Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 48847 | 24 March 2013 13:16:00 | On 3/23/13 it was identified that a conduit flood seal between an outside manhole and the switchgear rooms is displaced. This degraded flood seal compromises the flooding design of both the East and West Switchgear Rooms. Compensatory measures were implemented for the flood seal in accordance with the plants barrier control process. Repairs of the seal are in progress. Per the licensee these switchgear rooms contain both normal and safety related 4kV and 480 V electrical boards. Compensatory measures implemented include: Plant Maintenance personnel will take actions to seal any leak within 24 hours of a flooding event and also provide sump pumps to remove any water that has leaked in. The licensee notified the NRC Resident Inspector and the Vermont State Liaison.
This is an update to NRC Event No. 48847 reported on 3/24/13 at 1316 (EDT). On 3/27/2013 the extent of condition review identified two additional possible water intrusion paths from the outside to the switchgear rooms. Compensatory measures were implemented for these paths in accordance with plant procedures. Efforts to seal these paths are in progress. This is an on-going extent of condition assessment. The licensee will inform the NRC Resident Inspector and the Vermont State Liaison. Notified R1DO (Krohn). |
| ENS 47542 | 21 December 2011 15:38:00 | On December 20, 2011, Vermont Yankee (VY) was notified by its vendor laboratory that a water sample, taken from the Connecticut River on November 3, 2011, tested positive for a low level of tritium (1120 pCi/L). This report is being made in accordance with 10 CFR50.72(b)(2)(xi) since VY is notifying government agencies and issuing a press release. The VY Off-Site Dose Calculation Manual contains effluent dose calculations that account for groundwater releases of this type. There is no impact on public health and safety as a result of this event. The licensee has notified the NRC Resident Inspector and the state of Vermont. |
| ENS 46618 | 16 February 2011 15:29:00 | During system startup of (High Pressure Coolant Injection) HPCI for quarterly surveillance, audible and visual indications of steam leakage were observed. The system was secured and subsequently isolated (with outboard valve de-energized for configuration control). As a result of the steam leakage, a local fire alarm was received in the Control Room. HPCI is currently isolated and will not perform its safety function. Operators were dispatched to the Reactor Building fire panel to verify that the fire alarm was due solely to the steam leak. As a precautionary measure, personnel were evacuated from the Reactor Building. Operators entered (Off Normal Procedure) ON 3158, Reactor Building High Area Temperature/Water Level, and verified that room temperatures were decreasing after the steam line was isolated. No EOP-4, Secondary Containment Control, entry conditions were exceeded. The steam leak was isolated when HPCI was secured. Associated fire alarms were verified to be caused by the steam leak. There was no impact on other plant equipment or personnel safety. The source of the steam leak is suspected to be from a steam trap but this has not been confirmed. The licensee notified the NRC Resident Inspector and the State of Vermont Department of Public Service Nuclear Engineer. Notified R1DO (Ferdas) |
| ENS 46038 | 23 June 2010 15:16:00 | Event Description: An Unusual Event was declared at 1425 EDT due to reports from site personnel of an earthquake felt onsite. This was verified through the National Earthquake Information Center. Plant seismic monitors did not actuate. Actions Taken: Implemented OP 3127, Natural Phenomenon, for an earthquake. Plant personnel are walking down systems for any damage indications. (There is no indication of damage) at this time." The licensee informed state/local agencies and the NRC Resident Inspector. The licensee plans to issue a press release.
The Unusual Event was terminated at 1725 EDT. Plant walkdowns were completed with no damage noted. The licensee notified the NRC Resident Inspector. Notified the R1DO (Dwyer), NRR EO (Cunningham), DHS (Inzer), and FEMA (Hollis). |
| ENS 45958 | 27 May 2010 08:31:00 | At 0200 EDT on 5/27/10, operators identified that the FTS 2000, NAS (Nuclear Alert System) and commercial phones systems were not functional. ERDS is not functional. The loss of communications appears to be weather related. (The licensee) validated microwave communication with ISO New England and NRC is available. Cell phone communication is functional. The NRC and state were contacted using alternate means. The licensee has notified the NRC Resident Inspector.
