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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).

• * * UPDATE ON 04/04/24 AT 2313 EDT FROM YOLANDA GOOD TO IAN HOWARD * * *

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).

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. During Palo Verde Nuclear Generating Station Unit 2 containment pressurization for integrated leak rate testing in Mode 5, a containment fire alarm in Fire Zone 63B (Steam Generator 2 all elevations of containment) was received. Containment temperature and pressure at time of event were 72 degrees F and 13 PSIG. Due to the inability to access containment to validate the fire alarm, an Unusual Event (HU2.1) was declared at 0547 (MST) for a Fire in containment which was unable to be validated within 15 minutes of receipt. No safety functions have been impacted due to the fire alarm. No automatic or manual RPS or ESF actuations occurred and none were required. Actions are being taken to depressurize containment to enter and validate the fire alarm. The NRC Resident Inspector has been notified. There has been no effect on U-1 or U-3 due to this fire alarm. Notified DHS SWO, FEMA Ops Center, NICC Watch Officer and via E-mail only FEMA NWC and Nuclear SSA.

• * * UPDATE FROM ROB WARNER TO DONALD NORWOOD AT 1125 EST ON 11/9/2015 * * *

Containment was entered following depressurization. Operations and Fire Protection personnel inspection of containment and Fire Zone 63B identified no indication of fire or smoke and the fire alarm was determined to be invalid. No other impacts to plant equipment were identified. The Unusual Event was terminated on 11/9/2015 at 0901 MST. The NRC Resident Inspector has been notified. Notified R4DO (Proulx), NRR EO (Morris), and IRD (Grant). Notified DHS SWO, FEMA Ops Center, NICC Watch Officer and via E-mail only FEMA NWC and Nuclear SSA.

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. An event classification of Unusual Event (HU1.1) was declared at 22:17 MST for the Palo Verde Nuclear Generating Station because of an earthquake that originated 50km NW of Lordsburg, New Mexico at 21:59 MST. Per the USGS website, the magnitude of the earthquake was 5.2 on the Richter scale. Initial walkdowns of plant equipment and review of plant parameters have found no unusual conditions or damage to plant equipment. No abnormalities caused by the seismic event were observed. No reactor protection system (RPS) or engineered safety feature (ESF) actuations occurred and none were required. Palo Verde Unit 1, 2, and 3 are at 100 percent power with all offsite power supplies available. Initial analysis of the Seismic Monitoring Instrumentation System indicated a seismic event, below the magnitude of the 0.10g spectra Operating Basis Earthquake (OBE) and the 0.20g spectra Safe Shutdown Earthquake (SSE). The NRC Resident Inspector has been notified of seismic activity and this ENS call. This event time is 2206 MST because this is the time the control room was notified by plant Operators that an earthquake had been felt on site. Notified DHS, FEMA, and NICC. FEMA NWC and Nuclear SSA were notified via email.

• * * UPDATE AT 0424 EDT ON 6/29/2014 FROM DENNIS MARTIN TO MARK ABRAMOVITZ * * *

Emergency classification termination was declared at 6/29/14 01:12 MST. All required power block inspections were completed with no deficiencies noted. No other conditions require an emergency classification, there are no challenges to fission product barriers or radiological release, and plant conditions offer no possibility of adverse impact on health and safety of the public. The licensee notified the NRC Resident Inspector, state and local governments. Notified the R4DO (Allen), NRR (Hiland), IRD (Gott), DHS, FEMA, and NICC. FEMA NWC and Nuclear SSA were notified 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. On 7/2/2013, at approximately 2027 MST, Palo Verde Unit 1 experienced a reactor power cutback from 100% rated thermal power due to explosion (in a non-safety related load center (1ENGNL02)). The unit was at normal temperature and pressure prior to the cutback. At 2035 (MST) PVNGS Unit 1 declared an Unusual Event due to the explosion EAL HU 2.2. Unit 1 is stable at 61% rated thermal power. No ESF actuations occurred and none were required. The event did not result in any challenges to the fission product barrier or result in any releases of radioactive materials. There were no adverse safety consequences or implications as a result of this event. The event did not adversely affect the safe operation of the plant or health and safety of the public. The licensee will notify the NRC Resident Inspector. Notified DHS SWO, FEMA, DHS NICC, and Nuclear SSA via email.

