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| Start date | Title | Description | Topic | |
|---|---|---|---|---|
| ENS 48333 | 21 September 2012 18:00:00 | Unanalyzed Condition Identified in Appendix R Fire Scenario | On September 21, 2012, a condition was identified where hydrogen may become entrained in the charging pump suction after the credited pump is restarted as part of the alternate shutdown procedure for the Auxiliary Building basement and mezzanine levels. An air operated valve separates the Volume Control Tank (VCT) from the charging pump suction and this valve fails open on loss of air or power caused by the postulated fire. The alternate flow path from the Refueling Water Storage Tank (RWST) fails closed on a loss of air or power. A manual valve is provided to bypass this closed valve. However, due to hydrogen pressure in the VCT and the potential for significant pressure losses in the piping from the RWST to the charging pump suction, insufficient elevation head exists in the RWST to ensure that hydrogen will not become entrained. If this condition is left unmitigated, the credited charging pump is assumed to fail. Due to the location of the postulated fire and its impact on equipment and cables, no other inventory makeup sources are credited. Compensatory Measures have been implemented as follows: 1. All fire detection and suppression systems in the Appendix R fire zones have been verified functional. 2. All Hot Work in the area has been suspended. 3. Continuous Fire Watch has been posted in the Appendix R fire zone. 4. Combustion engine powered vehicles are restricted from entering the Auxiliary Building. 5. Within 24 hours remove all non-attended transient combustible materials from Appendix R fire zones. The NRC Resident Inspector has been notified. * * * RETRACTION FROM REISNER TO SNYDER ON 9/28/12 AT 1415 EDT * * * This is a retraction of ENS report 48333 that was submitted at 2028 EDT on Friday, September 21 , 2012. A 10 CFR 50.72(b)(3)(ii)(B) ENS notification was made due to a condition that was identified where hydrogen may become entrained in the charging pump suction after the credited pump is restarted as part of the alternate shutdown procedure in the event of a fire in the Auxiliary Building basement and mezzanine levels. A subsequent engineering evaluation calculated the amount of gas that will be entrained into the charging pump suction flow and the duration of the entrainment. This evaluation demonstrates that for the most limiting Appendix R scenario that the charging pump will entrain a minimal amount of gas for a short duration, and is unaffected by this condition. Inventory control for the reactor coolant system is maintained throughout the scenario. Based on the above information the 'Unanalyzed Condition' ENS notification made on September 21, 2012 is being retracted. The licensee notified the NRC Resident Inspector. Notified R1DO (Bellamy). | Unanalyzed Condition Continuous fire watch |
| ENS 46917 | 3 June 2011 04:39:00 | Unexpected Emergency Diesel Generator Actuation | On 6/3/2011 at 0039 hours, during the performance of a work order to test components associated with Service Water Isolation, Emergency Diesel Generator (EDG) 'A' unexpectedly started automatically and its supply breaker to Safeguards Bus 14 closed. The Control Room staff observed normal voltage on Diesel Generator 'A'. Bus 14 voltage was never lost during this event, however, they also noted an associated Bus 14 undervoltage annunciator on the Main Control Board. Seconds later, Emergency Diesel Generator 'A' tripped on Reverse Power and its supply breaker to Bus 14 tripped open. The initiating action was the removal of the Bus 14 Normal Feed Breaker Control Power Fuses as part of the work order package. The Ginna EDG's have the following automatic start signals and logic: manual, safety injection signal (1/2 trains), undervoltage on respective safeguards bus, 'A' EDG Bus 14 or 18 (1 out of 2 degraded voltage + 1 out of 2 loss of voltage), 'B' EDG Bus 16 or 17 (1 out of 2 degraded voltage + 1 out of 2 loss of voltage). Investigation has commenced to determine the cause of the EDG start and undervoltage signal. The NRC Resident Inspector has been notified.
