Semantic search
| Discovered date | Reporting criterion | Title | Description | LER | |
|---|---|---|---|---|---|
| ENS 42732 | 27 July 2006 02:00:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Limiting Condition for Operation 3.7.4 Deemed to Be Nonconservative | 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. Palo Verde Nuclear Generating Station Technical Specification Limiting Condition for Operation (LCO) 3.7.4 requires only one of two atmospheric dump valves (ADV) per steam generator (SG) to be operable. Palo Verde Unit 3 currently has one ADV inoperable on the #2 SG. All other ADVs in Unit 3 (and all ADVs in Units 1 and 2) are OPERABLE. On July 26, 2006 at approximately 19:00 MST, Palo Verde Engineering personnel determined that this LCO is nonconservative since it does not satisfy the single failure criterion for the safety analyses for the accidents that would render one SG inoperable, specifically steam generator tube rupture (SGTR) with loss of offsite power (LOOP) which utilizes both ADVs on the unaffected SG. In case of one SG inoperable due to the event, and single failure of one ADV fail to open, the plant cannot be brought to safe shutdown condition during those accidents and may result in exceeding the acceptance criteria. This LCO should have required two ADVs per SG to be operable in order to satisfy safety analysis assumptions. An administrative control in accordance with NUREG-1432, Standard Technical Specifications will be put in place for immediate compensatory action. NUREG-1432 LCO 3.7.4 Condition A, one required ADV line inoperable requires restoration of the ADV line to OPERABLE status within 7 days. Reperformance of the safety analyses is expected to be the long term solution. 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 notified the NRC Resident Inspector.
The notification is being retracted due to further evaluation by engineering and licensing personnel which has determined that the license basis for Palo Verde Nuclear Generating Station is bounded by a steam generator tube rupture with a stuck open ADV coincident with a loss of offsite power event. The safety analysis for this event relies on one ADV on the unaffected SG which, along with the stuck open ADV on the affected SG, limits the offsite dose consequences to within 10 CFR Part 100 guidelines. The safety analysis referred to in the initial ENS notification utilizes 2 ADVs on the intact SG to limit radiological doses to 10 per cent of Part 100 guidelines. However, as noted above, this analysis is not the bounding safety analysis for the SG tube rupture event. The administrative control identified in the initial notification will remain in effect until engineering and licensing personnel determine if a Technical Specification change is required to support ADV single failure criteria. The Resident Inspector has been notified of this retraction. Notified the R4DO (Cain). | |
| ENS 42734 | 6 June 2006 01:44:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Emergency Diesel Generator Start | '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 report is being made under 50.73 (a)(2)(iv)(A). On June 5, 2006, at approximately 1844 Mountain Standard Time (MST), Palo Verde Nuclear Generating Station Unit 1 experienced an invalid 'A' train emergency diesel generator (EDG) start in the emergency mode. The EDG had been stopped at 1835 MST following completion of troubleshooting steps related to the balance of plant engineered safety features actuation system (BOP-ESFAS) sequencer. The start occurred as additional troubleshooting steps progressed. The related 4160 vac class 1E bus, PBA-S03, remained energized by off-site power during the event. The EDG started successfully and remained unloaded until it was stopped at 2014 MST. No other engineered safety feature (ESF) equipment in the 'A' train actuated. (a) The specific train(s) and svstem(s) that were actuated: Unit 1 'A' train EDG started in the emergency mode. (b) Whether each train actuation was complete or partial: Only EDG 'A' started as a single component and remained unloaded until it was stopped. No other ESF equipment actuated or was required. Essential spray pond pump 'A' was already running to provide EDG 'A' cooling water, from the previous EDG run. Bus PBA-S03 remained energized by off-site power throughout the duration of the event. (c) Whether or not the system started and functioned successfully: EDG 'A' started successfully and reached required speed, frequency, and voltage. Loading onto bus PBA-S03 was not required. Operations noted the EDG started with no anomalies. The exact cause of the invalid start was not known at the time of this report. The licensee notified the NRC Resident Inspector. | |
| ENS 42847 | 19 September 2006 08:05:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Pressurizer Heater Capacity Less than Tech Spec Limit | 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 September 19, 2006, at approximately 01:05 hours Mountain Standard Time (MST), Palo Verde Nuclear Generating Station (PVNGS) Unit 1 commenced a reactor shutdown required by Technical Specification 3.0.3. Limiting Condition for Operability (LCO) 3.0.3 requires the unit shall be placed in a Mode or other specified condition in which the LCO is not applicable when an LCO is not met and the associated ACTIONS are not met, an associated ACTION is not provided, or if directed by the associated ACTIONS. LCO 3.4.9 Pressurizer, requires two groups of pressurizer heaters OPERABLE with the capacity of each group > (greater than) 125 Kw and capable of being powered from an emergency power supply. TS LCO 3.0.3 and 3.4.9.B were entered at 22:35 hours an 09/18/06 when the Pressurizer Class Heaters were declared INOPERABLE. Engineering personnel with input from the heater manufacturer informed the Unit 1 SM (Shift Manager) and STA that reasonable assurance of OPERABILITY no longer exists. Prompt Operability Determination research to date concludes that the Heaters will not perform their design function for the specified mission time. The heaters were meggered and showed low resistance. There is no affect on Units 2 and 3. LCO 3.4.9.B is in affect for modes 1-3. The licensee intends to go to mode 3 and will evaluate continuing to mode 5. The licensee notified the NRC Resident Inspector. | |
| ENS 42886 | 7 October 2006 18:40:00 | 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Axial Indications Identified on Pressure Boundry | 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 October 7, 2006, at approximately 11:40 Mountain Standard Time (MST), Engineering personnel performing preplanned in-service examination of the reactor vessel head vent piping notified the Unit 2 Control Room that two axial indications had been discovered. The indications are located on the inner diameter surface of the pipe adjacent to the J-weld to the reactor head and are part of the Reactor Coolant System (RCS) pressure boundary. The indications are characterized as axial, estimated 0.020 to 0.030 inches deep, and approximately 0.2 inches long. The indications do not appear to be through wall and there is no evidence of RCS pressure boundary leakage. Technical Specifications (TS) Limiting Conditions for Operation (LCO) 3.4.14 permits no RCS pressure boundary leakage and there is no evidence of pressure boundary leakage. Nevertheless, the indications are being conservatively identified as abnormal degradation of the RCS pressure boundary and will necessitate taking corrective action to restore the barrier's capability. Therefore, the ENS notification of this event is in accordance with 10CFR50.72(b)(3)(ii)(A). Unit 2 is currently shutdown for its 13th refueling outage and is in Mode 6. No ESF actuations occurred and none were required. There were no structures, systems, or components that were inoperable at the time of discovery that contributed to this condition. There were no failures that rendered a train of a safety system inoperable and no failures of components with multiple functions were involved. The event did not result In the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. An investigation of this event will be conducted in accordance with the PVNGS corrective action program. The licensee notified the NRC Resident Inspector. | 05000529/LER-2006-005 |
| ENS 42920 | 19 October 2006 18:47:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Trip Following the Trip of Secondary Condensate Pumps | 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 October 19, 2006, at approximately 1147 Mountain Standard Time (MST) Palo Verde Unit 3 plant operators manually tripped the reactor from approximately 100% rated thermal power. The reactor was tripped when lowering hotwell levels caused two condensate pumps to trip. The preliminary cause for the lowering hotwell level was the hotwell draw-off valve spuriously failing open. Unit 3 was at normal temperature and pressure prior to the trip. All CEAs inserted fully into the reactor core. This was an uncomplicated reactor trip. No ESF actuations occurred and none were required. Safety related buses remained energized during and following the reactor trip. The offsite power grid is stable. No significant LCOs have been entered as a result of this event. There was no loss of normal heat removal capabilities, or loss of any safety functions associated with this event. No major equipment was inoperable prior to the event that contributed to the event. 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 Resident Inspector was informed of the Unit 3 reactor trip and this notification. The current decay heat removal path is auxiliary feedwater supplying water to the steam generators steaming to the condenser. Emergency Diesel Generators are available. | |
