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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 54078 | 22 May 2019 06:56:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Technical Specification Required Shutdown | On 5/22/2019, the 'A' Control Structure Chiller (Div I) tripped due to a loss of (motor control center) MCC 0B136. The 'B' Control Structure Chiller was already inoperable due to Div II (Emergency Service Water) ESW being out of service for planned maintenance. With the loss of Control Structure HVAC System the ability to maintain temperatures in various spaces including relay rooms, Control Room Floor Cooling and Emergency Switchgear rooms was lost. The 'B' Control Structure Chiller was restarted at 0251 EDT and cooling was reestablished to the required areas, however the 'B' chiller is not considered operable at this time. Units 1 and 2 entered (Technical Specification) TS 3.0.3 at 0256 EDT and a controlled shutdown of both units commenced, Unit 2 at 0340 EDT and Unit 1 0350 EDT. This constitutes a TS required shutdown and requires a 4 hour (Emergency Notification System) ENS notification in accordance with 10 CFR 50.72(b)(2)(i). The failure also requires an 8 hour ENS notification in accordance with 10 CFR 50.72(b)(3)(v) due to the loss of a safety function. The licensee needs to restore the 'B' loop of ESW to exit the Limiting Condition of Operation (LCO). The licensee is currently performing a flow surveillance, once complete and assuming the data is acceptable, the licensee will be able to exit the LCO. The units are in a normal electrical lineup. The licensee will be notifying the state of Pennsylvania FEMA Operations Center. The licensee has notified the NRC Resident Inspector.
On 5/22/2019 at 0601 EDT Susquehanna Steam Electric Station reported a shutdown had been commenced at 0340 EDT for Unit 2 and 0350 EDT for Unit 1 due to inoperability of both control structure chillers. Power has been restored to MCC 0B136, and at 0901 EDT the 'A' control structure chiller was declared operable and LCO 3.0.3 was exited. Power reduction for both units was halted at 0901 EDT and preparations for power restoration initiated. As of 1255 EDT on 5/22/2019, Unit 1 power is 94% and Unit 2 power is 92%. Notified the R1DO (Arner). | HVAC | |
| ENS 52369 | 16 November 2016 15:45:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Failure of Unit 2 B Engineered Safeguards System Bus Sync Selector Switch | On November 16, 2016 at 1045 (EST), Unit 2 B ESS (Engineered Safeguards System) Bus Sync Selector switch failed and was unable to be switched out of the ON position. The failure rendered all other sync selector switches associated with Emergency Diesel Generators and Off-Site supplies to the ESS buses unable to fulfill their intended function of allowing manual transfer between power supplies to the ESS buses. This resulted in the inability of Unit 1 and Unit 2 to comply with SR (Surveillance Requirements) 3.8.1.8 and 3.8.1.16 thus requiring declaration of Operating AC Sources inoperable. This condition could have prevented the fulfillment of the safety function of systems required to maintain the reactor in a safe shutdown condition, remove residual heat, control the release of radioactive material, and mitigate the consequences of an accident. Subsequent actions were taken in accordance with station procedures to remove fuses for the affected sync circuit, restoring the manual transfer function to all but the Unit 2 B ESS bus. One Emergency Diesel and one offsite source remain inoperable with the fuses removed. At no time were any ESS buses disconnected from offsite power. All ESS buses remained capable of being automatically energized from their respective emergency diesel in an emergency. The licensee has notified the NRC Resident Inspector. | Emergency Diesel Generator | |
| ENS 40646 | 5 April 2004 15:40:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Loss of Safety Function for Emergency Diesel Generators During Surveillance Testing | At 1040 hrs during setup for Unit 1 Division 1 LOCA/LOOP Surveillance testing, the controlling procedure required making the Loss of Power instrumentation for the 1A and 1C ESS buses inoperable. The specification has a 1 hour time limit for restoration, or the associated Diesel Generators must be declared inoperable. Due to delays during the setup of equipment the time requirements were not met, and the 'E' (Substituting for 'A') and 'C' Diesel Generators were declared inoperable at 1140 hrs. The Loss of Power instruments were restored, and the Diesel Generators declared operable at 1206 hrs. Unit 1 is in Mode 5 requiring only 2 diesel generators