Semantic search
| Discovered date | Reporting criterion | Title | Description | LER | |
|---|---|---|---|---|---|
| ENS 56769 | 1 October 2023 03:14:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Trip | The following information was provided by the licensee via email: At 2014 (PDT) on 09/30/2023, with (Diablo Canyon) Unit 1 in Mode 1 at 11 percent reactor power in preparation for a pre-planned manual reactor trip into a scheduled refueling outage, the reactor was manually tripped due to a failed secondary system dump valve. Auxiliary feedwater was manually started in accordance with plant procedures. This event is being reported in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). There was no plant or public safety impact. The NRC Senior Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Diablo Canyon Unit 2 was unaffected. | |
| ENS 56781 | 8 August 2023 18:07:00 | 10 CFR 50.73(a)(1), Submit an LER | 60 Day Notification for an Invalid Specified System Actuation | The following information was provided by the licensee via phone and email: This 60-day telephone notification is being made in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A). On August 8, 2023, at 1107 hours pacific daylight time (PDT) with Unit 1 in Mode 1 at 100 percent power, an invalid actuation occurred when Unit 1 4-kV vital bus 'G' was automatically transferred from auxiliary power to startup power due to an invalid bus under voltage signal, which occurred during planned maintenance activities. As a result of the actuation signal, auxiliary salt water and containment fan cooling units transferred automatically and started as designed. Plant systems responded as expected. This event was entered into the Diablo Canyon Power Plant corrective action program for resolution. There was no plant or public safety impact. The NRC Senior Resident Inspector has been notified. | |
| ENS 56522 | 17 May 2023 13:49:00 | 10 CFR 26.719, FFD Reporting requirements | FITNESS-FOR-DUTY Violation | The following information was provided by the licensee via email: On May 17, 2023, at 0649 PDT, it was determined that a prohibited item had been found inside the protected area. The NRC Resident Inspector has been notified. | |
| ENS 56176 | 23 October 2022 15:30:00 | 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Reactor Coolant System (RCS) Pressure Boundary Degradation | The following information was provided by the licensee via email: At 0830 PDT on 10/23/2022, during routine outage inspections on Unit 2, it was determined that the RCS Pressure Boundary did not meet ASME Section XI acceptance criteria on a 2-inch vacuum refill connection line. This event is being reported pursuant to 10 CFR 50.72(b)(3)(ii)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | |
| ENS 55720 | 31 January 2022 21:50:00 | 10 CFR 26.719, FFD Reporting requirements | FITNESS-FOR-DUTY Report | The following information was provided by the licensee via fax or email: At 1350 PST on 01/31/2022, Pacific Gas and Electric determined that a non-licensed employee supervisor violated Diablo Canyon FFD policy and had a confirmed positive on a direct observed test. The employee's access to the plant has been terminated and permanent denial has been entered into PADS. The NRC Senior Resident Inspector has been notified. | |
| ENS 55526 | 16 October 2021 00:49:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Trip and Automatic Auxiliary Feedwater Actuation | On October 15, 2021, at 1749 PDT with Diablo Canyon Power Plant Unit 2 operating at approximately 90 percent power, the reactor was manually tripped in accordance with plant procedures due to increasing water level in feedwater heater 2-5B. The reactor trip was uncomplicated and the Auxiliary Feedwater system started as expected. The plant is stable in Mode 3. This notification is being made in accordance the requirements of 10 CFR 50.72(b)(2)(iv)(B) as a manual actuation of the reactor protection system and 10 CFR 50.72(b)(3)(iv)(A) as an automatic actuation of a specified safety system. The cause of the increased feedwater level is under investigation. There was no impact to the health and safety of the public or plant personnel. The Resident Inspector has been notified. | |
| ENS 55235 | 5 May 2021 04:39:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty Report | A non-licensed employee supervisor had a confirmed positive during a random fitness-for-duty test. The employee's access to the plant has been terminated. The NRC Resident Inspector has been notified.
