Reactor Protection System (RPS). The Auxiliary Feedwater system was in service and controlling Steam Generator water levels at the time of the event and did not receive any valid actuation signals. No other system actuations occurred as a result of this reactor trip and all systems operated as designed. The cause of the position indication system inoperability is currently under investigation. NRC Resident Inspector has been notified.
ENS 5285012 July 2017 16:05:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn July 12, 2017, at 1238 Eastern Daylight Time (EDT), Watts Bar Nuclear Plant (WBN) determined that a preliminary analysis shows adequate Essential Raw Cooling Water (ERCW) flow may not be in place during dual unit limiting design basis conditions of one unit in Hot Shutdown on Residual Heat Removal (RHR) cooling when the other unit experiences a Loss of Coolant Accident (LOCA). Based on preliminary analysis, during a Unit 1 LOCA, Unit 1 receives adequate flow when following existing procedural guidance; however, Unit 2 may not receive adequate flow to meet cool-down requirements with design basis maximum temperatures. During a Unit 2 LOCA, however, current procedural guidance is not adequate to ensure the proper system alignment to establish correct ERCW Component Cooling Water (CCS) Heat Exchanger A and B flow rates for either unit's cool down requirements. Unit 2 has been shutdown for an extended period of time such that the flow delivered by ERCW is adequate to serve both Unit 1 in a LOCA and Unit 2 in less than Mode 3. The NRC Resident Inspector has been notified.
ENS 5280815 June 2017 18:23:00Watts BarNRC Region 2Westinghouse PWR 4-LoopAt 1219 (EDT) on June 15, 2017, annulus vacuum exceeded its pressure limit. At that time, the Shield Building was declared inoperable in accordance with Technical Specification 3.6.15 Condition A and B, due to the inoperability of the Shield Building (CRE). At 1222 (EDT), annulus pressure returned to normal, Shield Building was declared operable and LCO 3.6.15, Condition A and B were exited. The temporary loss of the Shield Building resulted from a loss of pressure control in the Auxiliary Building caused by a loss of Auxiliary Building General Ventilation. The Auxiliary Building Gas Treatment System was started to maintain Auxiliary Building pressure within limits and the non-safety related Annulus Vacuum system automatically restored annulus pressure. The Shield Building ensures that the release of radioactive material from the containment atmosphere is restricted to those leakage paths and associated leakage rates assumed in the accident analysis during a LOCA. The EGTS system (Emergency Gas Treatment System) would have automatically started and performed it's design function to maintain Annulus Vacuum within required values. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). NRC Resident Inspector has been notified.
ENS 527906 June 2017 08:30:00Watts BarNRC Region 2Westinghouse PWR 4-LoopThis 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an invalid Auxiliary Feedwater (AFW) actuation at Watts Bar Nuclear Plant (WBN) Unit 1. On April 28, 2017 at approximately 0500 Eastern Daylight Time (EDT), Unit 1 maintenance personnel were performing 1-IMI-3.005, '18 Month Calibration of Anticipated Transient Without Scram System Actuation Circuitry (AMSAC),' when an AMSAC actuation signal was received. Both Motor Driven Auxiliary Feedwater Pumps (MDAFWPs) were already in service when this actuation occurred. The Turbine Driven Auxiliary Feedwater Pump (TDAFWP) did not start as it had been removed from service. Additionally, steam generator blowdown isolated as required. During this event, AMSAC actuation was complete and equipment functioned as expected by its operating state. Upon identification of the AMSAC actuation, maintenance activities were halted and a prompt investigation was initiated. WBN found that the procedure in use for the 18 month calibration had been recently revised. The procedure called for maintenance to connect an analog multi-meter set on resistance to incorrect points during performance of the procedure. When the analog multi-meter was connected to the incorrect points, a relay was energized resulting in an AMSAC actuation. The procedure was revised and the test completed. The licensee notified the NRC Resident Inspector.
ENS 527324 May 2017 19:53:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn May 4th, 2017, at 1709 EDT, Watts Bar Nuclear Plant Unit 1 reactor was manually tripped due to a failure of the #3 Reactor Coolant Pump normal feeder breaker to close during the planned power transfer to unit power following startup. Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed. All Control and Shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and Steam Generator Atmospheric Dump Valves. Unit 1 is in a normal shutdown electrical alignment. This reactor trip and system actuation is being reported under 10CFR 50.72(b)(3)(iv)(A) and 10CFR 50.72(b)(2)(iv)(B). There was no effect on WBN Unit 2. The NRC Senior Resident (Inspector) has been notified.
ENS 527252 May 2017 22:33:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn May 2nd, 2017, at 1945 EDT, Watts Bar Nuclear (WBN) Plant Unit 1 reactor was manually tripped due to a failure of the #3 Reactor Coolant Pump normal feeder breaker to close during the planned power transfer to unit power following startup. Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed. All control and shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via auxiliary feedwater and main steam dump systems. Unit 1 is in a normal shutdown electrical alignment. This reactor trip and system actuation is being reported under 10CFR 50.72(b)(3)(iv)(A) and 10CFR 50.72 (b)(2)(iv)(B). There was no effect on WBN Unit 2. The NRC Senior Resident (Inspector) has been notified.
ENS 526696 April 2017 22:40:00Watts BarNRC Region 2Westinghouse PWR 4-Loop