* * * UPDATE ON 7/3/13 AT 0229 EDT FROM JEONG LIM TO PETE SNYDER * * * 

Palo Verde Unit 1 is stable at 58% rated thermal power and is implementing abnormal operating procedures for reactor power cutback due to loss of one Main Feedwater Pump and degraded electrical power due to loss of non-class 13.8kV load center 1ENGNL02. Load center 1ENGNL02 was damaged from an apparent electrical malfunction that originated within the load center. The 13.8kV supply breaker to load center 1ENGNL02 tripped to deenergize the load center. Palo Verde Fire Department personnel responded but determined that the load center was deenergized and no fire existed and no extinguishing agents were applied. No damage to other equipment in proximity to load center 1ENGNL02 was identified during a preliminary inspection of the area around the damaged load center. The NRC Resident Inspector has been notified. At 2315 (MST) on 07/02/2013, the Unusual Event was terminated. Notified R4DO (Gaddy), NRR EO (Nieh), IRD MOC (Gott), DHS SWO, FEMA, DHS NICC, and Nuclear SSA via email.

On June 18, 2010, at approximately 0807 MST, a manual turbine trip was initiated due to loss of cooling for Main Transformer X01C. The power supplies for the transformer cooling system was lost due to an inadvertent actuation of the transformer fire protection deluge system. The damage to the energized equipment met the definition for an Emergency Action Level HU 2.2. Based on HU 2.2 the Unit 1 Shift Manager declared a Notification of an Unusual Event (NOUE) at 0808 MST applicable to Palo Verde Unit 1 only. The manual trip of the turbine initiated a Reactor Power Cutback Large Load Rejection actuation which was successful. The reactor is stable at 25% with Heat Removal via main feedwater and steam bypass to main condenser. A down power to approximately 12% power is being planned. No anomalies were noted during the manual turbine trip. (There is) no release in progress and no safety systems actuations were required. Palo Verde Unit 1 is in a normal post-trip electrical lineup. State and local authorities have been notified as well as the NRC Resident Inspector.

• * * UPDATE FROM BRIAN FERGUSON TO DONG PARK @ 1333 EDT ON 6/18/10 * * *

The licensee terminated the Unusual Event at 1030 MST. The reactor remains stable at approximately 12% power, and heat removal is via main feedwater and steam bypass to the main condenser. Notified IRD (Gott), NRR EO (Cheok), R4DO (Jones), DHS (Inzer) and FEMA (Hollis).

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. An Event Classification of Unusual Event (HU1.1) was declared at 1549 MST for the Palo Verde Nuclear Generating Station because of an earthquake that originated in Baja California, (Mexico) location 32.093?N, 115.249?W at 1542 MST. Per the USGS (U.S. Geological Survey) website, the magnitude of the earthquake was 6.9 on the Richter scale. Initial walkdowns of plant equipment and review of plant parameters have found no unusual conditions or damage to plant equipment. No abnormalities caused by the seismic event were observed. No Reactor Protection System (RPS) or Engineered Safety Feature (ESF) actuations occurred and none were required. Palo Verde Unit 1 is in mode 5 for a scheduled refueling outage, and Units 2 & 3 are at 100 percent power with all offsite power supplies available. Initial analysis of the Seismic Monitoring Instrumentation system indicated a seismic event, below the magnitude of the 0.10g spectra Operating Basis Earthquake (OBE) and the 0.20g spectra Safe Shutdown Earthquake (SSE). The licensee has notified the NRC Resident Inspector.