The purpose of this report is to retract the event discussed in Emergency Notification System report #46917 submitted on June 3rd, 2011. The ENS notification reported an unexpected start of Emergency Diesel Generator `A' during testing of a service water valve isolation circuit. As reported, Emergency Diesel Generator 'A' unexpectedly started and its supply breaker to Bus 14 closed. Seconds later, the Emergency Diesel Generator tripped on reverse power and its output breaker to Bus 14 opened. At the time of the event it was not understood why the diesel generator started. Subsequent troubleshooting and causal investigation identified that the signal was caused by a degraded control relay that unexpectedly changed state when control power was removed. This relay was expected to remain mechanically latched and would have remained in the desired position had control power not been removed as part of the test. Bus 14 voltage remained in the normal operating range throughout the event. Since this was not a valid undervoltage signal, the June 3rd, 2011 event is being retracted. A follow-up report will be made in accordance with 10CFR50.73(a)(1) and 10CFR50.73(a)(2)(iv). The NRC Resident Inspector has been notified. R1DO(Henderson) notified. See related EN #47094. | |
| ENS 46735 | 6 April 2011 19:30:00 | Degraded Fire Barrier | During walk downs for a planned site modification on April 6, 2011 at 1530 EDT, two degraded fire barrier seals were identified in the wall between the Auxiliary Building Basement and the Charging Pump Room. The wall is listed as an Appendix R wall between Fire Area (FA) ABBM and FA CHG. The wall separates redundant safe shutdown equipment. Two cylindrical six inch penetrations through the wall did not contain the required material to conform to a 3-hour fire rated barrier. This has been identified as a missing fire barrier such that the required degree of separation for redundant safe shutdown trains is lacking. A fire watch was established as a compensatory measure on 4/6/11. The discovery of this non-compliance is being reported as an unanalyzed condition as defined by 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified of this event.
The purpose of this report is to retract the event discussed in Emergency Notification System report #46735 submitted on April 6th, 2011. The ENS notification reported an inadequate fire barrier penetration seal discovered on April 6th, 2011 when maintenance inspected the penetration in preparation for a modification. Initial investigation concluded that the fire barrier penetration seal between the Charging Pump room and Auxiliary Building Basement was inoperable because there was inadequate seal material to provide the required three hour barrier rating. It appeared that when looking in the penetration sleeve that a fire board from the opposite room was visible and no foam material was present. Subsequently, an engineering review of the penetration has been completed. The review determined that a minimum of 8 inches of foam is required to maintain a 3-hour rating. Engineering identified that the design also requires a fire board on each side of the foam. Upon measurement it was confirmed that at least 11 inches of the penetration was filled, with a fire board on each side. Based on these measurements, the fire barrier met design requirements and was operable. The individuals performing the initial investigation did not recognize the thickness of the wall. On April 7th, Maintenance proceeded to penetrate the fire barrier for the modification and it was confirmed that foam was behind the fire board. With a 24 inch thick wall, a large portion at the penetration sleeve can be void of material and still meet the 3 hour rating. As such, the April 6th, 2011 event is being retracted. The licensee notified the NRC Resident Inspector. Notified the R1DO (Caruso) | Safe Shutdown Unanalyzed Condition Fire Barrier Fire Watch |
| ENS 46073 | 6 July 2010 17:05:00 | Post Contingency Low Voltage Alarm Received for Offsite Power | The Rochester Gas and Electric (RG&E) Energy Control Center (ECC) notified Ginna Operations that the Post Contingency Low Voltage Alarm was received for the offsite power system. Ginna Operations entered procedure O-6.9, Operating Limits for Ginna Station Transmission, and declared the offsite power inoperable per ITS 3.8.1 (72 hour LCO). Per NUREG-1022, section 3.2.7, if either offsite power or onsite emergency power is unavailable to the plant, it is reportable per 50.72(b)(3)(v)(A) regardless of whether the other system is available. The RG&E ECC monitors 115 kV voltage using their State Estimation and Contingency Analysis System. The State Estimation portion of the system evaluates real time system power flow and voltages on the 115 and 34.5 kV transmission systems. The Contingency Analysis portion analyzes the voltage effect of a Ginna main generator trip concurrent with worst case accident loading. If the Station 13A voltage would drop below the minimum required voltage for offsite power alignment a Ginna Post Contingency Low Voltage Alarm occurs. If the main generator should trip, then the absence of a Post Contingency Low Voltage Alarm on the RG&E State Estimation and Contingency Analysis System will ensure that the subsequent offsite 115kV system voltage transient will not result in Ginna Station experiencing an under voltage condition on the 480V Safeguard Busses. The RG&E ECC notified Ginna operations that the Post Contingency Low Voltage Alarm cleared at 1311 EDST on 07/06/2010. The plant was maintained at 100% steady state conditions throughout the event. Both circuits remain inoperable but available for use. And will be restored to operable status when the system reliability is assured. The licensee notified the NRC Resident Inspector.
