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| Entered date | Site | Region | Scram | Reactor type | Event description | |
|---|---|---|---|---|---|---|
| ENS 55988 | 12 July 2022 11:47:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | The following information was provided by the licensee via fax or email: At 0803 EDT on 7/12/2022, with the Unit 2 in Mode 1 at 100% power, an automatic scram was received on Unit 2 following a turbine trip due to high reactor water level. The trip was uncomplicated with all systems responding normally post trip. All rods inserted to their full-in positions. Due to the Reactor Protection System actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The cause of the transient is under investigation. Operations responded using the Emergency Operating Procedure and stabilized the plant in Mode 3. Decay heat is being removed using the steam bypass valves to the condenser and the safety relief valves did not lift as a result of the trip. Reactor vessel inventory and pressure are being maintained in normal control bands. Unit 3 was not affected by this transient. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 55528 | 16 October 2021 09:10:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | On October 16, 2021 at 0428 CDT, an automatic scram was received on Unit 3 following a turbine trip. All Rods inserted to their full in position. All systems actuated and operated as expected. Unit 3 is being maintained in Mode 3, hot standby. This event is being reported pursuant to 10CFR 50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical. The NRC Resident Inspector has been notified. The event is related to Event Number 55527. |
| ENS 54054 | 9 May 2019 07:01:00 | Dresden | NRC Region 3 | Automatic Scram | On May 9, 2019 at 0348 CDT, an automatic scram was received on Unit 2 following a turbine trip. All rods inserted to their full-in positions. All Group 2 and Group 3 automatic isolations actuated as expected. Systems operated as expected. Reactor vessel inventory and pressure are being maintained in normal control bands. This event is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical. The NRC Resident Inspector has been notified. Decay heat is being removed using the steam bypass valves to the condenser and the safety relief valves did not lift as a result of the trip. | |
| ENS 50792 | 6 February 2015 16:53:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | At 1227 CST on 06 Feb 2015, Dresden Unit 2 automatically scrammed due to a Reactor Water Level transient. Set up activities for weekend maintenance were being performed on the feedwater system at the time of the event. All rods inserted to their full-in positions. Systems operated as expected. Reactor vessel inventory and pressure are being maintained in normal control bands. The ultimate heat sink was maintained. The source of the transient was a loss of Feedwater Level Control and the reactor automatically scrammed on low reactor water level. Cause of the failure is under investigation. All three feed pumps tripped as a result of the transient. The 2B reactor feed pump was restored following the transient in accordance with station operating procedures. Level is being maintained with normal feedwater. High Pressure Coolant Injection initiated on a valid low-low reactor water level. Manual operator action was taken to prevent unneeded injection into the reactor coolant system. Group 2 Primary Containment and Group 3 Shutdown Cooling and Reactor Water Clean-up system isolations occurred as expected. Unit 2 and 2/3 (swing diesel) EDGs started as expected, but did not load onto their associated busses as offsite power was maintained. The licensee has notified the NRC Resident Inspector. |
| ENS 50733 | 13 January 2015 22:10:00 | Dresden | NRC Region 3 | Manual Scram | GE-3 | At 1904 Central Time 13 Jan 2015, Dresden Unit 2 was manually scrammed by Operators due to a Reactor Water Level transient. All rods inserted to their full-in positions. All systems operated as expected. Reactor vessel inventory and pressure are being maintained in normal control bands. The source of the transient was a failure of both controllers in the Feedwater Level Control system. Cause of the failure is under investigation. This condition is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (R) when the reactor is critical. There was no on-going work or testing during this time which could be attributed to the failure of the level controllers. Unit 2 is in a normal post scram electrical line-up and maintaining pressure and temperature. RHR cooling is available if required. Unit 3 was unaffected by this transient. The licensee informed the NRC Resident Inspector. |
