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Start date | Site | Region | Reactor type | Event description | |
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ENS 57066 | 4 April 2024 23:18:00 | Palo Verde | NRC Region 4 | CE | The following information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: On 4/4/2024 at 1618 MST, a Notification of Unusual Event, HU4.2 was declared based on an unverified fire alarm in the containment building greater than 15 minutes. Palo Verde, Unit 3 was operating in Mode 1 at 91 percent power due to end of cycle coast down to a refueling outage. There is no known plant damage at this time. Offsite assistance cannot enter the containment building, therefore, offsite assistance was not requested. The plant is stable in Mode 1. The licensee notified State and local authorities and the NRC Senior Resident Inspector. Notified DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).
The following information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: At 2013 MST, Palo Verde Unit 3 terminated the notification of unusual event. The basis for termination was that a containment entry was performed. All levels were inspected, and no fires were found. The NRC Resident Inspector has been notified. Notified R4DO (Deese), IR-MOC (Crouch), NRR-EO (Felts), DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email). |
ENS 57047 | 24 March 2024 23:34:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: At 1634 MST on March 24, 2024, an engineered safety features (ESF) service transformer deenergized resulting in a loss of power to the Unit 2 Train B 4.16 kV Class 1E Bus. The Unit 2 Train B emergency diesel generator (EDG) automatically started and energized the Unit 2 Train B 4.16 kV Class 1E Bus. As a result of the loss of power on the Unit 2 Train B 4.16 kV Class 1E Bus and subsequent load sequencing after the Unit 2 Train B EDG started, the Unit 2 Train B auxiliary feedwater (AFW) pump automatically started as designed. The Train B AFW pump was not needed for steam generator level control and no auxiliary feedwater valves repositioned. The Train B AFW Pump did not supply feedwater to the steam generators. All systems operated as designed. Per the emergency plan, no classification was required due to the event. Units 1, 2, and 3 remain in Mode 1 at 100 percent power. The 4.16 kV Class 1E Buses in Units 1 and 3 were not affected by the deenergization of the ESF service transformer. The cause of the ESF service transformer being deenergized is under investigation. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of emergency AC electrical power systems and auxiliary feedwater system. The NRC Resident Inspectors have been informed. |
ENS 56785 | 9 October 2023 22:07:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: On October 9, 2023, during the Palo Verde Nuclear Generating Station Unit 1 refueling outage, while performing a small nozzle inspection in support of boric acid walkdowns, boric acid leakage was found on the area of the weld of a pressurizer thermowell. At 1507 MST, non-destructive examination of the weld indicated leakage through the reactor coolant pressure boundary. The exam result constitutes welding or material defects in the primary coolant system that are unacceptable under ASME Section XI. This event is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(ii)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. |
ENS 56551 | 2 June 2023 11:05:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: 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 10 CFR 50.73. At 0405 MDT on June 2, 2023, the Unit 2 reactor automatically tripped on low steam generator water levels due to degraded flow from the A main feedwater pump. Steam generator water levels reached the automatic Auxiliary Feedwater Actuation System (AFAS) setpoint resulting in automatic AFAS-1 and AFAS-2 actuations and subsequent start of both class auxiliary feedwater pumps. Steam Generator water levels are being restored to normal band with the class 1E powered motor driven auxiliary feedwater pump. Following the reactor trip, all control element assemblies inserted fully into the core. No emergency plan classification was required per the Emergency Plan. Safety related buses remained powered from offsite power during the event and the offsite power grid is stable. Both emergency diesel generators automatically started on the AFAS-1 and AFAS-2 actuations as designed and are currently running unloaded. This event is being reported as a reactor protection system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B) and a specified system actuation in accordance with 10 CFR 50.72(b)(3)(iv)(A). The NRC Senior Resident Inspector has been informed. Unit 1 and 3 are in Mode 1 at 100 percent power. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Decay heat is being removed to main condenser via automatic steam bypass and B auxiliary feedwater pump. |
ENS 56539 | 24 May 2023 14:10:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via phone and email: On May 24th, 2023, at approximately 0710 MDT, a non-licensed contract supervisor had a confirmed positive for alcohol during a for-cause fitness-for-duty test. The individual's plant access has been terminated in accordance with station procedures. The NRC Resident Inspector has been notified. |
ENS 56487 | 26 April 2023 06:15:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: On 4/25/2023 at approximately 2315 (MST) it was reported that there was possible sodium hypochlorite actively leaking near the 'A' essential spray pond (ESP). Upon investigation, it was determined that the 'low flow' line of sodium hypochlorite supply to the 'A' spray pond had developed a leak. Sodium hypochlorite had pooled at the leak location and subsequently run down the ESP apron, into the road, and into the storm drain located in the protected area fence. An estimate of approximately 300 gallons of spilled sodium hypochlorite was determined based on the time frame that the sodium hypochlorite was scheduled to start injecting into the 'A' spray pond and the time the leak was isolated. The leak was isolated on 4/25/2023 at approximately 2330. The leak was contained in the storm drain with the storm gates closed, therefore nothing was released offsite. The cleanup effort in progress includes diluting the sodium hypochlorite with domestic service water, collecting it into the storm drain, pumping it to a tank truck, and transporting it to the Palo Verde Water Resources Facility for neutralization. Condition Report 23-04519 was generated to document the leak. The Palo Verde Senior Environmental Scientist was notified and subsequently informed the Environmental Protection Agency (EPA) National Response Center (NRC#1365638) on 4/26/23 at 0005 in accordance with the 91DP-0EN03 Environmental Spill Response (local procedure). The NRC Senior Resident Inspector was also notified. No personnel were injured and no equipment was damaged as a result of the spill. The Palo Verde Fire Department was notified and the area was barricaded off to prevent personnel from entering the area during the cleanup effort. |
ENS 56459 | 9 April 2023 04:44:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: 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. At 2144 MST on April 8, 2023, the Unit 1 reactor automatically tripped due to the loss of reactor coolant pumps stemming from the loss of 13.8 kV power to the pumps. Prior to the reactor trip, the main turbine tripped due to a loss of hydraulic pressure. The main generator output breakers did not automatically open on the turbine trip as expected so the control room operators opened the breakers per procedural guidance. Once the breakers were opened, the two 13.8 kV electrical distribution buses failed to complete a fast bus transfer, which resulted in the loss of power to the reactor coolant pumps, initiating the reactor trip. The control room operators manually actuated a main steam isolation signal per procedure, requiring use of the atmospheric dump valves. Following the reactor trip, all control element assemblies inserted fully into the core. No automatic specified system actuation was required or occurred. No emergency plan classification was required per the Emergency Plan. Safety related buses remained powered from offsite power during the event and the offsite power grid is stable. Unit 1 is stable and in Mode 3. Decay heat is being removed by the atmospheric dump valves and the class 1E powered motor driven auxiliary feedwater pump. The loss of hydraulic pressure, the main generator output breakers failing to automatically open and the fast bus transfer not actuating are being investigated. This event is being reported as a reactor protection system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B). The NRC Senior Resident Inspector has been informed. Unit 2 is in a refueling outage in Mode 5 and Unit 3 is in Mode 1 at 100 percent power.