• * * UPDATE FROM GORDON TIMOTHY TO VINCE KLCO AT 0003 EDT ON 4/5/2010 * * *

Emergency classification termination was declared at 4/4/10, 2045 MST. All required power block inspections were completed with no deficiencies noted. No other conditions require an emergency classification, there are no challenges to fission product barriers or radiological release, and plant conditions offer no possibility of adverse impact on health and safety of the public. NRC Resident Inspector has been notified of NUE termination. Notified the R4DO (Okeefe), NRR-EO (Bahadur), FEMA (Via), DHS (Wallace) and IRD via email (Gott).

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 March 7, 2010, at approximately 1124 MST Palo Verde Unit 1 declared a Notification of Unusual Event (NOUE) due to an electrical fault (explosion) experienced on the 13.8 KV Non-Class busses being supplied from the Unit Auxiliary Transformer. The fault resulted in a minor explosion and damage to the bus work leading from NAN S03 to NAN S01. The fault resulted in the loss of the NAN S01, which caused a reactor trip due to the loss of 2 of 4 reactor coolant pumps. There was no fire detected after the initial event. The reactor trip (RPS actuation at 1117 MST) was from 100% rated thermal power due to low departure from nucleate boiling (DNBR) trips on all four channels of the core protection calculators (CPCs). The unit was at normal temperature and pressure prior to the trip. All of the control rods fully inserted into the core. Four of eight steam bypass control valves quick opened, per design, directing steam flow to the condenser. No main steam or primary relief valves lifted and none were required. There was no loss of heat removal capability or loss of safety functions associated with the event. ESF Electrical buses remain energized from off-site power. The Shift Manager determined this event was an uncomplicated reactor trip. No significant LCOs have been entered as a result of this event. No major equipment was inoperable prior to the event nor contributed to the event.

Unit 1 is stable at normal operating temperature and pressure in Mode 3. No ESF actuations (other than RPS) occurred and none were required. The event did not result in any challenges to the fission product barrier or result in any releases of radioactive materials. There were no adverse safety consequences or implications as a result of this event. The event did not adversely affect the safe operation of the plant or health and safety of the public. Decay heat is being removed via the steam bypass valves to the condenser. The plant is in its normal shutdown electrical lineup with the exception of powering the NAN S01 bus. Unit 2 and Unit 3 were not affected by the transient on Unit 1. The licensee has notified the NRC Resident Inspector.

• * * UPDATE FROM ALFRED ERDELJI TO HOWIE CROUCH @ 1723 EST ON 3/7/10 * * *

Palo Verde Unit 1 has terminated the NOUE at 1516 MST. The termination criteria was that the plant is stable, the area around the fault has been inspected and no other conditions exist that would prevent termination of the event. Decay heat path has been changed from steam dumps to condenser to atmospheric dumps due to difficulty in maintaining temperature. There is no known primary to secondary leakage. The licensee has notified the NRC Resident Inspector. Notified R4DO (Cain), NRR EO (Holian), IRD (Gott), DHS (Roper) and FEMA (LaForte).

