Semantic search
| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 53764 | 1 December 2018 08:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Trip of Unit 2 Due to a Load Rejection | At 1006 (PST), on December 1, 2018, with Unit 2 at 100 percent power, the reactor automatically tripped due to a load rejection from the 500 kV offsite electrical system. Operations responded and stabilized the plant. Decay heat is being removed by the Main Steam system to the main condenser using the steam dump valves. The cause of the load rejection is currently under investigation. Due to the Reactor Protection System actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Additionally, due to the actuation of the Auxiliary Feedwater System, as expected, this event is being reported per 10 CFR 50.72(b)(3)(iv)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Senior Resident Inspector was notified. A press release is planned for this event. All control rods fully inserted and the trip was uncomplicated. There was no effect on Unit 1. | Reactor Protection System Auxiliary Feedwater Main Condenser Control Rod Main Steam | |
| ENS 53184 | 26 January 2018 03:01:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Screen Wash Pump Motor Fire | At 1901 PST on January 25, 2018, the Control Room received a fire alarm, followed by screen wash and 480v load center alarms a few minutes later. The intake operator and on-site fire department personnel were promptly dispatched to the scene and confirmed within 15 minutes there was no active fire. As a conservative measure, off-site fire assistance was initially requested, however (this request) was canceled a short time later. While on-site fire personnel were locally assessing the damage to screen wash pump 1-2, a brief flare-up occurred at the pump motor which was immediately extinguished. Units 1 and 2 remained stable and two screen wash pumps remain available. There is no risk to plant safety or personnel and both units continue to operate at power. Current efforts are focused on determining the cause of the situation. The licensee notified the NRC Resident Inspector and CAL FIRE. The licensee issued a media/press release. | ||
| ENS 52652 | 30 March 2017 23:30:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Onsite Fatality | At 1630 PDT on March 30, 2017, a non-work related fatality occurred on the Diablo Canyon Power Plant property. The individual's work location was outside of the Protected Area. The fatality was not related to the health and safety of the public. Specifically, a contractor for Pacific Gas and Electric (PG&E) was found in the Security Training Building unresponsive. The individual was promptly attended to by Diablo Canyon personnel. The individual was subsequently pronounced dead by the San Luis Obispo County Paramedics. PG&E has not observed any heightened public, media, or government concerns as a result of the fatality. Because the fatality is unrelated to Diablo Canyon Power Plant industrial or radiological health and safety, no news release is planned. Because the fatality was not work related, nor the result of an accident, no notification to other government agencies was made at the time. However, PG&E will make a notification to the California Occupational Safety and Health Administration. Thus this ENS notification is in response to a notification to another government agency in accordance with 10 CFR 50.72(b)(2)(xi). The NRC Senior Resident Inspector and Resident Inspector have been notified. | ||
| ENS 51655 | 14 January 2016 22:43:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Notification of Unusual Event - Security Condition That Does Not Involve Hostile Action | A security condition that does not involve a hostile action was reported by the Diablo Canyon security watch commander. At 1443 PST on 1/14/16, Diablo Canyon declared an Unusual Event, due to an unauthorized person in the Owner Controlled Area. Site Security was dispatched and assistance was requested from the local Sheriff's Department. The individual was apprehended. At 1602 PST on 1/14/16, Diablo Canyon terminated the Unusual Event after the individual was apprehended and placed in custody of local law enforcement. Diablo Canyon remained at 100 percent power for the duration of the event. No radiological release has occurred and all radiation levels are normal on both units. A press release is planned. The licensee has notified the NRC Resident Inspector and state and local authorities. Notified FEDS (DHS SWO, FEMA Ops, DHS NICC, and NuclearSSA via email.)