This update is being made to report the manual actuation of the B-train auxiliary feedwater pump and manual main steam isolation signal (MSIS) actuation affecting multiple main steam isolation valves (MSIVs) following the reactor trip. This event is being reported as a reactor protection system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B) and a specified system actuation in accordance with 10 CFR 50.72(b)(3)(iv)(A). The NRC Senior Resident Inspector has been informed of the update. Notified R4DO (Warnick)
This update is intended to clarify the initial description of the event that occurred on 4/8/2023. Prior to the reactor trip, the main turbine tripped due to a loss of hydraulic pressure. The main generator output breakers did not automatically open on the turbine trip. The control room operators manually opened the breakers per procedural guidance. Once the breakers were opened, the two 13.8 kV electrical distribution buses de-energized. A fast bus transfer did not occur per design, which resulted in the loss of power to the reactor coolant pumps, initiating the reactor trip. The control room operators manually actuated a main steam isolation signal per procedure, requiring use of the atmospheric dump valves. The NRC Senior Resident Inspector has been informed of the update. Notified R4DO (Gaddy) |
ENS 56127 | 26 September 2022 18:00:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: On September 26, 2022, at approximately 1100 Mountain Standard Time, a Reactor Operator's test results were confirmed positive for use of a controlled substance following a random Fitness For Duty (FFD) screening test and it was determined that the individual violated the station's FFD Policy. The individual's unescorted access has been terminated in accordance with station procedures. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The licensee will conduct an investigation of the individual's work history. |
ENS 56044 | 15 August 2022 00:02:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via phone and email: At 1702 MST on August 14, 2022, a start-up transformer de-energized, resulting in a loss of power to the Unit 1 Train B 4.16 kV Class 1E Bus and the Unit 3 Train A 4.16 kV Class 1E Bus. The Unit 1 Train B Emergency Diesel Generator (EDG) and Unit 3 Train A EDG automatically started and energized their respective 4.16 kV Class 1E Buses. As a result of the loss of power on the Unit 1 Train B 4.16 kV Class 1E Bus, the B Auxiliary Feedwater Pump automatically started, as expected. The B Auxiliary Feedwater Pump was not needed for steam generator level control and no auxiliary feedwater valves repositioned. The B Auxiliary Feedwater Pump did not supply feedwater to the steam generators. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of emergency AC electrical power systems and an auxiliary feedwater system. All systems operated as expected. Per the Emergency Plan, no classification was required due to the event. The 4.16 kV Class 1E Buses in Unit 2 were not affected by the de-energization of the start-up transformer since it was not aligned as normal power for Unit 2. Units 1, 2 and 3 remain in Mode 1 at 100% power. The cause of the start-up transformer being de-energized is under investigation. No plant transient occurred as a result of this failure. The NRC Resident Inspectors have been informed. |
ENS 55878 | 5 May 2022 02:55:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: At 1955 on May 4, 2022, a start-up transformer de-energized, resulting in a loss of power to the Unit 2 Train A 4.16 kV Class 1E Bus and the Unit 3 Train B 4.16 kV Class 1E Bus. The Unit 2 Train A Emergency Diesel Generator (EDG) and Unit 3 Train B EDG automatically started and energized their respective 4.16 kV Class 1E Buses. As a result of the Loss of Power on the Unit 3 Train B 4.16 kV Class 1E Bus, the B Auxiliary Feedwater Pump automatically started, as expected. The B Auxiliary Feedwater Pump was not needed for steam generator level control and no auxiliary feedwater valves repositioned. The B Auxiliary Feedwater Pump did not supply feedwater to the steam generators. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of emergency AC electrical power systems and an auxiliary feedwater system. |
ENS 55926 | 12 April 2022 03:45:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: 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 telephone notification is being made pursuant to the reporting requirements of 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to describe invalid actuations of the Palo Verde Nuclear Generating Station (PVNGS) Unit 1 B Train Auxiliary Feedwater (AF) system and Essential Spray Pond (ESP) system that occurred while in a refueling outage. On April 11, 2022, at approximately 2045 Mountain Standard Time, an automatic start of the Unit 1 B Train AF and ESP systems occurred during restoration from a surveillance test. The station was conducting a surveillance test during a Unit 1 refueling outage to verify the proper responses of the Engineered Safety Features Actuation Systems to simulated design basis events. The test portion was completed satisfactorily; however, during the restoration portion, the load sequencer inadvertently cycled between Mode 0 and Mode 1 three times in immediate succession. At the time of the system actuations, one of the actuation signals associated with this portion of the test had been reset per procedure. Another actuation signal was still in while restoration steps were ongoing, but the sequencer was not expected to cycle between Modes. The system actuations did not occur as a result of actual plant conditions or parameters and are therefore invalid. The Unit 1 B Train AF and ESP system actuations were complete and the systems started and functioned successfully. For the systems that did not actuate, the reasons are clearly understood as those systems were in an overridden condition due to test configuration. The spurious actuation was not able to be replicated and a direct cause was not identified. There were no adverse impacts to public health and safety nor to plant employees. The NRC Resident Inspectors have been informed. |
ENS 55796 | 19 March 2022 20:06:00 | Palo Verde | NRC Region 4 | CE | The following information was provided by the licensee via email: 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. At 1306 (MST) on March 19, 2022, the Technical Support Center (TSC) lost normal and alternate electrical power, resulting in the inability to perform emergency assessments at the TSC. At the time of the event, the normal power source to the TSC (offsite power) was under a clearance for maintenance activities and the alternate power source (backup generator) was running to provide electrical power to the TSC. At 1306, the alternate power source to the TSC was lost when the backup generator tripped. Power was restored to the TSC via the normal power source at 1723. The cause of the TSC backup generator trip is unknown at this time. All three units are stable and in Mode 1. No emergency classification was required per the Emergency Plan. The NRC Senior Resident Inspector has been informed. |
ENS 55626 | 6 December 2021 19:03:00 | Palo Verde | NRC Region 4 | CE | 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. At 1203 MST on December 6, 2021, the Unit 3 reactor automatically tripped on low departure from nucleate boiling ratio. A part-strength control element assembly was being moved at the time of the trip. Unit 3 is stable and in Mode 3. In response to the reactor trip, all control element assemblies inserted fully into the core. Safety-related electrical power remains energized from off-site power sources and reactor coolant pumps continue to provide forced circulation through the reactor. Decay heat is being removed by the steam bypass control system and main feedwater system. Required systems operated as expected. No emergency classification was required per the Emergency Plan. The NRC Senior Resident Inspector has been informed. Units 1 and 2 were unaffected by this transient. |
ENS 55534 | 20 October 2021 21:46:00 | Palo Verde | NRC Region 4 | CE | At 1446 MST on October 20, 2021, a start-up transformer de-energized, resulting in a loss of power to the Unit 1 Train B 4.16 kV Class 1E Bus and the Unit 3 Train A 4.16 kV Class 1E Bus. The Unit 1 Train B Emergency Diesel Generator (EDG) and Unit 3 Train A EDG automatically started and energized their respective 4.16 kV Class 1E Buses. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of emergency AC electrical power systems. All systems operated as expected. Per the Emergency Plan, no classification was required due to the event. Units 1 and 3 both remain in Mode 1 at 100 percent power. Unit 2 is currently in a refueling outage and defueled. The 4.16 kV Class 1E Buses in Unit 2 were not affected by the de-energization of the start-up transformer since it was not aligned as normal power for Unit 2. The cause of the start-up transformer being de-energized is under investigation. The NRC Resident Inspectors have been informed.
