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| Discovered date | Reporting criterion | Title | Event description | |
|---|---|---|---|---|
| ENS 56759 | 27 September 2023 15:41:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Actuation of Reactor Protection and Containment Isolation Systems | The following information was provided by the licensee via fax: (On 09/27/2023) at 1041 CDT, with the plant at 75 percent power and main turbine control valve testing in progress, a reactor pressure transient resulted in a reactor steam dome high pressure scram and subsequent group 1 primary containment isolation of the main steam lines (MSL). All main steam isolation valves closed as a result of the group 1 isolation signal. Additionally, a group 2 containment isolation signal was received due to reactor pressure vessel (RPV) level less than plus 9 inches during the transient. Operations personnel responded and stabilized the plant. The high-pressure coolant injection (HPCI) system was placed in service to control RPV pressure. HPCI did not inject into the RPV and was not needed to control RPV water level. The cause of the initial pressure transient is under investigation. The NRC Resident Inspector has been notified.
The utility notified the State of Minnesota and Wright and Sherburne counties. Notified R3DO (Orlikowski) |
| ENS 56673 | 10 August 2023 04:39:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Automatic Reactor Trip | The following information was provided by the licensee via email: At 0039 (EDT) on 8/10/23, with Unit 1 in Mode 1 at 100 percent power, the reactor automatically tripped during a reactor protection system (RPS) bus shift. All systems responding normally post-trip. There was no equipment inoperable at the time of the trip. Operations responded and stabilized the plant. Reactor water level being maintained via feedwater. Decay heat is being removed by cycling safety relief valves. An actuation of high-pressure core spray, division 3 diesel generator, and reactor core isolation cooling occurred during the scram and main steam line isolation closure. The reason for the auto-start was reaching Level 2 (130 inches in the reactor pressure vessel) during the transient. The systems automatically started as designed and injected to the reactor vessel when the Level 2 signal was received. The RPS actuation is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). The emergency core cooling system (ECCS) injection is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A). The ECCS actuation is being reported as a eight-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 56610 | 6 July 2023 16:32:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition | The following information was provided by the licensee via email: On July 6, 2023, at 1232 EDT, while operating in Mode 1 at 100 percent power, the supply check valve from the number 2 steam generator to the turbine driven auxiliary feedwater pump was determined during troubleshooting that it is not able to perform its isolation function. This failure would have resulted in the blowdown of both steam generators during a main steam line break in the number 2 steam generator main steam line upstream of the main steam isolation valves until the operators could isolate the faulted steam generator. Previous evaluation has determined that this condition constituted an unanalyzed condition that could impact containment pressure. There was no radioactive release to the environment. The steam line from the steam generator to the turbine driven auxiliary feedwater pump was isolated by use of a motor operated valve in the discharge line of the number 2 steam generator. There was no impact to Unit 3 which remains at 100 percent power. The NRC Senior Resident Inspector was notified. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(ii)(B) as a condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety. |
| ENS 56478 | 20 April 2023 05:48:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Trip Due to a Turbine Trip | The following information was provided by the licensee via phone and email: At 0148 Eastern Daylight Time (EDT) on April 20, 2023, with Unit 1 in Mode 1 at 100% power, the reactor automatically tripped due to a turbine trip. Turbine Bypass valves did not open on the trip due to Turbine Protection system power supply failure; the Safety Relief Valves (SRVs) opened automatically to control reactor pressure. Reactor Pressure reached approximately 1095 psig on the trip; exceeding the 1060 psig RPS trip setpoint. Operations responded and stabilized the plant. Operations was able to transition from SRVs to main steam line drains to the condenser. Reactor water level is being maintained via the Condensate / Feedwater system. Decay heat is being removed by discharging steam to the main condenser using the main steam line drains. Due to the Reactor Protection System (RPS) actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Reactor water level reached low level 1 (LL1) following the reactor trip. The LL1 signal causes Group 2 (i.e., floor and equipment drain isolation valves), Group 6 (i.e., monitoring and sampling isolation valves), and Group 8 (i.e., shutdown cooling isolation valves) isolations. The LL1 isolations occurred as designed; the Group 8 valves were closed at the time of the event. Due to the valid Primary Containment Isolation System (PCIS) actuation and RPS actuation from the reactor pressure signal, this event is also being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A). Unit 2 is not affected by this event. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 56455 | 6 April 2023 20:46:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Main Steam Line 'B' Leakage in Excess of Tech Spec Limits | The following information was provided by the licensee via phone and email: On March 4, 2023, it was determined that the main steam line (MSL) local leak rate test results for MSL 'B' were in exceedance of technical specification (TS) surveillance requirement (SR) 3.6.1.3.10 limits. Additionally, the leakage at the outboard main steam isolation valve (MSIV) 'B', was indeterminate due to a gross packing gland leak. An engineering calculation dated April 6, 2023, showed that this leakage, in conjunction with a design basis loss of coolant accident, would result in the radiological dose exceeding Updated Safety Analysis Report limits to the exclusion area boundary, the low population zone, and the control room. Therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(B) as a condition that results in the power plant being in an unanalyzed condition that degrades plant safety. Both inboard and outboard 'B' MSIVs have been reworked and are within the TS SR limits. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
| ENS 56373 | 19 February 2023 06:05:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Specified System Actuation | The following information was provided by the licensee via fax or email: At 0105 EST on February 19, 2023, with the James A. FitzPatrick Nuclear Power Plant (JAF) at 100 percent power, a valid high main steam line radiation signal was received. An actuation of a fire protection foam system caused migration of high conductivity water into a low conductivity sump. Organic compounds were introduced into the primary coolant and resulted in a temporary increase in nitrogen-16 which was detected by main steam line radiation monitors and actuated primary containment isolation signals in more than one system. The reactor water recirculation sample system isolated. The signal also went to the normally isolated main steam line drain system and condenser air removal system. The event is reportable in accordance with 10 CFR 50.72(b)(3)(iv)(A). The elevated radiation condition no longer exists. Health and safety of the public was not impacted by this event. The NRC Resident Inspector was notified. |
