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 Entered dateSiteRegionScramReactor typeEvent description
ENS 5216911 August 2016 11:09:00MillstoneNRC Region 1Manual ScramCEReactor operators manually tripped the reactor due to the loss of two out of four circulating water pumps which caused a drop in condenser vacuum. The trip was uncomplicated. The reactor is shutdown and stable with decay heat removal via steam dumps to the condenser. The cause of the circulating water pump trips is currently unknown, but initial indications are that the pumps tripped due to a lightning strike that caused an electrical perturbation. The reactor will remain shutdown while the licensee investigates the cause. Unit 3 was not affected. The licensee notified the NRC Resident Inspector and the State and Local governments.
ENS 5192915 May 2016 07:08:00MillstoneNRC Region 1Manual ScramWestinghouse PWR 4-Loop

At 0638 EDT on 5/15/2016, an Unusual Event (EAL GU.2) was declared on Millstone Unit 3 due to a Main Generator hydrogen gas leak into the Turbine Building. At 0645 EDT, operators manually tripped the reactor. All rods inserted. All systems functioned as expected following the reactor trip. Operators are currently venting the remaining hydrogen from the generator through the normal vent path. There is no safety related equipment out-of-service. The plant is in a normal post-trip electrical line-up. All Emergency Diesel Generators are available. The licensee notified the State of Connecticut and the NRC Resident Inspector. Notified DHS SWO, FEMA Ops Center, and DHS NICC Watch Officer. Notified via E-mail FEMA National Watch Center and NuclearSSA.

  • * * UPDATE FROM MIKE CICCONE TO HOWIE CROUCH AT 1044 EDT ON 5/15/16 * * *

At 0949 EDT, the licensee terminated the Unusual Event. At 0645 EDT on 5/15/16, a manual reactor trip was initiated at Millstone Unit 3 due to a hydrogen leak from the main generator. As expected, Auxiliary Feedwater System (AFW) initiated on the reactor trip. The trip was uncomplicated and the plant is currently in Mode 3 with a normal electric lineup and decay heat is being removed via steam dumps to the condenser. The cause of the hydrogen leakage is under investigation. This is reportable under 10 CFR 50.72(b)(2)(iv)(B) - RPS actuation while critical, and 10 CFR 50.72 (b)(3)(iv)(A) - valid specified system actuation. The licensee has notified Waterford Township, the State of Connecticut and the NRC Resident Inspector. Notified R1DO (Burritt), NRR ET (McDermott), NRR EO (Morris), IRD (Grant), DHS SWO, FEMA Ops Center, DHS NICC, FEMA National Watch Center (email) and NuclearSSA (email).

