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 Entered dateSiteRegionReactor typeEvent description
ENS 5432812 October 2019 15:54:00Diablo CanyonNRC Region 4One 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 5423422 August 2019 12:49:00Diablo CanyonNRC Region 4This 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 5382916 January 2019 15:10:00Diablo CanyonNRC Region 4A 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 537641 December 2018 16:56:00Diablo CanyonNRC Region 4At 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 5347125 June 2018 17:58:00Diablo CanyonNRC Region 4At 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 5336124 April 2018 14:44:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * UPDATE ON 4/24/18 AT 1716 EDT FROM ERIC THOMAS TO DONG PARK * * *

RM-30 was restored to service. Portable radiation monitoring is not required. The licensee will notify the NRC Resident Inspector. Notified R4DO (Vasquez).

ENS 5318426 January 2018 01:37:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt 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 5309629 November 2017 18:09:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopOn 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 5287628 July 2017 15:22:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * UPDATE FROM ALLEN DURACHER TO VINCE KLCO ON 7/28/17 AT 2142 EDT * * *

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 5268918 April 2017 15:55:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopThe testing laboratory returned results for a blind specimen that was inconsistent with what was expected. The licensee has notified the NRC Resident Inspector.
ENS 5265230 March 2017 21:58:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt 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 5263223 March 2017 13:55:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAn 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 5226023 September 2016 20:10:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * RETRACTION FROM FRANK LEE TO DONALD NORWOOD AT 1953 EST ON 11/18/2016 * * *

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 5201116 June 2016 16:19:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * UPDATE FROM MATTHEW PLEASANT TO DONALD NORWOOD AT 1955 EDT ON 6/16/2016 * * *

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 5196530 May 2016 19:11:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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 5165514 January 2016 18:10:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.)

  • * * UPDATE AT 1905 EST ON 02/23/16 FROM DOUG EVANS TO S. SANDIN * * *

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 5162023 December 2015 11:43:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopThe licensee discovered prohibited material inside the protected area. The material has been removed. The licensee has notified the NRC Resident Inspector.
ENS 5124621 July 2015 21:22:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopOn 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 5071131 December 2014 20:44:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt 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.
ENS 505861 November 2014 02:07:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt 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 5037015 August 2014 01:19:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopWhile 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 5033431 July 2014 23:49:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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).

  • * * RETRACTION RECEIVED FROM BOB KLINE TO JOHN SHOEMAKER AT 1839 EDT ON 09/24/14 * * *

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 5023527 June 2014 20:33:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt 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 498796 March 2014 19:33:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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."

  • * * UPDATE PROVIDED BY RUSS CRUZEN TO JEFF ROTTON AT 2245 EDT ON 09/09/2014 * * *

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 497862 February 2014 18:16:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopOn 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 4966319 December 2013 16:21:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopOn 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 4963414 December 2013 19:32:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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 493349 September 2013 16:05:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * UPDATE FROM ADAM PECK TO HOWIE CROUCH AT 1704 EDT ON 9/19/13 * * *

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 4928716 August 2013 02:36:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt 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 4918410 July 2013 16:13:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopOn 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 491733 July 2013 12:51:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * UPDATE FROM DAN STERMER TO JOHN SHOEMAKER AT 1948 EDT ON 7/3/13 * * *

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 4914826 June 2013 01:59:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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 4914724 June 2013 22:07:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt 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 4914324 June 2013 04:35:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * UPDATE FROM MICHAEL KENNEDY TO HOWIE CROUCH AT 1618 EDT ON 8/21/13 * * *

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 4881913 March 2013 00:58:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * UPDATE AT 0848 EDT ON 3/13/13 FROM MICHAEL QUITTER TO DONG PARK * * *

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).

ENS 487961 March 2013 04:00:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopOn 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.
ENS 4878626 February 2013 19:20:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt 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.
ENS 487266 February 2013 21:23:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

On February 06, 2012, at 1524 PST, engineers reviewing dose analyses for non-LOCA, non-fuel handling accident analyses identified deficiencies in the analyses. The analyses of concern include a locked reactor coolant pump rotor, a control rod ejection accident, main steam line break, and steam generator tube rupture. These deficiencies brought into question whether the 30 day control room operator dose received following one of these accidents would meet the station licensing basis limits of up to 5 rem whole body or its equivalent. In response to this concern, plant operators placed the control room ventilation system in its safeguards alignment, thereby ensuring the events would continue to be bounded by the analysis of the large break loss of coolant accident. The NRC Resident Inspector has been notified.