This Notification is being retracted. Upon further evaluation, Pacific Gas and Electric has determined that declaration of the Unusual Event was not required. The event did not constitute a threat or compromise to site security, did not involve a threat or risk to site personnel, did not represent a potential degradation to the level of safety of the plant, and did not affect the health and safety of the public. The licensee has notified the NRC Resident Inspector of the retraction. Notified R4DO (Whitten), IRD (Stapleton) and NRR (Morris). | ||
| ENS 51246 | 21 July 2015 21:53:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Single Emergency Siren Inadvertent Actuation | On 7/21/2015, at approximately 1453 Pacific Daylight Time (PDT), while performing quiet testing of the early warning system, a Pacific Gas and Electric (PG&E) Telecommunications Technician identified that a single emergency response siren was making a full sound output when it should not have been. PG&E Technicians took action and deactivated the single siren. The siren sounded for approximately 1 minute. As a result, this issue is being reported under 10 CFR 50.72(b)(2)(xi) for notifications to other offsite government agencies as the licensee notified the County of San Luis Obispo of the siren deactivation. The San Luis Obispo County Sheriff Watch Commander has been notified of the need to implement alternate means of alert and notification for the areas affected by the deactivation of the single siren. This was accounted for in pre-planning efforts and neither the utility nor 911 received any calls (from the public) related to this matter. The source of the activation signal has not been determined and is being investigated. There was no impact to the health and safety of the public as a result of this event as the offsite response capabilities remain functional with a single siren failure. The site is operating normally with no emergency conditions present. The NRC Resident Inspector has been notified. | ||
| ENS 50370 | 14 August 2014 23:31:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Unit 2 Technical Specification Required Shutdown Due to Multiple Inoperable Emergency Diesel Generators | While performing scheduled maintenance on Unit 2 Emergency Diesel Generator (EDG) 2-2, Diablo Canyon Power Plant (DCPP) identified a failed capscrew on engine cylinder 1L. As part of subsequent inspections to determine whether a similar condition existed on any of the other Unit 1 or Unit 2 EDGs, a degraded capscrew was identified on EDG 2-3 cylinder 8L at 1631 PDT on 08/14/2014. No capscrew issues were identified on the Unit 1 EDGs or on Unit 2 EDG 2-1. Although all operational tests of the diesels up to the time of discovery were satisfactorily performed with no indication of degraded performance, the EDG 2-3 was declared inoperable. Because two Unit 2 EDGs were inoperable concurrently, this is being reported as a condition that could have prevented fulfillment of a safety function per 10 CFR 50.72(b)(3)(v). Per the requirements of TS 3.8.1, with two EDGs inoperable, a plant shutdown was commenced at 2031 PDT on 08/14/2014. Therefore, this condition is also being reported in accordance with 10 CFR 50.72(b)(2)(i). Offsite power remained available throughout this condition. EDG 2-2 remains out of service as part of its scheduled maintenance window. This condition did not result in any adverse impact on the health and safety of the public. A press release is planned. The licensee informed the NRC Resident Inspector. The licensee also reported event notifications for 10 CFR 50.72(b)(3)(v)(C) - Control of Rad Release and 10 CFR 50.72(b)(3)(v)(D) - Accident Mitigation. The licensee plans to continue the shutdown to Mode 3 and is developing plans to return one of the two inoperable EDGs to operable status by the time the unit reaches Mode 5. | Emergency Diesel Generator | |
| ENS 50235 | 27 June 2014 22:35:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to an Inadvertent Activation of an Emergency Siren | At approximately 1535 Pacific Daylight Time (PDT) the Diablo Canyon Power Plant (DCPP) Emergency Planning Supervisor received a notification from an offsite DCPP employee that one of the emergency plan sirens had inadvertently actuated. The DCPP Shift Manager was notified of the situation by approximately 1545 PDT. The County of San Luis Obispo was notified of the inadvertent actuation of the single siren. At approximately 1550 PDT the County of San Luis Obispo sent out a county wide alert stating, 'Civil Emergency in this area until (1610) PDT prepare for action'. At approximately 1600 PDT the County of San Luis Obispo sent out another county wide alert stating, 'An early warning system siren was sounded in error. There is no emergency.' Field technicians have been sent out to the siren location and will shut the siren off. The cause of the inadvertent actuation of the siren is not known at this time. The licensee notified the NRC Resident Inspector and the County of San Luis Obispo. | ||