ENS 5168225 January 2016 03:21:00MillstoneNRC Region 1Automatic ScramWestinghouse PWR 4-LoopAt 0147 EST on 1/25/16, the 'B' Reactor Coolant Pump (RCP) tripped offline. This caused a reactor trip on low coolant flow. As expected, the Aux Feedwater System (AFW) initiated on the reactor trip. The trip was uncomplicated and the plant is currently shutdown in Mode 3 with a normal electrical lineup and decay heat is being removed via steam dumps to the condenser. The cause of the 'B' RCP trip is under investigation. A containment entry is planned for dayshift on 1/25/16 to inspect and troubleshoot the 'B' RCP. The Licensee has notified the NRC Resident Inspector.
ENS 515218 November 2015 02:55:00MillstoneNRC Region 1Manual ScramCEDuring power ascension following refueling outage, a decreasing oil level in the 'C' Reactor Coolant Pump was noted. When the oil level reached 69 percent, with the reactor at approximately 56 percent rated thermal power, per plant procedure, a rapid downpower was initiated which brought the plant to approximately 15 percent power and a manual reactor trip was initiated at that point. The reactor trip was uncomplicated and all plant equipment responded as expected. The licensee notified the NRC Resident Inspector.
ENS 495259 November 2013 16:09:00MillstoneNRC Region 1Automatic ScramCEMillstone Unit 2 automatically tripped following a turbine trip due to a loss of condenser vacuum. The loss of vacuum was caused by the trip of the "C" circ water pump with the "D" circ water pump out of service. The licensee is still investigating the trip of the "C" circ water pump. The MSIVs are open with steam generators discharging steam to the main condenser. Auxiliary feedwater automatically started as expected following the reactor trip. All rods fully inserted and there were no complications following the reactor trip. All systems functioned as required and the unit is stable in Mode 3. There was no impact on Unit 3. The licensee has notified state and local authorities and the NRC Resident Inspector.
ENS 492609 August 2013 22:27:00MillstoneNRC Region 1Automatic ScramWestinghouse PWR 4-LoopThe loss of a non-vital 480v bus resulted in a feedwater transient that caused steam generator water level to lower below the automatic reactor trip setpoint. The reactor trip and plant response was uncomplicated with all rods being inserted into the core. The auxiliary feedwater system automatically actuated and is currently being to used to feed the steam generators. Decay heat is being removed via the steam dumps to the condenser. No relief valves or safeties lifted during the transient. The plant is currently stable in Mode 3 at normal operating pressure and temperature and is in its normal shutdown electrical lineup. There was no impact on Unit 2 which is currently operating at 100% power. The licensee has notified state and local authorities and the NRC Resident Inspector.
ENS 5200012 June 2013 23:51:00MillstoneNRC Region 1Manual ScramWestinghouse PWR 4-Loop

At 2013 EDT on 6/12/16, Millstone Unit 3 commenced a Technical Specification (TS) required shutdown due to excessive Reactor Coolant System leakage from the "A" Reactor Coolant Pump (RCP) third stage seal. The leakage from the third stage seal was approximately two gpm which is greater than the Technical Specification (TS) limit of less than one gpm. During the shutdown, oscillations developed in the Main Feedwater which required the operator to initiate a manual reactor trip. Unit 3 is currently stable in Mode 3. Decay heat is being released via the Steam Dumps to the Main Condenser. Normal offsite power is available and the unit is in a normal shutdown electrical line-up. The cause of the Main Feedwater oscillations is being investigated. The licensee notified the NRC Resident Inspector. The licensee notified State and local government agencies.

  • * * UPDATE FROM WALTER ORF TO DONALD NORWOOD AT 0129 EDT ON 6/13/2016 * * *

The following clarifies Feedwater isolation vs. Feedwater oscillation: At 2337 EDT on 6/12/16, a manual reactor trip was initiated on Unit 3 following feedwater isolation. As expected, Aux Feedwater system (AFW) initiated on the reactor trip. The trip was uncomplicated and the plant is currently in Mode 3 with a normal electric line-up and decay heat is being removed via steam dumps to the condenser. This is reportable under 10 CFR 50.72(b)(2)(iv)(B) - RPS Actuation - Critical and 10 CFR 50.72(b)(3)(iv)(A) - Valid Specific System Actuation." The Feedwater isolation occurred due to high Steam Generator water level. The licensee notified the NRC Resident Inspector. Notified R1DO (Arner).

ENS 4903916 May 2013 10:20:00MillstoneNRC Region 1Manual ScramWestinghouse PWR 4-Loop

On May 16, 2013, at 0256 EDT, while in Mode 3 (subcritical), operators manually opened the reactor trip breakers as directed by procedure. During rod drop testing, demand position and digital rod position indication did not agree within procedural limits. As directed by procedure, operators opened the reactor trip breakers. The cause of the discrepancy is under investigation. The plant responded as expected and all rods inserted as required. The plant remains stable in Mode 3. This condition is reportable pursuant to 10 CFR 50.72(b)(3)(iv). The NRC Senior Resident Inspector has been notified.