The purpose of this report is to retract the event discussed in ENS report #46071 (July 6, 2010). The ENS report covered an offsite power related event which occurred on July 6, 2010. In this event, both sources of offsite power were declared inoperable following notification to the R.E. Ginna Nuclear Power Plant that the calculated post contingency off-site system voltage was below the required value necessary to ensure that offsite power would remain available following a design basis accident. Since the ENS report, an engineering analysis of the event has been completed. The analysis determined that the offsite power system was actually operable at all times on July 6, 2010. The 'Post Contingency Low Voltage Alarm (PCLVA)' computer model that is being utilized by the transmission system provider, Rochester Gas & Electric, to calculate the post contingency offsite system voltage, is inherently conservative in that it assumes the site is relying on a worst case single source of offsite power. However on July 6, 2010, both offsite power sources were available and the site was aligned in the 50/50 Normal offsite power configuration. The engineering analysis calculated the acceptable voltage in this configuration and identified that at no point did the calculated post contingency voltage decrease below the 50/50 Normal offsite power configuration's acceptable value. As such, the July 6, 2010 event is being retracted. The licensee notified the NRC Resident Inspector. R1DO (Burritt) was notified. | |
| ENS 42751 | 2 August 2006 15:27:00 | Post Contingency Low Voltage Alarm | The Rochester Gas and Electric (RG&E) Energy Control Center (ECC) notified Ginna Operations that the Post Contingency Low Voltage Alarm was received for the off site power system. Ginna Operations entered procedure O-6.9, operating Limits for Ginna Station Transmission, and declared the offsite power inoperable per ITS 3.8.1(72 hour LCO). Per NUREG-1022, section 3.2.7, if either offsite power or onsite emergency power is unavailable to the plant, it is reportable per 50.72(b)(3)(v)(A) regardless of whether the other system is available. The RG&E Energy Control Center (ECC) monitors 115 Kv voltage using their State Estimation and Contingency Analysis System. The State Estimation portion of the system evaluates real time system power flow and voltages on the 115 and 345 Kv transmission systems. The Contingency Analysis portion analyzes the voltage effect of a Ginna main generator trip concurrent with worst case accident loading. If the Station 13A voltage would drop below the minimum required voltage for offsite power alignment a Ginna Post Contingency Low Voltage Alarm occurs. If the main generator should trip, then the absence of a Post Contingency Low Voltage Alarm on the RG&E State Estimation and Contingency Analysis System will ensure that the subsequent offsite 115kV system voltage transient will not result in Ginna Station experiencing an under voltage condition on the 480V Safeguard Busses. The RG&E ECC notified Ginna operations that the Post Contingency Low Voltage Alarm cleared at 1408 EDST on 08/02/2006 and the LCO for ITS 3.8.1 was exited at 1704 after observation of grid stability. The plant was maintained at 100% steady state conditions throughout the event. The licensee notified the NRC Resident Inspector.
This is an additional notification for EN #42751 that was reported on 8/2/06 for offsite power being declared inoperable. A subsequent investigation revealed that offsite power was also inoperable on 7/17/2006 from 1427 to 1448 and on 8/1/2006 from 1022 to 1843 for which a notification was not completed. The licensee notified the NRC Resident Inspector. Notified R1DO P. Finney
The purpose of this report is to retract one of the events discussed in ENS report #42751 (August 2 and 3, 2006). The ENS report covered three separate off site power related events which occurred on July 17, 2006, August 1, 2006 and August 2, 2006. For each of the events, both sources of off-site power were declared inoperable following notification to R.E. Ginna Nuclear Power Plant that the calculated post contingency off-site system voltage was below the required value necessary to ensure that off-site power would remain available following a design basis accident. Since the ENS report, an engineering analysis of the July 17, 2006 event has been completed. The analysis determined that the off site power system was actually operable at all times on July 17, 2006, The 'post contingency low voltage alarm (PCLVA)' computer model that is being utilized by Rochester Gas & Electric to calculate the post contingency off site system voltage is inherently conservative in that many of the automatic voltage regulators associated with the other generating units are assumed to be in the manual mode. The computer simulation that resulted in the alarm was repeated and by 'turning on' the voltage regulators for four of the nearby generator units, the post contingency voltage improved to above the alarm set point. The four voltage regulators that were turned on in the computer simulation were confirmed to be in the automatic mode on July 17, 2006. As such, the July 17, 2006 event is being retracted. The licensee notified the NRC Resident Inspector. NRC R1DO (Ray Powell) notified. |