| ENS 49786 | 2 February 2014 19:29:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unit 2 Automatic Reactor Trip | On February 2, 2014, at 11:29 PST, Diablo Canyon Power Plant Unit 2 500kV line differential relay actuated. This action tripped the turbine and opened the generator output breakers to isolate the generator. With the turbine tripped and Unit 2 operating above the P-9 50% power permissive, a reactor trip was initiated from the reactor protection system. All systems operated as designed with no problems observed. All three Unit 2 Auxiliary Feedwater pumps started, the Containment Fan Cooling units started and ran in slow speed, and the standby Auxiliary Saltwater train started, all as expected. Unit 2 is stable at normal operating temperature and pressure. All power transferred to the plant startup source without incident. Condenser vacuum was maintained. The preliminary cause of the differential relay actuation was a flashover of Phase B 500 kV to ground across the Phase B lightning arrestor during a rainstorm. Decay heat is being removed by steam dumps to the condenser. No relief valves lifted during the transient. The steam generators are being supplied by the auxiliary feedwater pumps. There were no injuries to personnel. Unit 1 was not affected. NRC Senior Resident Inspector and Region Branch Chief have been informed of this event. A press release is planned for local media. | Steam Generator Reactor Protection System Auxiliary Feedwater | |
| ENS 49184 | 10 July 2013 16:50:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unit 2 Automatic Reactor Trip | On July 10, 2013, at 0950 PDT, the Diablo Canyon Power Plant Unit 2 500kV line differential relay actuated. This action tripped the turbine and opened the generator output breakers to isolate the generator. With the turbine tripped and Unit 2 operating above the P-9 50% power permissive, a reactor trip was initiated from the reactor protection system. All plant equipment responded as designed. All three Unit 2 Auxiliary Feedwater pumps started, the Containment Fan Cooling units started and ran in slow speed, and the standby Auxiliary Saltwater train started, all as expected. Unit 2 is stable at normal operating temperature and pressure. All power transferred to the plant startup source without incident. Condenser vacuum was maintained. The preliminary cause of the differential relay actuation was a flashover of Phase A 500 kV to ground across the Phase A lightning arrestor during maintenance activities to wash the 500 kV insulators. NRC Resident Inspector has been informed of this event. A press release is planned for local media. Decay heat is being removed by steam dumps to the condenser. No relief valves lifted during the transient. The steam generators are being supplied by the auxiliary feedwater pumps. There were no injuries to personnel. Unit 1 was not affected. | Steam Generator Reactor Protection System Auxiliary Feedwater | |
| ENS 49148 | 26 June 2013 04:58:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Plant Shutdown Required Due to Rhr System Socket Weld Leak | At 2158 PDT, plant personnel identified a through-wall leak in a Diablo Canyon Power Plant Unit 1 socket weld inside containment that provides a flow path to a relief valve that protects a common portion of both trains of the Residual heat Removal (RHR) system. The as-found condition did not comply with the requirements of equipment control guideline 7.6 and the ASME acceptance criteria. PG&E accordingly declared both Unit 1 trains of RHR inoperable and initiated plant shutdown at 2237 PDT in accordance with requirements of Technical Specification 3.0.3. PG&E will complete shutdown to Mode 4 and will perform repairs to restore compliance with ASME code requirements. The licensee notified the NRC Resident Inspector. * * * UPDATE AT 1303 EDT ON 6/26/13 FROM WESLEY FIANT TO PETE SNYDER * * * Pacific Gas and Electric Company is submitting an update based on a press release issued at 0915 PDT detailing the above information to local television, newspaper, and radio media outlets. San Luis Obispo County and State of California Offices of Emergency Services have already been notified. The licensee notified the NRC Resident Inspector. Notified R4DO (Pick). | Residual Heat Removal | |
| ENS 48400 | 11 October 2012 19:08:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unit 2 Experienced an Automatic Reactor Trip on a 500Kv Line Differential Relay Actuation | On October 11, 2012, at 1208 PDT, the Diablo Canyon Power Plant Unit 2 500kV line differential relay actuated, resulting in a unit trip. The unit trip actuated the turbine trip. With the turbine tripped and Unit 2 operating above the P-9 50% power permissive, a reactor trip was initiated from the reactor protection system. All plant equipment responded as designed. Unit 2 is stable at normal operating temperature and pressure. All power transferred to the plant startup source without incident. Condenser vacuum was maintained. The cause of the differential relay actuation is under investigation. Based on personnel observation it appears to have been initiated due to a flashover to ground across the phase 'A' main bank transformer capacitive coupled voltage transformer. PG&E will issue a press release regarding the Unit 2 trip. NRC Resident Inspectors have been informed of this event.