| ENS 42925 | 21 October 2006 22:48:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Automatic Reactor Trip Due to Control Element Assembly Position Transmitter Output Deviations | 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 October 21, 2006 at approximately 1549 MST Palo Verde Unit 1 experienced a reactor trip (RPS actuation) 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. Several minutes prior to the Reactor Trip, RSPT#1 (Reed Switch Position Transmitter) CEA deviation alarms were received for CEA#29 (Shutdown Group B CEA). Operators observed that the magnitude of the deviation was fluctuating erratically. While investigating the alarms CEAC #1 Sensor Fail alarms were received and at 1549 MST, the Reactor automatically tripped on a CPC generated Lo DNBR trips on all 4 channels of CPCs. The apparent cause is presently suspected to be a failure of RSPT#1. An investigation has commenced to determine the root cause of the reactor trip. All of the control rods fully inserted into the core. The Steam Bypass Control System operated as designed, 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. Electrical buses transferred to offsite power as designed. 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 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 NRC Resident was notified at 17:38 MST. | |
| ENS 42938 | 27 October 2006 06:53:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Loss of Power to the Unit 1 and Unit 3 Train B Safety Buses with Emergency Diesel Generator Actuation | 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 October 26, 2006, at approximately 23:53 Mountain Standard Time (MST) a valid actuation of the Palo Verde Nuclear Generating Station Unit 1 Train B Emergency Diesel Generator (EDG) and Unit 3 Train B EDG occurred as a result of undervoltage on their respective safety buses. Both EDGs started and loaded as designed. No Emergency Plan declaration was made and none was required. The loss of power to the two safety buses was the result of an apparent spurious protective relay actuation of Startup Transformer X01 output breakers to Unit 1 NAN-S06 and Unit 3 NAN-S06 busses. Unit 1 NAN-S06 bus was being supplied by its Alternate breaker (1ENANS06F) and Unit 3 NAN-S06 was being supplied by its Normal breaker (3ENANS06C). Prior to the event, maintenance personnel were restoring potential Transformer (PT) fuses at Unit 1 breaker 1ENANS06, Cubicle G. Preliminary information is that the two simultaneous LOP conditions occurred when the outer doors were closed on 1ENANS06, Cubicle G. This condition apparently caused the output breakers of Startup Transformer X01 to open. There was no electrical fault or damage to any electrical components. Both Units 1 and 3 entered Technical Specification LCO 3.8.1 Condition A for one (of two) required offsite circuits inoperable. (The licensee is) proceeding with restoration of Normal offsite power to each safety bus in Units 1 and 3. Once offsite power is restored, the LCOs will be exited and the Unit 1 and 3 train B EDGs will be returned to standby. Both Unit 1 and Unit 3 were at approximately 100% power, at normal operating temperature and pressure prior to and following the EDG actuations. Unit 2 was defueled and was not impacted by the electrical disturbance. No other ESF actuations occurred and none were required. No major equipment was inoperable prior to the event that contributed to the event. 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 licensee notified the NRC Resident Inspector. | |
| ENS 43140 | 3 February 2007 19:32:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Technical Specification 3.0.3 Entered During Routine Surveillance Testing of Control Element Assemblies (Cea'S) | On 2/3/2007 at approximately 12:32 MST, Palo Verde Control Room operators were performing a routine surveillance test. The purpose of this test is to demonstrate the operability of each full strength CEA not fully inserted in the core by verifying freedom of movement (trippability) by moving each individual full strength CEA that is not fully inserted in the core at least 5 inches (SR 3.1.5.3). While performing this test on Shutdown Group 'B', Subgroup 6, the 4 CEA's in the sub-group failed to withdraw after successfully inserting the CEA's the requisite 5 inches. The CEA's were inserted beyond the limit of 144.75" withdrawn as required per PVNGS TS LCO 3.1.6 to a position of 144" withdrawn. It was determined that this was not an analyzed condition. On 2/3/2007 at 13:15 MST, the Control Room staff identified the unanalyzed condition and PVNGS Unit 2 entered TS 3.0.3. It was determined that the unanalyzed condition had existed since 12:32 MST. On 2/3/2007 at 16:16 MST, following corrective maintenance to replace a phase sequence card, the 4 CEA's were recovered above the TS 3.1.6 insertion limit of 144.75", and Unit 2 exited LCO 3.0.3. The event did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. The required offsite power sources are operable and the electrical grid is stable. The NRC resident inspector has been notified of this event. | 05000529/LER-2007-002 |
| ENS 43173 | 19 February 2007 21:57:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Unit 2 Performed a Ts Required Shutdown | 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 02/19/2007 at approximately 14:57 hours Mountain Standard Time (MST), Palo Verde Nuclear Generating Station (PVNGS) Unit 2 initiated a plant shutdown as required by Condition 'C' of Technical Specification (TS) LCO 3.5.3 to be in Mode 3 with Pressurizer pressure < 1837 psia and Reactor Coolant System (RCS) Tc < 485 degrees F. Limiting Condition for Operability (LCO) 3.5.3 requires that two ECCS trains be Operable. High Pressure Safety Injection Pump (HPSI) 2A was declared inoperable on 02/16/2007 at 13:01 MST and was not restored to Operable status within the TS 72 hour Completion Time due to pump bearing oil leakage exceeding the allowable leakage limit. Efforts are in progress to correct the oil leakage issue. The event did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. The observed pump bearing oil leakage is approximately 3 drops/hr. Unit 2 completed a normal reactor shutdown with a manual reactor trip at 20% power. All rods fully inserted. Decay heat is currently being removed via the Main Condenser. The licensee informed the NRC Resident Inspector. | 05000529/LER-2007-001 |
| ENS 43697 | 6 October 2007 17:59:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Trip Due to Condenser Tube Rupture | 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 October 6, 2007, at approximately 10:59 Mountain Standard Time (MST) Palo Verde Unit 2 plant operators manually tripped the reactor from approximately 100% rated thermal power. The reactor was tripped when sodium levels in both steam generators reached trip criteria following a condenser tube rupture. Unit 2 was at normal temperature and pressure prior to the trip. All CEAs inserted fully into the reactor core. This was an uncomplicated reactor trip. No ESF actuations occurred and none were required. Safety related buses remained energized during and following the reactor trip. The offsite power grid is stable. No significant LCOs have been entered as a result of this event. There was no loss of normal heat removal capabilities, or loss of any safety functions associated with this event. No major equipment was inoperable prior to the event that contributed to the event. " No PORVs or MSSVs lifted. Decay heat is being removed with Auxiliary Feedwater feeding the steam generators steaming to the condenser. There are no primary to secondary tube leaks in the steam generators. Emergency buses are powered by offsite power with Emergency Diesel Generators in standby. 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 2 reactor trip and this notification. | |
| ENS 43736 | 22 October 2007 10:11:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Shutdown Due to Inoperable Steam Driven Auxiliary Feedwater Pump | The following report 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 Monday October 22, 2007, at 0311 Mountain Standard Time (MST) Palo Verde Nuclear Station Unit 1 initiated a normal reactor shutdown to comply with condition C of Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.7.5. At 0504 MST Mode 3 was entered. LCO 3.7.5 requires that three auxiliary feedwater (AF) pumps be operable in Modes 1, 2, and 3. The shutdown was necessary due to an inoperable steam supply for the essential steam driven AF pump turbine. The steam supply had been declared inoperable on October 15, 2007, at 0904 MST and will not be restored to operable status within the TS required 7 day completion time. Efforts are in progress to correct the condition. The event did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. The licensee notified the NRC Resident Inspector. | 05000528/LER-2007-006 |
| ENS 43764 | 2 November 2007 14:44:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Suspicious Explosive Device Discovered in Vehicle at Oca Access Checkpoint | On November 2, 2007 at 0744 (MST), Palo Verde Nuclear Generating Station Units 1, 2 and 3 declared a Notification of an Unusual Event as specified in the Emergency Plan. The basis for the Emergency Class declaration was detection of a credible threat: an explosive device was detected during a vehicle search at the site access check point. The site has entered its Deliberate Acts procedure. The device was discovered in a contract employee's vehicle at 0525 MST. It was confirmed to be an explosive device at 0730 MST by the Maricopa County Sheriff's Office (MCSO). The explosive device was removed from the site by MCSO and Federal Bureau of Investigation (FBI) at 0852. The individual driving the vehicle has been detained by MCSO. No other individuals were in the vehicle at the time. Palo Verde Unit 1 is in Mode 2 at approximately 2% power. Unit 2 is in Mode 1 at 100% power. Unit 3 is defueled undergoing steam generator replacement. No reactor protection system or engineered safety feature system actuations have occurred and none are required. No major structures, systems, or components are inoperable impacting the continued safe operation of the units. Plans are to continue Mode 2 operations in Unit 1 and Mode 1 full power operation in Unit 2. Further investigation is ongoing in cooperation with MCSO and the FBI. Security is conducting searches of the site. No additional concerns have been identified at this time. The security event has not resulted 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 the security event declaration. A news release was made at 11:10 a.m. The licensee notified the NRC Resident Inspector.