  • * * RETRACTION FROM DAVID BAHNER TO CHARLES TEAL ON 02/28/13 AT 1815 EST * * *

Pacific Gas and Electric Company (PG&E) is correcting the event date in the above Description to February 06, 2013, and is retracting EN 48726 based on the results from reanalysis of each affected non-loss-of-coolant accident (LOCA) event (i.e., steam generator tube rupture, main steam line break, control rod ejection, and reactor coolant pump locked rotor) for potential impact on control room operator dose. The new dose assessment determined that control room dose consequences from a large-break LOCA bound the non-LOCA events as assumed in the original analyses. Accordingly, PG&E concludes the Diablo Canyon Power Plant control room ventilation system remains capable of maintaining control room dose limits within General Design Criteria-19. Plant personnel notified the NRC resident inspector. Notified R4DO (Allen).

ENS 4860018 December 2012 02:07:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

This is a non-emergency notification. At 1804 PST on December 17, 2012, Diablo Canyon Unit 1 experienced a loss of plant vent continuous radiation monitors (RM) and redundant monitors 14/14R, 24/24R, 28/28R and 87. These radiation monitors are credited for Emergency Action Level (EAL) classification in the Diablo Canyon Emergency Plan. This event is reportable per 10 CFR 50.72(b)(3)(xiii) as described in NUREG-1022, Rev. 2. Compensatory measures of periodic sampling have been established in accordance with plant equipment control guidelines. Event classification can be performed by means of the sampling in accordance with plant procedures. Additionally, continuous radiation monitoring of the plant vent remains via high range radiation monitor RM-29. The cause of the loss of radiation monitors is not known at this time. This condition does not affect the health and safety of the public or the operation of the facility. The NRC Resident Inspector was informed.

  • * * UPDATE AT 0948 EST ON 12/18/12 FROM DAVE GOUVEIA TO HUFFMAN * * *

The licensee determined that the flow element on the sampling pump for the radiation monitors had failed. At 0630 EST, the condition was repaired and the radiation monitors returned to service. R4DO (Whitten) notified.

ENS 4854128 November 2012 02:38:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopThe control room ventilation system (CRVS) pressurization mode is required to be actuated by a safety injection signal, control room radiation atmosphere air intake, and operator manual actuation in accordance with Technical Specification (TS) 3.3.7. On November 27, 2012 at 2038 hrs. PST, Pacific Gas and Electric Company (PG&E) identified that none of the CRVS four pressurization fans would operate continuously if they started in response to a safety injection or control room radiation atmosphere intake actuation signal. All of the pressurization fans remain capable of continuous operation via manual actuation. At 2050 PST the Unit 2 CRVS was manually placed in pressurization mode in accordance with TS 3.3.7, ACTION B.1.1. This was determined to be caused by a recent flow balancing of the CRVS that raised the static air pressure. The increased system static pressure actuates the fan-run pressure switches for each of the four associated pressurization fans, when only a single pressurization fan is operated. This results in the system logic securing all pressurization fans started by the CRVS automatic actuation signals. If all pressure switches actuate, automatically started pressurization fans will be secured until air pressure decays below the fan-run switch setpoint, at which time the pressurization fan would restart. This would result in cyclic operation of the pressurization fan. The fan-run pressure switches are not part of the manual actuation circuitry for the pressurization fans. Diablo Canyon (DCPP) is making this 8-hour, non-emergency notification under 10 CFR 50.72(b)(3)(v)(D). Plant personnel notified the NRC Resident Inspector.
ENS 4842721 October 2012 03:25:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

HU1.1 Seismic event identified by earthquake felt in plant and US Geological Survey (USGS). An earthquake was felt onsite at approximately 0000 PDT. The licensee stated that two out of three methods for determining if an Unusual Event should be declared were met (i.e. the earthquake was felt in the plant and the earthquake was monitored by the USGS). The licensee characterized the earthquake as a "very mild" event. The licensee stated that, at the present time, there was no indication of damage to either unit and that both units remain at 100% power. The licensee is in the process of conducting walkdowns to confirm there was no damage to the plant. The USGS classified the magnitude of the earthquake as 5.3. The licensee notified state and local authorities and the NRC Resident Inspector. Notified other federal agencies (FEMA, DHS, DHS NICC and Nuclear SSA via email).