| ENS 56328 | 1 February 2023 05:43:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Scram Due to Turbine Trip | The following information was provided by the licensee via fax and telephone: Generator trip due to power load unbalance which caused a turbine trip and subsequent reactor scram. Experienced a trip on circulating water pump A. NRC Resident Inspector notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Off-site power available and unaffected. Decay heat removal via main steam line and drains to condenser. Plant is stable in mode 3. |
| ENS 55899 | 16 May 2022 19:52:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Scram Due to Electrical Transients | The following information was provided by the licensee via fax: Unit 2 experienced multiple electrical transients resulting in a Group I Primary Containment Isolation Signal (PCIS) isolation and subsequent unit reactor scram. Low reactor water level during the automatic scram caused PCIS Group II and III isolation signals. Following the PCIS Group I isolation, all main steam lines isolated. All control rods inserted and all systems operated as designed. The following additional information was obtained from the licensee via phone in accordance with Headquarters Operations Officers Report Guidance: Peach Bottom Unit 2 automatically scrammed from 100 percent power due to an electrical transient and subsequent PCIS Group I isolation (Main Steam Isolation Valve closure). Unit 2 lost main feedwater due to the PCIS Group I isolation, however, all other systems responded as expected following the scram. High Pressure Coolant Injection is maintaining pressure control while Condensate Pumps are maintaining inventory. The unit is currently stable and in Mode 3. Peach Bottom Unit 3's Adjustable Speed Drives were impacted by the electrical transients and the unit reduced power to 98 percent power. The NRC Resident Inspector was notified. |
| ENS 55576 | 14 November 2021 16:50:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | NON-FUNCTIONAL Steam Supply Check Valve to Turbine Driven Auxiliary Feedwater Pump | On November 14, 2021, at 1150 EST, while operating in Mode 1 at 100 percent power, the supply check valve from the Number 2 steam generator to the turbine driven auxiliary feedwater pump was determined during troubleshooting that it is not able to perform its isolation function. This failure would have resulted in the blowdown of both steam generators during a main steam line break in the Number 2 steam generator main steam line upstream of the main steam isolation valves until the operators could isolate the faulted steam generator. Previous evaluation has determined that this condition constituted an unanalyzed condition that could impact containment pressure. There has been no radioactive release to the environment. The steam lines from the steam generators to the turbine driven auxiliary feedwater pump have been isolated by use of a motor operated valve in the discharge line of the Number 2 steam generator. There has been no impact to Unit 3 which remains at 100 percent power. The NRC Senior Resident has been notified. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(ii)(B) as a condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety. |
| ENS 55565 | 6 November 2021 15:00:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Steam Supply Check Failure to Turbine Driven Auxillary Feedwater | During a Unit 2 refueling outage valve overhaul activity on the steam supply check valve from the number 2 steam generator to the turbine driven auxiliary feedwater pump, 2-MS-4B, the check valve was found with its disc separated from the disc arm. This failure would have resulted in the blowdown of both steam generators during a main steam line break in the steam generator number 2 main steam line upstream of the main steam isolation valves until the operators could isolate the faulted steam generator. On November 6, at approximately 1100 EDT evaluation determined that this condition constituted an unanalyzed condition that could impact containment pressure. There has been no radioactive release to the environment. The valve has been repaired. The check valve in the steam supply from the number 1 steam generator to the turbine driven auxiliary feedwater pump was inspected and found to be satisfactory. There has been no impact to Unit 3 which remains at 100% power. The Senior Resident has been notified. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(ii)(B) as a condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety. |
| ENS 55514 | 11 October 2021 17:21:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Automatic Reactor Scram After Main Turbine Trip | At 1321 EDT on October 11, 2021, Susquehanna Steam Electric Station Unit 2 reactor automatically scrammed due to a trip of the Main Turbine. Unit 2 reactor was being operated at approximately 95 percent RTP (rated thermal power) with no evolutions in progress. The Control Room received indication of a Main Turbine trip with both divisions of RPS (Reactor Protection System) actuated and all control rods inserted. Turbine bypass valves opened automatically to control reactor pressure and subsequently failed open causing the reactor to depressurize. When reactor pressure reached approximately 560 psig, the operations crew manually closed the Main Steam Isolation Valves (MISVs) to stop the depressurization. Reactor water level lowered to -31 inches causing Level 3 (+13 inches) isolations. No (automatic) ECCS (Emergency Core Cooling System) actuations occurred. HPCI (High Pressure Coolant Injection) and RCIC (Reactor Core Isolation Cooling) were manually initiated to control reactor water level. The Operations crew subsequently maintained reactor water level at the normal operating band using RCIC and reactor pressure was controlled with HPCI in pressure control mode and main steam line drains. The Reactor Recirculation Pumps tripped as designed on EOC-RPT (end of cycle recirculation pump trip). The reactor is currently stable in Mode 3. An investigation into the cause of the turbine trip is underway. The NRC Resident Inspector was notified. A voluntary notification to PEMA will be made. This event requires a 4 hour ENS notification in accordance with 10 CFR 50.72(b)(2)(iv)(A), 10 CFR 50.72(b)(2)(iv)(B) and an 8 hour ENS notification in accordance with 10 CFR 50.72(b)(3)(iv)(A). |
| ENS 55305 | 13 June 2021 03:27:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line (Msl) Radiation Monitor Non-Functional | At time 2227 CDT on 06/12/21, Main Steam Line 2-01 Radiation Monitor 2-RE-2325 was declared to be non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in Steam Generator 2-01 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity. Compensatory measures are in place to assure adequate monitoring capability. Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-01. Corrective actions are being pursued to restore 2-RE-2325 to functional status. The NRC Resident Inspector has been notified. |
| ENS 55304 | 12 June 2021 22:25:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line (Msl) Radiation Monitor Non-Functional | At time 1725 CDT on 06/12/21, Main Steam Line 2-03 Radiation Monitor 2-RE-2327 was declared to be non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in Steam Generator 2-03 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity. Compensatory measures are in place to assure adequate monitoring capability. Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-03. Corrective actions are being pursued to restore 2-RE-2327 to functional status. The NRC Resident Inspector has been notified. |