At 1447 MST site security posture has changed from Code Red to Code Yellow Heightened Awareness, and at 1504 MST licensee exited the Unusual Event,. The licensee has notified the NRC Resident Inspector, state and local agencies, and will be issuing a press release this evening. Notifications were given to the following: R4 (Art Howell), R4DO(Powers), NRR EO (Bateman), IRD Manager (Blount), ILTAB (Sandler), DHS (York), FEMA (Dunker), DOE (Wyatt), FBI-SIOC (Curry), HHS (White), USDA (Phillip).
The licensee downgraded the security posture at the site from Code Yellow Heightened Awareness to Code Yellow. The licensee notified the NRC Resident Inspector. Notified R4DO (Powers) and ILTAB (Sandler).
Arizona Public Service Company (APS) is retracting security-related Event Notification #43764 and notification of unusual event (NUE) reported on November 2, 2007. Based upon investigations performed by the Federal Bureau of Investigation (FBI), Maricopa County Sheriff's Office (MCSO) and Palo Verde Security department, APS has determined that there was no explicit nor credible threatened action as described in 10 CFR 73.71, Appendix G, Paragraph I. These investigations revealed that the previously reported explosive device was placed in the owner's truck bed without his knowledge. Therefore, there is no reason to believe that a person has committed or caused, or attempted to commit or cause, or has made a credible threat to commit or cause: theft or unlawful diversion of special nuclear material; or significant physical damage to a power reactor; or interruption of normal operation of a licensed nuclear power reactor. The licensee notified the NRC Resident Inspector. R4DO (Farnholtz) has been notified and an e-mail sent to ILTAB and the 73.71 group. | |
| ENS 43804 | 24 November 2007 05:26:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Technical Specification Required Plant Shutdown Due to Inoperable Load Sequencer | 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 Friday, November 23, 2007, at 22:26 Mountain Standard Time (MST) Palo Verde Nuclear Station Unit 1 initiated a normal reactor shutdown to comply with Condition H of Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.8.1. TS LCO 3.8.1 requires that automatic load sequencers for train A and B be operable in Modes 1, 2, 3 and 4. The shutdown is necessary due to an inoperable automatic load sequencer for train A in Unit 1. The train A automatic load sequencer was declared inoperable on November 22, 2007, at 19:30 MST and was not restored to operable status within the TS required 24 hour completion time of Condition F of TS 3.8.1. TS 3.8.1 Condition H requires the plant to be placed in MODE 3 within 6 hours and MODE 5 within 36 hours if the required actions and associated completion time of TS Condition F are not met. Efforts are in progress to correct the condition. The event did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. The licensee is taking measures to evaluating the extent of this condition from the remaining automatic load sequencers for Units 1, 2 and 3. The inoperability was discovered due to an invalid actuation of the A train load sequencer that resulted in a pond spray pump initiation. The licensee notified the NRC Resident Inspector. | 05000528/LER-2007-007 |
| ENS 43824 | 4 December 2007 14:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness 10 CFR 50.72(b)(3)(xii), Transport of a Contaminated Person Offsite | Offsite Notification Due to Potential Loss of Three Sirens | 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 December 04, 2007 at approximately 07:00 Mountain Standard Time (MST), the Palo Verde Emergency Preparedness Department discovered sirens 17, 18 and 23 out of service. Siren #23 was restored to service at 09:34 and siren 18 was restored to service at 10:32. Siren 17 remains out of service and is estimated to impact approximately 206 members of population in the emergency planning zone (EPZ) within 5 miles. Palo Verde's reporting criterion is a loss of capability to inform greater than 5% of the population within 5 miles. This call is being placed due to the relatively large segment of the population affected (10 CFR 50.72(b)(3)(xiii)). During an event, the Palo Verde Emergency Plan has a contingency for dispatching Maricopa County Sheriff's Office (MCSO) vehicles with loud speakers to alert persons within the affected areas when sirens are inoperable. In order to activate this contingency, Maricopa County Department of Emergency Management was notified of the failed siren at 12:58 (10 CFR 50.72(b)(2)(xi)). There are no events in progress that require siren operation. The NRC Resident Inspector has been notified of the siren 17 being out of service and this ENS call. The utility received a pulse check report at 0700 this morning which indicated that three sirens failed the initial pulse check. After the second pulse check, two of the three sirens responded correctly. However, the third siren (No. 17) remained OSS, and the licensee has dispatched a crew to repair it. | |
| ENS 43867 | 26 December 2007 22:22:00 | Information Only | Minor Fire on Cooling Tower Fan Shroud | On Wednesday, December 26, 2007, at approximately 15:22 MST, a fire occurred in a fan shroud for Palo Verde Nuclear Generation Station Unit 3 cooling tower number 3. The fire was knocked down by the on site fire department using the fire truck water cannon. Smoldering continued between fan shroud segments. Offsite assistance was requested in the event a pumper truck was needed due to the elevation of the cooling tower fan area. While the pumper truck was not needed, offsite personnel did assist in getting a fire hose to the top of the cooling tower. No press release is planned, but media attention has already been observed in response to media monitoring communications on local police/fire scanners. Palo Verde Unit 3 is shutdown and in Mode 5 in its thirteenth refueling outage. The cause of the fire is under investigation. Maintenance activities were in progress on the cooling tower at the time of the fire. The fire was completely extinguished at 16:45 hours and no emergency plan classification was declared or required as a result of the fire. The cooling towers are located on the owner control area outside of the protected area. The NRC Resident Inspector has been notified of the event and this ENS informational notification. | |
| ENS 43876 | 31 December 2007 15:40:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Death of an Employee Outside the Protected Area | 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 06:40 MST on December 31, 2007, at the water reclamation facility for the Palo Verde Nuclear Generating Station, an employee died. The death was not related to activities impacting or related to the safety of the public or other onsite personnel. Specifically, an individual collapsed and was promptly examined by a Palo Verde Emergency Medical Technician (EMT). An air evacuation was ordered however, prior to air evacuation the individual expired. The death does not appear to be work-related nor the result of an accident. The individual was outside of the Radiological Controlled Area and no radioactive material or contamination was involved. Palo Verde has not observed any heightened public or media concern as a result of the death. Since the death is apparently unrelated to Palo Verde's industrial or radiological health and safety, no news release is planned. The individual's name has not yet been released, pending notification of next-of-kin. The Arizona Division of Occupational Safety and Health was notified of the death at 0840 MST. The Maricopa County Sheriff's Office is conducting a routine investigation into the death." The licensee notified the NRC Resident Inspector. | |
| ENS 44127 | 8 April 2008 18:00:00 | 10 CFR 26.73 | Fitness for Duty - Non-Licensed Supervisor | At approximately 1100 Mountain Standard Time on April 8, 2008 at the Palo Verde Nuclear Generating Station, a non-licensed supervisor tested positive for alcohol during a random 'Fitness for Duty' test. The person's access authorization has been placed on hold in accordance with station procedures. This event is being reported pursuant to 10 CFR 26.73(a)(2)(ii). The NRC resident inspector has been notified of the event. | |
| ENS 44246 | 29 May 2008 04:34:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Trip Due to Improper Movement of Cea'S | 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 May 28, 2008, at approximately 2134 Mountain Standard Time (MST) Palo Verde Unit 2 operators manually tripped the reactor, as directed by procedures, when four Control Element Assembly (CEAs 7, 9, 11 &13) of shutdown bank A slipped to the fully inserted position while conducting low power physics testing following Unit 2's fourteenth refueling outage. Unit 2 was critical (Intermediate Range 5.0E-2)and at normal operating temperature and pressure prior to the trip. Following the manual reactor trip all remaining CEAs inserted fully into the reactor core. This was an uncomplicated reactor trip. No emergency classification was required per the Emergency Plan. No automatic ESF actuations occurred and none were required. 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. No LCOs have been entered as a result of this event. No major equipment was inoperable prior to the event that contributed to the event. Unit 2 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 or the health and safety of the public. The cause of the slipped CEAs is not known at this time and is under investigation. The Senior Resident Inspector was informed of the Unit 2 reactor trip. | |