  • * * UPDATE FROM HENRY CLARDY TO VINCE KLCO ON 10/21/12 AT 1448 EDT * * *

As of 1142 PDT on 10/21/12, the licensee terminated from the Unusual Event based on review of completed plant walkdowns. No damage was identified. Both Units are stable and in normal plant operations. The licensee notified state and local authorities and will notify the NRC Resident Inspector. Notified the R4DO (Pick), NRR EO (Bahadur), IRD MOC (Grant) and federal agencies (FEMA, DHS, DHS NICC and Nuclear SSA via email).

ENS 4840011 October 2012 18:44:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

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.

  • * * UPDATE FROM DAN STERMER TO DONG PARK AT 2259 EDT ON 10/11/12 * * *

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).

ENS 4839510 October 2012 00:32:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

On 10/9/12, at 16:30 PDT control room operators were questioned whether recently identified fire protection program deficiencies should have been reported to the NRC. On October 3 and October 8, 2012, DCPP (Diablo Canyon Power Plant) staff reviewing NFPA 805 Nuclear Safety Capability Assessment (NSCA) Variance From Deterministic Requirements (VFDRs) identified fire areas that neither conformed to Appendix R requirements nor had established, proceduralized and practiced compensatory measures in place. The issues were identified in the DCPP corrective action program and compensatory measures were established in accordance with the DCPP fire protection program requirements. Event: 10/3/12 Fire areas containing cables associated with startup transformers 1-2 and 2-2 could result in loss of startup power and also prevent the emergency diesels from performing their Appendix R safe shutdown function. Event: 10/8/12 Fire areas containing reactor coolant pump (RCP) breakers could result in loss of RCP seal cooling and prevent the credited local manual trip of the RCPs, contrary to the specified method of performing the Appendix R safe shutdown function. Event: 10/8/12 Fire areas containing cables for the ventilation systems of the 480V switchgear, DC panels, and battery chargers could require unproceduralized use of portable fans to maintain adequate cooling of the electrical equipment necessary to perform the Appendix R safe shutdown function. Operators established fire watches as compensatory measures as required by the DCPP fire protection program requirements. The above late notification of discovery of the unanalyzed conditions has been entered into the DCPP corrective action program. NRC Resident Inspector has been notified.

          • UPDATE AT 0028 EDT ON 11/01/12 FROM GLENN GOELZER TO S. SANDIN*****

This is an update to EN #48395 reported on October 10, 2012, at 0032 EDT. During the NRC's Fire Protection Triennial Inspection the NRC identified that several Alternate Compensatory Measures (ACMs) were not in the current post-fire procedure CP M-10. The ACMs address potential Appendix R non-conformance issues identified via the initiative to convert the DCPP fire protection program to NFPA 805. PG&E has established compensatory measures for all the identified areas in accordance with the DCPP fire protection program requirements. (The) NRC Resident Inspector has been notified. Notified R4DO (Deese).

  • * * UPDATE FROM D. BAHNER TO V. KLCO ON 11/30/12 AT 1618 EST * * *

This is an update to EN #48395 reported on October 9, 2012, at 2132 PST. During the ongoing evaluation of the issues previously identified in this event notification, PG&E (Pacific Gas & Electric) has concluded that a fire in the fire areas containing cables associated with startup transformers 1-2 and 2-2 would not result in loss of startup power or prevent the emergency diesels from performing their Appendix R safe shutdown function. This issue was reported as an unanalyzed condition. However, it is analyzed and controlled in plant procedure CP M-10, 'Fire Protection of Safe Shutdown Equipment.' PG&E retracts the initial event documented on October 3, 2012, thus making the date on which the first unanalyzed condition was discovered October 8, 2012. Therefore, PG&E will submit the 60-day Licensee Event Report by December 7, 2012. The NRC Resident Inspector has been notified. Notified the R4DO(Whitten).