At 1620 EDT on April 6, 2017, a Main Control Room (MCR) door was found ajar. At that time, both control room ventilation filtrations trains (CREVS) were declared inoperable in accordance with Technical Specification 3.7.10, condition B, due to the inoperability of the Control Room Envelope (CRE). At 1623 EDT, the door was closed, CREVS was declared operable and LCO 3.7.10, Condition B was exited. The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. Additionally, it ensures that the occupants are protected from hazardous chemicals and smoke. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). NRC Resident Inspector has been notified.

  • * * RETRACTION FROM DAVID ALLEN TO S. SANDIN ON 5/18/17 AT 1459 EDT * * *

Event Notification EN 52669, made on 4/06/2017, is being retracted because additional reviews have been performed supporting that a loss of safety function did not occur. Watts Bar Unit 2 has concluded that there was no loss of safety function, because when the door was found open it was capable of being closed and able to support the control room envelope function. A simulation performed on 04/07/17 also showed that with the door in question opened 1-2 inches that the control room pressure would have remained above the TS required positive pressure of 0.125 inches of water. The control room envelope is designed such that the door is expected to be opened to allow personnel entry and exit, and thus positive pressures in the control room will fluctuate. The event that occurred is similar to a number of individuals entering and exiting the control room in series. Since the control room envelope function was not lost, this event is not reportable and NRC Event Number 52669 is being retracted. The basis for this conclusion will be provided to the NRC Resident Inspector." The licensee informed the NRC Resident Inspector. Notified R2DO (Blamey).