  • * * RETRACTION FROM TODD STRINGFELLOW TO DANIEL MILLS ON 7/10/2013 AT 1418 EDT * * *

The purpose of this call is to retract the report made on May 16, 2013, Event Number 49039. Operators manually opened the reactor trip breakers in MODE 3 during hot control rod drop testing as directed by procedure. The condition has been determined to be an invalid actuation of the RPS since boron concentration, and not control rods, were being relied upon for safety function during rod testing. The details of the engineering review will be provided to the NRC Senior Resident Inspector. Notified R1DO (Cook).

ENS 4746120 November 2011 20:37:00MillstoneNRC Region 1Manual ScramWestinghouse PWR 4-LoopMillstone Unit 3 was manually tripped at low power during startup following the loss of condenser vacuum. The loss of vacuum was caused by the loss of the auxiliary steam boiler. The auxiliary steam boiler supplies gland seal steam to the turbine at low power and without the gland seal steam, the licensee could not maintain a condenser vacuum. All rods fully inserted and there were no complications during the trip. All systems functioned as required and the unit is stable in Mode 3. There was no impact on Unit 2. The licensee has notified state and local authorities and the NRC Resident Inspector.
ENS 4697120 June 2011 13:01:00MillstoneNRC Region 1Manual ScramCEAt 1152 EDT on 6/20/11 while operating at 60% power, the "B" MFW Pump tripped for reasons unknown. There was no maintenance or I&C work on-going at the time involving this pump. Operators initiated a manual reactor trip, however, (they) are not certain whether the automatic reactor trip setpoint of 49.5% Steam Generator Water Level Narrow Range (SGWL NR) was reached first. SGWL decreased to the Auxiliary Feedwater (AFW) setpoint of 26.8% NR causing the initiation of both motor-driven AFW Pumps. All Control Rods fully inserted. Unit 2 is currently stable in Mode 3, Hot Standby, removing decay heat via the Main Steam line to the Condenser. Operators secured AFW and will initiate feed to the Steam Generators using the "A" MFW Pump. Unit 2 is in a normal post-trip electrical lineup with all sources of offsite power available. The licensee has the cause of the "B" MFW Pump trip under investigation. The licensee informed both state/local (Waterford Dispatch) and the NRC Resident Inspector
ENS 4644128 November 2010 17:27:00MillstoneNRC Region 1Automatic ScramCELoss of two circulating water pumps in one condenser caused a high main condenser backpressure. The high main condenser back pressure caused an automatic main turbine and reactor trip while critical >15%. Low steam generator water level following the trip caused an automatic Auxiliary Feedwater actuation. The low water level condition has cleared. Normal post-trip response has been verified and the plant is stable. The licensee removed one circulating water pump from service in preparation of performing scheduled maintenance when the other circulator unexpectedly tripped. The cause of the pump trip is under investigation. During the trip, all rods inserted into the core. There were no primary safety valves that lifted during the transient but main steam safeties "chattered" during the transient and have fully reseated. There is no known primary to secondary leakage. The electrical grid is stable and supplying plant loads in a normal shutdown electrical lineup. The reactor is stable at normal operating pressure and temperature with decay heat being removed via the steam dumps to condenser. The licensee has notified the State of Connecticut Department of Environmental Protection, the town of Waterford, CT, and the NRC Resident Inspector.
ENS 4594522 May 2010 17:46:00MillstoneNRC Region 1Manual ScramCEThe licensee experienced a feedwater transient which initiated the event. All safety systems are available. All control rods fully inserted. The electrical lineup is normal. The decay heat path is through the condenser steam dumps. No relief valves or safety valves lifted during the transient. Primary plant temperature is 533 degrees Fahrenheit and primary plant pressure is 2256 psia. The licensee is investigating the cause of the feed transient. The licensee notified the NRC Resident Inspector, the Waterford Dispatch, and the State Department of Environmental Protection. Earlier, the licensee was experiencing oscillations in the feedwater regulating valve (FRV) for the #2 steam generator when the valve was in automatic control. Troubleshooting planning was underway but no troubleshooting activities were in progress at the time of the trip. When the operator placed the #2 steam generator FRV in manual control, the steam generator water level began to increase and could not be recovered. The operator then manually tripped the reactor prior to reaching the high steam generator level trip setpoint. An Auxiliary Feed Water system actuation did occur during the transient. The trip and plant response was considered uncomplicated.
ENS 4593117 May 2010 12:27:00MillstoneNRC Region 1Automatic ScramWestinghouse PWR 4-LoopSystem Affected: RPS actuation and reactor trip. Actuation Initiation Signals: AFW auto initiation. Cause: Low level 'C' steam generator. Effect of event on Plant: Reactor and turbine trip. Actions taken or Planned: Standard post trip actions. Additional information: Plant stabilized at NOP/NOT. The licensee experienced a feedwater transient which initiated the event. All safety systems are available. All control rods fully inserted. The electrical lineup is normal. The decay heat path is through the condenser steam dumps. There were no relief valve or safety valve lifted during the transient. Primary plant temperature is 555 degrees Fahrenheit, and primary plant pressure is 2250 psig. The licensee is investigating the cause of the feed transient. The licensee notified the NRC Resident Inspector, the Waterford Dispatch, and the State Department of Environmental Protection,
ENS 4572926 February 2010 11:48:00MillstoneNRC Region 1Manual ScramCEThe "C" Circulating Water Pump tripped on high delta pressure across the screens. Another Circulating Water Pump was out of service for maintenance. This condition required a shutdown, therefore the reactor was manually tripped. This caused the steam generator level to reach the low level setpoint. There was a loss of Main Feedwater Pumps when breaking condenser vacuum. Auxiliary Feedwater Pumps started automatically upon low level in the steam generators. The letdown system was isolated post trip and the charging and letdown systems are restored to normal lineup. The plant is in Mode 3. All rods fully inserted. Decay heat is being removed via atmospheric dump valves. There are no known primary to secondary leaks in the steam generator tubes. The electrical lineup is normal with offsite power. The licensee has notified the NRC Resident Inspector.
ENS 4558320 December 2009 00:06:00MillstoneNRC Region 1Automatic ScramWestinghouse PWR 4-LoopAn automatic reactor trip occurred due to a turbine trip caused by a generator electrical fault trip. The cause of the electrical fault is under investigation. All rods fully inserted into the reactor. The auxiliary feedwater pump started and is maintaining steam generator level. The reactor is NOP and NOT. The post trip electrical line-up is being back-fed from off-site power through the RSST transformer. All other post trip actions are standard and all systems are operating as expected. There was no affect on Unit-2. The licensee will contact the NRC Resident Inspector.
ENS 4456411 October 2008 23:35:00MillstoneNRC Region 1Automatic ScramWestinghouse PWR 4-Loop