  • * * UPDATE AT 1944 EST ON 1/30/13 FROM KLINE TO TEAL* * *

This is an update to EN #48395 reported on October 9, 2012, at 2132 PDT. On October 31, 2012, at 2128 PDT, PG&E provided an update to this event notification identifying that several alternate compensatory measures (ACMs) were not in plant procedure, CP M-10, 'Fire Protection of Safe Shutdown Equipment.' PG&E has evaluated this further and concluded that ACMs had been adequately implemented in CP M-10, and therefore retracts the EN update of (November 1, 2012 at 0028 EDT). NRC resident inspector has been notified. Notified R4DO (Walker).

ENS 4833925 September 2012 09:46:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

On September 25, 2012, power was removed from various Technical Support Center (TSC) systems to perform planned system preventative maintenance (PM) and corrective maintenance (CM) activities. During these maintenance activities, the normal TSC and Operational Support Center (OSC) are unavailable for use during an emergency. The Plant Data Network (PDN) will not be available to the TSC. This will render the Safety Parameter Display System (SPDS), Emergency Response Facility Display System (ERFDS), Emergency Assessment and Response System (EARS) and the Post LOCA Sampling System in the TSC unavailable. System alarms and data displays will still be available to the plant operators in the Control Room. The expected duration of the power outage is approximately 39 hours. As compensatory measures, the backup emergency response facilities will be manned during an emergency. This compensatory measure has been communicated to the emergency response organization. It is expected that appropriate assessment of plant conditions, notifications, and communications could still be made, if required, during the time that the normal TSC and OSC are unavailable. This report is being made in accordance with 10 CFR 50.72(b)(3)(xiii), which is any event that results in a major loss of emergency assessment capability, offsite response capability, or offsite communications capability. An update message will be provided when the emergency response facilities are restored. The licensee will notify the NRC Resident Inspector.

  • * * UPDATE FROM GOELZER TO KLCO ON 9/27/12 AT 0025 EDT * * *

This is an update to EN #48339 report on September 25, 2012, where Pacific Gas & Electric company (PG&E) reported that a planned maintenance power outage caused the normal Technical Support Center (TSC) and Operational Support Center (OSC) to be unavailable for use during an emergency. PG&E has completed all preventative maintenance (PM) and corrective maintenance (CM) activities that required the power outage to the TSC and OSC and has completed the restoration of these emergency response facilities. Plant personnel have been notified that the normal emergency response facilities have been restored. PG&E personnel have informed the NRC Resident Inspector. Notified the R4DO (Werner).

ENS 4824629 August 2012 00:16:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

On August 28, 2012, 17:00 PDT, Pacific Gas and Electric Company (PG&E) identified additional release pathways that could affect the control room (CR) operator dose following a Large-Break Loss-of-Coolant Accident (LBLOCA). Consequently, PG&E declared the control room envelope (CRE) inoperable and is establishing mitigative actions in accordance with TS 3.7.10, Action B.1, 'Initiate action to implement mitigating actions' immediately, and Action B.2, 'Verify mitigating actions ensure CRE occupant exposures to radiological hazards will not exceed limits, and CRE occupants are protected from smoke and chemical hazards' within 24 hours. PG&E is establishing mitigative actions in accordance with TS 3.7.10 and RG 1.196. These mitigative actions are for operations control room personnel to administer potassium iodide and don self-contained breathing apparatus equipment in a timely fashion should a LBLOCA occur. They will be communicated and controlled by a standing order to the control room staff. PG&E previously established controls on other release pathways that offset the potential increases to the maximum predicted offsite dose due to the new release pathways. No increase in maximum predicted offsite dose is expected from the new release pathways. Diablo Canyon (DCPP) is making this 8-hour, non-emergency notification under 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v)(D). Plant personnel notified the NRC Resident Inspector.