As a result of the Loss of Power on the Unit 1 Train B 4.16 kV Class 1E Bus, the B Auxiliary Feedwater Pump automatically started, as expected. The B Auxiliary Feedwater Pump was not needed for steam generator water level control and no auxiliary feedwater valves repositioned. The B Auxiliary Feedwater Pump did not supply feedwater to the steam generators. The NRC Resident Inspector will be notified. Notified R4DO (Taylor). |
ENS 55521 | 13 October 2021 21:20:00 | Palo Verde | NRC Region 4 | CE | On October 13, 2021, at 1420 MST, a Non-Licensed Supervisor's test results were confirmed positive for use of a controlled substance following a random Fitness For Duty test which resulted in determination that the individual violated the station's FFD Policy. The Non-Licensed Supervisor's unescorted access has been terminated in accordance with station procedures. The NRC Senior Resident Inspector has been notified. |
ENS 55444 | 1 September 2021 03:50:00 | Palo Verde | NRC Region 4 | CE | 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. On 8/31/21 at 2050 (MST), the Seismic Monitoring System was discovered Non-Functional. This constitutes an unplanned loss of emergency assessment capability for an operational basis earthquake. There is currently no seismic activity in the area according to the U.S. Geological Survey. The NRC Resident Inspector was notified of the loss of seismic monitoring capability. |
ENS 55265 | 19 May 2021 10:15:00 | Palo Verde | NRC Region 4 | CE | At 0315 MST on May 19, 2021, Unit 2 reactor automatically tripped during testing of the Plant Protection System. The Reactor Protection System actuated to trip the reactor on High Pressurizer Pressure, although no plant protection setpoints were exceeded. Main Steam Isolation Signal (MSIS), Safety Injection Actuation Signal (SIAS), and Containment Isolation Actuation Signal (CIAS) were received. No injection of water into the Reactor Coolant System occurred. Auxiliary Feedwater Actuation Signals (AFAS) 1 and 2 actuated on low Steam Generator water level post trip as designed. This event is being reported as a reactor protection system and a specified system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). Following the reactor trip, all (Control Element Assemblies) CEAs inserted fully into the core. All systems operated as expected. No emergency plan classification was required per the Emergency Plan. Safety related busses remained powered during the event from offsite power and the offsite power grid is stable. Unit 2 is stable and in Mode 3. Steam Generator heat removal is via the class 1 E powered motor driven auxiliary feedwater pump and Atmospheric Dump Valves. The NRC Senior Resident Inspector has been informed.
The Unit 2 reactor tripped because of actual High Pressurizer Pressure that occurred as a result of a Main Steam Isolation Signal actuation. At 0337 MST, both trains of Low Pressure and High Pressure Safety Injection (LPSI and HPSI) were made inoperable when the injection valves were overridden and closed in accordance with station procedures. At 0346 MST, in accordance with station procedures, both trains of Containment Spray, LPSI, and HPSI pumps were overridden and stopped, rendering Containment Spray inoperable as well. This represents a condition that would have prevented the fulfillment of a safety function required to mitigate the consequences of an accident per 10 CFR 50.72(b)(3)(v)(D). Additionally, at the time of the Safety Injection Actuation Signal (0315 MST), both trains of Emergency Diesel Generators actuated as required and both 4160 VAC busses remained energized from off-site power. The NRC Senior Resident Inspector has been informed. Notified R4DO (Young)
The inoperability of both trains of Low Pressure and High Pressure Safety Injection (LPSI and HPSI) and both trains of Containment Spray (CS) following the Unit 2 reactor trip has been determined to be an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B). Additionally, inoperability of both trains of HPSI resulted in a reportable condition that could prevent fulfillment of its credited safety function to maintain the reactor in a safe shutdown condition per 10 CFR 50. 72(b)(3)(v)(A). The additional reporting criteria were discovered during review of the event and corresponding safety analyses. The NRC Senior Resident Inspector has been informed. Notified R4DO (Werner) |
ENS 55205 | 22 April 2021 16:25:00 | Palo Verde | NRC Region 4 | CE | At 0925 Mountain Standard Time (MST) on April 22, 2021, Palo Verde Nuclear Generating Station staff received reports that Emergency Notification sirens were activated. Current information indicates that the inadvertent activation of the sirens was caused by an offsite agency during performance of a planned silent test that occurred at approximately 0916 MST. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi). All sirens remain functional, and the NRC Resident Inspectors have been notified of the issue. Additional notifications will be made as needed. |
ENS 55114 | 26 February 2021 17:33:00 | Palo Verde | NRC Region 4 | CE | 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. At 1033 MST on February 26, 2021 the Unit 2 reactor automatically tripped due to a loss of two Reactor Coolant Pumps stemming from a loss of a 13.8 kV non-class bus during maintenance. Following the reactor trip, all Control Element Assemblies inserted fully into the core. All systems operated as expected. No emergency plan classification was required per the Emergency Plan. Unit 2 is stable and in Mode 3. Decay heat is being removed by the Steam Bypass Control System and Main Feedwater System. The NRC Senior Resident Inspector has been informed. Unit 1 and Unit 3 were not affected by the Unit 2 reactor trip. |
ENS 55037 | 15 December 2020 22:00:00 | Palo Verde | NRC Region 4 | CE | A plant employee, after being selected for a random fitness-for-duty test, admitted to use of a controlled substance. The employee's unescorted access to the facility has been placed on hold pending an investigation. The NRC Resident Inspector has been notified. |