On June 14, 2004, at approximately 07:44 Mountain Standard Time (MST) all three units at the Palo Verde Nuclear Generating Station experienced automatic reactor trips coincident with a grid disturbance and loss of offsite power in the Palo Verde Switchyard. Unit 2 declared an ALERT Emergency Plan classification at approximately 07:54 due to a loss of AC power to essential buses reduced to a single power source for greater than 15 minutes such that any additional single failure would result in a station blackout. Subsequently, at 09:51 Unit 2 downgraded the Emergency Plan classification to a NOTIFICATION OF UNUSUAL EVENT when AC power was restored from a single essential bus to both essential buses. Units 1 and 3 declared a NOTIFICATION OF UNUSUAL EVENT at 07:53 MST due to a loss of offsite power to essential buses for greater than 15 minutes. The NOTIFICATION OF UNUSUAL EVENT was terminated for all 3 units at 12:07 MST. Unit 1 and 2 manually initiated a Main Steam Isolation System ESF actuation by procedure. Unit 3 received an automatic Main Steam Isolation System ESF actuation. Due to the loss of offsite power, the Emergency Plan Technical Support Center (TSC) was unavailable. The Unit 2 Satellite TSC was to be staffed by the Emergency Response Organization in response to the loss of assessment capability. Power to the TSC has since been restored. The Emergency Plan ALERT declaration includes staffing of the Joint Emergency New Center to address expected media interest. All three units were at normal operating temperature and pressure prior to the trip. All CEAs inserted fully into the reactor cores. All Emergency Diesel Generators (EDGs) (2 per unit) associated with each of the 3 units started as expected in response to the loss of offsite power to their safety buses. Unit 2's train "A" EDG started, but did not indicate volts or amps and was manually shutdown. The offsite power grid had several perturbations for approximately one hour following the event but has been stable since. LCO 3.8.1, AC Sources - Operating, was entered in each unit as a result of this event. Heat removal is to atmosphere via atmospheric dump valves in natural circulation. Main steam safety valves may have lifted for a brief time. Restoration of forced reactor coolant circulation is pending assurance that the offsite power grid can reliably support the load. No major equipment was inoperable prior to the event that contributed to the event. All 3 units are stable at normal operating temperature and pressure in Mode 3. 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 NRC Resident Inspector was notified. FBI Jeff Muller and Mr. Rosales (Mexican National Commission of Nuclear Safety and Safeguards (CNSNS)) were notified.

• * * Update at 1815 @ 06/14/04 * * *

Notified Reg 4 RDO (Graves), NRR (Bateman), DHS (Lee), FEMA (Canupp), DOE (Sal Moroni), EPA (Stalcup), EPA (Crews), HSS (Davidson), and Mexico (Rosales) NOTE: See events 40815, 40816 and 40818

On June 14, 2004, at approximately 07:44 Mountain Standard Time (MST) all three units at the Palo Verde Nuclear Generating Station experienced automatic reactor trips coincident with a grid disturbance and loss of offsite power in the Palo Verde Switchyard. Unit 1 declared a NOTIFICATION OF UNUSUAL EVENT at 07:53 MST due to a loss of offsite power to essential buses for greater than 15 minutes. The NOTIFICATION OF UNUSUAL EVENT was terminated at 12:07 MST. Unit 1 manually initiated a Main Steam Isolation System ESF actuation by procedure. Due to the loss of offsite power, the Emergency Plan Technical Support Center (TSC) was unavailable. The Unit 2 Satellite TSC was to be staffed by the Emergency Response Organization in response to the loss of assessment capability. Power to the TSC has since been restored. The unit was at normal operating temperature and pressure prior to the trip. All CEAs inserted fully into the reactor cores. All Emergency Diesel Generators (EDGs) (2 per unit) associated with the unit started as expected in response to the loss of offsite power to their safety buses. The offsite power grid had several perturbations for approximately one hour following the event but has been stable since. LCO 3.8.1, AC Sources - Operating, was entered as a result of this event. Heat removal is to atmosphere via atmospheric dump valves in natural circulation. Main steam safety valves may have lifted for a brief time. Restoration of forced reactor coolant circulation is pending assurance that the offsite power grid can reliably support the load. No major equipment was inoperable prior to the event that contributed to the event. The Unit is stable at normal operating temperature and pressure in Mode 3. 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 NRC Resident Inspector was notified. FBI Jeff Muller and Mr. Rosales (Mexican National Commission of Nuclear Safety and Safeguards (CNSNS)) were notified.

• * * Update at 1815 @ 06/14/04 * * *

Notified Reg 4 RDO (Graves), NRR (Bateman), DHS (Lee), FEMA (Canupp), DOE (Sal Moroni), EPA (Stalcup), EPA (Crews), HSS (Davidson), and Mexico (Rosales) Note: see related events # 40814, 40816 and 40818