The initial event notification should have characterized the test type as a follow-up fitness-for-duty test, rather than a random test. R4DO (Dixon) and FFD Group via email. | |
| ENS 55058 | 7 January 2021 15:43:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty Report | A non-licensed employee supervisor had a confirmed positive for alcohol during a follow-up test. The employee's access to the plant has been terminated. The licensee informed the NRC Resident Inspector. | |
| ENS 54828 | 10 August 2020 16:15:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness-For-Duty Test Positive for Non-Licensed Supervisor | At 0915 PDT, on August 10, 2020, Pacific Gas and Electric determined a non-licensed employee supervisor had a confirmed positive during a random fitness-for-duty test. The employee's access to the plant has been terminated. The NRC Senior Resident Inspector has been notified. | |
| ENS 54789 | 17 July 2020 20:46:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation | Manual Reactor Scram Due to Increased Hydrogen Usage | On July 17, 2020, at 1346 PDT with Diablo Canyon Power Plant Unit 2 operating at 100 percent power, the reactor was manually tripped in accordance with plant procedures due to increasing hydrogen usage in the Unit 2 main generator. The reactor trip was uncomplicated and the Auxiliary Feedwater system started as expected. The plant is stable in Mode 3. This notification is being made in accordance the requirements of 10 CFR 50.72(b)(2)(iv)(B) as a manual actuation of the reactor protection system and 10 CFR 50.72(b)(3)(iv)(A) as an automatic actuation of a specified safety system. The cause of the increased hydrogen usage is under investigation. There was no impact to the health and safety of the public or plant personnel. The Senior Resident Inspector has been notified. | |
| ENS 54721 | 18 May 2020 18:57:00 | 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | Part 21 Report - Inadequate Dedication of Replacement Thermocouples | The following is a summary from the Diablo Canyon Part 21 Report submitted: On May 18, 2020, Pacific Gas and Electric (PG&E) completed its evaluation of a deviation concerning commercial-grade thermocouples dedicated at Diablo Canyon Power Plant. The original defect was discovered on April 10, 2020 during bench testing where two separate thermocouples exhibited leakage during static pressure testing. The two thermocouples were tested as part of a spare safety-related pump motor refurbishment. Upon subsequent review, it was identified that a pressure boundary test had not been required as part of the dedication process, but should have for its safety-related application. These components were not installed in the plant and there was no risk to the health and safety of the public. Thermocouples from the same batch have been quarantined to prevent installation, and it has been confirmed that none of the suspect batch of thermocouples have been installed in the plant. The thermocouple replacement part evaluation has been revised to include a pressure boundary test as part of the commercial-grade dedication prior to acceptance. Thermocouple Make and Model: March Bellofram 3060-2-JJ-2-13.00-0-1-000 The NRC Resident Inspectors have been notified. This report only affects Diablo Canyon Power Plant. The person informing the Nuclear Regulatory Commission: Kenneth Cortese Quality Verification Director Diablo Canyon Power Plant Pacific Gas and Electric 805-440-367 | |
| ENS 54524 | 13 February 2020 18:25:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Technical Specification Required Shutdown | On February 13, 2020, at 1025 hours (PST), during the performance of the quarterly control rod exercise surveillance test, Shutdown Bank 'B' Group 1 became misaligned greater than 12 steps from its group demand position. In accordance with Technical Specification 3.1.4, 'Rod Group Alignment Limits,' Action D, a Unit 2 shutdown to Mode 3 was commenced at 1233 hours. Investigation into the cause of the rod bank misalignment is in progress. There is no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified. | |
| ENS 54417 | 30 November 2019 19:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Both Trains of Containment Spray Removed from Service | On November 30, 2019, at 1100 PST, with Unit 2 in Mode 4, Operations identified that both trains of containment spray had been removed from service earlier at approximately 0217 hours as part of preparations for a planned Mode 5 entry. The containment spray pumps are required to be operable (along with the containment fan cooler units) in Modes 1 through 4 in accordance with Technical Specification 3.6.6. With both containment spray pumps inoperable, TS 3.6.6 Action F requires the Unit to be shut down in accordance with TS 3.0.3. At 1125 hours, both trains of containment spray were returned to operable and the required actions of TS 3.6.6 and TS 3.0.3 were exited. The five containment fan cooler units remained operable for the duration of the occurrence. This notification is being made in accordance with the requirement of 10 CFR 50.72(b)(3)(v) as an event or condition that could have prevented fulfillment of a safety function, and 10 CFR 50.72(b)(3)(ii) as an event or condition that may have resulted in the plant being in an unanalyzed condition. The NRC Senior Resident Inspector has been notified. | |