operable, therefore not impacted by the Loss of Power instrumentation inoperability. Also during the surveillance, two pump start timers failed to meet the required acceptance criteria. The 'A' ESW Pump timer actuated at 47.86 seconds (criteria; 36 sec. to 44 sec) and the 'C' ESW Pump timer actuated at 50.38 seconds (criteria: 39.6 sec. to 48.4 sec). With failure of the timers, proper loading on the Diesel Generators is not assured, and they were declared inoperable until the associated pump control breakers were opened. The 'E' Diesel Generator was declared inoperable at 1448 hrs, when the data analysis identified that the 'A' ESW pump timer did not meet acceptance criteria. The 'E' Diesel Generator was returned to operable at 1453 hrs when the DC Knife switches for the 'A' ESW pump were open. The 'C' Diesel Generator was declared inoperable at 1524 hrs, when the data analysis identified that the 'C' ESW pump timer did not meet acceptance criteria. The 'C' Diesel Generator was restored to operable at 1706 hrs after supported systems were realigned to prevent further loss of safety function and the DC Knife switches for the 'C' ESW pump were open. The Susquehanna safety analysis requires three operable Diesel Generators to safely shutdown the plant. Therefore with only two operable Diesel Generators, the condition requires an 8 hr ENS notification in accordance with 10CFR50.72(b)(3)(v)and (vi). All times referenced above are EDT. The licensee informed the NRC Resident Inspector. * * * RETRACTION FROM R. FRY TO M. RIPLEY 1419 ET ON 05/27/04 * * * * The following is a retraction of ENS Notification #40642 AND #40646: On April 5, 2004, PPL Susquehanna, LLC reported three events to the NRC associated with Unit 1 Division 1 LOCA/LOOP surveillance testing. In each case, the safety function of two (out of 4) emergency diesel generators was brought into question during the testing. In two of these events, the E (substituting for A) and C diesel generators were administratively declared inoperable per Technical Specifications. This was necessary because Loss of Power instrumentation for the 1A and 1C buses, rendered inoperable in support of the test procedure, was not restored within 1 hour. In the third event, the E (for A) and C emergency diesel generators were, again, declared inoperable when two ESW pump start timers failed to meet acceptance criteria thus bringing the proper start sequencing of emergency loads into question. Because the Susquehanna Safety Analysis requires three diesel generators to safely shutdown an operating unit, the potential compromise of the diesel generator safety function was a concern for Unit 2 in each instance. (NOTE: Unit 1 was in Refueling Mode 5 and was, therefore, not impacted by these events.) Accordingly, Control Room personnel conservatively initiated ENS reporting under 10CFR50.72(b)(3)(v) in response to the apparent loss of safety function for Unit 2. Subsequent engineering analysis has concluded that, although the declaration of diesel generator inoperability was correct and in accordance with Technical Specifications, fulfillment of these administrative actions did not result in an actual loss of safety function during any of the above described events. Details of the analysis show that the diesel generators were available to supply emergency power to the ESS buses and/or that sufficient redundant equipment was available to fulfill the safety function needs of Unit 2. These analysis conclusions provide the basis for retraction of the ENS reports made on April 5, 2004." The licensee notified the NRC Resident Inspector. Notified R1DO (R. Conte) | Emergency Diesel Generator | |
| ENS 40642 | 5 April 2004 05:30:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | Loss of Safety Function for Emergency Diesel Generators During Surveillance Testing | At 0030 (ET) during setup for Unit 1 Division 1 LOCA/LOOP Surveillance testing, the controlling procedure required making the Loss of Power instrumentation for the 1A and 1C ESS buses inoperable. The specification has a 1 hour time limit for restoration, or the associated Diesel Generators must be declared inoperable. Due to delays during the setup of equipment the time requirements were not met, and the associated Diesel Generators were declared inoperable at 0130. The Susquehanna Safety Analysis requires three operable Diesel Generators to safely shutdown. Therefore, this condition is reportable for Unit 2 under 10CFR50.72(b)(3)(v). Unit 1 is in Mode 5 and therefore not impacted. The Loss of Power instruments were restored, and the Diesel Generators declared operable at 0223. The licensee notified the NRC Resident Inspector.