ENS 55032 | 11 December 2020 07:00:00 | Palo Verde | NRC Region 4 | CE | On October 13, 2020, at approximately 02:25 (MST), an automatic start of the Unit 1 'A' Train EDG and SP systems occurred following the restoration of power to the 'A' Train 4160 Volt Class Bus. The station was conducting a surveillance test during a Unit 1 refueling outage to verify the proper responses of the EDG and the Engineered Safety Features Actuation Systems to simulated design basis events. During the test, technicians installed a jumper across incorrect relay points that caused the running Unit 1 'A' Train EDG to trip, resulting in a loss of power to the 'A' Train 4160 Volt Class Bus. Following restoration of normal offsite power to the 'A' Train 4160 Volt Class Bus, the Loss of Power Actuation signal was reset, however, EDG start relay logic was not reset at the EDG Local Panel. This resulted in the Unit 1 'A' Train EDG and SP system actuations with the EDG running unloaded. The system actuations did not occur as a result of valid plant conditions or parameters and are therefore invalid. The Unit 1 'A' Train EDG and SP system actuations were complete and the systems started and functioned successfully. The event was attributed to a human performance error and entered into the corrective action program. There was no adverse impact to public health and safety nor to plant employees. The NRC Resident Inspectors have been informed. |
ENS 54832 | 11 August 2020 21:32:00 | Palo Verde | NRC Region 4 | On August 11, 2020, at approximately 1432 MST, a licensed operator's test results were confirmed positive for use of a controlled substance following a random Fitness For Duty screening test. The individual's unescorted access has been terminated in accordance with station procedures. The NRC Resident Inspector has been notified. | |
ENS 54678 | 22 April 2020 17:54:00 | Palo Verde | NRC Region 4 | A licensed operator had a confirmed positive for alcohol during a random fitness-for-duty test. The individual's unescorted access has been terminated. | |
ENS 54621 | 19 March 2020 07:00:00 | Palo Verde | NRC Region 4 | The following is a summary of information obtained from Palo Verde via email: During pre-installation testing, five Masoneilan Model transducers were identified as unable to be calibrated prior to installation. These transducers were received by the vendor as safety-related components and are used to provide remote control operation of the Atmospheric Dump Valves (ADVs). The ADVs provide a safety grade method for cooling the unit to Shutdown Cooling System entry conditions, should Palo Verde's preferred heat sink via the Steam Bypass Control System to the condenser and/or atmosphere not be available. The transducer receives a 4-20 mA signal and translates it to a 3-15 psi output to the ADV positioner. This is accomplished by varying the supply air from 23-30 psi down to the appropriate 3-15 psi signal. Palo Verde provided an Interim 10 CFR 21 Report for the five Masoneilan Model 8005N transducers, Part 21 log number 2019-36-00, ML 19323C971, which was submitted by Arizona Public Service (APS) Company on November 15, 2019. An evaluation of the transducers was completed on March 19, 2020. The evaluation concluded that the inability of the transducers to be calibrated represented a defect. The licensees affected are undetermined at this time. Palo Verde has been in communication with the vendor. The vendor has currently not provided an extent of condition. Point of Contact: Lorraine Weaver (602) 448-5915 | |
ENS 54701 | 14 March 2020 19:44:00 | Palo Verde | NRC Region 4 | The following event descriptions are based on information currently available. If through subsequent reviews of these events additional information is identified that is pertinent to the events 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 telephone notification is being made pursuant to the reporting requirements of 10 CFR 50.73(a)(2)(iv)(A) and 50.73(a)(1) to describe invalid actuations of both trains of the Palo Verde Nuclear Generating Station (PVNGS) Unit 3 essential spray pond (SP) system, which serves as an emergency service water system that does not normally run and serves as an ultimate heat sink as described in 10 CFR 50.73(a)(2)(iv)(B)(9). This notification covers two similar, but separate invalid actuations occurring in Unit 3 on March 14, 2020 at 12:44 (MST) and again on April 25, 2020 at 12:10 (MST). On each day, an invalid actuation of the Unit 3 train "B" Fuel Building Essential Ventilation Actuation Signal (FBEVAS) occurred during performance of the Balance of Plant Engineered Safety Features Actuation System weekly auto test. The auto/manual pushbutton was depressed to initiate the test and the sequencer immediately tripped FBEVAS train "B" with subsequent cross trip of FBEVAS train "A". These actuations resulted in complete and successful actuations of both trains of essential spray pond pumps. The events were entered into the PVNGS corrective action program and a station evaluation is in progress. There was no adverse impact to public health and safety nor to plant employees. The NRC resident inspectors have been informed. | |
ENS 54570 | 6 March 2020 14:30:00 | Palo Verde | NRC Region 4 | A non-licensed contract supervisor had a confirmed positive for a controlled substance during an initial Fitness For Duty screening test. The individuals plant access has been terminated. The NRC Resident Inspector has been notified. | |
ENS 54560 | 4 March 2020 03:50:00 | Palo Verde | NRC Region 4 | At 2050 MST on March 3, 2020, Unit 2 reactor automatically tripped on Low Steam Generator (SG) Number 1 level signal from the Reactor Protection System. The low SG level occurred as the result of a trip of both Main Feedwater Pumps, which tripped during restoration of power to the Main Feedwater Pump Lube oil control panel. Auxiliary Feedwater (AFAS-1 and AFAS-2) actuated due to low SG levels in both SG post reactor trip as designed. This event is being reported as a reactor protection system and a specified system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). Following the reactor trip, all (control element assemblies) CEAs inserted fully into the core. All systems operated as expected. No emergency plan classification was required per the Emergency Plan. Safety related busses remained powered during the event from offsite power and the offsite power grid is stable. Unit 2 is stable and in Mode 3. Steam Generators are being fed via the class 1E powered motor driven auxiliary feedwater pump. The NRC Senior Resident Inspector has been informed. Units 1 and 3 were unaffected by the trip and remain at 100 percent power.