| ENS 54328 | 12 October 2019 15:55:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness-For-Duty Report - Unopened Can of Beer Found Inside Protected Area | One unopened can of beer was discovered in a break room refrigerator within the plant's Protected Area. The individual that brought in the can of beer was identified. That individual is a Pacific Gas and Electric employee but does not normally work at Diablo Canyon. That individual was brought in to support work during the Unit 2 refueling outage. When questioned, the individual stated that the can of beer had been brought in to give to another person to see if that person liked that brand of beer (the beer was apparently from a small specialty brewery). A behavioral observation was performed on the individual who brought in the can of beer. There was no indication of alcohol use by the individual. The individual's access to the plant has been suspended pending further investigation. | |
| ENS 54234 | 27 June 2019 08:30:00 | 10 CFR 50.73(a)(1), Submit an LER | Automatic Transfer of 4-Kv Vital Bus from Auxiliary to Startup Power | This 60-day telephone notification is being made in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) regarding an invalid Engineered Safety Feature actuation signal. On June 27, 2019, at 0130 hours Pacific Daylight Time (PDT), with Unit 2 operating at 100 percent power, the U2 4-kV Vital Bus F was automatically transferred from its auxiliary power to its startup power due to an invalid loss of bus voltage signal. The cause of the invalid signal was due to a test jumper that was inadvertently left in place during surveillance testing. As a result, one auxiliary saltwater pump started and two containment fan cooler units started in slow speed. At 1245 PDT, Vital Bus F was transferred back from startup power to auxiliary power which is the normal plant operating configuration. This event was entered into the Diablo Canyon Power Plant corrective action program for resolution. This event did not result in any adverse impact on the health and safety of the public. The plant responded as expected. In accordance with 10 CFR 50.73(a)(1), a telephone notification is being made in lieu of submitting a written Licensee Event Report. The licensee has notified the NRC Senior Resident Inspector. | |
| ENS 53829 | 15 January 2019 08:00:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness-For-Duty Report Regarding a Non-Licensed Supervisor | A non-licensed supervisor failed to disclose information as required by the fitness-for-duty program. The employee's access to the plant has been terminated. The NRC Resident Inspector has been informed. | |
| 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. | |
| ENS 53471 | 25 June 2018 07:00:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness-For-Duty Test Positive for Non-Licensed Supervisor | At 1029 PDT on June 25, 2018, Pacific Gas and Electric determined a non-licensed employee supervisor had a confirmed positive for alcohol during a random fitness-for-duty test. The employee's access to the plant has been terminated. The NRC Resident Inspector has been notified | |
| ENS 53361 | 24 April 2018 10:57:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Containment Radiation Monitors Inoperable | At 0357 (PDT), Unit 2 Containment High Range Radiation Monitor RM-31 was declared inoperable due to erratic indication. At this time, Containment High Range Radiation Monitor RM-30 was out of service for routine calibration. With both containment high range radiation monitors inoperable, this impacted DCPP's (Diablo Canyon Power Plant's) ability to evaluate containment radiation data for an unmonitored release in the event of an emergency. Compensatory measures were promptly put in place with the use of a portable radiation monitor as required by emergency preparedness procedures. This condition is being reported as a loss of assessment capability in accordance with 10 CFR 50.72(b)(3)(xiii). Actions are in progress to restore RM-30 and RM-31 to operable status. The NRC Senior Resident Inspector has been notified.
RM-30 was restored to service. Portable radiation monitoring is not required. The licensee will notify the NRC Resident Inspector. Notified R4DO (Vasquez). | |
| 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 53096 | 29 November 2017 19:25:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness-For-Duty Report Involving Discovery of Kombucha Tea Inside the Protected Area | On 11/29/2017, at approximately 1125 (Pacific Time), an employee reported finding a container of herbal tea (Kombucha) in a refrigerator in a warehouse building break room, which is located inside the Protected Area. Kombucha tea is a fermented tea containing trace amounts of alcohol. Based on the product labeling, which indicates the beverage may contain more than 0.5 percent alcohol by volume, and which also includes a government alcoholic beverage health warning label, this is being considered an alcoholic beverage, and is being reported under the requirements of 10 CFR Part 26.719. An investigation is under way to identify who may have brought the kombucha tea on-site. The NRC Senior Resident Inspector has been notified. | |
| ENS 52876 | 28 July 2017 19:06:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Alert Declared Due to Low Oxygen Levels Inside Containment | Containment atmosphere oxygen level was measured at 18.4 percent. This is below normal habitability level. The cause of the low oxygen level is a nitrogen leak inside containment Nitrogen has been isolated from containment and operators are preparing to purge containment. The licensee notified the State of California, local authorities and the NRC Resident Inspector. Notified the DHS SWO, FEMA OPS, USDA OPS, HHS OPS, DOE OPS, DHS NICC, EPA EOC. Notified FDA EOC, NuclearSSA, FEMA NWC and FEMA NRCC SASC via email.