ENS 5263023 March 2017 02:48:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn March 23, 2017, at 0014 EDT, Watts Bar Nuclear Plant Unit 2 (WBN2) experienced an unplanned trip of both Turbine Driven Main Feed Pumps (TDMFP) following a loss of Main Condenser Vacuum. The trip of both TDMFPs caused an automatic start of both Motor Driven Auxiliary Feed Water Pumps and the Turbine Driven Auxiliary Feed Water Pump. (The) cause of the loss of Main Condenser Vacuum is currently under investigation. The plant was performing a normal startup, and had just synced the main generator to the grid. Subsequent to the event, the plant was transitioned to Mode 3. All rods are fully inserted. Decay heat is being removed via the atmospheric relief valves. Unit 1 remains in Mode 5 for a refueling outage. The licensee has notified the NRC Resident Inspector.
ENS 5262520 March 2017 10:17:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn March 20, 2017 at 0813 EDT, Watts Bar Nuclear Plant (WBN) Unit 2 operations personnel manually tripped the plant from approximately 91 percent power based on lowering steam generator levels. Prior to the plant trip, the 2A Hotwell pump tripped at 0758 EDT and the 2C Condensate Booster Pump subsequently tripped at 0802 EDT. Operations personnel commenced to lower plant power after the 2A Hotwell pump trip in an attempt to maintain steam generator levels, but were unable to recover level and manually tripped the unit. All control rods fully inserted and all automatically actuated safety related equipment operated as designed. At 0905 EDT, operations personnel exited the emergency operating instructions after the plant was stabilized. The cause of the event is under investigation. This event is reportable to the NRC within four hours under 10 CFR 50.72(b)(2)(iv)(B) as a result of the actuation of the Reactor Protection System and in eight hours under 10 CFR 50.72(b)(3)(iv)(A) as a result of actuation of the Auxiliary Feedwater system. The licensee notified the NRC Resident Inspector.
ENS 5261817 March 2017 17:08:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn March 9, 2017 at 0120 EST, the equalizing valve for the Watts Bar Nuclear Plant (WBN) Unit 2 upper containment airlock inboard door was found not closed while the outboard airlock door was open. This created a containment bypass with leakage potentially greater than allowed by the design. The operator immediately identified, after opening the outer door of the elevation 757 Air Lock, the pressure equalizing valve for the inner door was not fully closed. The outer door was promptly shut to isolate the airlock. The inner door was then cycled which closed the equalizing valve. The total time that a containment bypass was present is estimated at five minutes. This condition was initially recognized as being potentially reportable. However, the assessment performed at the time, based on operator control of the outer airlock door, concluded there was a reasonable assurance of meeting the safety function. A subsequent independent review of this condition identified that this should have been reported under 10 CFR 50.72(b)(3)(v)(C) within eight hours of the event. The NRC Resident Inspector has been informed of this event. The licensee is planning on replacing the equalizing valve in the near future.
ENS 525398 February 2017 13:04:00Watts BarNRC Region 2Westinghouse PWR 4-LoopThis 60 day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an Invalid Containment Ventilation Isolation (CVI) actuation at Watts Bar Nuclear Plant (WBN) Unit 2. On December 15, 2016 at 1332 Eastern Standard Time (EST), Unit 2 maintenance personnel were preparing to perform a breaker swap for the normal feed to the 2B1B C and A vent board. When the power was removed from Radiation Monitor 2-RM-90-131, the B Train master isolation signal status panel was unexpectedly lit for CVI. The only automatic action observed from the containment isolation status panel was that 2-FCV-30-037, Lower Compartment Purge Control valve, went closed. The loss of power to 2-RM-90-131 de-energized the relay associated with the high radiation setpoint, resulting in an invalid Train B CVI actuation. During this event, the train B CVI actuation was complete and equipment functioned as designed. Upon identification of the Train B CVI, maintenance activities were halted and a prompt investigation was initiated. WBN found that the work order to perform the breaker swap was planned to lift leads to disable actuation of CVI. The work order lifted the lead for the K622 relay, which was insufficient to prevent the actuation. Two other leads on relays should have been lifted to prevent the actuation in Mode 1. A contributor to this error was that this work had been rescheduled several times prior to actual performance. From the time it was planned to the actual performance, mode changes had been performed on the Unit and no further reviews were performed. The licensee notified the NRC Resident Inspector.
ENS 5240029 November 2016 09:54:00Watts BarNRC Region 2Westinghouse PWR 4-Loop

On 11/29/16 at 0654 EST, a chemical spill of approximately 525 gallons of Flo-guard was reported to the main control room from the raw water system chemical treatment control building (near the intake pumping station). No personnel injuries have resulted from this spill. The spill has stopped and is contained to the immediate area of the building. The spill has not reached the waters of the United States. The hazardous constituent of Flo-guard is Zinc Chloride. Source of spill was a piping failure that allowed the contents of a storage tank to drain onto the ground in the immediate vicinity overnight. The area has been contained and does not impact any plant operations.

At 0728, TVA determined that due to the volume of spill (approximately 525 gal.) being greater than 306 gal. of Zinc Chloride, this event is reportable under the WBN (Watts Bar Nuclear) Integration Pollution Prevention Plan. The Shift Manager notified the National Spill Response Center at 0732 and the Tennessee Emergency Management Agency at 0738. Rhea County Emergency Response, Nuclear Duty Officer and NRC Resident have been informed. This is being reported under 10 CFR 50.72(b)(2)(xi), 'Any event or situation, related to the health and safety of the public or onsite personnel, or protection of the environment, for which a news release is planned or notification to other government agencies has been or will be made,' due to the notification of other government agencies of the spill.

ENS 5221030 August 2016 21:49:00Watts BarNRC Region 2Westinghouse PWR 4-Loop

A fault occurred on the unit 2 "B" main bank transformer resulting in an oil fire. The main turbine tripped resulting in a reactor trip. All control rods fully inserted and no safety or relief valves lifted. Decay heat is being removed via steam dumps to the main condenser and feeding steam generators with auxiliary feedwater. Electrical power is through the normal shutdown electrical lineup. Offsite assistance was requested from the county and off duty fire brigade members. At 2228, the fire was reported as out. Spray is continuing and a reflash watch is being set. Unit 1 continued to operate at 100% power throughout the event. Notified the DHS SWO, FEMA Ops Center, DHS NICC, FEMA National Watch Center (E-mail) and Nuclear SSA (E-mail).