The event reported on March 4, 2020 (EN 54560) also included actuations of the Emergency Diesel Generators in response to the AFAS-1 and AFAS-2 actuations. The Class 4.16kV buses remained energized from off-site power. The NRC Senior Resident Inspector has been informed. Notified R4DO (Drake). | |
ENS 54272 | 12 September 2019 01:24:00 | Palo Verde | NRC Region 4 | 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 54224 | 16 August 2019 15:21:00 | Palo Verde | NRC Region 4 | At 0821 MST, on August 16, 2019, a main turbine trip occurred followed by a loss of power to all reactor coolant pumps. The Palo Verde Nuclear Generating Station (PVNGS) Unit 2 control room then received reactor protection system alarms for low departure from nucleate boiling ratio and an automatic reactor trip occurred. Following the reactor trip, auxiliary feedwater was manually started to maintain steam generator levels. A Main Steam Isolation Signal was manually initiated as directed by the Emergency Operating Procedures. Unit 2 is currently stable in Mode 3. Prior to the reactor trip, Unit 2 was operating normally at 100 percent power. No major equipment was inoperable prior to the event that contributed to the event or challenged operator response. All control element assemblies fully inserted into the core and no emergency classification was required per the PVNGS Emergency Plan. The cause of the reactor trip is under investigation. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The event did not adversely affect the safe operation of the plant or the health and safety of the public. The NRC Resident Inspector has been informed of the Unit 2 reactor trip. Decay heat is being removed via the atmospheric steam dump valves. Units 1 and 3 were unaffected by this event. | |
ENS 53968 | 1 April 2019 03:06:00 | Palo Verde | NRC Region 4 | At 2006 (MST), on 3/31/2019, the Palo Verde Nuclear Generating Station Unit 1 Shift Manager was informed that leakage was measured from the Train A Emergency Core Cooling System (ECCS) piping at approximately 100 ml/minute through a High Pressure Safety Injection (HPSI) A drain valve. This value exceeds the assumed 3000 ml/hour ECCS leakage for a large break loss of coolant accident analysis. At 0230 (MST) on April 1, 2019, the valve was flushed and the leakage reduced to 10 ml/minute (600 ml/hour) and was no longer above the limit of the safety analysis. This condition is being reported as an unanalyzed condition per 10 CFR 50.72(b)3)(ii)(B) and a condition that could have prevented the fulfillment of a safety function to the control the release of radioactive material per 10 CFR 50.72(b)(3)(v)(C). This event did not result in an abnormal release of radioactive material. Notification received by Caty Nolan and emailed to HOO.HOC@NRC.GOV The NRC asked a followup question: Why was the criterion for Control of Radioactive Material selected? per the PVNGS Unit 1 Shift Manager, this criterion was selected due to the potential of exceeding offsite dose projections, post recirculation, following a Design Basis Accident. The resident inspector has been notified.
An engineering evaluation concluded that the as-found ECCS leakage would not have degraded the performance of the Pump Room Exhaust Air Cleanup system; therefore, it remained operable. The evaluation also concluded that the as-found leakage was within the analysis margins for HPSI pump hydraulic performance and containment flood level following a Large Break Loss of Coolant Accident; therefore, the ECCS also remained operable. Based on the above information, the condition identified on March 31, 2019, was an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B), but did not prevent the fulfillment of the safety function of the structures or systems that are needed to control the release of radioactive material per 10 CFR 50.72(b)(3)(v)(C). The NRC resident inspectors have been informed. Notified R4DO (Proulx). | |
ENS 54309 | 3 March 2019 07:00:00 | Palo Verde | NRC Region 4 | On March 3, 2019, during overhaul activities of the medium voltage power (Magne-blast) circuit breakers, three General Electric Hitachi (GEH) Stationary Primary Contact Fingers Q0114C5382P002 were identified as having contact surfaces with a finish that was rough and unlike the typically smooth finish provided on electrical contact surfaces. These Stationary Primary Contact Fingers are the primary current carrying device for the circuit breaker. On October 1, 2019, Arizona Public Service Company (APS) completed an evaluation of a deviation, and concluded the condition represented a defect under 10 CFR 21. On October 4, 2019, the Palo Verde Nuclear Generating Station Vice President, Nuclear Engineering, was notified of a defect of GEH Stationary Primary Contact Fingers which met the reporting criteria of 10 CFR 21.21. There are no medium voltage power (Magne-blast) circuit breakers with stationary primary contact fingers impacted by this condition installed in the plant. APS concluded this condition, if installed, could result in the breaker failing to perform its safety function and thus could create a substantial safety hazard. The NRC resident inspector has been informed. | |
ENS 53702 | 29 October 2018 07:00:00 | Palo Verde | NRC Region 4 | 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. At approximately 03:30 MST on October 29, 2018, an Arizona Public Service Company (APS) employee developed a personal medical condition in the Owner Controlled Area outside of the Secured Owner Controlled Area at Palo Verde Generation Station (PVGS). PVGS Emergency Medical Technicians responded and transported the individual to an offsite emergency trauma center. Upon arrival at the trauma center, medical personnel declared the individual deceased at approximately 05:35 MST. The fatality was not work related and the individual was outside of the Radiological Controlled Area and no radioactive material or contamination was involved. No news release by APS is planned. Notifications were made to the Arizona Division of Occupational Safety and Health at 08:15 MST. The NRC Resident Inspectors have been notified. | |
ENS 53575 | 31 August 2018 07:00:00 | Palo Verde | NRC Region 4 | 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 | Palo Verde | NRC Region 4 | 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 53477 | 27 June 2018 07:00:00 | Palo Verde | NRC Region 4 | 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 10 CFR 50.73. On June 27th, 2018 at approximately 2310 Mountain Standard Time (MST), in Palo Verde Unit 3, the #1 Steam Generator Economizer valve started closing. This caused Steam Generator #1 water level to decrease. Both Feed water pumps speed increased to raise Steam Generator level. At approximately 2311 (MST), the B Main Feed water pump tripped resulting in a Reactor Power Cutback. Steam Generator #1 level continued to decrease resulting in an Automatic Reactor Trip on Low Steam Generator #1 water level. All control rods inserted to shut down the Reactor to Mode 3 using Main Feed water and Steam Bypass. Post trip Steam Generator #1 level then increased and at approximately 2316 (MST) a Main Steam Isolation Signal (MSIS) was received on high Steam Generator level. The 'B' Auxiliary Feed water pump was manually started to maintain Steam Generator water levels and Steam Generator pressure was controlled using the Atmospheric Dump Valves (ADVs). Following the reactor trip, all CEAs (Control Element Assemblies) inserted fully into the core. All systems operated as expected. No emergency plan classification was required per the Emergency Plan. Safety related busses remained powered during the event from offsite power and the offsite power grid is stable. No major equipment was inoperable prior to the event that contributed to the event or complicated operator response. Unit 3 is stable and in Mode 3 feeding Steam Generators with Auxiliary Feed water Pump 'B'. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The event did not adversely affect the safe operation of the plant or the health and safety of the public. The NRC Resident Inspector was informed of the Unit 3 reactor trip. Unit 1and Unit 2 were unaffected by the Unit 3 trip. | |