The ALERT was terminated on 7/28/17 at 1819 PDT. The containment atmosphere was restored to normal conditions. The nitrogen source was isolated. The cause of the nitrogen leak into containment is under investigation. The licensee will notify the NRC Resident Inspector. The licensee has notified the State of California and the local authorities. The licensee plans to issue a press release. Notified the R4DO (Hay), NRR EO (Miller), IRD MOC (Grant). Notified the DHS SWO, FEMA OPS, USDA OPS, HHS OPS, DOE OPS, DHS NICC, EPA EOC. Notified FDA EOC, NuclearSSA, FEMA NWC and FEMA NRCC SASC via email. | |
| ENS 52689 | 18 April 2017 18:00:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty Report - False Negative Occurred on Quality Assurance Test | The testing laboratory returned results for a blind specimen that was inconsistent with what was expected. The licensee has notified the NRC Resident Inspector. | |
| 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 52632 | 23 March 2017 13:00:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness-For-Duty Report Involving Discovery of Kombucha Tea Inside the Protected Area | An employee reported finding a container of herbal tea (Kombucha) in the Administrative Building refrigerator which is inside the Protected Area. Kombucha tea is a fermented tea containing trace amounts of alcohol. A similar incident occurred on 6/16/2016. The licensee issued a communication to all employees at that time identifying that Kombucha tea is not permitted on-site. The licensee will re-issue their communication to all employees and continue their investigation to identify who may have brought the tea on-site. The licensee informed the NRC Resident Inspector and R4 (Haire). | |
| ENS 52260 | 21 September 2016 03:47:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Steam Line Pipe Whip Restraint Coupling Sleeve Found Not Engaged | On 9/20/2016, a coupling sleeve on a pipe whip restraint located on the 119 foot elevation of the turbine building associated with Unit 2 main steam line 4 was found to be not engaged. As a result of the detached coupling, the restraint was not capable of performing its restraint function for a postulated pipe whip event on the main steam line. The coupling was reconnected on 9/20/2016, restoring its functionality. An extent of condition walkdown was subsequently performed for the other Unit 1 and Unit 2 steam line restraints and no similar issues were identified. This concern did not result in any adverse effect on the radiological health and safety of the public. The purpose of this whip restraint is to restrain the steam line for a postulated loss at the G-line anchor (east side of Turbine Building above the 104 foot elevation). The restraint protects the floor slab at the 104 foot elevation, which extends over the Unit 2 component cooling water heat exchangers. With the detached coupling, equipment in the area may have been vulnerable to damage if a pipe whip event occurred. Further analysis is needed to conclude whether the heat exchangers and other equipment would have remained protected in such an event and whether this would have significantly affected the designed plant response to a pipe event. Based on the need for further analysis, this event is being reported as an unanalyzed condition that may have significantly degraded plant safety in accordance with 10 CFR 50.72(b)(3)(ii)(B). The NRC Senior Resident Inspector was notified.
The purpose of this notification is to retract a previous report made on EN #52260, reported 9/23/2016. NRC notification was initially made as a result of a condition that required further analysis to determine whether the condition would have significantly degraded plant safety in accordance with 10 CFR 50.72(b)(3)(ii)(B). Further analysis of the condition concluded that PG&E Design Class I equipment located inside the Turbine Building would have remained undamaged and capable of performing their safety functions. The Turbine Building would not have experienced failure of major structural elements or adverse impact to the overall building stability. Therefore, the coupling sleeve on a pipe whip restraint located on the 119 foot elevation of the Turbine Building associated with Unit 2 main steam line 4 that was found to be not engaged did not constitute an unanalyzed condition that may have significantly degraded plant safety in accordance with 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified. Notified R4DO (Azua) | |
| ENS 52011 | 16 June 2016 14:45:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty - Unopened Herbal Tea Identified in the Protected Area | An employee self-reported possession of an unopened herbal tea containing naturally occurring alcohol in the protected area. The drink was removed from the protected area. The licensee will notify the NRC Resident Inspector.