| ENS 54929 | 30 September 2020 13:15:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Radiation Monitors Required for Event Assessment Out of Service for Planned Maintenance | At time 0815 (CDT) on 09/30/20, Main Steamline Radiation Monitor 2-RUK-2325/2327 (Main Steam Line 2-01/2-03 Radiation Monitor) was removed from service for planned maintenance. Compensatory measures were in place prior to removing the monitor from service to assure adequate monitoring capability available to implement the CPNPP (Comanche Peak Nuclear Power Plant) emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-01 and MSL 2-03. With this radiation monitor non-functional, compensatory measures in place and the monitor not restored to service within 72 hours, the condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is negligible safety significance to the current condition with respect to the public health and safety perspective. Corrective actions are being pursued to complete maintenance and restore 2-RUK-2325/2327 to functional status. The NRC Resident Inspector has been notified. |
| ENS 54597 | 22 March 2020 16:55:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Scram | At 1255 Eastern Daylight Time (EDT) on March 22, 2020, with Unit 1 in Mode 2, stabilized at 2 percent power, coming out of a refueling outage, all 4 main turbine Bypass Valves (BPVs) opened unexpectedly. As a result, the main control room inserted a manual reactor scram. All control rods inserted as expected during the scram. In accordance with plant procedures, the main control room closed all Main Steam Line Isolation Valves (MSIVs) to arrest the cooldown resulting from BPVs remaining open. The condensate system remained aligned for injection and pressure control was initially via main steam line drains. RHR (residual heat removal) shutdown cooling was placed in operation for decay heat removal and pressure control once the MSIVs were closed. All systems responded as designed, with the exception of the BPVs. 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). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. There was no impact to Unit 2. |
| ENS 54431 | 1 November 2019 00:19:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of the Unit 2 Turbine Driven Auxiliary Feedwater Pump (Tdafwp) | This report describes an invalid actuation of the Unit 2 Turbine Driven Auxiliary Feedwater Pump that occurred on October 31, 2019. This report is being made in accordance with 10CFR50.73(a)(1), which states, in part, 'In the case of an invalid actuation reported under 10CFR50.73(a)(2)(iv), other than actuation of the Reactor Protection System (RPS) when the reactor is critical, the licensee may, at its option, provide a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER.' On October 31, 2019, Comanche Peak Nuclear Power Plant Unit 2 was in Mode 1 operating at 100% power. At 1919 CDT, the Main Steam Line 2-01 steam supply valve to the TDAFWP opened due to a loss of continuity between the fuse supplying control power to the valve positioner and the fuse clips. Operators initiated a 50MW load reduction to maintain power less than 100%. The steam supply to the TDAFWP was closed, the TDAFWP was stopped, and the fuse clips were tightened. Unit 2 was returned to full power at 2055 CDT. The specific train and system that actuated was the third AFW train on Unit 2. The train actuation was complete and during the TDAFWP start the system started and functioned correctly. The NRC Resident Inspector was notified. |
| ENS 54430 | 10 December 2019 03:26:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line (Msl) Radiation Monitor to Be Non-Functional | 1-RE-2328 Main Steam Line #1-04 MSL181 received an operate failure on loss of counts. At time 2126 (CDT), the radiation monitor was declared non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 1-04 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity. There is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and additionally Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 1-04. Corrective actions are being pursued to restore 1-RE-2328 to functional status. The NRC Resident Inspector has been notified. |
| ENS 54338 | 18 October 2019 07:07:00 | 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 | En Revision Imported Date 11/20/2019 | EN Revision Text: INADVERTENT OPENING OF MAIN TURBINE BYPASS VALVES POTENTIONALLY AFFECTED SAFE SHUTDOWN CAPABILITY At 0207 (CDT), the Bypass Electro-Hydraulic Control (EHC) system was secured for planned maintenance. When the Bypass EHC pumps were secured, both of the Main Turbine Bypass Valves unexpectedly opened to approximately 4.5 percent. Plant parameters indicated no impact to Turbine Control Valve position, Reactor Pressure, Turbine First Stage Pressure, or Main Steam Line flows. There were no other abnormal indications noted. With the Turbine Bypass Valves partially open, there is a potential to affect instrumentation that trips on high Turbine First Stage Pressure. Therefore, this event is being reported as a potential loss of Safety Function. At 0256, the Bypass EHC system pumps were restored and the Turbine Bypass Valves Closed. No radiological releases have occurred due to this event from the unit. The licensee has notified the NRC Resident Inspector.
This Event Notification was contingent on the Main Turbine Bypass Valves opening which resulted in the inoperability of Turbine First Stage Pressure monitoring instrumentation. A detailed review of system design and plant parameter trends has confirmed that the Main Turbine Bypass Valves remained closed for the duration of the event, permitting the instrumentation systems dependent on accurate Turbine First Stage Pressure to perform their respective design and licensing basis functions. Valve drift in the open direction was observed by position indication when hydraulic control pressure was removed. However, the valves were at an over-travel closed position prior to the event allowing the valves to settle at a position where an internal spring could provide closing force to the valve disc. Multiple plant parameter trends including Turbine First Stage Pressure, Reactor Pressure, Main Steam Line flows, and Main Turbine Bypass Valve discharge line temperatures indicate that the Main Turbine Bypass Valves remained closed for the duration of the event. The licensee has notified the NRC Resident Inspector. Notified R4DO (O'Keefe). |
| ENS 54329 | 14 October 2019 14:11:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line (Msl) Radiation Monitor Removed from Service for Planned Maintenance | At time 0911 (CDT), Main Steamline Radiation Monitor 2-RUK-2325/2327 (MAIN STEAM LINE 2-01/2-03 RADIATION MONITOR) was removed from service for planned maintenance. Compensatory measures were in place prior to removing the monitor from service to assure adequate monitoring capability available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL (Main Steam Line) 2-01 and MSL 2-03. With this radiation monitor non-functional, with compensatory measures in place, and the monitor NOT expected to be returned to service within 72 hours, the condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is negligible safety significance to the current condition with respect to the public health and safety perspective. Corrective actions are being pursued to complete maintenance and restore 2-RUK-2325/2327 to functional status. The NRC Resident Inspector has been notified. |