ENS 53424 | 23 May 2018 18:28:00 | Palo Verde | NRC Region 4 | CE | 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. On May 23, 2018, at approximately 1128 Mountain Standard Time (MST), the Palo Verde Nuclear Generating Station (PVNGS) Unit 2 control room received reactor protection system alarms for low departure from nucleate boiling ratio and an automatic reactor trip occurred. Prior to the reactor trip, Unit 2 was operating normally at 100 percent power. Plant operators entered the reactor trip procedures and diagnosed an uncomplicated reactor trip. All CEAs (control element assemblies) fully inserted into the core. No emergency classification was required per the PVNGS Emergency Plan. The Unit 2 safety-related electrical buses remained energized from normal offsite power during the event. There was no impact to the required circuits between the offsite transmission network and the onsite Class 1E Electrical Power Distribution System; the offsite power grid is stable. No major equipment was inoperable prior to the event that contributed to the event or complicated operator response. Unit 2 is currently stable in Mode 3 with the reactor coolant system at normal operating temperature and pressure. The cause of the reactor trip is under investigation. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The event did not adversely affect the safe operation of the plant or the health and safety of the public. The NRC Resident Inspector has been informed of the Unit 2 reactor trip. Decay is being removed via steam dumps to condenser. Units 1 and 3 at Palo Verde were unaffected by the transient and continue to operate at 100 percent power. |
ENS 53215 | 16 February 2018 04:53:00 | Palo Verde | NRC Region 4 | CE | 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. On February 15, 2018, at approximately 2153 Mountain Standard Time (MST), the Palo Verde Nuclear Generating Station (PVNGS) Unit 1 Control Room received Reactor Protection System alarms for Low Departure from Nucleate Boiling Ratio and an automatic reactor trip occurred. Prior to the reactor trip, Unit 1 was operating normally at 100 percent power. Plant operators entered the emergency operations procedures and diagnosed an uncomplicated reactor trip but noted that Reactor Coolant Pumps 1B and 2B were not running due to a loss of power. All CEAs (Control Element Assemblies) fully inserted into the core. Following the reactor trip, all nuclear instruments responded normally. No emergency classification was required per the PVGS Emergency Plan. The PVGS Unit 1 safety related electrical busses remained energized from normal offsite power during the event. The Unit 1 'B' Diesel Generator is currently removed from service for maintenance. Due to ongoing planned maintenance on NAN-X02, Startup Transformer 2, fast bus transfer for NAN-S02 (from NAN-S04) was blocked. This resulted in a loss of offsite power to NAN-S02 and NBN-S02. The offsite power grid is stable. Unit 1 is currently stable in Mode 3 with the reactor coolant system at normal operating temperature and pressure. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The event did not adversely affect the safe operation of the plant or the health and safety of the public. The NRC Resident Inspector has been informed of the Unit 1 reactor trip.
Unit 1 is stable in Mode 3 following an uncomplicated trip. Offsite power has been restored to non-safety related electrical busses. Troubleshooting continues to determine the cause of the event. During performance of the alarm response procedure, it was identified that the seismic monitoring (SM) system had been in alarm since the reactor trip and was incapable of performing its emergency plan function. Pursuant to 10 CFR 50.72(b)(3)(xiii), this condition constitutes a major loss of emergency assessment capability. Compensatory measures have been implemented in accordance with PVNGS procedures to provide alternative methods for HU2.1 event classification with the SM system out of service. Maintenance is currently in progress to restore SM system functionality. The licensee notified the NRC Resident Inspector. Notified R4DO (Werner).
Station staff completed an evaluation of event EN #53215 reported on February 15, 2018, and determined that the seismic monitoring system remained capable of assessing a seismic event following the reactor trip. Therefore, a major loss of emergency assessment capability pursuant to 10 CFR 50.72(b)(3)(xiii) did not occur as reported in the update on February 16, 2018. The NRC Resident Inspectors have been notified. Notified the R4DO (Gaddy). |
ENS 53015 | 14 October 2017 02:48:00 | Palo Verde | NRC Region 4 | CE | At approximately 19:48 Mountain Standard Time on October 13, 2017, Palo Verde Nuclear Generating Station (PVNGS) staff confirmed a non-licensed supervisor tested positive for drugs during a random 'Fitness for Duty' test. The person's access authorization was terminated in accordance with station procedures. The NRC resident inspector has been notified by the licensee. |
ENS 53010 | 12 October 2017 16:30:00 | Palo Verde | NRC Region 4 | CE | A contract employee supervisor had a confirmed positive for illegal drugs during an initial screening test. The individual's access to the plant has been terminated. The NRC Resident Inspector has been notified by the Licensee. |
ENS 52989 | 22 September 2017 22:00:00 | Palo Verde | NRC Region 4 | CE | 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) for a major loss of emergency assessment capability at the Palo Verde Nuclear Generating Station (PVNGS). On September 21, 2017 at 0915 MST, the seismic monitoring (SM) computer was declared non-functional for the performance of a planned surveillance test. On September 21, 2017 at 1201 MST, the SM system computer became non-responsive during the performance of the test. Control room staff attempted to reboot the computer and were unsuccessful. Maintenance and troubleshooting efforts began thereafter to initiate repairs. As a compensatory measure, PVNGS procedures for seismic event evaluation provide alternative methods for event classification of a seismic event with the SM system out of service. The SM system functions to provide indication that the Operational Basis Earthquake (OBE) threshold has been exceeded following a seismic event and is used in the PVNGS Emergency Plan to perform classification of Initiating Condition 'Seismic event greater than OBE levels' and Emergency Action Level HU2.1. On September 22, 2017 at 1500 MST, maintenance personnel performing software repair efforts determined hardware replacement is required. The required component will not be available before 72 hours from the start of the event. Because the SM system is not expected to be restored within 72 hours, this condition is being reported as a planned event constituting a major loss of emergency assessment capability with viable compensatory measures in place. The NRC Resident Inspector has been informed of this condition. |
ENS 52670 | 5 April 2017 07:00:00 | Palo Verde | NRC Region 4 | CE | On April 5, 2017, Arizona Public Service Company (APS) completed an evaluation of a deviation, and concluded the condition represented a defect under 10 CFR 21. APS previously submitted an interim report (ADAMS Accession Number ML 16344A118) for this condition pursuant to 10 CFR 21.21(a)(2). A GE-Hitachi Type AKR-2BE-50, 2000 Amp circuit breaker (used to connect Class 1E batteries to the related Class 1E 125 VDC busses) exhibited arcing and smoking during current injection testing performed to test the overcurrent trip setpoint prior to installation. Arcing occurred at one of two hex bolts anchoring the protective trip device to the line side bus. The electrical arcing resulted from inadequate tightening of both hex bolts which caused a loose electrical connection on the bus within the breaker. APS concluded this condition could result in the breaker failing to perform its safety function and thus could create a substantial safety hazard. The breaker had been refurbished by GE-Hitachi and was received by APS and tested on October 13, 2016. Following the test failure, the damaged bolt was replaced, both bolts were tightened, and the breaker was retested and installed. Pre-installation inspection and testing that includes current injection testing, recommended in GEH document GEK-64459, should, and did, detect faults such as the condition identified in this notification. GE-Hitachi entered this failure into their corrective action program. Vendor: GE HITACHI NUCLEAR ENERGY, 3901 CASTLE HAYNE RD., WILMINGTON, NC 28402-2819 Device: Breaker Model AKR-2BE-50, 2000 Amp, Serial No. N8682600001 The NRC Resident Inspector has been informed. |
ENS 52435 | 15 December 2016 11:10:00 | Palo Verde | NRC Region 4 | CE | 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. During a scheduled surveillance test run of the PVNGS (Palo Verde Nuclear Generating Station) Unit 3 'B' Train Emergency Diesel Generator, there was a catastrophic failure of a piston to include crankcase damage and diesel trip. The Emergency Plan has been entered and an ALERT was declared at 0410 (MST) on 12/15/16 based on an explosion resulting in visible damage to a safety system required for safe shutdown. The cause of the failure is unknown at this time. PVNGS Fire Department responded and no fire was observed. Unit 3 remains on line at 100% power. No other safety functions are impacted. No personnel injuries occurred. The unit is in a ten day technical specification on an emergency diesel generator being inoperable. The licensee notified the NRC Resident Inspector. Notified DHS, DOE, EPA, FEMA, NICC, USDA, HHS, FDA, NSSA, Mexico, and OIP (Skeen).