While investigating the incident for EN #52011, it was determined that 'cooking wine' used in the cafeteria should be removed from the protected area. The licensee will notify the NRC Resident Inspector. Notified R4DO (Proulx) and FFD Group via email. | |
| ENS 51965 | 30 May 2016 16:30:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Opening of Reactor Trip Breakers Due to Rod Position Error Greater than 12 Steps | On 5/30/2016 at 0930 (PDT), Unit 2 was in its 19th refueling outage in Mode 4 (hot shutdown, reactor subcritical). Routine post-maintenance testing of digital rod position indication (DRPI) was in progress in accordance with Surveillance Test Procedure (STP) R-1C. Rod Shutdown Bank A was being withdrawn. With Shutdown Bank A Group 1 demand indicating 14 steps, and Group 2 demand indicating 13 steps, Bank A DRPI indicated 12 steps but control rod B4 DRPI indication remained at Step 0. With the bank demand position exceeding rod B4's DRPI indication by greater than 12 steps, Operators manually opened the Reactor Trip Breakers, placing all the rods in a known position due to an inoperable DRPI system. All systems actuated as required and rods fully inserted. Manual initiation of a reactor trip where the actuation is not part of a pre-planned evolution is reportable under 10 CFR 50.72 (b)(3)(iv)(A). While the reactor trip was initiated in accordance with the STP's instructions, the manual actuation was not a preplanned outcome of the STP. Subsequently, it was determined that rod B4 had remained on the bottom at Step 0 as indicated by DRPI. A moveable gripper fuse was blown, preventing that rod from being withdrawn. The blown fuse was replaced and testing continued in accordance with the procedure. There was no impact to public, employee, or plant safety. The NRC Resident Inspector was 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 51620 | 22 December 2015 21:30:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty Report - Discovery of a Prohibited Item in the Protected Area | The licensee discovered prohibited material inside the protected area. The material has been removed. The licensee has notified the NRC Resident Inspector. | |
| 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 50711 | 31 December 2014 18:05:00 | 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Through Wall Seepage Affecting Rhr System | At 1105 PST, plant personnel identified through-wall seepage in a Diablo Canyon Power Plant Unit 1 socket weld inside containment that provides a flow path to a relief valve protecting a common portion of both trains of the Residual Heat Removal (RHR) System. The as-found condition falls under the requirements of the ASME acceptance criteria. Unit 1 was already in Mode 3, or offline, due to a planned maintenance outage. PG&E accordingly declared both Unit 1 trains of RHR inoperable and has initiated a transition from Mode 3 to Mode 4 in accordance with requirements of Technical Specification 3.0.3. The licensee notified the NRC Resident Inspector. | 05000275/LER-2015-001 Both Trains of Residual Heat Removal Inoperable Due to Circumferential Crack on a Socket Weld |
| ENS 50586 | 1 November 2014 00:40:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Emergency Diesel Generator Start Due to Loss of Offsite 230Kv Startup Power Supply | At 1740 PDT, Diablo Canyon Power Plant experienced a loss of the offsite 230 kV startup power source. This was due to a 230 kV switchyard bus differential relay actuation during a rainstorm, resulting in valid anticipatory starts of each unit's three emergency diesel generators. All diesels successfully started but were not loaded. All systems operated as designed with no problems observed. The 230 kV startup power source is the offsite power system designed to be immediately available following an accident. However, the safety related onsite emergency diesel system would have provided power to mitigate the consequences of an accident while the 230 kV (supply) was unavailable. Unit 1 remains on line at 100 percent power. Unit 2 is currently in Mode 5 in the process of completing a planned refueling outage. Unit 2 power was supplied from the 500kV offsite power source at the time of this event and was therefore unaffected. The offsite 230 kV startup power source has been restored to service. The NRC Resident Inspector has been notified. The normal offsite power supply remained available and unaffected. | |
| 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. | |
| ENS 50334 | 1 August 2014 00:29:00 | 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)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Unanalyzed Condition | On 07/31/2014 at 1729 PDT, Diablo Canyon Power Plant (DCPP) identified an unanalyzed condition involving the three class 1E 4160 volt buses on Unit 1 and on Unit 2. Following a postulated main steam line High Energy Line Break (HELB) in the Turbine Building, steam could enter the 4160 volt bus rooms through ventilation ducts that exhaust to the turbine deck where the steam lines are located. New analysis identified that the relative humidity (RH) of the 4160 volt bus rooms could reach 100%, which exceeds the design RH used in the analyses for the protective devices in the room. The high-humidity could possibly prevent the protective devices from operating as intended and could therefore result in the unavailability of the 4160 volt buses to supply power to engineered safety feature systems. This concern is being reported as an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B) and as a condition that could have prevented fulfillment of a safety function per 10 CFR 50.72(b)(3)(v). Compensatory measures were taken to isolate the ventilation ducts between the 4160 volt bus rooms and the turbine deck, thereby preventing steam entry into the 4160 volt bus rooms, assuring the protective devices would not be subjected to conditions exceeding the design RH. With this compensatory measure all three 4160 buses on each unit are assured of performing their expected design function following the postulated main steam line break. This concern did not result in any adverse affect on the health and safety of the public. The licensee informed the NRC Resident Inspector. In addition to the 10 CFR sections listed in the header of this event notification, the licensee is also reporting this under 10 CFR 50.72(b)(3)(v)(D).