At 2236 on 10/11/08 while reducing power for a planned refueling outage, "C" Steam Generator water level decreased and the turbine tripped. The reactor tripped on the turbine trip. Auxiliary feedwater initiated as expected and decay heat is being removed via the condenser steam dumps. All control rods fully inserted. No significant safety equipment is out of service and all safety buses are being supplied by offsite power. Emergency Diesel generators are available if needed. No PORVs or primary/secondary relief valves lifted. The licensee is evaluating cause of steam generator level excursion. Unit 2 is unaffected.

The licensee notified the NRC Resident Inspector.
ENS 4432628 June 2008 12:54:00MillstoneNRC Region 1Manual ScramCEAt 1146, the reactor was manually tripped due to a feedwater transient that was caused by a loss of both feedwater pumps. The exact cause of the loss of both feedwater pumps is still being investigated. Prior to the reactor trip, the licensee was performing main turbine stop valve testing and during that testing received an isolation of extraction steam. On the manual reactor trip, all control rods fully inserted. No RCS PORVs or reactor safety valves lifted. The steam generator atmospheric dump valves did lift and reseat. Decay heat is being removed to the condenser via the turbine dump valves. Auxiliary Feedwater (AFW) initiated and fed the steam generators after the loss of both main feedwater (MFW) pumps. MFW was restored and is controlling steam generator levels. AFW has been secured. The electric plant is in a normal shutdown lineup and the EDGs are available. There was no effect on Unit 3. The licensee has notified the NRC Resident Inspector, Connecticut Department of Environmental Protection, and all local emergency response organizations.
ENS 4423824 May 2008 10:03:00MillstoneNRC Region 1Automatic ScramCE