Notified by the licensee that FTS 2000, NAS, commercial phone systems and ERDS are functional. The licensee will notify the NRC Resident Inspector. Notified the R1DO (Dwyer). |
| ENS 45957 | 26 May 2010 17:25:00 | At 1526 on 5/26/2010, while operators were increasing power with reactor recirculation flow, an RPS (Reactor Protection System) actuation occurred in both channels and all control rods inserted. RPV (Reactor Pressure Vessel) level decreased to 114.5 inches (Low level setpoint is less than 127 inches). Following the scram, the PCIS (Primary Containment Isolation System) groups 2, 3, 4 and 5 received actuation signals and all open valves isolated. Both trains of standby gas treatment system actuated. Plant actions taken included entering procedures OT-3100, Reactor Scram on RPS Actuation and EOP-1, RPV Control on Low Level Signal. The EOP-1 was exited per shift manager direction because of no emergency. The operators stabilized the plant and reset both RPS and PCIS. An investigation into the cause of the scram is continuing. Electrical power is being supplied from offsite sources through the startup transformers. The licensee notified the NRC Resident Inspector. |
| ENS 46070 | 6 July 2010 11:38:00 | Invalid Primary Containment And Vessel Isolation Control System (PCIS) signal results in partial actuation of Emergency Core Cooling System (ECCS) components: The following information is provided as a sixty (60) day telephone notification to the NRC in accordance with 50.73(a)(1) in lieu of the submittal of a written LER to report a condition that resulted in an invalid actuation of the high pressure coolant injection (HPCI) and reactor core isolation coolant (RCIC) systems. NUREG-1022, Revision 2, identifies the information that needs to be reported as discussed below. On May 17, 2010, during the Refueling Outage 28 ECCS test control room personnel identified the reactor vessel level was lowering. Valves HPCI-15 and 16 automatically isolated due to an invalid high steam flow isolation signal. The control room personnel immediately started both control rod drive (CRD) pumps as required by procedure. It was determined that the lowering of reactor vessel level was due to water flowing down the HPCI system and RCIC system turbine steam supply lines. The RCIC-15 valve was manually isolated terminating the event. At this time one CRD pump was secured. Acceptable water level in the reactor vessel was maintained throughout the event. The condition has been entered into the Vermont Yankee Nuclear Power Station Corrective Action Program for evaluation and implementation of corrective actions to preclude recurrence. The high steam flow isolation signal is considered invalid because: 1) At the time of the event, the unit mode switch was in a mode where PCIS was not required; 2) No steam was being generated; and 3) The water flow past differential pressure instrument generated a false high steam flow signal. The event is being reported in accordance with 50.73(a)(1) and 50.73(a)(2)(iv)(A) as an event or condition that as a result of an invalid initiation signal resulted in the actuation of one or more of the systems listed in paragraph 50.73 (a)(2)(iv)(B). The licensee has notified the NRC Resident Inspector. |
| ENS 43729 | 18 October 2007 12:36:00 | This notification is being made in accordance with 10CFR50.73(a)(2)(iv)(A) to provide information pertaining to an invalid Primary Containment Isolation System (PCIS) Group 3 actuation signal that affected containment isolation valves in more than one system. On 09/15/07, with the reactor at 100% power, an invalid PCIS Group 3 actuation occurred from a momentary spike of the 'A' Refuel Floor radiation monitor which reached the instrument's high radiation trip setpoint. Radiation protection technicians dispatched to the refuel floor verified dose rates in the vicinity of the 'A' radiation monitors detector to be normal and below the alarm set points. The radiation monitor was verified to be indicating normally to expected radiation levels. Subsequent visual inspection and functional checks of the radiation monitor were completed satisfactory and the instrument channel was returned to service. The cause of the spurious spike is attributed to an unknown source of electrical noise. Both trains of the Standby Gas Treatment System started as designed and Reactor Building ventilation isolated. The train actuation was complete. The PCIS functioned successfully providing a complete Group 3 isolation. The PCIS Group 3 isolation involves the following systems and isolation valves: Drywell and Suppression Chamber air purge and vent: V16-19-6, 6A, 6B, 7, 7A, 7B, 8, 9, 10, 23 Containment Makeup: V16-20-20, 22A, 22B Containment Air Sampling: VG-23, 26, V109-76A, 76B Containment Air compressor suction: V72-38A, 38B Containment Air Dilution: VG-9A, 9B, 22A, 22B, NG-11A, 11B, 12A, 12B, 13A, 13B In accordance with 10CFR50.73(a)(i) a telephone notification is being made instead of submitting a written Licensee Event Report. The licensee will notify the NRC Resident Inspector. |