The following is a retraction of ENS Notification #40642 AND #40646: On April 5, 2004, PPL Susquehanna, LLC reported three events to the NRC associated with Unit 1 Division 1 LOCA/LOOP surveillance testing. In each case, the safety function of two (out of 4) emergency diesel generators was brought into question during the testing. In two of these events, the E (substituting for A) and C diesel generators were administratively declared inoperable per Technical Specifications. This was necessary because Loss of Power instrumentation for the 1A and 1C buses, rendered inoperable in support of the test procedure, was not restored within 1 hour. In the third event, the E (for A) and C emergency diesel generators were, again, declared inoperable when two ESW pump start timers failed to meet acceptance criteria thus bringing the proper start sequencing of emergency loads into question. Because the Susquehanna Safety Analysis requires three diesel generators to safely shutdown an operating unit, the potential compromise of the diesel generator safety function was a concern for Unit 2 in each instance. (NOTE: Unit 1 was in Refueling Mode 5 and was, therefore, not impacted by these events.) Accordingly, Control Room personnel conservatively initiated ENS reporting under 10CFR50.72(b)(3)(v) in response to the apparent loss of safety function for Unit 2. Subsequent engineering analysis has concluded that, although the declaration of diesel generator inoperability was correct and in accordance with Technical Specifications, fulfillment of these administrative actions did not result in an actual loss of safety function during any of the above described events. Details of the analysis show that the diesel generators were available to supply emergency power to the ESS buses and/or that sufficient redundant equipment was available to fulfill the safety function needs of Unit 2. These analysis conclusions provide the basis for retraction of the ENS reports made on April 5, 2004." The licensee notified the NRC Resident Inspector. Notified R1DO (R. Conte) | Emergency Diesel Generator | |
| ENS 40134 | 5 September 2003 13:33:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Pressure Coolant Injection (Hpci) Declared Inoperable. | At 09:30 EDT, Unit 1 was performing the HPCI Quarterly Flow verification surveillance. Shortly after the initiation of the system an abnormally loud bang was heard. System flow of approximately 5200 gpm and discharge pressure of approximately 1300 psi was achieved at approximately 09:33. Approximately 4 seconds after reaching rated system flow HPCI discharge pressure increased to approximately 1675 psi and system flow dropped to approximately 2700 gpm. HPCI had been declared inoperable at 08:35 EDT to perform the surveillance and will remain inoperable until the cause of the loss of system flow is corrected. Because HPCI is a single train ECCS (Emergency Core Cooling System) safety system, this event results in the loss of an entire safety function which requires an 8 hour ENS notification in accordance with 10CFR50.72(b)(3)(v) and the guidance provided under NUREG-1022, rev. 2. There are no other ECCS systems presently out of service. Reactor Core Isolation Cooling (RCIC) is fully operable and HPCI entered Tech Spec 3.5.1 (14 day Limiting Condition of Operation). All other ECCS systems are fully operable. The NRC Resident Inspector was notified of this event by the licensee.
On 09/05/2003, PPL Susquehanna LLC made an ENS notification per 10CFR50.72(b)(3)(v) in response to an apparent loss of the HPCI (High Pressure Coolant Injection) safety function. In the event, results of HPCI Quarterly Flow Surveillance testing did not meet acceptance criteria established for the system. Investigation into the cause of the failed HPCI surveillance revealed a 360-degree weld crack on the HPCI Test Line to Condensate Storage Tank (CST) Valve, HV155F008. HV155F008 is not in the reactor vessel injection flowpath. The impact of this crack, which was located between the valve seat cage assembly and the valve body, was that the HPCI Test Line to CST valve was not capable of throttling over the full range of HPCI system flows. Valve performance became erratic at higher flows because the valve seat cage was lifted out of the valve body into the flow path, increasing system resistance, and preventing attainment of design flow in the HPCI test loop. While the ability to effectively test the HPCI system using the test return path to the CST was compromised, the HPCI injection flowpath to the reactor vessel was not adversely affected by the damaged valve. Accordingly, the HPCI system maintained full capability for providing sufficient coolant to the reactor vessel in the event of a small break loss-of-coolant accident. Because the HPCI safety function was not compromised by the identified test path obstruction, this ENS notification is being retracted. The Licensee has notified the NRC Resident Inspector. Notified R1DO (Cobey). | High Pressure Coolant Injection Reactor Core Isolation Cooling |