| ENS 44274 | 6 June 2008 06:56:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Tech Spec Required Shutdown Due to Leak in Safety Injection Tank Vent Line | On Thursday June 5, 2008 at 2356 MST Palo Verde Nuclear Station Unit 1 initiated a normal reactor shutdown to comply with condition C of Technical Specification (TS) LCO 3.5.1 and to facilitate a weld repair on a nitrogen leak found on the Safety Injection Tank (SIT) 1A vent line. LCO 3.5.1 requires that all four SITs be operable in Modes 1 and 2. On June 5, 2008, at 0225 hours MST, Unit 1 entered Condition B which provides allowance for one SIT to be inoperable for a 24 hour period. The SIT will not be restored to operable status within the TS required 24 hour period, therefore, Condition C will be applicable at 0225 MST on June 6 2008. Condition C requires shutdown to Mode 3 in six hours and to reduce pressurizer pressure to less than 1837 psia within 12 hours. On June 06 at 0148 hours MST, Unit 1 was manually tripped from approximately 20% power. The shutdown did not result in a release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. The primary plant is being stabilized in Mode 3 in forced circulation with both steam generators used for heat removal. Unit 1 is stable at normal operating temperature and pressure in Mode 3. S/G's are being feed via main feed. All other safety related systems are operable. Decay heat is via SBC system to the condenser. There is no impact on the other units. The licensee notified the NRC Resident Inspector. | 05000528/LER-2008-003 |
| ENS 44401 | 8 August 2008 22:20:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification to Maricopa County Environmental Services | Arizona Public Service Co. made an offsite notification to Maricopa County Environmental Services at 1520 MST on 8/8/08 to report a loss of power to the Palo Verde Nuclear Generating Station drinking water supply pumps. The pumps were out of service on 8/8/08 between the hours of 0532 and 0620 MST. Full service has been restored. The licensee notified the NRC Resident Inspector. | |
| ENS 44496 | 16 September 2008 21:00:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Trip During Troubleshooting of Control Rod Drive Mechanism Motor Generators | 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 September 16, 2008 at approximately 1400 hours Mountain Standard Time (MST) Palo Verde Nuclear Station Unit 3 experienced a manual reactor trip. At the time of the trip trouble shooting efforts were in progress to investigate abnormalities with the control element drive mechanism (CEDM) motor generators (MG). The MGs (2 - 100% each) normally operate in parallel to supply the necessary power to grip, move and hold the control element assemblies (CEA). During the trouble shooting activities the 'B' MG was removed from service. The 'A' MG initially provided power to the CEDMs but did not maintain the power. As a result of the pre-job briefing contingency actions, a manual reactor trip was ordered. All CEAs fully inserted into the core. No other emergency actuation signals were initiated and none were required. Off site power provided power to the class buses during and after the event. Decay heat removal is being provided by the steam bypass control system to the main condenser. No major equipment was inoperable prior to the event that contributed to the event. The unit is in Mode 3, Hot Standby, at normal temperature and pressure. The cause of the MG abnormality is under investigation. Normal feedwater remained in service providing water to the steam generators. The licensee notified the NRC Resident Inspector. | 05000530/LER-2008-001 |
| ENS 44525 | 28 September 2008 04:51:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Unit 3 Reactor Manually Tripped Following Automatic Turbine Trip on High Vibration | 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 under the reporting requirements of 10CFR50.73. On September 27, 2008, at approximately 21:51 Mountain Standard Time (MST) Palo Verde Unit 3 operators manually tripped the reactor from approximately 34% rated thermal power in response to an automatic trip of the main turbine. The unit was being shutdown from 100% power due to a chemistry excursion in the secondary plant. Following the manual reactor trip all CEAs fully inserted into the reactor core. This was an uncomplicated reactor trip. No emergency classification was required per the Emergency Plan. No automatic ESF actuations occurred and none were required. 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. No LCOs have been entered as a result of this event. No major equipment was inoperable prior to the event that contributed to the event. Unit 3 is stable at normal operating temperature and pressure in Mode 3. Decay heat removal is via the Steam Generators and Main Feedwater to the Main Condenser using the Steam Bypass Control 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 event did not adversely affect the safe operation of the plant or the health and safety of the public. The main turbine tripped on high vibration. The Senior Resident Inspector was informed of the Unit 3 reactor trip. | 05000530/LER-2008-002 |
| ENS 44606 | 28 October 2008 16:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Maintenance on Public Prompt Notification System Emergency Sirens | The following event description is based on information currently available. If through subsequent reviews of the event, additional information is identified that is pertinent to this event or alters the information being provided at the time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73. From October 28, 2008 until October 31, 2008, Palo Verde personnel will be performing maintenance on public prompt notification system sirens. One siren at a time will be removed from service, and will be restored prior to continuing to the next siren. Siren #42 provides notification to approximately 558 members of the public within 5 miles of Palo Verde. Siren #44 provides notification to approximately 210 members of the public within 5 miles of Palo Verde. Siren #25 provides notification to approximately 302 members of the public within 5 miles of Palo Verde. Siren #23 provides notification to approximately 498 members of the public within 5 miles of Palo Verde. Siren #22 provides notification to approximately 855 members of the public within 5 miles of Palo Verde. Siren #18 provides notification to approximately 396 members of the public within 5 miles of Palo Verde Siren #17 provides notification to approximately 1106 members of the public within 5 miles of Palo Verde. Siren #36 provides notification to approximately 301 members of the public within 5 miles of Palo Verde. Siren #15 provides notification to approximately 940 members of the public within 5 to 10 miles of Palo Verde. Each of these are considered by Palo Verde to be a 'large segment of the population.' The Palo Verde Emergency Plan has a contingency for dispatching Maricopa County Sheriff's Office (MCSO) vehicles, during an actual event, with loud speakers to alert persons within the affected area when sirens are inoperable. There are no events in progress that require siren operation. A follow-up call will be placed when the affected sirens are returned to service. The NRC Resident Inspector has been notified of the siren maintenance and this ENS call. These sirens are utility owned.
The following information was received as an update to this report: This is an update of ENS call # 44606. At this time, maintenance on the Palo Verde public prompt notification for sirens identified in ENS #44606, has been completed, siren testing was successful and the sirens are operable and in service at this time. The NRC Resident Inspector has been notified of the siren maintenance and this ENS call. Notified R4DO (Spitzberg). | |
| ENS 44692 | 2 December 2008 23:20:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of One (1) Emergency Siren | 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 December 2, 2008, at approximately 1620 Mountain Standard Time (MST), the Palo Verde Emergency Planning Department discovered that public warning system siren No. 17 was not responding, and therefore, is out of service. The loss of siren No. 17 could potentially impact a population of approximately 1106 people in the 5-mile emergency planning zone (EPZ). Since the loss of siren No. 17 could impair Arizona Public Service Company's ability to inform greater than 5% of the population within the EPZ, this notification is being made in accordance with 10 CFR 50.72(b)(3)(xiii). If an event occurs while siren No. 17 is out of service, the Palo Verde Emergency Plan has a contingency for dispatching Maricopa County Sheriff's Office (MCSO) vehicles with loud speakers to alert persons within the affected area. The MCSO is prepared to implement this contingency should it become necessary. Troubleshooting to determine the cause of the failure will start tomorrow morning (December 3, 2008). The NRC Resident Inspector has been notified of siren No. 17 being out of service and this ENS call.