This update to clarify the status of the auxiliary feedwater system during the above noted transient. Both motor driven pumps and the steam driven pump automatically started as expected. In addition, on October 11, 2012, at 12:26 PDT, the Diablo Canyon Power Plant Unit 2 turbine driven auxiliary feedwater pump was secured by plant operators manually closing the steam supply valve to the pump turbine. This action was performed in accordance with plant operating procedures after the operators had verified that the indicated steam generator levels were greater than the procedural requirement of 16%. However, because the steam generator low level bistables associated with the auxiliary feedwater actuation circuits had not yet cleared, the emergency safeguards actuation signal drove the steam supply valve back open, restarting the turbine driven auxiliary feedwater pump. Operators increased steam generator levels to clear the bistables and successfully reclosed the steam supply valve. The NRC Resident Inspector has been informed of this event. Notified R4DO (Hagar). | Steam Generator Reactor Protection System Auxiliary Feedwater | |
| ENS 47865 | 26 April 2012 05:27:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Press Release Issued for Shutdown of Unit 2 Due to Salp Influx | On April 25, 2012, at 2227 PDT, Diablo Canyon Power Plant (DCPP) U2 was manually taken offline and the reactor shut down due to an influx of sea salp - a small, jellyfish-like organism - in the intake structure. Operators manually started the auxiliary feedwater pumps in accordance with the plant operating procedures. PG&E will not restart Unit 2 until conditions improve at the intake structure. As previously announced, Unit 1 was safely shut down for a planned refueling and maintenance outage. All systems operated as designed and no unexpected equipment performance issues were noted. The licensee notified the NRC Resident Inspector. The licensee plans on issuing a press release. | Auxiliary Feedwater | |
| ENS 47758 | 21 March 2012 14:49:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Inadvertent Offsite Notification During Simulator Training | At 0749 PDT on March 21, 2012, during a training scenario in the plant simulator, plant personnel inadvertently issued an Alert notification for Diablo Canyon Power Plant (DCPP), Unit 1. This Alert should be disregarded. The Alert was issued as a loss of the Unit 1 fuel cladding barrier with no radioactive release. There is no Alert declaration at DCPP Units 1 or 2, and both units are operating normally. DCPP contacted notified parties to clarify that the Alert notification was inadvertent. DCPP is making this 4-hr, non-emergency notification under 10 CFR 50.72(b)(2)(xi) as a situation for which an (inadvertent) notification to other government agencies has been made. The licensee is investigating this inadvertent notification but believes that the notification system was still set up from the emergency plan drill which was conducted last week. The licensee notified the NRC Resident Inspector, San Luis Obispo County, and the State. | ||
| ENS 47733 | 12 March 2012 14:42:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification - Non-Work Related On-Site Fatality | At 0742 PDT on March 12, 2012, a non-work related on-site fatality occurred at the Diablo Canyon Power Plant. The fatality was not related to the health and safety of the public or on-site personnel. Specifically, a contractor for Pacific Gas and Electric (PG&E) was found in the Engineering Offices before work hours with no pulse or life signs. The individual was promptly attended to by Diablo Canyon Industrial Fire Officers and a transfer to a local hospital by ambulance was completed. The individual was pronounced dead at the hospital. The individual was outside of the Radiological Controlled Area and no radioactive material or contamination was involved . The work location was outside of the Protected Area. PG&E has not observed any heightened public, media, or government concern as a result of the fatality. Because the fatality is unrelated to Diablo Canyon Power Plant industrial or radiological health and safety, no news release is planned. Because the fatality was not work-related, nor the result of an accident, no notification to other government agencies was made at the time. However, PG&E may make a notification to the California Occupational Safety and Health Administration due to a cardiac arrest on-site. Thus this ENS notification is in response to a notification to another government agency in accordance with 10CFR50.72(b)(2)(xi). The deceased person worked for Enercon Services. The licensee notified the NRC Resident Inspector. | ||