  • * * UPDATE AT 2352 EDT ON 08/30/2016 FROM MICHAEL BOTTORFF TO JEFF HERRERA * * *

On August 30, 2016, at 2110 EDT, Watts Bar Nuclear Plant Unit 2 reactor tripped due to an electrical fault affecting the 2B Main Bank Transformer, resulting in a fire in the transformer. Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed. All Control and Shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and main steam dump systems. Unit 2 is in a normal shutdown electrical alignment. The fire was out at 2230 EDT. The cause of the fire is currently under investigation. The fire was reported at 2149 EDT. Local Fire Departments responded to the site as requested. The reactor trip and system actuation is being reported under 10CFR50.72(b)(3)(iv)(A) and 10CFR50.72 (b)(2)(iv)(B). There was no effect on WBN Unit 1. The NOUE was exited at 2342. The NRC Senior Resident Inspector has been notified. The Licensee notified the State of Tennessee. Notified the R2DO (Bartley), IRD MOC (Stapleton), NRR EO (Miller), DHS SWO, FEMA Ops Center, DHS NICC, FEMA National Watch Center (E-mail) and Nuclear SSA (E-mail).

ENS 5219423 August 2016 15:30:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn August 23, 2016, at 1356 EDT, Watts Bar Nuclear Plant (WBN) Unit 2 reactor was manually tripped due to a loss of main feedwater. Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed. All control and shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and main steam dump systems. Unit 2 is in a normal shutdown electrical alignment. The cause is currently under investigation. This is being reported under 10CFR 50.72(b)(3)(iv)(A) and 10CFR 50.72(b)(2)(iv)(B). There was no effect on WBN Unit 1. The NRC Senior Resident Inspector has been notified.
ENS 5217713 August 2016 08:51:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn August 13, 2016 at 0330 EDT, Watts Bar Nuclear Plant Unit 2 (WBN2) was being stabilized following a pre-planned reactor trip. Both motor driven auxiliary feed water pumps and the turbine driven auxiliary feed water pump (TDAFW pump) were in operation maintaining steam generator water level 6 - 50 percent in accordance with the Reactor Trip Response Procedure. At 0333 EDT the TDAFW pump was secured by procedure and steam generator water level lowered to the Low Low Alarm setpoint (17 percent). The trip time delay at 0 percent power is three (3) minutes. At 0336 EDT, the TDAFW pump automatically started with steam generator water levels less than the Low Low alarm setpoint (lowest level reached was 15 percent). Steam generator water level was restored to the normal shutdown control band (38 percent). Unit 1 remains in Mode 1 at 85 percent. Unit 2 is stable in Mode 3 with normal shutdown power alignment. The reactor coolant system is being cooled down to 400 degrees F for a planned maintenance period, with decay heat removal via the Main Condenser Steam dumps and the AFW system. This event is being reported pursuant to 10 CFR 50.72(b)(3)(iv)(A). TVA has notified the NRC Resident Inspector.
ENS 521639 August 2016 16:58:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn 8/09/2016 at 1415 EDT, TVA (Tennessee Valley Authority) notified the National Response Center that Watts Bar Nuclear (WBN) Plant has noted an oil sheen in the Unit 2 Cooling Tower Basin. An oil sheen was observed within the Unit 2 Cooling Tower Basin at WBN. The sheen did not cover the entire cooling tower basin. The sheen covered approximately 4 square feet. No oil sheen was visible in the yard holding ponds or Tennessee river from the bank above the diffuser pipes. Notifications were also made to TEMA (Tennessee Emergency Management Agency). Oil levels from the suspected source did not indicate any change in oil reservoir levels. Unit 1 remains in Mode 1 at 85 (percent) power - reduced power due to main condenser back pressure limits. Unit 2 remains in Mode 1 at 25 (percent) power - initial startup testing. This event is reportable under 10 CFR 50.72(b)(2)(xi) as a condition that was reported to an outside Government Agency. The NRC Resident Inspector has been notified.
ENS 5212626 July 2016 16:39:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn 7/26/2016 at 1536 EDT, TVA (Tennessee Valley Authority) notified the National Response Center that Watts Bar Nuclear Plant had noted an oil sheen on the Cooling Tower Basin. An oil sheen was observed within the U1 Cooling Tower basin at WBN. The sheen did not cover the entire Cooling Tower basin. The sheen covered approximately two square feet. Estimate of oil released into the Cooling Tower basin is less than four ounces. No oil sheen was visible in the Tennessee River from the bank above the diffuser pipes. Notifications were also made to TEMA (Tennessee Emergency Management Agency). Follow-up observations within 20 minutes of the sheen being reported indicated that the oil sheen had dissipated and was no longer visible. Oil levels from the suspected source did not indicate any change in oil reservoir levels. Unit 1 remains in Mode 1 at 79 percent power - reduced power due to main condenser back pressure limits. Unit 2 remains in Mode 1 at 74 percent power - initial startup testing This event is reportable under 10 CFR 50.72(b)(2)(xi) as a condition that was reported to an outside Government Agency. The NRC Resident Inspector has been notified.
ENS 5202620 June 2016 17:19:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn June 20, 2016 at 1540 EDT, Watts Bar Nuclear Plant Unit 2 reactor tripped due to (reaching the) automatic Lo-Lo steam generator trip (setpoint) on (the) #4 steam generator. Concurrent with the reactor trip the Auxiliary Feedwater system actuated as designed. All control and shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and main steam dump systems. The station is in a normal shutdown electrical alignment. The cause is currently under investigation. This is being reported under 10 CFR 50.72(b)(3)(iv)(A) and 10 CFR 50.72 (b)(2)(iv)(B). The NRC Senior Resident has been notified. There was no effect on Unit 1.
ENS 5202118 June 2016 14:05:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn 6/18/16 at 1106 EDT, TVA (Tennessee Valley Authority) notified the National Response Center that Watts Bar Nuclear Plant has an oil sheen on the Cooling Tower Basin. 1. Oil sheen was observed within the Cooling Tower basin at WBN (Watts Bar Nuclear). Sheen was light brown to red and did not cover the entire Cooling Tower basin. Estimate of oil released into the Cooling Tower basin is less than 1 quart. 2. No oil sheen was visible in the Tennessee River from the bank above the diffuser pipes. 3. Notifications were also made to TEMA (Tennessee Emergency Management Agency). 4. Follow-up observations within one hour of the sheen being reported indicated that the oil sheen had dissipated and was no longer visible. Oil levels from the suspected source did not indicate any change in oil reservoir levels. Unit 1 remains in Mode 1 at 92% power - reduced power due to main condenser back pressure limits Unit 2 remains in Mode 1 at 33% power - initial startup testing This event is reportable under 10 CFR 50.72(b)(2)(xi) as a condition that was reported to an outside Government Agency. The NRC Resident Inspector has been notified.
ENS 5200113 June 2016 08:40:00Watts BarNRC Region 2Westinghouse PWR 4-Loop