Siren 17 was returned to service on Wednesday, December 3, 2008, at 0829 MST. Notified R4DO (Proulx). | |
| ENS 44846 | 11 February 2009 20:18:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Possibly Inadequate Backup Nitrogen Supply for Atmospheric Dump Operation | 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 of under the reporting requirements of 10 CFR 50.73. Palo Verde Nuclear Station declared all three Unit's atmospheric dump valves (ADV) inoperable at 1318 MST. The reason for the inoperability is the discovery by engineering personnel that the ADV backup nitrogen capacity, required to operate the valves to mitigate certain accident scenarios, was not adequate. There are 4 ADVs (one on each steam line with two steam lines per steam generator) for each of the three units. Engineering review of a loss of offsite power event determined that the current nitrogen supply of 13.3 hours will not be adequate to get the plant to shutdown cooling entry conditions during a natural circulation asymmetric cooldown (i.e. Feedwater Line Break, Main Steam Line Break, and Steam Generator Tube Rupture). Actions are in progress to restore the operability of the ADVs. If unsuccessful, all three units will be required by the Technical Specifications to be in Mode 3, Hot Shutdown, by 1918 MST on February 12, 2009. The licensee notified the NRC Resident Inspector. * * * RETRACTION FROM RAY BUZARD TO PETE SNYDER AT 1840 ON 2/12/09 * * * This is a retraction of the condition reported in EN # 44846 on February 11, 2009 at 19:31 EST. Upon further review of the condition, engineering personnel have determined that the ADV nitrogen supply was adequate to mitigate the consequences of the postulated events and the ADVs were declared operable at 04:30 MST on February 12, 2009. Therefore, no reportable condition existed. The licensee notified the NRC Resident Inspector. Notified R4DO (Miller). | |
| ENS 44865 | 19 February 2009 18:20:00 | 10 CFR 50.72(b)(3)(xii), Transport of a Contaminated Person Offsite | Injured Worker Transported to Offsite Medical Facility | 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 19, 2009, at approximately 11:20 Mountain Standard Time (MST), an employee of Arizona Public Service (APS) was injured while working at the Palo Verde Independent Spent Fuel Storage Installation (ISFSI) which is considered to be a radiologically controlled area (RCA). The ISFSI is located within the owner controlled area but outside the plant's protected area. The ISFSI has been evaluated as having a very low probability for contamination, so administrative controls are used to allow workers access into the ISFSI and return to the appropriate Unit RCA egress point located in the protected area where personnel monitoring for contamination is performed prior to leaving the site. Upon exiting the ISFSI area, the individual was initially transported to the Palo Verde Medical Clinic to attend to the injury. Subsequently, the individual was transported to an offsite medical facility for further evaluation. The individual was not monitored for contamination prior to being transported offsite. The individual and the transporting vehicle were frisked offsite and found to be free of contamination. There were no exposures from licensed material and no consequence to the public or environment." Injured person was an employee of licensee. Employee was transported to the hospital via private owned vehicle. The NRC Resident Inspector was notified. | |
| ENS 44924 | 21 March 2009 16:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Various Control Room Annunciators and Alarms Out of Service Due to Maintenance on Power Supply | 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 21, 2009, from approximately 09:00 Mountain Standard Time (MST) until 14:00 MST, Palo Verde maintenance personnel will be performing scheduled maintenance to repair one of two redundant 120 VAC power supplies in Unit 2 that provides power to various alarms in the main control room. This work will require both power supplies to be de-energized resulting in approximately 50 percent of the Unit 2 plant annunciators being unavailable. The following compensatory measures will be in place for the duration of the scheduled work: Other assessment indications will remain available:
Plant Monitoring System
Qualified Safety Parameter Display System
Emergency Response Facility Data Acquisition System
No changes in plant power or operating mode are planned.
A third licensed operator will be in the control room.
The NRC Resident Inspector has been notified of the scheduled outage and this ENS call.
The power supply was successfully repaired and all annunciators were restored to normal as of 1515 MST. The Licensee will notify the NRC Resident Inspector. Notified R4DO (Hay) and NRR EO (Holian). | |
| ENS 44970 | 4 April 2009 06:54:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Scram Due to High Vibrations in the Turbine | 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 April 3, 2009, at approximately 2345 Mountain Standard Time (MST), Palo Verde Unit 3 operators manually tripped the reactor from approximately 29% rated thermal power in response to increasing vibration on the main turbine. The unit was being shutdown from 100% power for a refueling outage at the time of the trip. Following the manual reactor trip, all CEAs fully inserted into the reactor core. This was an uncomplicated reactor trip. No emergency classification was required per the Emergency Plan. No automatic ESF actuations occurred and none were required. 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. No LCOs have been entered as a result of this event. No major equipment was inoperable prior to the event that contributed to the event. No relief or safety valves lifted during the event. Decay heat is being removed via the steam dump to condenser valves. The licensee will continue to cool the plant down to support their planned refueling outage. There was no effect on Unit 1 or Unit 2. The licensee has notified the NRC Resident Inspector.
This notification is being made to retract Event Notification (EN 44970) made by Arizona Public Service Company (APS) on April 4, 2009, that reported a reactor protection system actuation in Unit 3 during a planned shutdown for a refueling outage. Further review of the reporting guidance in NUREG 1022 (revision 2) has concluded that since the manual trip was not initiated to mitigate an event and the decision to trip the reactor was at the discretion of the licensed operators the reporting threshold was not met. The procedure for a normal reactor shutdown directs that a manual reactor trip be initiated at approximately 20% rated thermal power. Due to prior issues with vibration of the main turbine monoblock rotor during power reductions related to plant shutdown, just-in-time training was provided to the plant operators which included action to trip the reactor if main turbine bearing vibration increased. Without the pre-determined discretion provided through the just-in-time training, the main turbine alone could have been tripped, followed by lowering reactor power to 20%, and then tripping the reactor. The plant design does not include an automatic reactor trip when the main turbine is tripped. Event Summary: On April 3, 2009, at approximately 23:45 Mountain Standard Time (MST) Palo Verde Unit 3 operators manually tripped the reactor from approximately 29% rated thermal power in response to increasing vibration on the main turbine. The unit was being shutdown from 100% power for a refueling outage at the time of the trip. Following the manual reactor trip all CEAs fully inserted into the reactor core. This was an uncomplicated reactor trip. No emergency classification was required per the Emergency Plan. No automatic ESF actuations occurred and none were required. 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. No LCOs have been entered as a result of this event. No major equipment was inoperable prior to the event that contributed to the event. NRC Resident Inspector has been notified. Notified R4DO (William Jones) | |
| ENS 45305 | 27 August 2009 16:20:00 | 10 CFR 26.719, FFD Reporting requirements | Confirmed Positive Fitness for Duty Test by Non-Licensed Supervisor | A non-licensed employee supervisor had a confirmed positive for illegal drugs during a random fitness for duty test. The employee's access to the plant has been terminated. Contact the Headquarters Operations Officer for additional details. | |
| ENS 45425 | 11 October 2009 11:50:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Reactor Water Level Indication Inoperable | 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. On 10/11/2009 at 0450 MST Palo Verde Nuclear Station Unit 1 declared both trains of the Qualified Safety Parameter Display (QSPDS) inoperable due to the discovery that an installed temporary modification (TMOD) impacted the reactor vessel level indication parameter in a non-conservative manner. The modification jumpered failed heater junction thermal connections (HJTC) at the heated and unheated HJTC points. Unit 1 has two failed detectors with TMODs installed. During a design event where these detectors would be needed, these detectors will not alarm at the correct vessel levels. The emergency operating procedures use this indication and pressurizer level indications (which are unaffected by this condition) to throttle safety injection flow during certain accidents. With the TMOD providing incorrect indication the operators could throttle flow when full flow should be maintained. In addition the QSPDS reactor level indication is used in the Emergency Plan to classify emergencies. The standard Appendix 101 to Palo Verde emergency procedures provides guidance for an alternate method for determining reactor vessel level when RVLMS (Reactor Vessel Level Monitoring System) is out of service. This alternate method determines level by manually determining sub-cooled, saturation or superheated conditions based upon input of reactor vessel pressure and the "raw" QSPDS - RVLMS thermocouple temperature indications. This compensatory measure ensures that classification of events can continue to be completed in a timely manner. Unit 1 has entered the LCO (Limiting Condition of Operation) required action for this condition which requires at least one channel be restored to operable status within 7 days. Unit 2 is in a refueling and is not impacted at this time. Unit 3 does not have the TMOD installed. According to the licensee Train A TMOD which was installed 2/3/08 and the train B TMOD which was installed 12/12/08. The licensee checked the installation of these TMODs after reviewing operating experience reports from Calvert Cliffs. The licensee has notified the NRC Resident Inspector.