| ENS 54272 | 12 September 2019 01:24:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line Radiation Monitor Communication Failure | The following event description is based on information currently available. If through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73. Radiation monitor RU-140 (#2 Steam Generator Main Steam Line radiation monitor) experienced a communication failure on both ports A and B. The RU-140 monitor is off line and non-functional at this time. At least one channel of RU-140 is required to perform a Steam Generator Tube Rupture (SGTR) dose assessment. This represents an unplanned loss of radiological assessment capability for the inability to perform dose assessments that require the radiation monitor. The ability to make emergency classifications from other radiological data collection methods such as field sampling remains available. Actions have been initiated to restore the radiation monitor. The NRC Resident Inspector has been informed. |
| ENS 54175 | 19 July 2019 13:45:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Trip Due to Main Steam Isolation Valve Failing Shut | At 0945 (EDT) on July 19, 2019, with Unit 2 in Mode 1 and 100 percent power, the reactor automatically tripped due to Loop 2 'B' Main Steam Isolation Valve failing shut. The Auxiliary Feedwater system (AFW) started automatically as a result of the automatic reactor trip. The trip was not complex, with all systems responding normally. Operations stabilized the plant in Mode 3. Decay heat is being removed through the main steam lines through the steam dumps and into the condenser. 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). Due to the valid AFW actuation from the reactor trip, this event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A). Unit 1 was not affected. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspectors have been notified. All control rods fully inserted. |
| ENS 54103 | 18 April 2019 05:10:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification Due to Invalid Specified System Actuation | 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 54083 | 18 April 2019 06:49:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of a Unit 2 Containment Isolation Logic Due to a Blown Fuse | This 60-Day telephone notification is being made per the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of Limerick Generating Station Unit 2 containment isolation logic. On April 18, 2019, while performing a relay replacement on the Division 2/4 Main Steam Line logic, a partial containment isolation occurred due to a blown fuse. The following systems had components that actuated due to the partial isolation: Reactor Water Clean-Up System Primary Containment Instrument Gas System Drywell Chilled Water System Reactor Enclosure Cooling Water System Core Spray System The Residual Heat Removal System received an isolation signal; however, the system remained in service because the isolation was defeated in accordance with plant procedures. This event resulted in partial Group 2A, 3, 7A, 8A, and 8B isolations. The systems successfully functioned per the plant design and plant configuration. The licensee notified the NRC Resident Inspector. |
| ENS 54012 | 20 April 2019 10:07:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Both Reactor Feed Pumps Trip Causing Manual Reactor Scram and Eccs Injection | At 0507 (CDT on April 20, 2019), the DAEC (Duane Arnold Energy Center) experienced a trip of both reactor feed pumps. Operators inserted a manual scram. All control rods inserted, as required. As a result of the feed pump trips and scram, HPCI and RCIC automatically injected. Also, containment isolations occurred, as expected for this event. All systems responded as designed. Operators are currently taking the unit to cold shutdown conditions. Vessel level is being controlled by RCIC with Condensate System available. Pressure is being controlled using Main Steam Line drains and the Main Condenser is available. Normal electrical lineup remains. The cause of the reactor feed pumps tripping is believed to be an instrument air leak to flow control valves, causing loss of suction to both feed pumps. The licensee notified the NRC Resident Inspector. |
| ENS 53967 | 31 March 2019 01:30:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Trip Due to Msiv Failing Closed | At 2130 (EDT) on March 30, 2019, with Unit 2 in Mode 1 at 30 percent reactor power, the reactor was manually tripped due to a main steam isolation valve failing closed. The trip was not complex, with all systems responding normally. Operations stabilized the plant in Mode 3. Decay heat is being removed through the main steam lines through the steam dumps and into the condenser. The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). Unit 1 was not affected. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspectors have been notified. |
| ENS 53815 | 5 January 2019 15:40:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | En Revision Imported Date 2/12/2019 | EN Revision Text: POTENTIAL LOSS OF MSIV SCRAM FUNCTION DURING MAIN STEAM LINE ISOLATION VALVE TESTING At approximately 1040 EST on January 5, 2019, during evaluation of test results for the 'C' Main Steam Isolation Valve (MSIV), it was determined that closure of three of four Main Steam Lines would not necessarily have resulted in a full scram during testing due to failure of a limit switch (LS-6) associated with MSIV-1C while in the test configuration. This condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v), 'Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to: (A) Shut down the reactor and maintain it in a safe shutdown condition.' The system was restored from the testing configuration at 1057 EST and the failed trip channel was placed in the tripped condition at 1326 EST thus restoring the design function. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
The purpose of the notification is to retract ENS Notification 53815 made on 01/05/19 for Pilgrim Nuclear Power Station. The previous notification reported that there was a potential loss of Main Steam Isolation Valve (MSIV) scram function during main steam line isolation valve testing, at the time of discovery, due to failure of a limit switch (LS-6) associated with MSIV-1C while in the test configuration. Subsequent evaluation has demonstrated that the scram function credited in the design basis was not lost. Specifically, after an Engineering Evaluation, it has been determined that the MSIV position RPS logic was not lost for those functions within the design basis and, as such, was capable of performing its intended safety function. The NRC Resident Inspector has been notified. Notified the R1DO (Cahill). |
| ENS 53788 | 12 December 2018 06:00:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | En Revision Imported Date 12/17/2018 | EN Revision Text: MANUAL REACTOR SCRAM DUE TO FAILED OPEN TURBINE BYPASS VALVE At 1351 CST, the reactor was manually shutdown due to 'A' Turbine Bypass Valve opening. The Main Steam Line Isolation Valves were manually closed to facilitate reactor pressure control. Reactor level is being maintained through the use of Reactor Core Isolation Cooling System, Control Rod Drive System, and High Pressure Core Spray System. High Pressure Core Spray System was manually started to initially support reactor water level control. Reactor Pressure is being controlled through the use of the Safety Relief Valves and the Reactor Core Isolation Cooling System. The plant is stable in MODE 3. The cause of the 'A' Turbine Bypass Valve opening is under investigation at this time. The NRC Resident Inspector has been notified.