This serves as the notification of the termination of Alert HA2.1 declared at 0410 MST at Palo Verde Nuclear Generation Station. The event terminated at 0636 MST. The licensee will notify the NRC Resident Inspector. Notified R4DO (Keller), NRR EO (Miller), IRD (Stapleton), DHS, DOE, EPA, FEMA, NICC, USDA, HHS, FDA, NSSA, Mexico, and OIP (Skeen). |
ENS 52309 | 20 October 2016 01:30:00 | Palo Verde | NRC Region 4 | CE | While performing a scheduled inservice inspection on a section of safety injection system piping, a flaw was identified in a circumferential weld on the 14 inch safety injection line from the 2A safety injection tank to the 2A reactor coolant loop. Examination results indicate that the flaw constitutes a welding defect that cannot be found acceptable under ASME Section XI, IWB-3600, or Table IWB-3410-1. Further analysis is being conducted. The unit had been shutdown for its 19th refueling outage (3R19) on October 8, 2016, at 0000. The NRC Resident Inspectors have been informed of this condition. This piping is required to be operable in modes one through four.
Subsequent engineering examination of the weld on the 14" safety injection line from the 2A safety injection tank to the 2A reactor coolant loop using enhanced examination techniques concluded the indication in the circumferential weld does not represent a flaw constituting a weld defect. The indication was the result of a metallurgical weld interface in the area of a previously documented weld repair. Therefore, the indication is acceptable under ASME Section XI with no further analysis required. Based on the above information, PVNGS has determined the indication does not represent a degraded condition of a principal safety barrier as defined by 10CFR 50.72(b)(3)(ii)(A) and event notification #52309 is retracted. The NRC Resident Inspectors have been notified. Notified R4DO (Campbell). |
ENS 52413 | 17 October 2016 22:19:00 | Palo Verde | NRC Region 4 | CE | 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. This telephone notification is being made pursuant to the reporting requirements of 10 CFR 50.73(a)(2)(iv)(A) and 50.73(a)(1) to describe an invalid actuation of the Palo Verde Nuclear Generating Station (PVNGS) Unit 1 train A emergency diesel generator (EDG), train A high pressure safety injection (HPSI) pump, and train A essential spray pond (SP) pump. These components are portions of the emergency ac electrical power system, the emergency core cooling system, and the emergency service water system, respectively, as described in 10 CFR 50.73(a)(2)(iv)(B). On October 17, 2016 at approximately 1519, Mountain Standard Time, a portion of the Unit 1 train A engineered safety features equipment was automatically started by the balance-of-plant (BOP) engineered safety features actuation system (ESFAS) while the plant was at steady state conditions. Initiation of the train A ESFAS actuation signal was momentary, and the ESFAS actuation signal cleared 0.2 seconds after being initiated. The invalid ESFAS signal initiated a test-mode start signal for the train A EDG and started the train A HPSI pump. The train A essential SP pump started in support of the train A EDG. All actuated components started and functioned successfully. No systems started in response to actual plant conditions, and no actuation was required to mitigate the consequences of an event. The invalid HPSI actuation neither resulted in an emergency core cooling system discharge, nor should it have. The invalid actuation was the consequence of a spurious momentary signal into the BOP-ESFAS control panel due to an intermittent high resistance electrical connection. The event was entered into the PVNGS corrective action program. There were no adverse impacts to public health and safety nor to plant employees. The NRC Resident Inspectors have been informed. |
ENS 52229 | 9 September 2016 01:56:00 | Palo Verde | NRC Region 4 | CE | 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) for a loss of emergency assessment capability at the Palo Verde Nuclear Generating Station (PVNGS). On September 8, 2016 at 1856 (MST), seismic monitoring (SM) system computer AJSMNXYQI0001**INSTRU was determined to be non-functional due to a power spike which caused a temporary loss of power to the seismic instrumentation and resulted in a locked in the Control Room alarm. At 2305, I&C technicians re-booted the computer and verified the SM system was functioning. On September 8, 2016, at approximately 2353, further review of this equipment failure and the related impact to the capability of the SM system determined that this was a reportable loss of emergency assessment capability during the period between 1856 and 2305. This specific SM functions to provide indication that the Operational Basis Earthquake threshold has been exceeded following a seismic event and is used in the PVNGS Emergency Plan to perform classification for emergency action level HA1.1, Natural or Destructive Phenomena affecting Vital Areas. As a compensatory measure, PVNGS procedures for seismic event evaluation provide alternative methods for HA1.1 event classification with the SM out of service. Maintenance to correct the condition has been completed. The NRC Resident Inspector has been informed of this condition. |
ENS 52226 | 8 September 2016 04:31:00 | Palo Verde | NRC Region 4 | CE | On September 7th, 2016 at approximately 2131 Mountain Standard Time (MST), Palo Verde Unit 1 was manually tripped due to a stuck open main spray valve. Unit 1 was operating at 100 percent power at normal operating temperature and pressure prior to the event. A 120 VAC non-class instrument distribution panel was being transferred to its alternate power supply to establish maintenance conditions. The distribution panel failed to transfer. The panel remained energized from its normal power supply; however, multiple components powered from the distribution panel began to exhibit uncharacteristic behavior. At this time, it was noted that a reactor coolant system main spray valve was open. The alarm response procedure was followed; however, the actions taken were unsuccessful at closing the main spray valve. The plant was then manually tripped due to pressurizer pressure continuing to lower. The reactor coolant pumps were turned off to terminate main pressurizer spray flow to control pressurizer pressure due to the inability to close the main spray valve. No ESF (Engineered Safety Features) actuations occurred and none were required. No emergency classification was required per the emergency plan. Safety related buses remained energized during and following the reactor trip. The emergency diesel generators did not start and were not required. The offsite power grid is stable. Limiting condition for operation 3.4.1 was entered due to low pressurizer pressure. No major equipment was inoperable prior to the event that contributed to the event. Unit 1 is stable at normal operating temperature and pressure in Mode 3. Reactor coolant pumps are secured and natural circulation has been verified. Primary pressure is being maintained at its normal operating pressure manually with pressurizer heaters and auxiliary spray, from the charging system. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The minimum RCS pressure was approximately 2070 psia (normal 2250). The event did not adversely affect the safe operation of the plant or the health and safety of the public. All rods inserted and the trip was uncomplicated. Units 2 and 3 were not affected and continue to run at full power. The NRC Resident Inspector has been notified. |