On 10/11/2009 at 12:26 MST Palo Verde Nuclear Station Unit 1 reported the inoperability of both trains of the Qualified Safety Parameter Display System (QSPDS) due to the discovery that an installed temporary modification impacted the reactor vessel water level indication parameter in a non-conservative manner. After further Operations and Engineering review it was concluded that the modification, installed due to one inoperable heated junction thermal couple (HJTC) in each train, does not result in the inoperability of either train of QSPDS since the Technical Specification required number of heated junction thermal couples (HJTC) (two each in the upper and lower level indication) remain operable with the temporary modification installed. In addition, the Control Room operators would understand the QSPDS indication and would correctly control the plant per the emergency operating procedures using this indication along with pressurizer level indication to throttle safety injection flow during certain accidents. The QSPDS reactor level indication is also used in the Emergency Plan to classify emergencies and the modification would not impact this function. Unit 1 has exited the LCO Condition for two inoperable QSPDS reactor vessel water level instrument channels. The licensee has notified the NRC Resident Inspector. R4DO (Okeefe) notified. | |
| ENS 45448 | 20 October 2009 14:10:00 | 10 CFR 26.719, FFD Reporting requirements | Random Fitness for Duty Failure | A non-licensed contract supervisor had a confirmed positive for illegal drugs during a random fitness-for-duty test. The employees access to the plant has been terminated. Contact the Headquarters Operations Officer for additional details. The licensee has notified the NRC Resident Inspector. | |
| ENS 45537 | 3 December 2009 11:30:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Trip After Loss of Instrument Air to Containment | On December 3, 2009 at approximately 04:30 Mountain Standard Time (MST) Palo Verde Unit 3 operators manually tripped the reactor from approximately 100% rated thermal power due to loss of Instrument Air (IA) to Containment. This loss was apparently caused by a failure (closed) of the outboard IA Containment Isolation Valve (CIV) solenoid valve. Loss of IA to Containment resulted in closure of the inboard Reactor Coolant Pump (RCP) controlled seal bleedoff CIV. The RCP seal bleedoff was then being diverted via relief valve to the Reactor Drain Tank (RDT) inside Containment. Following the manual reactor trip all CEAs (Control Element Assemblies) fully inserted into the reactor core. All 4 RCPs were stopped to allow for isolation of bleedoff to the RDT. Upon completion of Standard Post Trip Actions, the crew entered the Optimal Recovery Procedure for Loss of Forced Circulation. No emergency classification was required per the Emergency Plan. No automatic ESF actuations occurred and none were required. 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. LCO 3.6.3 was entered due to failure of the IA CIV. No major equipment was inoperable prior to the event which contributed to the need for manual reactor trip. The reactor was manually tripped for equipment preservation. No safety or relief valves lifted other than noted above. After the trip, decay heat was being removed using the turbine bypass valves and steam generator level was being maintained with the auxiliary feedwater pumps. The licensee also entered LCO 3.4.5, "RCS Loop Operability" because the RCPs were stopped. The licensee notified the NRC Resident Inspector. | 05000530/LER-2009-001 |
| ENS 45575 | 16 December 2009 13:11:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty - Non-Licensed Supervisor | A non-licensed supervisor had a confirmed positive for alcohol during a "for cause" fitness-for-duty test. The employee's access to the plant has been terminated. Contact the Headquarters Operations Officer for additional details. The licensee notified the NRC Resident Inspector. | |
| ENS 45576 | 16 December 2009 17:39:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty - Licensed Operator | A licensed operator supervisor had a confirmed positive for alcohol during a "for cause" test. The employee's access to the plant has been terminated. Contact the Headquarters Operations Officer for additional details. The licensee notified the NRC Resident Inspector.
The licensed operator was not a supervisor. Notified the R4DO (Whitten) via e-mail. | |
| ENS 45748 | 7 March 2010 18:24:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Notification of Unusual Event Due to Electrical Fault Causing Damage to Equipment | 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.
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). | 05000528/LER-2010-001 |
| ENS 45783 | 22 March 2010 20:39:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty Report - Contract Supervisor | A contract supervisor had a confirmed positive for drugs as a result of a pre-access fitness for duty test. The individual's access to the plant has been terminated. Contact the Headquarters Operations Officer for additional details. The licensee notified the NRC Resident Inspector. | |
| ENS 45784 | 23 March 2010 01:11:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Notification of Unusual Event Due to Unidentified Leakage Greater than 10 Gpm | 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 requirement of 10CFR50.73. On March 22, 2010 at approximately 1756 MST, Palo Verde Nuclear Generating Station (PVNGS) Unit 1 identified a rising level and temperature trend in the Reactor Drain Tank (RDT). PVNGS Unit 1 was in Mode 1 (Power Operation) at 93% power with normal RCS temperature and pressure at the time of discovery. Containment temperature and humidity trends are normal. Technical Specification Limiting Condition for Operation 3.4.14 (RCS Operational Leakage), Condition 'A' was entered at 1811 due to unidentified leakage >10 gpm and the LCO allows 4 hours to restore leakage to <1 gpm. Also at 1811, a Notification of Unusual Event (NOUE) was declared due to unidentified leakage >10 gpm (MU5.1). PVNGS Unit 1 remains at power with all normal systems in operation; periodic pumping of the RDT is occurring. No automatic or manual reactor protection system or engineered safety features actuations occurred and none were required. There were no other component failures, testing or work in progress that contributed to the leak. The leak is located within the containment building, therefore there is no release of radioactivity to the environment and no impact to the health and safety of the public. There is no elevated RCS activity and heat removal is via normal steaming to the main turbine condenser. The electric grid is stable. Current plans are to enter containment and identify the source of leakage. State and Local authorities have been notified. The NRC Senior Resident Inspector has been notified. The licensee notified the following state and local agencies: Maricopa County Sheriff, Arizona Department of Public Safety, Buckeye Police Department, Arizona Radiation Regulatory Agency, Arizona Division of Emergency Management, and the Maricopa County Emergency Management Agency.
At 2112 MST, the shift manager advised that the Pressurizer Main Spray Valve, 100E, packing leakage has been manually isolated. As of 2125 MST, the level trend in the RDT has stabilized. The licensee is working to verify the leakage rate, and remains in an Unusual Event. The plant remains stable in Mode 1 at 93% power. The licensee has notified the NRC Resident Inspector, and the NRC Resident Inspector remains on site.
At 2146 MST, the licensee exited Technical Specification Limiting Condition for Operation 3.4.14, RCS Operational Leakage. At 2219 MST, the Unusual Event was terminated. The licensee will notify the NRC Resident Inspector. Notified R4DO (Deese), NRR EO (Brown), IRD (McDermott), DHS (Moore), and FEMA (Canupp). | |
| ENS 45811 | 4 April 2010 22:42:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared Due to an Earthquake | 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.
