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| Entered date | Event description | |
|---|---|---|
| ENS 54103 | 6 June 2019 12:02:00 | This 60-day telephone notification is being made in accordance with the reporting requirements specified by 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of a general containment isolation signal affecting multiple Main Steam Isolation Valves (MSIVs). On April 18, 2019 at approximately 0110 EDT, during performance of an ASME reactor vessel leak check, all four inboard MSIVs closed as a result of actuation of the Main Steam Line (MSL) high flow instrumentation. The high flow signal was spurious on the 'D' channel with no flow in the MSLs. Since an actual high flow condition did not exist at the time of the actuation, the actuation was considered invalid. The MSIVs functioned as designed on actuation of the MSL high flow instrumentation. All outboard MSIVs were closed at the time of the actuation in accordance with the vessel leak check procedure. The NRC Resident Inspector has been notified. |
| ENS 52973 | 16 September 2017 15:53:00 | On September 16th, 2017 at 1330 hrs. (EDT), a loss of secondary containment differential pressure (D/P) occurred due to an equipment failure. This caused a reduction in Reactor Building Zone 2 (Unit 2) D/P to less than the required 0.25 inches WC per SR (Surveillance Requirement) 3.6.4.1.1. 2V206B, Reactor Building Zone 2 Equipment Compartment Exhaust Fan, was manually started and Reactor Building Zone 2 D/P was restored to greater than 0.25 inches WC by 1333 hrs. Reactor Building Zone 1 (Unit 1) and Zone 3 (Units 1&2) ventilation remained in service and stable. This event is being reported under 10 CFR 50.72(b)(3)(v)(c) and per the guidance of NUREG 1022, Rev. 3, section 3.2.7, as a loss of a Safety Function. There is no redundant Susquehanna Secondary Containment system. The licensee has notified the NRC Resident Inspector. |
| ENS 52552 | 15 February 2017 18:10:00 | On February 15, 2017 at 1337 (EST), Secondary Containment Zone 1 (Unit 1 Reactor Building) differential pressure lowered to 0 inches WG (Water Gauge) due to a trip of the running Unit 1 B Filtered Exhaust Fan. Required differential pressure per SR (Surveillance Requirement) 3.6.4.1.1 could not be maintained. Zone 1 differential pressure recovered to greater than 0.25 inches WG less than one minute later after start of the standby Zone 1 Filtered Exhaust Fan. Zone 2 (Unit 2 Reactor Building) and Zone 3 (Common Areas of Unit 1&2 Reactor Buildings) ventilation remained in service and stable. This event is being reported under 10 CFR 50.72(b)(3)(v)(C) and per the guidance of NUREG-1022, Rev 3 section 3.2.7 as a loss of a Safety Function. There is no redundant Susquehanna Secondary Containment System. Post-maintenance testing was underway when the fan tripped. While the investigation is on-going to determine the cause, the licensee does not believe the maintenance or testing caused the fan to trip The licensee has notified the NRC Resident Inspector.
The Unit 1 B Filtered Exhaust Fan trip that resulted in loss of secondary containment differential pressure occurred during post maintenance testing (PMT). The PMT was being performed following replacement of a flow controller associated with the Unit 1 B Filtered Exhaust Fan. In support of the PMT, Technical Specification (TS) 3.6.4.1 Condition A had been entered and was in effect at the time of the fan trip. The maintenance and the associated PMT were performed in accordance with approved work instructions/procedure. Subsequent to the initial report, Susquehanna troubleshooting determined that the fan trip was the result of an internal leak in the newly installed controller that prevented the new controller from functioning properly. The condition was therefore determined to have been the result of the completed maintenance. NUREG-1022, Section 3.2.7, includes the following guidance: '...reports are not required when systems are declared inoperable as part of a planned evolution for maintenance or surveillance testing when done in accordance with an approved procedure and the plant's TS (unless a condition is discovered that would have resulted in the system being declared inoperable).' Following completion of the troubleshooting, Susquehanna determined that, per NUREG-1022, Section 3.2.7, the event was not reportable. Secondary Containment was declared inoperable as a part of a planned evolution for maintenance which was done in accordance with an approved procedure and the Susquehanna TS. The discovered condition was not a pre-existing condition that would have resulted in the system being declared inoperable prior to the planned maintenance activity. The licensee notified the NRC Resident Inspector. Notified R1DO (Jackson). |
| ENS 51987 | 8 June 2016 07:01:00 | Susquehanna Unit 1 identified RPV (reactor pressure vessel) pressure boundary leakage from (local power range monitor) LPRM 24-09 housing above the flange during an under vessel leak inspection on 06/08/2016 at 0226 EDT. The leakage point is a through wall indication on the ASME Class 1 LPRM stub tube. The leakage is not isolable from the reactor vessel. The reactor was in Mode 4 at the time of discovery. This event is being reported as a degraded condition pursuant to 10CFR50.72(b)(3)(ii)(A). A repair plan is being formulated. The licensee has notified the NRC Resident Inspector. |