This is an update to EN # 53788 to correct an error on the event classification block of the form. The original notification did not have the block for 8 hour notification for Specified System Actuation checked. The actuation of Reactor Core Isolation Cooling System was discussed in original notification. The licensee notified the NRC Resident Inspector. Notified R4DO (Taylor). |
| ENS 53759 | 28 November 2018 06:00:00 | 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 | Discovery of a Condition That Could Have Prevented Fulfillment of a Safety Function | On November 28, 2018, while performing an engineering review of the bases for environmental qualification (EQ) requirements for the Atmospheric Steam Dumps (ASDs), it was determined that applicable EQ requirements had not been applied to a key component of each of the ASDs. The result of this issue is that it the availability of the ASDs for a controlled plant cooldown following a postulated steam line break outside containment cannot be assured. Callaway is developing a compensatory action temporary plant modification to install insulation that will protect the affected ASD components from the post Main Steam Line Break temperature. This condition is reportable 10 CFR 50.72(b)(3)(v) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to (B) remove residual heat, or (D) mitigate the consequences of an accident. The issue places the plant in a 24-hour Technical Specification (TS) Limiting Condition for Operations (LCO), 3.7.4. The licensee has notified the NRC Resident Inspector. |
| ENS 53575 | 31 August 2018 07:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Unplanned Loss of Steam Line Monitor Channels | The following event description is based on information currently available. If through subsequent reviews of this event additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10 CFR 50.73. This event is being reported pursuant to 10 CFR 50.72(b)(3)(xiii) as a Loss of Emergency Preparedness Capabilities at Palo Verde Nuclear Generating Station (PVNGS) Unit 2. On August 31, 2018, at approximately 0544 Mountain Standard Time (MST), the Unit 2 control room experienced an unplanned loss of Steam Generator #1 steam line monitor (RU-139), Channels A and B. This main steam line monitor is used in the PVNGS Emergency Plan to perform dose assessment in the event of a steam generator tube rupture. The NRC Resident Inspectors have been notified. |
| ENS 53522 | 23 July 2018 07:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Unplanned Loss of Steam Line Monitor Channels | The following event description is based on information currently available. If through subsequent reviews of this event additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS (Emergency Notification System) or under the reporting requirements of 10CFR50.73. This event is being reported pursuant to 10CFR50.72(b)(3)(xiii) as a Loss of Emergency Preparedness Capabilities at Palo Verde Nuclear Generating Station (PVNGS) Unit 2. On July 23, 2018, at approximately 1631 Mountain Standard Time (MST), the Unit 2 control room experienced an unplanned loss of Steam Generator #1 steam line monitor (RU-139), channels A and B. This monitor is used to assess dose projections for Main Steam line exhaust while in Modes 1-4 and is used in the PVNGS Emergency Plan to perform classification of Initiating Conditions 'RS1' and' RG1' and Emergency Action Levels (EALs) 'RS1.2' and 'RG1.2'. The PVNGS Emergency Plan does have two additional EALs that can be assessed for each Initiating Condition. The loss of this monitor constitutes a reportable loss of emergency assessment capability. The NRC Resident Inspector has been informed of this condition. |
| ENS 53484 | 3 July 2018 04:00:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Trip Due to High Steam Generator Water Level | At 0954 (EDT) on July 3, 2018, with Unit 1 in Mode 1 at 100 percent power, the reactor was manually tripped due to high steam generator water level. The trip was not complex, with all systems responding normally. Operations stabilized the plant in Mode 3. Decay heat is being removed through the main steam lines through the steam dumps and into the condenser. The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). Unit 2 was not affected. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspectors have been notified. All control rods inserted and Unit 1 is in an electrical shutdown lineup. The cause of the high steam generator water level transient is being investigated. |
| ENS 53472 | 26 June 2018 05:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line Radiation Monitor Determined to Be Non-Functional | At time 0003 (CDT), Main Steamline Radiation Monitor 2-RE-2326 (Main Steam line 2-02) reading spiked and (was) declared non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 2-02 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is negligible safety significance to the current condition (with respect to the) public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-02. Corrective actions are being pursued to restore 2-RE-2326 to functional status. The NRC Resident Inspector has been notified. |
| ENS 53459 | 16 June 2018 05:00:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Trip During Startup | At 1121 CDT on June 16, 2018, Arkansas Nuclear One, Unit 1 (ANO-1) performed a manual reactor trip due to a Turbine Bypass valve failing open on reactor startup. At the time, ANO-1 was in Mode 2 at approximately 2 percent power. The failed Turbine Bypass valve resulted in an overcooling event and the Overcooling Emergency Operating Procedure (EOP) was entered. Main Steam Line Isolation (MSLI) automatic actuation occurred on 2 of the 4 channels of Emergency Feedwater Initiation and Control during the overcooling event in the 'B' Steam Generator. The remaining channels of MSLI were manually actuated by the control room staff from the control room. Overcooling was terminated after the closure of the Main Steam Isolation Valve (MSIV) and reactor coolant parameters were stabilized as directed by the Overcooling EOP. Additionally, Gland Sealing Steam was lost to the main turbine due to the closure of the 'B' Steam Generator MSIV and Loss of Condenser Vacuum Abnormal Operating Procedure was entered. This is a 4-hour non-emergency 10 CFR 50.72 (b)(2)(iv)(B) notification due to a Reactor Protection System actuation (scram) and an 8-hour non-emergency 10 CFR 50.72 (b)(3)(iv)(A) notification for safety system actuation." All control rods fully inserted into the core during the trip. Heat removal is via the Atmospheric Dump Control valves to atmosphere. The NRC Resident Inspector has been notified. The licensee also notified the State of Arkansas. |
| ENS 53388 | 7 May 2018 18:35:00 | 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 | Discovery of a Condition That Could Have Prevented Fulfillment of a Safety Function | On May 7, 2018, during an engineering review of mission time requirements for Technical Specification related equipment, a deficiency was discovered regarding the Emergency Operating Procedure (EOP) guidance for natural circulation cooldown with a stagnant loop. This condition could be the result of a postulated Main Steam Line Break with a loss of offsite power. During a natural circulation cooldown with a faulted steam generator, flow in the stagnant reactor coolant system (RCS) loop associated with the isolated faulted steam generator (SG) could stagnate and result in elevated temperatures in that loop. This becomes an issue when RCS depressurization to residual heat removal system (RHR) entry conditions is attempted. The liquid in the stagnant loop will flash to steam and prevent RCS depressurization. In this condition, the time required to complete the cooldown would be sufficiently long that the nitrogen accumulators associated with Callaway's atmospheric steam dumps and turbine driven auxiliary feedwater pump flow control valves would be exhausted. The atmospheric steam dumps and turbine driven auxiliary feedwater pump would not be capable of performing their specified safety functions of cooling the plant to entry conditions for RHR operation. This issue has been analyzed by Westinghouse in WCAP-16632-P. This WCAP determined that to prevent loop stagnation, the RCS cooldown rate in these conditions should be limited to a rate dependent on the temperature differential present in the active loops. The WCAP analysis was used to support a revision to the generic Emergency Response Guideline (ERG) for ES-0.2 "Natural Circulation Cooldown." Figure 1 in ES-0.2 provides a curve of the maximum allowable cooldown rate as a function of active loop temperature differential which is directly proportional to the level of core decay heat. At the time of discovery of this condition, Callaway's EOP structure did not ensure that the ES-0.2 guidance would be implemented for a natural circulation cooldown with a stagnant loop. Callaway has issued interim guidance to the on-shift personnel regarding this concern and is in the process of revising the applicable EOPs. This condition is reportable per 10 CFR 50.72(b)(3)(v) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to (A) Shutdown the reactor and maintain it in a safe shutdown condition, (B) Remove residual heat, or (D) mitigate the consequences of an accident." The licensee notified the NRC Resident Inspector of this condition. |
| ENS 53290 | 26 March 2018 18:38:00 | Other Unspec Reqmnt | Technical Specifications Required Shutdown Due to Inoperable Main Steam Isolation Valve | On March 25, 2018 at 1833 CDT, while at 100 percent power, Farley Unit 1 (FNP-1) conservatively declared a single Main Steam Isolation Valve (MSIV) inoperable on the 1C Steam Generator line due to indication of Steam Generator pressure rise with a corresponding reduction in flow of that loop. FNP-1 began a reactor shutdown at 0400 CDT on March 26, 2018 to establish plant conditions to support testing the affected main steam line MSIVs while in the required action time of Technical Specification 3.7.2. At 1338 CDT on March 26, 2018, testing confirmed that the single MSIV was inoperable and that valve disassembly will be required. The duration of the valve repair would exceed the required action time of Technical Specification 3.7.2. This report is being made in accordance with 10 CFR 50.72(b)(2)(i), as a plant shutdown required by technical specifications. The licensee has notified the NRC Resident Inspector.