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). | |
| ENS 45823 | 8 April 2010 17:15:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Earthquake | 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 reporting requirements of 10 CFR 50.73. An Event Classification of Unusual Event (HU1.1) was declared at 10:15 MST for the Palo Verde Nuclear Generating Station because of an earthquake that originated in Baja California location 32.220 N, 115.276 W at 09:44 MST. Per the USGS website and via phone conversation at 10:03, the magnitude of the earthquake was preliminarily 5.5 on the Richter scale. Initial walk downs 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 6 for a scheduled refueling outage and Units 2 & 3 are at 100 percent power with all offsite power supplies available. Seismic Monitoring Instrumentation system is currently functional and did not indicate a seismic event. Currently based on the Modified Mercalli scale the seismic event was below the magnitude of the 0.10g spectra Operating Basis Earthquake (OBE) and the 0.20g spectra Safe Shutdown Earthquake (SSE). The licensee notified the NRC Resident Inspector. * * * UPDATE FROM JIM BLAZEK TO PETE SNYDER AT 1606 ON 4/8/10 * * * Emergency classification termination was declared at 4/08/10, 12:54 MST. All required power block inspections were completed with no deficiencies noted. No other conditions required 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 NRC Resident Inspector has been notified of NUE termination. Notified R4DO (Proulx), NRR EO (Thorp), DPR (McDermott), DHS (McDonald), and FEMA (Hollis). | |
| ENS 45968 | 1 June 2010 14:15:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Public Warning System Siren Out of Service | 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 June 01, 2010, at approximately 0715 Mountain Standard Time (MST), the Palo Verde Emergency Planning Department discovered that public warning system siren No. 17 was not responding, and therefore, is out of service. The loss of siren No. 17 could potentially impact a population of approximately 1196 people in the 5-mile Emergency Planning Zone (EPZ). Since the loss of siren No. 17 could impair Arizona Public Service Company's ability to inform greater than 5% of the population within the EPZ, this notification is being made in accordance with 10 CFR 10.72(b)(3)(xiii). If an event occurs while siren No. 17 is out of service, the Palo Verde Emergency Plan has a contingency for dispatching Maricopa County Sheriff's Office (MCSO) vehicles with loud speakers to alert persons within the affected area. The MCSO is prepared to implement this contingency should it become necessary. The NRC Resident Inspector has been notified of siren No. 17 being out of service and this ENS call.
Siren number 17 was returned to service at 1435 MST. The NRC Senior Resident Inspector has been notified. The remote radio was replaced and all post-maintenance testing was completed. Notified R4DO (Werner). | |
| ENS 46025 | 18 June 2010 15:08:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared Due to Damaged Energized Equipment | 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.
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). | |
| ENS 46140 | 30 July 2010 14:20:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Emergency Siren | On July 30, 2010, at approximately 0720 Mountain Standard Time (MST), the Palo Verde Emergency Planning Department discovered that public warning system siren No. 17 was not responding, and therefore, is out of service. The loss of siren No. 17 could potentially impact a population of approximately 1196 people in the 5-mile emergency planning zone (EPZ). Since the loss of siren No. 17 could impair Arizona Public Service Company's ability to inform greater than 5% of the population within the EPZ, this notification is being made in accordance with 10 CFR 50.72(b)(3)(xiii). If an event occurs while siren No. 17 is out of service, the Palo Verde Emergency Plan has a contingency for dispatching Maricopa County Sheriff's Office (MCSO) vehicles with loud speakers to alert persons within the affected area. The MCSO is prepared to implement this contingency should it become necessary. Troubleshooting to determine the cause of the failure has commenced. The NRC Resident Inspector has been notified. | |
| ENS 46188 | 18 August 2010 14:42:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Several Public Warning System Sirens | On August 18, 2010, at approximately 0742 Mountain Standard Time (MST), the Palo Verde Emergency Preparedness Department discovered that public warning system sirens Nos. 17, 23, and 34 were not responding, and therefore, were out of service. The loss of these sirens could potentially impact a population of approximately 1800 people in the 5-mile emergency planning zone (EPZ). Since the loss of these sirens could impair Arizona Public Service Company's ability to inform greater than 5% of the population within the EPZ, this notification is being made in accordance with 10 CFR 50.72(b)(3)(xiii). If an event occurs while the sirens are out of service, the Palo Verde Emergency Plan has a contingency for dispatching Maricopa County Sheriff's Office (MCSO) vehicles with loud speakers to alert persons within the affected area. The MCSO is prepared to implement this contingency should it become necessary. Troubleshooting to determine the cause of the failure has commenced. The NRC Resident Inspector has been notified of the out of service sirens and this ENS call. (At the time of the notification to the NRC), siren #23 was restored at 1316 MST. The out of service sirens are now Nos. 17 and 34 with an affected population of 1196 within the 5 mile EPZ.
The licensee restored siren #17 at 1647 MST on 8/18/10. The restoration of this siren provided coverage to all the population within the 5-mile EPZ. The licensee has notified the NRC Resident Inspector and will also notify State and local authorities. R4DO (Miller) notified. | |
| ENS 46331 | 14 October 2010 16:15:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Emergency Sirens Will Be Taken Out of Service for Planned Maintenance | 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. From October 14, 2010 to October 22, 2010, Palo Verde personnel will be performing maintenance on public prompt notification system sirens. Sirens will be removed from service one at a time, and then each will be restored prior to continuing to the next siren. Siren #36 provides notification to approximately 470 members of the public within five miles of Palo Verde. Siren #23 provides notification to approximately 614 members of the public within five miles of Palo Verde. Siren #25 provides notification to approximately 335 members of the public within five miles of Palo Verde. Siren #18 provides notification to approximately 586 members of the public within five miles of Palo Verde. Siren #15 provides notification to approximately 1133 members of the public within five to ten miles of Palo Verde. Siren #22 provides notification to approximately 1015 members of the public within five miles of Palo Verde. Siren #17 provides notification to approximately 1196 members of the public within five miles of Palo Verde. Each of these are considered by Palo Verde to be a 'large segment of the population.' This notification is being made in accordance with 10 CFR 50.72(b)(3)(xiii). The Palo Verde Emergency Plan has a contingency for dispatching Maricopa County Sheriff's Office (MCSO) vehicles with loud speakers to alert persons within the affected area. The MCSO is prepared to implement this contingency should it become necessary. There are no events in progress that require siren operation. A follow-up call will be placed when the affected sirens are returned to service. The NRC Resident Inspector has been notified of the siren maintenance and this ENS call.
Maintenance on the Palo Verde public prompt notification sirens listed on ENS #46331 has been completed. The sirens are operable and are back in service. The NRC Resident Inspector has been notified of the siren maintenance and this ENS call. Notified R4DO (Proulx). | |
| ENS 46556 | 20 January 2011 01:41:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Reactor Trip Due to Main Feedwater Pump Trip | 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 January 19, 2011, at approximately 1840 Mountain Standard Time (MST), Palo Verde Unit 3 received a Reactor Power Cutback (RPCB) due to the 'B' Main Feedwater Pump (MFP) tripping on low suction pressure in response to the 'A' MFP mini-flow valve failing open. Reactor power lowered to approximately 60% in response to the RPCB. Steam Generator levels continued to decrease and a Reactor Trip occurred on Low Steam Generator #1 level at 18:41. Unit 3 was at normal operating temperature and pressure prior to the trip. Following the automatic reactor trip all CEAs (Control Element Assemblies) inserted fully into the reactor core. No emergency classification was required per the Emergency Plan. An AFAS-2 (Auxiliary Feedwater Actuation Signal) occurred at 1844 on low Steam Generator #2 level. Safety related busses remained energized during and following the reactor trip. The Emergency Diesel Generators started in response to the AFAS-2 actuation but did not energize the class 4.16kV buses as they remained energized from off-site power. The offsite power grid is stable. No major equipment was inoperable prior to the event that contributed to the event. Unit 3 is stable at normal operating temperature and pressure in Mode 3 feeding the steam generators with Auxiliary Feedwater 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) Senior Resident Inspector was informed of the Unit 3 reactor trip. Unit 3 is in a normal post-trip electrical lineup. Decay heat is being removed via the turbine bypass valves to the main condenser. No safety valves on the secondary or primary side opened. | 05000530/LER-2011-001 |
| ENS 46633 | 22 February 2011 03:01:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Auto Start and Load of Edgs on Units 1&3 Following Loss of Start-Up Transformer | On February 21, 2011, at approximately 2001 Mountain Standard Time (MST) a valid actuation of the Palo Verde Nuclear Generating Station Unit 1 Train 'B' Emergency Diesel Generator (EDG) and Unit 3 Train 'A' Emergency Diesel Generator occurred as a result of undervoltage on their respective safety buses. Both EDGs started and loaded as designed to energize the respective safety buses. No Emergency Plan declaration was made and none was required. The loss of power to the Unit 1 and Unit 3 safety buses was the result of protective relay actuations on the A-E-NANX02 Startup Transformer which deenergized the transformer and the Unit 1 13.8KV Intermediate Bus 1-E-NAN-S06 and the Unit 3 13.8KV Intermediate Bus 3-E-NAN-SOS. The affected intermediate buses provide power to the Unit 1 safety bus 1-E-PBB-S04 and the Unit 3 safety bus 3-E-PBA-S03 respectively. The Auxiliary Operators responded to inspect the Startup Transformer and affected buses and determined that there was no fire or smoke and no obvious equipment damage to transformers or associated 13.8 KV Buses. At the time of the actuations, the Unit 1 Control Room received alarms for Startup Transformer A-E-NAN-X02 'Phase, Winding Ground Differential Trip'. Subsequent inspection by the Electricians identified damage to the cabling from the 'Y' winding of A-E-NAN-X02 Start-Up Transformer to the alternate supply breaker on Unit 2 Intermediate Bus 2-E-NAN-SOS. Unit 1 and Unit 3 entered Technical Specification LCO 3.8.1, Condition 'A', for one (of two) required offsite circuits inoperable. Unit 2 currently has the 'B' EDG out of service for a planned maintenance outage and the Unit 2 safety buses and required offsite circuits were unaffected by the Startup Transformer trip. Unit 2 safety buses are being supplied by Startup Transformers A-E-NAN-X01 and A-E-NAN-X03. Both Unit 1 and Unit 3 were at approximately 100% power, at normal operating temperature and pressure prior to and following the EDG actuations. No other ESF actuations occurred and none were required. No major equipment was inoperable prior to the event that contributed to the event. 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 notified of the ESF actuations and this ENS notification. The licensee is working to restore normal electrical power to the affected safety buses from alternate available sources on Startup Transformers X01 and X03. The licensee stated that no significant non-safety related equipment has been deenergized. The licensee noted that while the cause of the damaged cabling noted in the above report is still under investigation, water intrusion repairs were recently conducted near the location where the current damages were found.