ENS 52209 | 30 August 2016 16:35:00 | Palo Verde | NRC Region 4 | CE | A non-licensed employee supervisor had a confirmed positive for alcohol during a random fitness-for-duty test. The employee's access to the plant has been suspended. |
ENS 52083 | 12 July 2016 20:00:00 | Palo Verde | NRC Region 4 | CE | 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. During the performance of a fire seal and barrier surveillance test, a degraded fire seal barrier that provides 1 hour separation between two fire zones containing redundant safe shutdown trains was identified in the 100 foot elevation of the PVNGS Unit 1 Auxiliary Building. This condition is reportable in accordance with 10CFR50.72(b)(3)(ii)(B) as an unanalyzed condition. Fire protection detection and mitigation systems in both fire zones are operable and compensatory measures (fire watches) have been implemented for affected areas. The NRC Resident Inspector has been notified. The degraded fire barrier consists of two holes in the through wall fire barrier surrounding two two-inch conduits. The two holes are approximately one to one and a half inches across.
Subsequent Engineering evaluation concluded the degraded fire seal in PVNGS Unit 1 reported on July 12, 2016, did not place PVNGS in an unanalyzed condition that significantly degraded plant safety. The degraded fire seal would have continued to provide the required degree of separation for redundant safe shutdown trains. The evaluation found a fire initiated in a fire zone on either side of the barrier would not propagate within one hour into the adjacent zone with redundant safe shutdown equipment. These conclusions were based on an existing fire analysis which was used to demonstrate that the required degree of separation between safe shutdown equipment remained intact. Based on the above information, PVNGS is retracting event notification report #52083, as the degraded fire seal did not place PVNGS Unit 1 an unanalyzed condition that significantly degraded plant safety. The NRC Resident Inspectors have been informed. Notified R4DO (Proulx). |
ENS 52228 | 12 July 2016 12:50:00 | Palo Verde | NRC Region 4 | CE | 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. This telephone notification is being made pursuant to the reporting requirements of 10CFR50.73(a)(2)(iv)(A) and 50.73(a)(1) to describe an invalid actuation of both trains of the Palo Verde Nuclear Generating Station (PVNGS) Unit 2 essential spray pond (SP) system. The SP system serves as an emergency service water system that does not normally run and serves as an ultimate heat sink as described in 10CFR50.73(a)(2)(iv)(B)(9). On July 12, 2016, at approximately 0550, Mountain Standard Time, Unit 2 experienced a manual actuation of both trains of the SP system. Approximately 20 minutes earlier, the failure of a +15VDC power supply on the containment purge isolation actuation signal (CPIAS) module resulted in a trip of the B train CPIAS and a momentary cross trip of the A train CPIAS, and both trains of the control room essential filtration actuation system (CREFAS). These brief actuation signals resulted in starting of some but not all essential equipment because the actuation signals cleared before most of the equipment received a start signal. Both trains of the SP system were started manually in accordance with the alarm response procedure. The A train CPIAS and both trains of CREFAS were reset. The B train CPIAS remained in a partially tripped state because of the failed power supply. The manual actuation of both A and B trains of the SP system was complete. Both trains of the SP system started and functioned successfully. The invalid actuation was the consequence of a failed +15VDC power supply on the B train CPIAS module which resulted in momentary trips of both trains of CPIAS and CREFAS. The containment building radiation monitors that actuate CPIAS exhibited normal radiation levels which would not have required CPIAS actuation. The event was entered into the PVNGS corrective action program. There was no adverse impact to public health and safety nor to plant employees. The NRC Resident Inspectors have been informed. |
ENS 51910 | 5 May 2016 12:00:00 | Palo Verde | NRC Region 4 | CE | 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. At 0500 MST on May 5, 2016, engineering personnel determined that leakage from the bonnet seal weld of the Train B High Pressure Safety Injection (HPSI) system loop 2A injection valve, SIBUV0616, constituted reactor coolant system pressure boundary leakage. This is being reported as a degradation of a principal safety barrier pursuant to 10 CFR 50.72(b)(3)(ii)(A). The leak was identified during a planned activity in which Operations was filling the refueling pool using HPSI pump B. Leakage was stopped when a plant operator closed SIBUV0616. PVNGS Unit 1 was shut down for its 19th refueling outage (1R19) on April 9, 2016, at 0000 MST and is in Mode 6. The NRC Resident Inspectors have been informed of this condition.
Subsequent engineering evaluation of the leak condition concluded the leakage from the bonnet seal weld of SIBUV0616 was not reportable reactor coolant system pressure boundary leakage. This conclusion was based on further reviews of the PVNGS licensing bases, ASME Code requirements, and design features of the valve with vendor assistance, which determined that the body-to-bonnet threads provide the structural support for the mechanical joint and the seal weld is not required for structural integrity of the component. Based on the above information, PVNGS has determined the leakage did not represent a degraded condition of a principal safety barrier as defined by 10 CFR 50.72(b)(3)(ii)(A) and Event Notification No. 51910 is hereby withdrawn. The NRC Resident Inspectors have been informed. Notified R4DO (Werner) |