| ENS 51983 | 6 June 2016 08:13:00 | Susquehanna Unit 1 commenced a manual shutdown on 06/05/2016 for a maintenance outage. At 2202 hours (EDT) on 06/05/2016, operators began reducing power in accordance with plant procedures. At 0352 hours on 06/06/2016, the Main Turbine was tripped with reactor power at approximately 15%. The Mode switch was taken to 'STARTUP/HOT STANDBY' (Mode 2) at 0515 hours on 06/06/2016. Manual insertion of control rods was paused as scheduled for entry into the drywell for inspections. There were no ESF actuations. At 0556, the licensee identified leakage from a weld on seal water line piping connected to the 1B reactor recirculation pump seal area. The location is within the reactor recirculation loop isolation valves, therefore is isolable from the reactor vessel. The piping is ASME Class 2 and is reactor coolant pressure boundary. The reactor was in Mode 2 at the time of discovery. This event is being reported as a plant shutdown required by technical specifications pursuant to 10CFR50.72(b)(2)(i) and degraded condition pursuant to 10CFR50.72(b)(3)(ii)(A). Activities are continuing to achieve cold shutdown. The licensee informed the Commonwealth of Pennsylvania and the NRC Resident Inspector. |
| ENS 51851 | 6 April 2016 17:27:00 | On April 6th, 2016 at 1337 (EDT) and 1343 (EDT) Secondary Containment became inoperable due to failure to meet a Surveillance Requirement (SR 3.6.4.1.3) on Unit 1 and Unit 2. The inoperability was caused when two separate sets of Reactor Building airlock doors were sequentially opened during a medical emergency to transport an individual. Each set of airlock doors was opened momentarily to allow passage. Secondary Containment was restored April 6, 2016 at 1344 (EDT) when the transport evolution was complete. This event is being reported under 10 CFR 50.72(b)(3)(v)(c) and per the guidance of NUREG 1022 Rev 3 section 3.2.7 as a loss of a Safety Function. There is no redundant Susquehanna Secondary Containment system. The NRC Resident Inspector has been notified. |
| ENS 51838 | 31 March 2016 12:45:00 | On March 31, 2016 at 0603 (EDT), with Susquehanna Unit 1 in its 19th Refueling and Inspection Outage, Unit 1 received a valid isolation signal. Preliminary investigation indicates the isolation signal was the result of a human performance error. The systems affected by the isolation signal responded as designed for the current shutdown plant conditions. This isolation of multiple primary containment isolation systems is being reported under 10CFR50.72(b)(3)(iv)(A) and per the guidance of NUREG 1022, Rev. 3, section 3.2.6 as a system actuation. The licensee notified the NRC Resident Inspector. |
| ENS 51532 | 12 November 2015 15:15:00 | At 1132 hours (EST) on November 12, 2015, Susquehanna Steam Electric Station Unit 1 reactor automatically scrammed due to one Main Steam Isolation Valve (MSIV) unanticipated closure causing a High Pressure RPS (Reactor Protection System) trip. All control rods inserted and both reactor recirculation pumps tripped due to reactor water level 2. Reactor water level lowered to -37 inches causing Level 3 (+13 inches) and level 2 (-38 inches) (Division 2 only) isolations. RCIC (Reactor Core Isolation Cooling) automatically initiated and was overridden by control room operators after RPV (Reactor Pressure Vessel) water level was restored to the normal band with feedwater. All isolations and initiations occurred as expected. No main steam relief valves opened. Pressure was controlled via main turbine bypass valve operation. All safety systems operated as expected. The Unit 1 reactor is currently stable in Mode 3. Investigation into the cause of the MSIV closure is underway. Unit 2 was unaffected and continues power operation. The NRC Resident Inspector has been notified. A voluntary notification to PEMA (Pennsylvania Emergency Management Agency) and press release will occur. The plant is in its normal shutdown electrical lineup. |
| ENS 51533 | 12 November 2015 17:47:00 | On November 12, 2015 at 1132 hrs. (EST), Secondary Containment became inoperable due to failure to meet SR 3.6.4.1.1 requirements on Unit 2. The inoperability was caused when RB (Reactor Building) Zone II differential pressure (D/P) oscillated between 0.23 and 0.43 inches WG (water gauge) (less than SR 3.6.4.1.1 requirement of greater than or equal to 0.25 inches WG). The oscillations subsided at 1501 (EST) and RB Zone II D/P continues to be maintained at approximately 0.35 inches WG. This event is being reported under 10 CFR 50.72(b)(3)(v)(c) and per the guidance of NUREG 1022 Rev 3 section 3.2.7 as a loss of a Safety Function. There is no redundant Susquehanna Secondary Containment system. The licensee notified the NRC Resident Inspector. |
| ENS 51017 | 27 April 2015 15:46:00 | On 4/27/2015 at 0850 (EDT), Secondary Containment (Unit 1 Reactor Building) Boundary Door-721 was found ajar. The door was closed by operators. A status walkdown was performed and no other doors were found in this condition. Although, Secondary Containment differential pressure was maintained throughout the time period that the door was not fully closed and latched. The door serves as a Secondary Containment boundary and is required to be closed for Secondary Containment Operability. This event is being reported under 10 CFR 50.72(b)(3)(v) and per the guidance of NUREG 1022 Rev 3 section 3.2.7 as a loss of a Safety Function. There is no redundant Susquehanna Secondary Containment System. This door is in the railroad bay and was posted as a containment boundary door. Investigation into why this door was not closed and latched is continuing. The licensee notified the NRC Resident Inspector. |
| ENS 50976 | 11 April 2015 11:23:00 | On 4/11/15, Unit 2 drywell entry was performed during a planned Unit 2 refueling inspection outage. At 0958 EDT, the licensee identified leakage from a weld on the 3/4 inch seal vent piping connected to the 2A reactor recirculation pump seal area. The location is within the reactor recirculation loop isolation valves, therefore it is isolable from the reactor vessel. The piping is ASME Class 2 and is a reactor coolant pressure boundary. The reactor was in mode 3 at the time of discovery. This event is being reported as a degraded condition pursuant to 10CFR50.72(b)(3)(ii)(A). The licensee notified the NRC Resident Inspector. |