The licensee has restored offsite power to the affected safety buses. The Unit 3 safety bus was restored from Startup Transformer X03 at 0106 MST. The Unit 1 safety bus was restored from Startup Transformer X01 at 0153 MST. The EDGs are in the process of being shutdown and reset. The LCO for required offsite power source to the buses has been exited. R4DO (Gaddy) and NRR (Brown) notified. | 05000528/LER-2011-001 |
| ENS 46634 | 22 February 2011 16:09:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Loss of Potable Water Supply | Arizona Public Service Co. made an offsite notification to the Maricopa County Environmental Services Division at 0909 MST on February 22, 2011, to report a loss of power to the Palo Verde Nuclear Generating Station drinking water supply pumps which resulted in the depressurization of the site domestic water supply header. The pumps were out of service on February 21, 2011, between the hours of 2001 and 2300 MST. Full service has been restored. The loss of power was related to the loss of Startup Transformer A-E-NAN-X02 as reported in ENS #46633 at 0023 on February 21, 2011. The NRC Resident Inspectors have been notified. | |
| ENS 46639 | 15 February 2011 23:22:00 | 10 CFR 21.21 | Part 21 Report - Misaligned Bell Alarm Switch Brackets on 480 Vac Class 1E Circuit Breakers | The following event description is based on information currently available. The condition is being reported under 10 CFR 21.21(d)(1). On February 15, 2011, Palo Verde Nuclear Generating Station (PVNGS) completed an evaluation of prior deviations related to the alignment of bell alarm switches that were installed by the manufacturer Asea Brown Boveri / ITE Imperial Company (ABB) on K-600S 480 VAC Class 1E circuit breakers. Had the breakers been placed into service as received, the misaligned bell alarm switch brackets could have prevented the automatic or remote closure of the breakers installed in safety-related applications. The station concluded the deviations were defects that are reportable per 10 CFR 21. The discussion below provides the technical details that were discovered for the bracket misalignments and the circumstances for the breakers in which this condition was identified. The ABB K-600S breakers contain a protective indication feature related to the overcurrent trip. An overcurrent trip actuates a reset indicator which moves an armature roller away from the bell alarm switch (ABB part number 706747-T07/BBC) to open the alarm switch contact. The alignment of the bell alarm switch bracket affects the range of contact between the bell alarm switch and the reset indicator armature. This alignment is critical because the vibration of breaker closure can cause the switch and the armature to lose contact momentarily to create an unintended 86 lockout and trip the breaker open during the closure sequence. The breaker will not be able to be reclosed until the 86 lockout and the bell alarm switch have been manually reset. This defeats the safety function of the breaker to provide power to the supported component. When the condition was identified, the station adjusted the bell alarm switch brackets (ABB part number 709827A00) on the breakers to correct the condition. The breakers were inserted into the intended breaker enclosures after further testing. The breakers were not returned to ABB. The first condition that was known to have been documented in the corrective action program was discovered during pre-service testing that occurred on November 5, 2009 . The breaker had been refurbished by ABB and was accepted by PVNGS Quality Control Receiving on October 2, 2009. A similar condition occurred on October 21, 2010, on a new breaker that was accepted on June 3, 2010. The untimely evaluation and defect reporting have been entered into PVNGS's corrective action program. This condition has not resulted in any reportable failures of in-service safety-related breakers under 10 CFR 50.73. The extent of this condition has been evaluated under an operability assessment and corrective actions to inspect potentially affected in-service breakers are in progress . The manufacturer and refurbisher, ABB, has been notified and since has provided tolerance information and instructions for inspection and adjustment of the bracket alignment . The use of ABB / ITE K600S breakers is common throughout the industry in nuclear safety-related applications. The station is unaware of which other licensee's use the bell alarm switch to actuate an 86 lockout feature. The station has not provided any of these breakers from its own stock to any other licensee. The PVNGS reporting officer was notified on February 22, 2011. The licensee notified the NRC Resident Inspector. | |
| ENS 46898 | 3 April 2011 21:44:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-Day Optional Notification of Invalid Start of the 'A' Emergency Diesel Generator | 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 report is being made under 10 CFR 50.73 (a) (2) (iv) (A) for a reportable invalid actuation. On April 3, 2011, at approximately 1444 Mountain Standard Time, Palo Verde Nuclear Generating Station Unit 2 experienced an invalid actuation (start) of the 'A' Emergency Diesel Generator (EDG). EDG 'A' inadvertently started during integrated safeguards surveillance testing to demonstrate that the EDG overspeed trip is not bypassed. Prior to the test, the EDG overspeed governor was actuated, but the butterfly valve was not verified to be fully closed as required. The valve closure actuates a limit switch which activates the interlock that prevents the EDG start following an overspeed trip. The test requires the operator to ensure the butterfly valve is fully closed because it may not fully close as the EDG is not running when it is actuated for the overspeed test. When the demand signal was inserted, the EDG started unexpectedly since the butterfly valve was not fully closed and the limit switch was not engaged. EDG 'A' Train completely actuated in the Emergency Mode and the EDG came up to rated speed and voltage as designed. The supporting 'A' train Essential Spray Pond System, used for engine cooling, was already running prior to the test. The Essential 'A' Train EDG Exhaust Room air handling unit started as required. No damage occurred to the EDG or related equipment as a result of the unplanned actuation. The EDG was secured and the test was successfully re-performed. This report is not considered an LER. The licensee has notified the NRC Resident Inspector. | |
| ENS 47050 | 14 July 2011 21:11:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | News Release Regarding Arrest of Illegal Immigrant Working at Palo Verde | 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 event is being reported as a newsworthy concern to the public under 10 CFR 50.72(b)(2)(xi). Palo Verde Nuclear Generating Station (PVNGS) was notified that the Maricopa County Sheriff's Office (MCSO) issued a news release at 1411 on July 14, 2011, regarding entrance to the PVNGS site property by an individual who MCSO alleged to be an undocumented immigrant. The individual had entered Palo Verde's Security Owner Controlled Area on July 13, 2011, but was not granted access to the site's Protected Areas surrounding the three units and Independent Spent Fuel Storage Installation. PVNGS Security contacted MCSO to validate the identification card furnished by the individual at the Security Owner Controlled Area. MCSO determined the identification card to be suspicious, responded to the site, detained the individual, and transported him off-site for questioning. The station notified NRC Resident Inspectors and Region IV staff of the condition on July 13, 2011. Arizona Public Service is planning to issue a news release and is responding to media inquiries regarding the matter. |