Diablo Canyon Power Plant is retracting this event notification based on the following: Subsequent to the identification of this event, PG&E conducted additional analysis and testing to support a past operability evaluation. Testing and analysis was completed successfully, demonstrating that the full population of associated components would perform their design safety function in 100% relative humidity conditions during a postulated high energy line break. Based on these analysis and testing results, PG&E concludes that the associated equipment remained operable, and did not represent an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B) or a condition that could have prevented fulfillment of a safety function per 10 CFR 50.72(b)(3)(v). Therefore, PG&E retracts its notification of 7/31/2014. The licensee has notified the NRC Resident Inspector. Notified the R4DO (Drake). | |
| 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 49879 | 6 March 2014 17:06:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Regarding Potential Tornado Missile Damage to Emergency Diesel Exhaust Plenum | The condition described below is being reported as an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B) and per the guidance of NUREG-1022, Rev. 3. On 03/06/2014 at 0906 PST, Diablo Canyon Power Plant (DCPP) identified a nonconforming condition involving the Emergency Diesel Generator (EDG) ventilation exhaust plenums installed in Unit 1 and Unit 2. Specifically, the radiator exhaust plenums and exhaust piping need to be re-evaluated to ensure adequate protection against flying debris that could be generated by a tornado. The occurrence of such an event is highly unlikely and there is no imminent concern regarding severe weather involving tornados. The EDGs are located inside the power plant structure and are capable of performing their safety function. Compensatory measures are being developed to address the associated nonconformance. This event does not adversely affect the health and safety of the public. The licensee informed the NRC Resident Inspector."
This condition does not adversely affect the health and safety of the public. Based on an extent of condition review being performed for this event, the issue identified in the original event notification 49879 has also been determined to similarly affect the ventilation systems associated with the Unit 1 and 2 Vital 480 volt AC switchgear and battery/inverter equipment. The condition described in this update is being reported as an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B) and as an event or condition that could have prevented the fulfillment of a safety function per 10 CFR 50.72(b)(3)(v)(A). Compensatory measures are being developed to address the associated condition. The licensee informed the NRC Resident Inspector. Notified R4DO (Azua) | |
| 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. | |
| ENS 49663 | 19 December 2013 15:52:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Two of Three Emergencey Diesel Generators Inoperable at the Same Time | On 12/19/13 Unit 1 Emergency Diesel Generator (EDG) 1-2 was inoperable for scheduled maintenance. During an operational walk-down of the Unit 1 EDG 1-3, the associated fuel oil priming pump discharge fitting and pump housing were inadvertently damaged. Pacific Gas and Electric Company declared EDG 1-3 inoperable on 12/19/13 at 0752 PST. Since both Unit 1 EDGs were inoperable at the same time, this condition is reportable in accordance with 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v)(D). The NRC Senior Resident Inspector has been notified. | |
| ENS 49634 | 14 December 2013 23:03:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Affecting Unit 1 Emergency Diesel Generator | At 1503 PST on December 14, 2013, Pacific Gas and Electric Company identified that, if atmospheric conditions were to develop that had both sustained high winds exceeding 60 miles per hour from the NW to NNE direction, and ambient air temperature exceeding 97 degrees Fahrenheit, the combination of these conditions could result in inadequate heat removal to support continuous operation of the Unit 1 emergency diesel generators. Upon identification of this condition, shift orders were issued requiring implementation of existing procedural guidance to open plant doors to allow additional air flow that would provide adequate emergency diesel generator cooling to support continuous operation of the U1 emergency diesel generators. This report addresses a condition as described in 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified of this condition. This condition was discovered during a license basis verification review. | |
| ENS 49334 | 9 September 2013 20:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Planned Partial Loss of Communications Capability in Technical Support Center | This is a non-emergency eight hour notification for a planned loss of communications capability at the DCPP Technical Support Center (TSC). This event is reportable in accordance with 10CFR50.72(b)(3)(xiii) because planned maintenance affects the functionality of some TSC communications systems. Planned maintenance activities on the TSC communications systems begins 09/09/13. The work includes removing phones and normal business use computers from service to support a minor remodel which includes the installation of new furniture and painting in the TSC command room. The communications equipment scope of work is confined to the TSC command room only and there is no expected loss of capability in the engineering, administrative or radiological rooms within the TSC. There is no expected loss of plant display systems (SPDS, ERDS, or ERFDS) in the TSC during this planned maintenance. The work is scheduled to complete by 09/26/2013. If an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing emergency planning procedures. A select group of TSC ERO personnel have been pre-designated to respond to their backup TSC location in accordance with applicable site procedures. If a complete relocation of the TSC becomes necessary, the Site Emergency Coordinator will relocate the remaining TSC staff to a backup location in accordance with applicable site procedures. The Emergency Response Organization teams have been notified of the planned maintenance and the possible need to relocate during an emergency. The NRC Resident Inspector has been notified. This planned maintenance poses no threat to the public or station employees.