This 60-day telephone notification is being submitted in accordance with paragraphs 10 CFR 50.73(a)(1) and 50.73(a)(2)(iv)(A) to report an invalid Containment Vent Isolation (CVI) actuation at Watts Bar Nuclear Plant (WBN) Unit 2. On April 14, 2016 at 1344 Eastern Daylight Times (EDT), Unit 2 technicians performing calibration checks on the Auxiliary Building general supply fan, connected test equipment to the wrong intake temperature switch, causing an invalid train B auxiliary building isolation (ABI) signal in both Unit 1 and Unit 2.

Because the Unit 2 containment purge system was, at that time, configured in the 'refuel' mode, the invalid train B ABI concurrently initiated a train B CVI in WBN Unit 2. Consequently, the train B CVI caused the Unit 2 containment lower compartment radiation monitor to trip and control room operators entered Technical Specification Limiting Condition for Operation (LCO) 3.4.15 RCS Leakage Detection Instrumentation at 1344 EDT. By 1422 EDT, Unit 2 control room personnel had reset the containment purge system and by 1854 EDT had completed procedural steps to restore auxiliary building ventilation to its normal alignment. By 1858 EDT, Unit 2 control room personnel had completed the procedural steps to restore the containment purge system. During this event, the train B ABI and CVI actuations were complete and equipment functioned as designed. Upon identification of the train B ABI/CVI condition, the calibration activities were halted and a prompt investigation was initiated. WBN evaluators determined the apparent cause of the event was incorrect work instructions, with a contributing cause that technicians failed to use human performance error prevention tools to ensure they were calibrating the correct equipment. Personnel responsible for performing the calibration checks have been coached and corrective actions have been taken to correct the work instructions. The licensee notified the NRC Resident Inspector.