| ENS 50085 | 3 May 2014 15:15:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | At 1209 CDT on 3 May 2014, Dresden Unit 2 automatically scrammed on a Generator-Turbine Load Mismatch signal following a main generator trip. All rods inserted to their full in positions. All systems operated as expected. Reactor vessel inventory and pressure are being maintained in automatic. The cause of the scram was due to a main generator trip that occurred during a voltage regulator channel transfer. Troubleshooting is in progress to determine the exact cause of the generator trip. This condition is being reported pursuant to 10CFR50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical. The plant is in a normal shutdown electrical lineup. Main feedwater is being used to maintain reactor vessel level and decay heat is being removed by the main condenser via the turbine bypass valves. There was no impact on Unit 3 which remains stable at 100 percent power. The licensee notified the NRC Resident Inspector. |
| ENS 50030 | 12 April 2014 13:24:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | At 1012 CDT on April 12, 2014, Dresden Unit 2 automatically scrammed on TR-2 sudden pressure relay actuation. All rods inserted to their full-in positions. Following the reactor scram, the 'A' reactor recirculation pump did not run back to minimum speed automatically. Operators took action to run the recirculation pump to minimum speed manually. All other systems operated as expected. Reactor vessel inventory and pressure are being maintained in automatic. The cause of the scram was due to a trip of the sudden pressure relay for Main Power Transformer 2. Troubleshooting is in progress to determine the cause (of the trip of the sudden pressure relay). This condition is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B), any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical. Normal offsite power remains available. There was no impact on Unit 3. The NRC Resident Inspector has been informed. |
| ENS 46325 | 11 October 2010 13:38:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | On October 11, 2010 in preparation for maintenance, the 'A' Reactor Protection System Bus was being transferred from the normal to the reserve power supply. As a part of the transfer, a half scram is expected. During the transfer a (full) reactor scram occurred. All rods inserted to their full-in positions. Following the reactor scram, all systems operated as expected. Reactor vessel inventory is being maintained by the Condensate / Feedwater system. Following the scram, the Unit 2/3 Emergency Diesel Generator auto started due to the transfer of the Auxiliary Power system. Currently the cause of the full Reactor Protection System (scram) is unknown. Troubleshooting is in progress to determine the malfunction. This condition is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B), Any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical. The auto-start of the EDG was expected as a result of the 'A' RPS bus transfer and has been secured and placed back in standby. Decay heat is being discharged to the condenser. The Unit is in a normal shutdown electrical line-up. The scram had no impact on Unit 2. The licensee characterized the scram as uncomplicated. The NRC Resident Inspector has been notified.
The second to last paragraph of the original report has been updated to read as follows: The auto-start of the EDG was anticipated as a result of the Auxiliary Power System transfer and has been secured and placed back in standby. The R3DO (Orth) has been notified. |
| ENS 45409 | 3 October 2009 20:26:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | On 10/03/09 at 1734 CDT, Unit 3 scrammed due to a Group 1 MSIV closure. The cause of the event is being investigated. The 2/3 Emergency Diesel Generator also auto-started during the event. The cause of the auto start is also being investigated. All rods fully inserted. The reactor is currently stable in Mode 3 with makeup water coming from the control rod drive system and decay heat removal from the isolation condenser. All systems functioned as required with the exception of the unexplained MSIV closure and the auto start of the 2/3 EDG. There was no impact on Unit 2 and the plant is in a normal post-scram electrical lineup. There was no need for the 2/3 EDG to auto-start and it did not load. Group 2 and 3 isolations were also received during the transient which is expected and normal. Reactor water level is being maintained between 8 and 48 inches and pressure between 800 and 1060 psi. Investigation of the cause of the MSIV closure is in progress The licensee stated that there were no activities or surveillances in progress at the time that could have caused the MSIV closure. The NRC Resident Inspector has been notified. |
| ENS 43346 | 5 May 2007 02:13:00 | Dresden | NRC Region 3 | Manual Scram | GE-3 | The condensate prefilters isolated earlier in the day and the bypass valve automatically opened. The computer controlling these valves was in the process of being replaced when the bypass valve shut. Unit experienced a loss of feedwater due to condensate pre-filter valves going closed. The reactor was manually scrammed and HPCI was used to restore reactor water level. MSIVs closed and the U2 and U2/3 EDGs auto started on low level. All rods fully inserted on the manual scram. Minimum level was approximately -54 inches. Decay heat is being removed using the isolation condenser and level is being maintained with Control Rod Drive leak by. No safety or relief valves lifted during this event. The plant is in the normal shutdown electrical lineup. The licensee notified the NRC Resident Inspector. |