The planned maintenance on the TSC communications systems is complete. DCPP restored the emergency response communications capability at 1400 PDT on September 19, 2013. The licensee has notified the NRC Resident Inspector. Notified R4DO (Deese). | |
| ENS 49287 | 16 August 2013 01:24:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Loss of Startup Power Results in Valid Starts of All Three Emergency Diesel Generators | At 1824 PDT on August 15, 2013, Unit 1 experienced a loss of startup power due to a failure of Startup Transformer 1-1 load tap changer. This loss caused a valid auto-start signal to all three emergency diesel generators and they all started successfully. At 1921, all EDGs were shutdown and returned to standby per plant procedures. As a result of the loss of startup power, power was also lost to site service buildings. ERDS was lost but compensatory measures are in place to transmit required data via the ENS line if required. The plant is in a 72-hr. shutdown LCO action statement under T.S. 3.8.1 for the loss of one of three qualified circuits. The two other qualified circuits (vital power via auxiliary transformers and the EDGs) remain operable. The licensee has notified the NRC Resident Inspector. | |
| 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. | |
| ENS 49173 | 3 July 2013 07:00:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Emergency Response Communications Due to a Loss of Ancillary Power | At 0156 PDT on July 3, 2013, Diablo Canyon Power Plant experienced a loss of power to ancillary facilities on site. This affected power supplies to data systems used by the Emergency Response Facilities (EOF). All plant status and performance data in the TSC (Technical Support Center) and EOF is available via telephone bridge line and control room phone talker. Additionally, the Emergency Response Data System (ERDS) has been determined to be unavailable. The data system loss occurred following depletion of backup batteries in the affected data center." The licensee notified the NRC Resident Inspector and will notify state and local agencies.
At 2120 PDT on 6/23/13, Diablo Canyon Power Plant (DCPP) experienced a loss of the offsite 230 kV startup power source due to an offsite transmission system relay actuation (see EN# 49143). At 1000 PDT on 7/3/13, PG&E identified that the conditions present on 7/3/13 that resulted in loss of plant status and performance data in the Technical Support Center (TSC) and Emergency Operations Facility (EOF) (see EN# 49173) also existed on 6/23/13. This update reports the 6/23/13 loss of plant status and performance data in the TSC and EOF due to loss of power in the data center that supports those facilities. All plant status and performance data required for emergency assessment and communication remained available via a telephone bridge line and control room phone talker. The data became unavailable in the TSC and EOF following depletion of backup batteries in the affected data center. On 7/3/13 PG&E reconfigured the TSC workstations to ensure they would function and provide data for emergency assessment capability independent of the status of the data center power supplies. The Emergency Response Data System was also unavailable following the loss of 230 kV startup power on 6/23/13 due to loss of power to the data center. This unavailability was as designed and as expected. This delayed event notification has been entered into the DCPP corrective action program. The licensee has notified the NRC Resident Inspector. Notified the R4DO (Gaddy) and ERDS Group via email. | |
| 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). | |
| ENS 49147 | 24 June 2013 23:15:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Emergency Diesel Generators Unavailable for Auto-Start | At 16:15 PDT on 6/24/13, an operator performing a post-event annunciator alarm review of the event reported in EN #49143 identified that the operators the previous night had momentarily disabled all three Unit 1 emergency diesel generators, prior to restoring them to their automatic standby control alignment. Between 22:01:10 PDT and 22:02:54 PDT, on 6/23/13, less than the required minimum two diesel generators were available to automatically respond to a design basis accident. Due to the event reported in EN #49143, the start-up 230 kV power source was also unavailable at this time. At the time of this event the operators were in the procedurally guided process of placing the running diesel generator controls to manual, shutting down the running diesel generators, and returning them to the automatic standby control alignment. In this event the operators placed all the diesel generators in manual and shut them down before returning them to automatic control. During this time the operators would have responded to a plant event by returning the affected diesels to auto, whereupon the normal starting and loading sequence would have resumed in accordance with existing accident analyses. At the time of discovery all offsite and onsite power sources were operable. The licensee notified the NRC Resident Inspector. | |
| ENS 49143 | 24 June 2013 04:20:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Loss of 230 Kv Offsite Power Results in the Automatic Start of Emergency Diesel Generators | At 2120 PDT, Diablo Canyon Power Plant experienced a loss of the offsite 230 kV startup power source due to an offsite transmission system relay actuation, resulting in valid anticipatory starts of Units 1 and 2 three emergency diesel generators on each unit. All diesels successfully started but were not loaded. All systems operated as designed with no problems observed. The 230 kV startup power source is the only offsite power system designed to be immediately available following an accident. However, the safety related onsite emergency diesel system would have provided power to mitigate the consequences of an accident while the 230 kV was unavailable. Restoration of the 230 kV offsite power system is in progress." The licensee will notify the NRC Resident Inspector.