ENS 519958 June 2016 17:23:00Watts BarNRC Region 2Westinghouse PWR 4-Loop

At 1526 Eastern Daylight Time on 6/8/2016, a determination was made involving the potential impact of a tornado on the Emergency Diesel Generators (EDGs). The EDGs are required to be operable to provide power to ensure that acceptable fuel design limits, reactor coolant system pressure boundary limits, and containment integrity are not exceeded during abnormal transients. Further, the EDGs are designed with a crankcase pressure trip (setpoint = 1 inch water), which is bypassed during an emergency start. Engineering has determined that a tornado could potentially cause actuation of the crankcase pressure trip due to a low barometric condition. If an emergency start signal has NOT previously occurred, then during a tornado, actuation of the crankcase pressure trip would energize the shutdown relay causing an EDG lockout condition. The EDG lockout condition prevents subsequent EDG starts (normal or emergency) until operators manually reset the lockout condition locally at the EDG. This condition could potentially affect all four EDGs simultaneously. The EDGs are operable but degraded. All EDGs have successfully passed their required surveillances within the appropriate frequency. No severe weather warnings or watches are forecast in the local areas, which could challenge the crankcase pressure trip.

This condition places both units in an unanalyzed condition that potentially significantly degrades plant safety, 10 CFR 50.72 (b)(3)(ii)(B). A compensatory measure has been established, that upon notification of a Tornado Warning, the EDGs would be 'emergency started' and run during the time the Tornado Warning was in effect. This action bypasses the crankcase pressure trip function and allows the EDGs to perform their required safety function. The NRC Senior Resident Inspector has been notified.

ENS 519825 June 2016 16:22:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn June 5, 2016 at 1227 Eastern Daylight Time (EDT), Watts Bar Nuclear Plant (WBN) Unit 2 was in MODE 1 at approximately 12.5% power when a safety injection actuation occurred, followed by an automatic reactor protection system (RPS) trip. Preliminary data suggests that the #1 high pressure turbine governor valve failed open causing a steam header pressure rate of decrease safety injection (SI) actuation signal. As designed, the safety injection actuation caused both trains of the shared Emergency Gas Treatment System (EGTS) to align to Unit 2, requiring WBN Unit 1 to enter Technical Specification (TS) LCO 3.0.3 at 1227 (EDT). Also as designed, Unit 1 annulus pressure momentarily increased, causing operation personnel to enter LCO 3.6.15 Condition B at 1240 (EDT). At 1242 (EDT), after annulus pressure normalized, operations personnel exited LCO 3.6.15. At 1245 (EDT), Operations personnel secured safety injection and Unit 2 was stabilized in MODE 3 at normal operating pressure and temperature. By 1349 (EDT), Unit 1 Operations personnel had restored both trains of EGTS to standby readiness, and exited TS 3.0.3. No primary safety barriers (RCS, containment and fuel clad) were challenged and no primary or secondary safety or relief valves actuated during the event. The Unit 2 plant trip was uncomplicated and safety equipment operated as expected. Unit 2 is stable in Mode 3 at normal operating temperature and pressure, in normal shutdown power alignment. Unit 1 is stable in Mode 1 at 100% power. The Senior Resident Inspector has been notified of this event. The MSIVs are shut with the steam generators (SG) discharging steam using the atmospheric dump valves. There is no primary to secondary leakage. Motor driven AFW pumps are running to maintain SG levels. RCS pressure remained above ECCS (Emergency Core Cooling System) discharge pressure.
ENS 5194017 May 2016 23:06:00Watts BarNRC Region 2Westinghouse PWR 4-LoopOn May 17, 2016, at 1630 hours while restoring from a plant modification related to new 'loss of phase' circuitry, the 1 B-B 6.9kV buss de-energized resulting in a loss of voltage on the buss. The loss of voltage was caused by the loss of voltage relays that separated offsite power from the 1 B-B 6.9kV buss. At the time, the 1 B-B emergency diesel generator was removed from service for planned maintenance. In response to the loss of power on the 1 B-B 6.9kV buss, the operators entered abnormal operating instruction, AOI 43.02, Loss of Unit 1 Train B Shutdown Boards, and started emergency diesel generators 1 A-A, 2 A-A, and 2 B-B. All equipment operated properly. The emergency diesel generators were not required to be paralleled to the boards. Offsite power was restored to the 1 B-B 6.9kV buss at 1802 hours on May 17, 2016. This condition did not result in any adverse impact on the health and safety of the public. This event is reportable under 10 CFR 50.72(b)(3)(iv)(A), 'Any event or condition that results in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B) of this section, except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation.' The NRC Resident Inspector has been notified.