| ENS 41517 | 24 March 2005 07:59:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | The licensee provided the following information via email (licensee text in quotes): On 3/24/05 at approximately 0529 Unit 2 received a Group 1 isolation on main steam line high flow. All Group 1 valves closed as required and the reactor scrammed. The Isolation Condenser was manually initiated to control reactor pressure. Group 2 and 3 Containment Isolations occurred as expected. Investigation as to the cause of the Group 1 isolation is in progress. All systems responded as required with no abnormalities noted. The licensee also indicated that a Main Turbine Generator EHC transient occurred at the time of the isolation. All control rods fully inserted, the electrical grid is stable, and decay heat is being removed via the Isolation Condenser System. The licensee notified the NRC Resident Inspector. |
| ENS 40713 | 28 April 2004 18:50:00 | Dresden | NRC Region 3 | Manual Scram | GE-3 | On 4/28/04 at 1536 (CDT), Dresden Unit 2 experienced a trip of the 2A Recirc MG set and associated recirc pump. This placed the unit in the immediate scram region of the power to flow map. The Unit NSO manually scrammed the reactor in accordance with the immediate operator actions of DOA 202.01. Troubleshooting is in progress to determine the cause of the 2A Recirc MG set trip. There were no Electromatic Relief or Safety Relief Valve actuations. There were no ECCS initiations. PCIS Group 2 and Group 3 Isolations occurred as expected due to normal reactor water level decrease following the scram. All systems responded as expected following the reactor scram. This report is being made in accordance with 10 CFR 50.72 (b)(2)(iv)(B) for an actuation of the RPS and 10 CFR 50.72(b)(3)(iv)(A) for Group 2 and 3 actuations. All control rods fully inserted, the electrical grid is stable, ECCS and the EDGs remain operable. The licensee notified the NRC Resident Inspector. |
| ENS 40702 | 24 April 2004 09:00:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | This report is being made in accordance with 10 CFR 50.72 (b)(2)(iv)(B) . On 04/24/2004 at 06:03 (CDT), Dresden Unit 2 experienced an automatic Scram from 20% Reactor power due to Main Steam Isolation Valve closure, cause is under investigation. There were no Electromatic Relief or Safety Relief Valve actuations and the Isolation Condenser was initiated manually for pressure control. There were no ECCS initiations. PCIS Group 2 and Group 3 Isolations occurred as expected due to normal reactor water level decrease following the scram. All other systems responded as expected. All control rods fully inserted on the automatic scram. The electric plant is in a normal lineup and being supplied from offsite power. The licensee notified the NRC Resident Inspector. |
| ENS 40491 | 30 January 2004 14:35:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | Unit 3 experienced an automatic reactor scram due to a main turbine trip. The main turbine tripped due to low oil pressure, the cause of which is under investigation. Primary Containment Isolation System Group 2 and 3 isolations occurred as expected due to the reactor water level decrease following the scram. After reactor water level was restored to normal (+30 inches), level continued to increase to the reactor feed pump high level trip setpoint. Reactor level was subsequently restored to normal and the reactor feed pumps were restarted and are currently supplying the reactor. Decay heat is being removed by the main steam system via auxiliary loads. All other systems responded as expected. Current reactor pressure is 850 psi, and level is stable at 30 inches. The NRC Senior Resident Inspector is in the control room. |
| ENS 40388 | 12 December 2003 01:25:00 | Dresden | NRC Region 3 | Manual Scram | GE-3 | Manual scram was inserted during a Stator Cooling Runback that was not expected. Cause of the Stator Cooling Runback is under investigation. Group 2 & 3 Primary Containment Isolation System (PCIS) isolations occurred as expected due to reactor level drop during the scram. All other systems operated as expected. All controls rods were fully inserted during the manual scram. The MSIVs are open with decay heat being removed via steam to the main condenser using the turbine bypass valves. The condensate and feedwater system is in operation maintaining reactor vessel water level. Current Reactor Pressure is 880 psig and Reactor Level +30 inches. The electrical plant lineup is stable and in a normal lineup for this condition. The manual scram of this unit had no affect on the other unit onsite which is in a refueling outage. The licensee has notified the NRC Resident Inspector. |
| ENS 40209 | 30 September 2003 23:11:00 | Dresden | NRC Region 3 | Automatic Scram | GE-3 | Dresden Unit 2 automatically scrammed on low reactor vessel water level after "2C" reactor feed pump tripped (1 of 2 running). All systems responded as required (all rods fully inserted). Investigation into reactor feed pump trip cause has begun. The NRC Resident Inspector will be notified of this event by the licensee. |