| ENS 47079 | 20 July 2011 20:18:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification - Press Release After Fire on Site | On July 20, 2011 at 1318 PDT, during performance of STP M-9A, 'Diesel Engine Generator Routine Surveillance Test,' personnel reported a fire on the Unit 1 Emergency Diesel Generator (EDG) 1-1. No abnormal indications were observed in the control room and no annunciator for 'Fire Detected' was received. Operators shutdown the EDG and the onsite fire department responded immediately. On July 20, 2011 at 1322 PDT, personnel reported that the fire, which was centered around the exhaust insulation material, had been extinguished. EDG 1-1 is in a scheduled Maintenance Outage Window (MOW) and is not being relied on for emergency onsite power. The two sources of offsite power (the 230 kV startup system and the 500 kV system) along with the remaining two EDGs, are available and operable. Unit 2 was not affected by the event. The NRC Resident Inspector has been notified. A press release will be issued by the licensee. | Emergency Diesel Generator | |
| ENS 46251 | 14 September 2010 15:15:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Minor Diesel Fuel Spill Into the Ocean | On September 14, 2010, at approximately 0815 PDT, a minor diesel fuel spill was discovered at the boat dock in the intake cove at the Diablo Canyon Power Plant. A rainbow sheen was observed on the water around the kelp harvester. Harvester operators immediately began deploying absorbent booms and absorbent pads to contain the sheen. It is estimated that less than 2 ounces of diesel fuel reached the water. Mechanics on scene discovered that a small hose clamp had failed on the diesel fuel return line. Repairs were made and the spill was contained. Absorbent pads were used to clean up the residual diesel fuel on the pontoons of the harvester. Repairs were complete and most of the diesel fuel has been absorbed by pads and booms. The licensee notified the NRC Resident Inspector. The licensee also notified the California State Office of Emergency Services, National Response Center, San Luis Obispo County Environmental Health and the Regional Water Quality Control Board. | ||
| ENS 46036 | 23 June 2010 17:48:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Alert Declared for a Cardox Discharge in the Turbine Building | A CARDOX release occurred in the Unit-1 main turbine lube oil room and an Unusual Event was declared. The release resulted in an atmosphere immediately dangerous to life and health resulting in an Alert notification. No injuries resulted, however, the crane bay in the center of the turbine building was evacuated. Approximately 30% of the CARDOX storage tank was discharged due to a malfunctioning solenoid valve. This valve had recently been replaced. The licensee notified the NRC Resident Inspector.
The licensee provided the following information as an update: On June 23, 2010, at 1035 PDT, an accidental discharge of CARDOX into Unit 1 Main Lube Oil Reservoir Room occurred during testing. On June 23, at 1048 PDT, an Unusual Event was declared for DCPP Unit 1. On June 23, at 1056 PDT, an Alert was declared for DCPP Unit 1. The DCPP Unit 1 reactor remains at full power. No safety related equipment has been impacted. There were no injuries to personnel and no equipment damage. Offsite assistance was requested to assist in event response. Pacific Gas and Electric Company issued the first press release at 1225 PDT on June 23, 2010. Further press releases will be issued as necessary until the event is terminated. The licensee notified the NRC Resident Inspector." The licensee also informed state and local agencies. Notified R4DO (Pick).