This EN (event notification) is being updated to clarify the reporting criteria as 'Voluntary'. Farley Technical Specification 3.7.2 allows continuous operation in MODE 2 with an INOPERABLE MSIV as long as the other MSIV in the affected Main Steam Line is closed. The initiation of the shutdown was performed as a prudent action to repair and restore OPERABILITY of the affected MSIV and was not a requirement of the Farley Technical Specifications. The licensee notified the NRC Resident Inspector. The R2DO (Masters) was notified. |
| ENS 53212 | 15 February 2018 09:06:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line Radiation Monitor Determined to Be Non Functional | At time 0306 (CST), Main Steamline Radiation Monitor 2-RE-2326 (Main Steamline 2-02) reading spiked and declared non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 2-02 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10CFR50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL 2-02. Corrective actions are being pursued to restore 2-RE-2326 to functional status. The NRC Resident Inspector has been notified. |
| ENS 53154 | 6 January 2018 17:26:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line Radiation Monitor Determined to Be Non-Functional | At 1126 (CST), main steamline radiation monitor 2-RE-2326 (Main Steamline 2-02) reading was determined to be erratic and was declared non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 2-02 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. The N16 (Nitrogen-16) radiation monitor serves as a backup with alarm function and Radiation Protection technicians have been briefed on taking local readings with a Geiger-Mueller tube on MSL (Main Steam Line) 2-02. Corrective actions are being pursued to restore 2-RE-2326 to functional status. The NRC Resident Inspector has been notified. |
| ENS 53105 | 6 December 2017 02:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Unplanned Loss of Multiple Radiation Monitors During Maintenance | At 2000 (CST), Comanche Peak experienced a failure of SCADA B of the PC11 Radiation Monitor System. This failure caused a loss of Unit 1 Main Steam Line 1-01 and 1-03 Radiation Monitors (1-RE-2325 and 1-RE-2327) and Train A and Train B Station Service Water Radiation Monitors (1-RE-4269 and 1-RE-4270). With the Main Steam Line Radiation Monitors nonfunctional, all of the emergency action levels for a steam generator tube rupture in steam generators 1-01 and 1-03 could neither be evaluated nor monitored. With the Station Service Water Radiation Monitors non-functional, all of the emergency action levels for a radioactive release through station service water could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity, reactor coolant system integrity, and fuel cladding integrity and there is a negligible safety significance to condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator, reactor coolant system, or the fuel cladding. Until these radiation monitors were restored, Operations implemented compensatory measures to monitor the Condenser Off Gas Radiation Monitor for early signs of a steam generator tube leak/rupture and Radiation Technicians were briefed on taking local readings with a Geiger-Mueller tube on the Main Steam Lines. Chemistry Technicians were performing hourly samples of Station Service Water and reporting results to the Control Room. Corrective actions were pursued to restore the non-functional radiation monitors back to service. Those actions are complete and all radiation monitors have been restored to service. The NRC Resident Inspector has been notified. PC11 is a computer common to both Units. The failure happened during radiation monitor maintenance to a single monitor, which unexpectedly affected multiple monitors. |
| ENS 52950 | 6 September 2017 15:57:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Scram on Low Reactor Vessel Water Level | On September 6, 2017 at 1157 (EDT), Nine Mile Point Unit 1 experienced an automatic reactor scram with a Main Steam Isolation Valve (MSIV) and Containment isolation. The scram was due to reactor vessel low water level. The cause of the reactor vessel low water level is under investigation. All control rods fully inserted. Following the scram, pressure was momentarily controlled through the use of the Emergency Condenser (EC) system. At 1205, pressure control was established through the main steam lines to the condenser through the turbine bypass valves. All plant systems responded per design following the scram. The reactor scram is a 4-hour report per 10 CFR 50.72(b)(2)(iv)(B). The following systems automatically actuated after the scram as expected. These system actuations are an 8-hour report per 10 CFR 50.72(b)(3)(iv)(A): 1. The High Pressure Coolant Injection (HPCI) system. HPCI initiated at 1157 and was reset at 1158 when RPV level was restored above the HPCI system low level actuation set point. HPCI is a flow control mode of the normal feedwater systems, and is not an Emergency Core Cooling System. 2. The Core Spray system actuated, but did not discharge to the Reactor Coolant system. The Core Spray system was secured at 1216. 3. Containment and MSIV isolation on reactor vessel low-low water level signal. Nine Mile Point Unit 1 is currently in Hot Shutdown, with reactor vessel water level and pressure maintained within normal bands. Decay heat is being removed via steam to the main condenser using the turbine bypass valves. The offsite grid is stable with no grid restrictions or warnings in effect. The licensee has notified the NRC Resident Inspector. No safety relief valves lifted during the transient. The main steam isolation valves were opened after the isolation signal cleared to facilitate decay heat removal. Offsite power is supplying all plant loads. There was no effect on Unit 2. The licensee notified New York State Department of Environmental Protection and will be issuing a press release. |
| ENS 52772 | 3 April 2017 01:27:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification of Invalid Specified System Actuation | This 60-day telephone notification is being made in accordance with the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting multiple Main Steam Isolation Valves (MSIVs). On April 2, 2017 at approximately 2127 Eastern Daylight Time, during performance of a 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 two channels 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. The NRC Resident Inspector has been notified. |
| ENS 52363 | 13 November 2016 16:12:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | One Main Steam Line Radiation Monitor Failed | At 1012 (CST), Unit 1 Main Steam Line 1-01 Radiation Monitor (1-RE-2325) failed high. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 1-01 could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. Until this radiation monitor can be restored, Operations has implemented compensatory measures to monitor the main steamline 1-01 N-16 (Nitrogen-16) radiation monitor for early signs of a steam generator tube leak/rupture and pre-brief radiation protection technicians on taking local readings with a Geiger-Muller tube on Main Steam Line 1-01 and reporting the reading to the Control Room. Corrective actions are being pursued to restore 1-RE-2325 to functional status. The NRC Resident Inspector has been notified. Radiation monitor 1-RE-2325 is not in the plant technical specifications but is important to safety and the Emergency Plan. |