230 kV was restored to Operable on 06/24/13 at 0200 PDT. Normal 500 kV Offsite Power remained operable and was unaffected by this event. Following further review, Diablo Canyon Power Plant (DCPP) has determined that the loss of the 230 kV system was not a condition that could have prevented fulfillment of the safety function of a system credited to mitigate the consequences of an accident. This power source is not considered to be a safety-related system that is credited to mitigate any accident as described in the DCPP UFSAR, Chapters 6 and 15 accident analyses. PG&E concludes that the emergency diesel generators are the only power source needed to fulfill the accident mitigation function, and they did not become inoperable as a result of this event. The licensee will be notifying the NRC Resident Inspector. Notified R4DO (Werner). | |
| ENS 48819 | 13 March 2013 00:06:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | Unit 2 Loss of Shutdown Monitoring Instrumentation System | On March 12, 2013, at 1706 PDT, with the reactor coolant system not intact, plant operators identified (an) unexpected increase in nuclear reactivity count rate as indicated by source range instrumentation channel N-32. This increase was NOT indicated on redundant wide range instrumentation channels N-51 and N-52. Operators identified that technicians working in the area of the N-32 cable routing had bumped the cabling, resulting in the false increase in the count rate. The source range channel N-32 was subsequently declared inoperable. Prior to this event the other source range channel N-31 had been declared inoperable. The above event resulted in loss of control room audible indication required by DCPP (Diablo Canyon Power Plant) technical specification to monitor the core reactivity condition and consequently caused loss of the monitoring system. Operators retained capability of monitoring core reactivity conditions through use of the two wide range nuclear instrumentation channels N-51 and N-52. In response to this concern, plant operators verified all core alterations were suspended, verified boron concentration was within acceptable limits for current conditions, suspended operations that could dilute the boron concentration, verified reactor trip breakers were open and control rods incapable of withdrawal, and initiated actions to restore to service one of the source range instrumentation channels with its associated control room audible count rate indication. NRC Resident Inspectors have been notified.
This is an update to EN #48819 reported on March 12, 2013 at 2158 PDT. This update informs the NRC that PG&E, in accordance with provisions of TS 3.0.4b, will be restoring the source range instrumentation channel N-32 to service in Mode 5, maintaining the availability and monitoring of the wide range instrumentation channels while in Mode 5 until the source range channel is returned to service. The licensee has notified the NRC Resident Inspector. Notified R4DO (Powers). | 05000323/LER-2013-002 |
| ENS 48796 | 1 March 2013 05:54:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Emergency Bus Inadvertently De-Energized with Unit Defueled | On February 28, 2013, at 2154 PST, Unit 2 4kV ESF Bus G deenergized while attempting a repair to the bus automatic transfer circuitry. The deenergization of 4kV ESF Bus G initiated a start signal to Diesel Generator 2-1, which supplies emergency power to 4kV ESF Bus G. Diesel Generator 2-1 did not start due to being placed in manual control to prevent starting automatically during the repair. However, a valid actuation signal was generated to start Diesel Generator 2-1. As the Diesel Generator was shut down and in manual control, no actuation occurred. This is reportable as a valid system actuation that was not part of a pre-planned sequence during testing. Unit 2 is currently defueled, with the core offloaded into the spent fuel pool. No loss of cooling occurred as spent fuel pool cooling equipment had been selected to unaffected buses. The NRC resident has been notified. | 05000323/LER-2013-001 |
| ENS 48786 | 27 February 2013 00:30:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Assessment Capability Due to Vital Inverter Maintenance | At approximately 1630 PST on February 26, 2013, Pacific Gas & Electric (PG&E) will be performing repairs on a vital inverter. The clearance will remove power from various inputs to the Safety Parameter Display System (SPDS), Emergency Response Data System (ERDS), and Emergency Response Data and Recall Recorder Subsystem (ERFDS). PG&E expects to have the equipment repaired and returned to service within 12 hours. During this time, a dedicated licensed operator will be available to provide plant data to the NRC's Emergency Operations Center. DCPP is making this 8-hour, non-emergency notification under 10 CFR 50.72(b)(3)(xiii) as any event that results in a major loss of emergency assessment capability, offsite response capability, or offsite communications capability. The licensee notified the NRC Resident Inspector. |