Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 44846 | 11 February 2009 19:31:00 | 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 44692 | 2 December 2008 19:36:00 | 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 43173 | 19 February 2007 19:14:00 | 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. |
| ENS 42387 | 5 March 2006 11:12:00 | 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 March 5, 2006 at approximately 0710 MST Palo Verde Unit 3 experienced a reactor trip (RPS actuation) from 100% rated thermal power due to low departure from nucleate boiling (ratio) (DNBR) trips on all four channels of the core protection calculators (CPCs). The unit was at normal temperature and pressure prior to the trip. Prior to the reactor trip, at approximately 0704 MST, a CEAC (Control Element Assembly Calculator) #1 sensor fail alarm was received. While investigating the alarm, at 0710 MST, a control element assembly (CEA) deviation alarm for CEAC #1, all four CPC channel sensor fail alarms, and a CEA withdrawal prohibit alarm were received. The reactor tripped six seconds later. A CEA calculator (CEAC) fail alarm was received on CEAC #1. The apparent cause is presently suspected to be a failure of CEAC #1. An investigation has commenced to determine the root cause of the reactor 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. 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 3 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 resulted 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. |
| ENS 41497 | 15 March 2005 23:07:00 | The following information was provided by the licensee via facsimile (licensee text in quotes): 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 15, 2005 at approximately 18:51 Mountain Standard Time (MST), the Palo Verde Nuclear Generating Station informed another government agency, the EPA/DOT National Response Center, of a caustic spill, related to the protection of the environment. Notification was also made to the Arizona Department of Environmental Quality and the Arizona Department of Public Safety (State Police). No news release is planned or expected. A commercial tanker truck was transferring caustic sodium hydroxide at Unit 1 when a drip was observed from the transfer hose at approximately 16:54 MST. The spill was limited to approximately one quart outside of the spill containment berm. The evolution was terminated and the tanker truck was driven out of the Protected Area. A drip trail was later discovered at approximately 18:00 along the path of the truck out of the Protected Area, including a puddle of approximately 3 gallons in the sally port (access point). The truck was returning to Phoenix, AZ. The spill quantity on-site is not estimated to have approached a reportable quantity (1,000 pounds), but due to the evidence that the truck was leaking while in transit to Phoenix, the Palo Verde Hazardous Materials Emergency Coordinator conservatively elected to make the government notifications. Additionally, Palo Verde notified the trucking company which ultimately located the truck upon its return to the company yard. No leak existed at that time, suggesting the leakage was limited to the caustic that remained in the truck's discharge pipe after the transfer was stopped. There was no impact to control room habitability and no safety systems, including essential ventilation, were actuated or required. The spill did not hamper site personnel in the performance of duties necessary for the safe operation of the nuclear power plant. The NRC Resident inspector was notified of the chemical spill and this ENS notification. |