The licensee entered an Unusual Event after an automatic reactor trip due to a loss of offsite power per EAL Designation PU-1. Currently the plant is stable in Mode 3 with power being supplied to the "A" & "B" Emergency Diesel Generators (EDG) running supplying power to the safety buses. Decay heat is being removed by the motor driven Auxiliary Feedwater Pump supplying water to the steam generators exhausting to atmosphere via atmospheric relief valves. There are no primary to secondary tube leaks. NRC Resident Inspector has been notified.

  • * * UPDATE FROM SKIP JORDAN TO JOHN KNOKE AT1252 EDT ON 05/25/08 * * *

At 1252 EDT the licensee terminated from their Unusual Event. After the loss of offsite power due to a failure of the Reserve Station Service Transformer (RSST) the licensee began to troubleshoot the problem as well as beginning to restore offsite power. At 1106 on 5/24/08 a cross-tie from Unit 3 was connected to Unit 2 and "A" EDG was secured. At 0950 on 5/25/08 the RSST was powered up and the non-vital busses were energized. At 1136 the "B" and "D" Reactor Coolant Pumps were started. At 1230 the vital bus was energized and the "A" EDG was secured. The licensee notified the NRC Resident Inspector. Notifications to: R1 (Marc Dupas, David Lew), R1DO (Mel Gray), NRR EO (Fred Brown), IRD MOC (William Gott), DHS (Fred Hill), FEMA (Dan Sullivan), USDA (Amanda Jimenez,), HHS (Mason Pyle), DOE (Julia Muse). The NRC Resident Inspector was notified.

ENS 4236723 February 2006 11:16:00MillstoneNRC Region 1Manual ScramCELoss of main feedwater occurred due to an instrument air line failure during a maintenance activity. The reactor was manually tripped and all control rods inserted fully. Auxiliary feedwater received an auto start signal and is providing feedwater to the steam generators. No safety relief valves or PORVs lifted. Decay heat removal is via the turbine bypass valves to the condenser. The plant is in a normal shutdown plant electrical lineup and there was no effect to Unit 3. The licensee notified the State of Connecticut and the city of Waterford. A media press release will be made at a later time. The licensee notified the NRC Resident Inspector.
ENS 421801 December 2005 15:50:00MillstoneNRC Region 1Automatic ScramWestinghouse PWR 4-LoopWhile reducing power in order to enter containment, and following a manual main turbine trip due to high vibration, an automatic reactor trip on low steam generator level was received as a result of the turbine trip transient. Containment was being entered to investigate the source of an RCS identified leakage, which was less than the Technical Specification limit. In conjunction with the reactor trip, an automatic actuation of the Auxiliary Feedwater System was received as expected. All control rods fully inserted on the automatic trip. The current decay heat removal path is via the steam dumps to the main condenser. No primary or secondary relief valves lifted during the transient. There are no known primary to secondary leaks. All safety related buses are powered from offsite power. With the exception of one diesel out of service for planned maintenance, all emergency diesel generators are available and in standby. Unit 2 was not affected. The licensee notified State and local agencies and the NRC Resident Inspector.
ENS 4202429 September 2005 14:49:00MillstoneNRC Region 1Manual ScramWestinghouse PWR 4-LoopThe licensee reported that high wind and wave action at the site has resulted in sea weed and related debris buildup at the Unit 3 intake structure. The traveling screens were unable to keep pace with the debris buildup and two out of six circulating water pumps tripped on high differential pressure across the traveling screens. Based on procedural requirements, the licensee is required to manually trip the plant due to the loss of the two circ water pumps. The reactor trip was characterized as uncomplicated with all systems functioning as required. All rods fully inserted. No primary or secondary relief valves lifted. Auxiliary feedwater automatically started as expected and is supplying cooling water to the steam generators. Decay heat is being discharged to the condenser via the turbine bypass valves. The plant is stable in hot standby at no-load temperature and pressure. The plant trip had no impact on Unit 2. The debris buildup on the Unit 2 intake is being monitored but is less of a problem due to the orientation of the Unit 2 intake structure. The NRC Resident Inspector has been notified by the licensee. The licensee has also notified State and local authorities and has made a press release.
ENS 4160717 April 2005 09:23:00MillstoneNRC Region 1Automatic ScramWestinghouse PWR 4-Loop