| ENS 41868 | 25 July 2005 17:35:00 | At 1525 the plant experienced a load reject generator trip due to a catastrophic failure in the 345 Kv switchyard. A reactor scram occurred as a result. The degraded AC power system prevented a fast transfer from occurring. Degraded bus voltage caused the emergency diesel generators (EDGs) to start. A residual bus transfer restored power to the 4 Kv busses. The (main steam isolation valves) (MSIVs) closed on a low-low reactor water level of 82.5 inches. (Reactor Core Isolation Cooling) and (High Pressure Coolant Injection) (HPCI) also started on the low-low reactor vessel water level. The (Safety Relief Valves) were cycled twice for pressure control. OT 3100 Reactor Scram procedure was executed. EOP-3 was entered due to elevated torus water temperature and both loops of (Residual Heat Removal) (RHR) are in torus cooling. Water level has restored and is being maintained by feedwater. The MSIVs have been reopened and the scram reset. EDGs were secured. The plant is currently shutdown and stable with all control rods fully inserted. Decay heat removal is being accomplished with HPCI in pressure control mode. The licensee is transitioning to feeding with normal feedwater and steam exhausting through drains. Both trains of RHR are providing torus cooling. Electric power is being provided by offsite power. The licensee is currently investigating the event in the switchyard. The licensee notified the NRC Resident Inspector and will issue a press release.
Corrected incorrect entry for Scram Code from N (N/A) to A/R (Automatic/with Rod Motion). R1DO (Glenn Meyer) notified. |
| ENS 40343 | 20 November 2003 11:19:00 | At 0925, while performing the HPCI time to rated flow surveillance, operators discovered the HPCI flow controller to be operating sluggishly in the automatic mode. The surveillance was stopped and HPCI was declared inoperable. The licensee entered a 24-hour LCO per Technical Specification 3.5.5.2 due to Torus Cooling being in service on RHR loop "A". The licensee is now in a 14-day LCO as a result of securing Torus Cooling and restoring RHR LPCI loop "A". Troubleshooting was performed with I&C prior to securing HPCI. I&C is pursuing controller restoration to operability. The licensee has notified the NRC Resident Inspector.
BASIS FOR RETRACTION: NRC Notification 40343 was conservatively made to ensure that the Eight-Hour Non-Emergency reporting requirements of 10CFR50.73 were met pending the evaluation of an atypical condition observed with the High Pressure Coolant Injection (HPCI) Flow Controller while performing scheduled preventative maintenance testing for the HPCI System. After the off-site vendor lab completed testing the circuit board, the HPCI Flow Controller performed sluggishly, and it was determined that the initial NRC Notification was not required. During surveillance testing on 11/20/03, the HPCI System was started and met or exceeded the Technical Specification minimum requirements designed to demonstrate HPCI System Operability. While testing the specific components of the system, the HPCI Flow Controller was observed to be behaving erratically. Although the HPCI System was still capable of performing its required design safety function, the Shift Manager declared the system inoperable with a concern that further degradation of the flow controller "could have" prevented the HPCI System from performing its design safety function. Troubleshooting determined that the amplifier circuit board for the controller was not performing as expected. This board was subsequently replaced with one from stock and tested satisfactorily before declaring HPCI fully operational. The faulty amplifier circuit board was sent to an off-site vendor lab for testing and analysis. The vendor determined that the problem was due a capacitor failure on the board. The capacitor was removed, and the board was re-tested to determine the extent of the effect that this condition would have on the HPCI System performance. This testing revealed the same indications and system response that was initially observed by Vermont Yankee personnel during testing and troubleshooting. Therefore, it has been concluded that with the preventative maintenance system's surveillance as-found condition, the HPCI System was capable of performing its design safety function, and the flow controller's performance would not have degraded any further as a result of this condition. Therefore ENS Event Number 40343, made on 11/20/03, is being retracted. The NRC Resident Inspector was notified. Reg 1 RDO( Holody) was informed. |