The licensee has terminated the Alert at 1715 PDT based on restoring accessibility to all plant area. The licensee will inform state/local agencies, the NRC Resident Inspector and issue a follow-up press release. Notified R4DO (Pick), NRR EO (Cunningham), IRD (Morris), DHS (Inzer), FEMA (Hollis), DOE (Yates), USDA (Petrick), and HHS (Lee). | Main Turbine | |
| ENS 45994 | 9 June 2010 18:12:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Press Release Concerning a Caustic Spill | On June 9, 2010, at 10:32 PDT, a caustic spill occurred in the DCPP Unit 1 Turbine Building buttress area. On June 9, 2010, at 10:59 PDT the area was restricted for normal access with SCBAs required for entry into the area. On June 9, 2010, at 11:12 PDT an Unusual Event was declared for DCPP Unit 1. The DCPP Unit 1 reactor remains at full power. No safety related equipment has been impacted. The Unusual Event was declared based on EP G-1 Attachment 2 - 'HU3.1 Report or detection of toxic, corrosive asphyxiant or flammable gases that have entered or could enter the Owner Controlled Area in amounts that can adversely affect normal plant operations.' The spill amount was reported as 5 gallons. The spill was due to a ruptured delivery hose. The hose was isolated initially at the delivery truck and the tank being filled. Hose continued to drain due to residual caustic in the hose. It was reported as 'confined' on June 9, 2010 at 11:02 PDT. The spill was reported as 'contained' on June 9, 2010 at 11:44 PDT. Access to the immediate area of the spill is still restricted. The licensee notified the NRC Resident Inspector. | ||
| ENS 45260 | 13 August 2009 20:04:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Potential Media Interest Due to Planned Maintenance Outage | On August 13, 2009, at 1304 PDT, Unit 2 was shut down in accordance with established plant procedures to perform more in-depth analysis of the main electrical transformer 'A' phase 500 kV bushing. Diablo Canyon Unit 2 was taken off line in a planned maintenance outage to investigate a power-factor condition currently identified by the 500 kV bushing monitoring instrumentation. The main electrical transformer 'A' phase 500 kV bushing will be replaced if warranted by the results of testing. The licensee notified the NRC Resident Inspector. | ||
| ENS 45178 | 30 June 2009 22:13:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Potential Media Interest Due to Forced Outage | On June 30, 2009, at 1513 PDT, Unit 2 commenced a ramp(-down) in accordance with the annunciator response guidance to enter Operating Procedure (OP) Abnormal Procedure AP-25 due to loss of forced cooling to main transformer bank (MTB) C-Phase transformer. At 1538, Unit 2 was separated from the grid in accordance with plant OP AP-25 initiation of a main generator unit trip. At 1554 PDT, the Reactor Trip Breakers (RTBs) were manually opened per OP AP-25 Step 24.j. (Reactor) power was being held in Mode 2 at about 3% reactor power per the procedure when the RTBs were opened. The investigation into the cause is continuing. This event is being reported in accordance with 10 CFR 50.72(b)(2)(xi), Offsite Notification, as Pacific Gas and Electric plans to make a news release regarding the event that may raise media interest. The licensee notified the NRC Resident Inspector. | Main Transformer | |
| ENS 44675 | 21 November 2008 19:08:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification and Media Briefing Due to Potential Discovery of Offshore Fault Near Plant | As part of the ongoing seismic monitoring program, PG&E (Pacific Gas & Electric) in conjunction with the US Geological Survey (USGS) is studying a pattern of seismic activity in close proximity to the Diablo Canyon Power Plant (DCPP). The discovered pattern of seismic activity suggests a potential offshore fault near DCPP. PG&E and the USGS were previously unaware of this potential fault. Initial evaluation shows that the potential fault is closer to DCPP and much smaller than the Hosgri fault, which is the current bounding seismic feature for DCPP. Initial assessment indicates that the ground motion from this potential fault is expected to be bounded by the existing seismic design basis for DCPP. The possible impact of this potential fault, including potential ground deformation is the subject of an ongoing evaluation. Given the available data, PG&E and the USGS estimate that it will take up to a year to determine if a seismic fault exists. This issue was discussed with US NRC Region IV and Office of US NRC Nuclear Reactor Regulation on November 21, 2008. PG&E is planning a media briefing. The licensee has notified the NRC Resident Inspector. | ||