At 09:23 the licensee indicated that several Main Steam Relief Valves lifted and stayed open. A high pressure flow signal from the secondary Steam Generator caused initiation of Unit 3 Safety Injection, which in turn caused the Reactor to trip. All rods fully inserted as required. Activation of the Safety Injection subsequently caused the Pressurizer level to go solid. About 30 minutes into the event the primary Reactor Coolant and Main Steam Systems stabilized, including the Pressurizer level and pressure. During the initial briefing, about 09:35, the licensee reported that all secondary Safety Relief Valves have reseated. Decay heat is being directed to the Atmospheric Dumps due to the Main Condenser not being available. The licensee is attempting to establish ERDS. Initial assessment of this incident is believed not to be security related, however, follow-up is being conducted to verify same. At 09:48, NRC management made a decision to enter into Monitoring Mode. At about 11:15 the licensee indicated that a valve in the Charging System indicated some leakage, therefore it was isolated. Licensee stated that no radiological releases and no S/G tube leakage was indicated. Licensee notified State and local emergency response agencies. They will notify the NRC Resident Inspector. Notified DHS (Doyle), FEMA (Biscue), DOE (Smith), USDA (Magners), and HHS (Hogan).

  • * * UPDATE FROM D. DODSON TO W. GOTT 1328 EDT 04/17/05 * * *

At approximately 0830 on April 17, 2005 Millstone Unit 3 experienced an automatic reactor trip from full power. The Reactor is in a stable shutdown condition and is proceeding to Mode 5 cold shutdown. No release of radioactivity other than those minor releases associated with normal plant operation has occurred. There were no personnel injuries associated with the event. In addition to the Reactor Trip, half-train Safety Injection (SI) and half-train Main Steam Isolation (MSI) actuations occurred. Control room personnel were successful at manually initiating full SI and MSI. SI has since been terminated and RCS pressure control has been restored. Multiple steam line safety valves (MSSV) lifted with at least one MSSV indicating a failure to reclose. As a result, an ALERT was declared at approximately 0853 due to the failure of at least one MSSV failing to reclose. All MSSVs are currently closed. Auxiliary Feedwater (AFW) actuated automatically as expected, however, the turbine driven auxiliary feedwater pump (TDAFWP) tripped on start-up and was subsequently reset locally. Both motor driven auxiliary feedwater pumps (MDAFWPs) operated as expected to maintain steam generator water levels. Due to the additional inventory injected to the Reactor Coolant System (RCS) as a result of the SI actuation, the pressurizer filled and a primary system safety valve (PSSV) actuated at a lower than expected pressure. All PSSVs are currently closed, however, there is indication of leakage past either a PSSV or Pilot Operated Relief Valve (PORV). Upon alignment of the Charging system to Refueling Water Storage Tank recirculation flow path, 2 valves had indication of packing leakage. Those packing leaks have been terminated. The cause of the event is under investigation. The licensee has issued a press release. The licensee will notify the NRC Resident Inspector. Notified R1 DO (J. White) and IRD Manager (T. McGinty)

  • * * UPDATE FROM D. DODSON TO W. GOTT AT 1915 ON 04/17/05 * * *

The previously reported time of the Alert declaration should be corrected to read 08:42. Millstone Unit 3 entered Mode 4 (Hot Shutdown) at approximately 19:03 on April 17, 2005. The event at Millstone Unit 3 was terminated at 19:05. The cause of the event is under investigation. A recovery plan is being formulated. Internal NRC notifications, DHS (Frost), NRC/EPA (Threatt), FEMA (Erwin), DOE (Morone), USDA (Smeltzer), HHS (Desi) The licensee will notify the NRC Resident Inspector. At 23:45 the Agency exited Monitoring Mode and entered into Normal Mode.