| ENS 52261 | 25 September 2016 06:03:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Actuation of Group 1 Isolation Signal | At 0103 CDT a Group 1 Isolation signal was received on Main Steam Line (MSL) A High Flow while attempting to un-isolate MSL A. During plant cooldown for refueling outage, all inboard MSIV's were closed to minimize steam flow to control cooldown rate. With all inboard MSIV's closed and all outboard MSIV's open, MSL drains in-service, and reactor pressure at approximately 330 psig, an attempt was made to un-isolate MSL A by opening A inboard MSIV. This resulted in a MSL high flow signal on MSL A as the valve was being opened, resulting in a Group I Isolation and closure of all MSIV's and MSL Drain Valves. Pressure was equalized to less than 200 psid across MSIV A prior to attempting to open the valve in accordance with plant procedures. All valves actuated as expected and the cause of the event is under investigation. There are no indications of a leak. The Group I Isolation has been reset. The licensee notified the NRC Resident Inspector. |
| ENS 52260 | 21 September 2016 03:47:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Steam Line Pipe Whip Restraint Coupling Sleeve Found Not Engaged | On 9/20/2016, a coupling sleeve on a pipe whip restraint located on the 119 foot elevation of the turbine building associated with Unit 2 main steam line 4 was found to be not engaged. As a result of the detached coupling, the restraint was not capable of performing its restraint function for a postulated pipe whip event on the main steam line. The coupling was reconnected on 9/20/2016, restoring its functionality. An extent of condition walkdown was subsequently performed for the other Unit 1 and Unit 2 steam line restraints and no similar issues were identified. This concern did not result in any adverse effect on the radiological health and safety of the public. The purpose of this whip restraint is to restrain the steam line for a postulated loss at the G-line anchor (east side of Turbine Building above the 104 foot elevation). The restraint protects the floor slab at the 104 foot elevation, which extends over the Unit 2 component cooling water heat exchangers. With the detached coupling, equipment in the area may have been vulnerable to damage if a pipe whip event occurred. Further analysis is needed to conclude whether the heat exchangers and other equipment would have remained protected in such an event and whether this would have significantly affected the designed plant response to a pipe event. Based on the need for further analysis, this event is being reported as an unanalyzed condition that may have significantly degraded plant safety in accordance with 10 CFR 50.72(b)(3)(ii)(B). The NRC Senior Resident Inspector was notified.
The purpose of this notification is to retract a previous report made on EN #52260, reported 9/23/2016. NRC notification was initially made as a result of a condition that required further analysis to determine whether the condition would have significantly degraded plant safety in accordance with 10 CFR 50.72(b)(3)(ii)(B). Further analysis of the condition concluded that PG&E Design Class I equipment located inside the Turbine Building would have remained undamaged and capable of performing their safety functions. The Turbine Building would not have experienced failure of major structural elements or adverse impact to the overall building stability. Therefore, the coupling sleeve on a pipe whip restraint located on the 119 foot elevation of the Turbine Building associated with Unit 2 main steam line 4 that was found to be not engaged did not constitute an unanalyzed condition that may have significantly degraded plant safety in accordance with 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified. Notified R4DO (Azua) |
| ENS 52042 | 24 June 2016 16:15:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Scram Due to Reactor Recirculation Pumps Degradation | At 1215 (EDT) on 6/24/2016, James A. FitzPatrick (JAF) was at 100% power when Breaker 710340 tripped and power was lost to L-gears L13, L23, L33, and L43. These provide non-vital power to Reactor Building Ventilation (RBV), portions of Reactor Building Closed Loop Cooling (RBCLC), and 'A' Recirculation pump lube oil systems. Off-site AC power remains available to vital systems and Emergency Diesel Generators (EDG) are available. Due to the loss of RBV, Secondary Containment differential pressure increased. At 1215 (EDT), Secondary Containment differential pressure exceeded the Technical Specifications (TS) Surveillance Requirement SR-3.6.4.1.1 of greater than or equal to 0.25 inches of vacuum water gauge. The Standby Gas Treatment (SBGT) system was manually initiated and Secondary Containment differential pressure was restored by 1219 (EDT). The 'A' Recirculation pump tripped at 1215 (EDT) and reactor power decreased to approximately 50%. 'B' Recirculation pump temperature began to rise due to the degraded RBCLC system. At 1236 (EDT), a manual scram was initiated. Reactor Pressure Vessel (RPV) water level shrink during the scram resulted in a successful Group 2 isolation. All control rods have been inserted. The RPV water level is being maintained with the Feedwater System and pressure is being maintained by main steam line bypass valves. A cooldown is in progress and JAF will proceed to cold shutdown (Mode 4). Due to complete loss of RBCLC system, the Spent Fuel Pool (SFP) cooling capability is degraded but the Decay Heat Removal system remains available. SFP temperature is slowly rising and it is being monitored. The time (duration) to 200 degrees is approximately 117 hours. The initiation of reactor protection systems (RPS) due to the manual scram at critical power is reportable per 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). The general containment Group 2 isolations are reportable per 10 CFR 50.72(b)(3)(iv)(A). In addition, the temporary differential pressure change in Secondary Containment is reportable per 10 CFR 50.72(b)(3)(v)(C), as an event that could have prevented fulfillment of a safety function. The licensee notified the NRC Resident Inspector and the State of New York. |
| ENS 51925 | 13 May 2016 05:10:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Manual Reactor Scram Due After Loss of an Essential Motor Control Center | At approximately 0110 hours (EDT) on May 13, 2016, Susquehanna Steam Electric Station Unit Two reactor was manually scrammed by plant operators due to a sustained loss of AC power to essential plant loads. Power to MCC 2B246 was lost at 2355 on May 12, 2016, resulting in a loss of Drywell cooling. Drywell pressure increased to 1.3 psig when operators placed the mode switch to the shutdown position to manually SCRAM the reactor. All rods inserted as expected. Reactor water level lowered to -27 inches and was immediately restored by normal feedwater level control. Level 3 (+13 inch) PCIS isolations occurred, along with an initiation of the RCIC system (-30 inches). Once adequate level was verified, RCIC was overridden. Pressure was controlled with turbine bypass valves, and subsequently main steam line drains. All safety systems functioned as expected. The power loss also tripped Reactor Building HVAC, causing a loss of secondary containment differential pressure resulting in a loss of safety function. Due to the loss of drywell cooling, high drywell pressure actuations and a second reactor SCRAM signal, this signal was automatic, occurred at 0314 hours. HPCI (which automatically initiated on high drywell pressure) was subsequently overridden and declared inoperable, resulting in a loss of safety function. (HPCI did not inject into the vessel). The reactor is currently stable in Mode 3. Initial reports from the field indicate a phase to phase fault on the MCC 2B246 bus bars. The licensee has notified the NRC Resident Inspector and will be issuing a press release. |