| ENS 44588 | 22 October 2008 03:51:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unit 2 Manual Reactor Trip Due to Jellyfish Intrusion | On October 21, 2008, with both units operating at 100% power, Operators manually actuated the Unit 2 reactor protection system (RPS/reactor trip) due to high differential pressure (DP) across the circulating water pumps' intake traveling screens. The high DP resulted from a rapid influx of jellyfish. All systems responded as designed. All control rods fully inserted. Auxiliary feedwater actuated as designed. The grid is stable with power being supplied by 230 Kv startup power. Diesel generator (DG) 2-2 and 2-3 are operable in standby. DG 2-1 is inoperable due to scheduled maintenance. The traveling screens for the safety-related auxiliary saltwater system (ASW) are not degraded and are managing the influx of jellyfish with no significantly elevated DP. Unit 2 is stable in Mode 3 at normal operating temperature and pressure. This event is being reported in accordance with 10 CFR 50.72(b)(2)(iv)(B), 'RPS actuation,' and 50.72(b)(3)(iv)(A), 'Specified System Actuation.' Operators reduced power on Unit 1 in response to the potential loss of normal flow to the condenser due to the jellyfish influx on the traveling screens. Currently, the traveling screens are maintaining DP within limits and the unit is stable at 50% power. Unit 2 decay heat removal is being performed by Auxiliary Feed Water to four steam generators blowing down via the 10% steam dumps to atmosphere. No other safety related equipment was out of service at the time of the trip. The licensee notified the NRC Resident Inspector.
The licensee issued a press release regarding this issue. Notified R4DO (Deese). | Steam Generator Reactor Protection System Auxiliary Feedwater Decay Heat Removal Control Rod | 05000323/LER-2008-002 |
| ENS 44357 | 21 July 2008 16:08:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Declared - Unable to Validate a Fire Alarm within 15 Minutes | The licensee received a fire alarm (smoke alarm) for the Auxiliary Building Ventilation Room at 0853 PDT. An operator was dispatched to visually inspect the area of the fire alarm. The area was not able to be accessed due to a high delta pressure across the door. Operators were not able to access the area within 15 minutes of receiving the alarm and declared EAL HU 2.1 at 0908 PDT. A maintenance worker in the area of the alarm opened the door from the other side and an operator was able to visually inspect the area. The area was free of smoke and fire and the Unusual Event was exited at 0915 PDT. The licensee performed required notifications to the State of California and the local government. The NRC Resident Inspector was notified.
The licensee plans to issue a press release concerning the Unusual Event. The NRC Resident Inspector will be notified. R4DO (Deese) informed. | ||
| ENS 44230 | 21 May 2008 22:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Mobile Crane Caused Damage to Met Tower | During the performance of work activities in the vicinity of the Met Tower at 10 AM, a mobile crane made contact with a support wire causing damage to the tower. All instrumentation on the tower continues to function, but conservatively has been called inoperable. All instrumentation on the back up Met Tower continues to function. The backup Met Tower provides full assessment capability. Due to the structural damage to the tower, as a precaution the area around the tower including the simulator training building and the maintenance training building have been evacuated. Experts from Transmission and Distribution are assessing damage to the tower to determine what additional actions may be necessary. The local media requested information about this event at 1500. Information has been released to the media. The senior resident inspector has been notified. | ||
| ENS 40836 | 23 June 2004 21:25:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification and Media Interest in Fire in Cafeteria | At 1425 PDT, a grease fire started in the cafeteria which is in the protected area. The fire was extinguished by onsite fire fighting personnel. The fire reflashed and was again extinguished. Due to the reflash, the California Department of Forestry was notified for offsite fire assistance. Offsite fire fighting personnel responded. There were no injuries. There has been one media inquiry. The licensee notified the NRC Resident Inspector. |