ENS 4059115 March 2004 20:57:00MillstoneNRC Region 1Automatic ScramCEThe licensee reported that an automatic reactor trip occurred on 3/15/04 at 2020 EST due to the spurious trip of one main feed pump which caused a low steam generator water level trip signal. The plant has two main feed pumps. Operators reset the tripped main feed pump but steam generator levels didn't recover in time. The lowest level observed was in the "B" steam generator at 15% level as compared to the normal level of 65%. The trip setpoint is at 50% level. All control rods properly inserted into the core. The auxiliary feed water system automatically initiated as designed and expected. The plant remains stable in mode 3 while the licensee commenced the post trip review to determine the cause of the main feed pump trip. Decay heat removal was established using the AFW system to feed steam generators and bleed steam to the main condenser through the condenser dump valves. The licensee notified the NRC Resident Inspector.
ENS 405706 March 2004 02:02:00MillstoneNRC Region 1Manual ScramCEThe licensee reported that the "B" Steam Generator Feed Pump tripped unexpectedly and would not reset causing lowering steam generator water levels. Operators manually tripped the reactor and all control rods properly inserted. The auxiliary feed water (AFW) system automatically initiated to restore steam generator water levels. The lowest steam generator water level observed during the event was 55% level as opposed to the normal level of 70%. No primary relief valves lifted. Operators established decay heat removal capability using AFW system and the atmospheric steam dump valves. The licensee initiated a post trip review to determine the cause of the feed pump trip. The NRC Resident inspector has been notified by the licensee.
ENS 4036128 November 2003 22:57:00MillstoneNRC Region 1Manual ScramCEAt 2205 EST on 11/28/03 while at 11% power, Millstone Unit 2 performed a required manual reactor trip when main turbine vibration reached a turbine trip set point of 12 MILS. The turbine vibration did not reduce when the turbine was tripped which required breaking condenser vacuum and ultimately a manual reactor trip. The main turbine vibrations were anticipated during power ascension due to a newly installed low pressure "Mono-Block" rotor. All control rods fully inserted during the reactor trip and no ECCS injection occurred or primary relief valves lifted. The licensee informed the NRC Resident Inspector.
ENS 4035827 November 2003 06:51:00MillstoneNRC Region 1Manual ScramCE

While rolling the turbine when at 20% power they experienced an over speed turbine trip. During a second attempt when at 23% power, the turbine had high vibration so they manually tripped the reactor. Cause for the vibration is being investigated since a new rotor had just been installed in the turbine. All rods fully inserted during the reactor trip and no ECCS injection occurred or primary relief valves lifted. The licensee notified the NRC Resident, the State of Connecticut and Local agencies

  • * * UPDATE AT 1423 EST ON 11/28/03 FROM FRANKS TO GOTT * * *

The following clarifying information was provided by the licensee. While at 23% power of a scheduled power ascension following a refueling outage, Millstone Unit 2 performed a required manual reactor trip when main turbine vibration reached a trip set point of 12 MILS. The main turbine vibrations were anticipated during the power ascension due to a newly installed low pressure "Mono-Block" rotor. All control rods fully inserted during the reactor trip and no ECCS injection occurred or primary relief valves lifted. The overspeed trip discussed in the original report was a test conducted prior to placing the main turbine on the grid. Notified R1DO (Dimitriadis). The licensee will notify the NRC Residence Inspector.