| ENS 51871 | 19 April 2016 18:43:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Main Steam Line Radiation Detector Determined to Be Non Functional | While performing a monthly check source on radiation monitor 1-RE-2328 (Main Steamline 1-04 Radiation Detector), the monitor was determined to be non-functional. With this radiation monitor non-functional, all of the emergency action levels for a steam generator tube rupture in steam generator 1-04 could neither be evaluated nor monitored. This unplanned condition is reportable as a major loss of assessment capability per 10 CFR 50.72(b)(3)(xiii). Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity and fuel cladding integrity and there is a negligible safety significance to the current condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator or fuel cladding. Until this radiation monitor can be restored, Operations has implemented compensatory measures to monitor main steamline 1-04 N16 Radiation Monitor for early signs of a steam generator tube leak/rupture, pre-brief radiation protection technicians on taking local readings with a geiger-mueller tube on main steam line 1-04 and reporting the reading to the Control Room. Corrective actions are being pursued to restore 1-RE-2328 to functional status. The NRC Resident Inspector has been notified. |
| ENS 51864 | 13 April 2016 18:30:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition | At approximately 1430 hours EDT on 4/13/2016, it was determined that the source document for the mass and energy release parameters used to determine the containment pressure and temperature response to a Main Steam Line Break (MSLB) does not adequately account for all possible single active failure scenarios in the steam or feedwater line isolation provisions. The source document addresses the active failure of the Main Feedwater Control valves to close in the faulted steam generator feed line, but not the failure of a feedwater bypass valves to close in the faulted steam generator feed line. An active failure of a feedwater regulating bypass valve whereby the valve fails to close will increase the secondary mass available for release to the containment structure. This can result in a higher peak containment pressure that could challenge the containment design pressure. This condition is only a concern when the feedwater regulating bypass valves are in the open position in modes 1, 2 or 3, and they fail to close on a engineered safeguards actuation signal. The feedwater regulating bypass valves are currently closed. This determination is being reported as an unanalyzed condition in accordance with 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified. |
| ENS 51850 | 6 April 2016 20:45:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared Due to Main Steamline High High Radiation Condition | At 1545 CDT on 04/06/16 Browns Ferry Unit 3 declared and exited the declaration of an unusual event due to a main steam line high high radiation condition. Power to Unit 3 was reduced to 91 percent power. The high radiation condition alarm cleared at 1526 CDT. Browns Ferry Unit 3 reported that the high radiation conditions were due to resin intrusion from the condensate demineralizers into the reactor and hydrogen water chemistry was a potential contributor to the event. The cause is still under investigation. The NRC Resident Inspector has been notified. State and Local notifications were made. Notified DHS SWO, FEMA Ops Center, NICC Watch Officer, FEMA NWC and Nuclear SSA (email).
At 1941 (CDT) BFN (Brown's Ferry) determined this notification to be potentially newsworthy due to receiving notification that counties (surrounding the plant) were alerted of this event. No plant conditions changed. The licensee may issue a press release. The licensee will notify the NRC Resident Inspector. Notified R2DO (Nease). |
| ENS 51720 | 9 February 2016 19:15:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Eccs Discharge to Rcs Via Charging System | At 1415 EST on 02/09/2016, Sequoyah Unit 1 was at 0 percent power (mode 3, 526F, 2235 psig) when a low steam line pressure Safety Injection actuated from Loop 2 Steam Generator. Prior to this event, the Loop 2 Main Steam Isolation Valve bypass was opened at 1413 EST for main steam line warm up in preparation for unit startup. Loop 2 Main Steam Isolation Valve bypass closed automatically following low steam line pressure Safety Injection. Following the Safety Injection, all safety-related equipment operated as designed. Current Reactor Coolant System temperature and pressure - Unit 1 is currently being maintained in Mode 3 at approximately 517 F and 2235 psig, with auxiliary feedwater supplying the steam generators and decay heat removal via steam generator atmospheric relief valves. There is no indication of any primary to secondary leakage. The electrical alignment is normal with shutdown power supplied from off-site power. There is no operational impact to Unit 2. The cause of the Safety Injection actuation is under investigation. This event had no impact on the health and/or safety of the public. The NRC Resident Inspector has been notified. Due to RCS pressure, the only system that injected into the RCS was the charging system. The AFW system initiated to feed the steam generators and the Emergency Diesel Generators started but did not load. |
| ENS 51480 | 23 August 2015 16:42:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Telephonic Notification of Invalid Primary Containment Isolation Signal | On 8/23/2015 at 1242 (EDT), with the reactor at 100% power, an invalid RPS MG (Reactor Protection System Motor-Generator) set 'A' trip resulting in a loss of RPS bus 'A'; this occurred during testing of the RPS instrument channels. All equipment operated as designed as a result of the loss of power to the 'A' RPS bus. The invalid trip was determined to be a result of the overvoltage relay being set too low. The above event meets the reporting criteria of 10CFR50.73(a)(2)(iv)(A) since the loss of RPS bus resulted in primary containment isolation signals affecting containment valves in more than one system. The following systems isolated as a result of the loss of 'A' RPS bus: Reactor Water Cleanup, Reactor Building ventilation, 'A' Containment Atmosphere Dilution, Torus Vent and Purge, Drywell Equipment and Floor Drain Sumps, 'A' Drywell Containment Atmospheric Monitors, Recirculation System Sample Line, Main Steam Line Drains and Residual Heat Removal drain valve to radwaste. 'A' Standby Gas Treatment System started as designed. This notification is being made in accordance with 10CFR50.73(a)(2)(iv)(A) to provide information pertaining to an invalid 'A' Reactor Protection System actuation. Completed actions were the replacement of overvoltage relay and voltage setpoint change, completed on 9/11/2015. In accordance with 10CFR50.73(a)(i) a telephone notification is being made instead of submitting a written Licensee Event Report. |