* * * UPDATE AT 1600 EDT ON 9/8/12 FROM GLEN GOELZER TO PETE SNYDER * * * 

PG&E is retracting EN 48246, based on the results from a new dose analysis coupled with compensatory measures implemented to ensure that the analysis input parameters and assumption will not be inadvertently exceeded. The analysis concluded that the CRE was operable and that CR doses remained below regulatory limits. Plant personnel notified the NRC resident inspector. Notified R4DO (Gaddy).

ENS 481719 August 2012 11:47:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopAt about 1000 PDT on August 9, 2012, Pacific Gas and Electric Company (PG&E) will disconnect the Diablo Canyon Power Plant (DCPP) Plant Data Network to the Emergency Operations Facility (EOF) and redirect the data via the Utility Data Network for hosting the emergency facility data systems. These systems include the Safety Parameter Display System, Plant Process Computer, Emergency Response Facility Display System, and Emergency Assessment and Response System in the EOF. PG&E expects to have the Emergency Response Data System and the EOF data network unavailable for about 8 hours. During this time, if needed, the TSC will have command and control once staffed, and will have classification, notification and dose assessment responsibility until the display systems are restored to the EOF. Also, if required, a dedicated licensed operator will be available in the control room 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 has notified the NRC Resident Inspector.
ENS 480027 June 2012 11:56:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopOn June 7, 2012, at 0129 PDT, both trains of the low temperature overpressure (LTOP) system were rendered inoperable when the vital 120 VAC panel PY-13 was de-energized due to a human performance error. DCPP Unit 1 was in Mode 5, reactor coolant system loops not filled. Technicians were troubleshooting an existing de-energized vital 120 VAC panel PY-14 that had resulted from the supply breaker tripping open. The technician incorrectly opened the supply breaker to panel PY-13 instead of PY-14. With PY-14 de-energized, one train of LTOP was inoperable due to loss of signal from Reactor Coolant System (RCS) wide range pressure transmitter PT-405A. With PY-13 de-energized, the second train of LTOP was rendered inoperable due to loss of signal from RCS wide range pressure transmitter PT-403A. Operations immediately recognized the error and had the technician reclose the PY-13 supply breaker, thereby re-energizing panel PY-13, returning one train of LTOP back to its operable condition. Plant personnel notified the NRC Resident Inspector.
ENS 4787229 April 2012 17:35:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopThis report constitutes a 10 CFR Part 21 notification. On March 23, 2012, Scientech (a business unit of Curtis Wright Flow Control), sent a 10 CFR Part 21 report (Letter Number 12-09-BB) to Pacific Gas & Electric Company. Diablo Canyon Nuclear Plant (DCPP) entered this report into its corrective action program on April 23, 2012. This Part 21 report identified that eight AMS286 and AMS287 hand controllers supplied to DCPP had a deviation from the purchase specification. DCPP specified the controllers to be qualified to meet electromagnetic interference (EMI) / radio frequency interference (RFI) emissions and susceptibility in accordance with NRC Regulatory Guide 1.180, Rev. 1. Contrary to this requirement, Scientech did not perform the EMI / RFI testing on the AMS286 controllers shipped to DCPP with a Certificate of Conformance to DCPP's specification. Scientech tested the AMS287 controllers, which failed some of the required testing, but were shipped to DCPP with a Certificate of Conformance nonetheless. DCPP accepted the controllers based on the Certificates of Conformance, but did not install them. Following acceptance of the controllers, DCPP identified the nonconformance with its specification, and had another vendor modify the controllers to subsequently pass required testing. DCPP determined the deviation could have potentially created a substantial safety hazard if the controllers were installed at DCPP. The controllers were intended to control auxiliary feedwater from the Unit 1 control room and the hot shutdown panel as part of an upcoming process control system modification. Following a postulated fire in the control room, plant shutdown would be managed from the hot shutdown panel. In this instance, radios would be used to communicate with operators at the panel. The controllers would be susceptible to EMI/RFI interference and could potentially affect the operators' ability the safely shut down the plant and maintain it in a safe shutdown condition. DCPP notified Scientech of this conclusion on 4/27/12. The licensee notified the NRC Resident Inspector.
ENS 4786526 April 2012 04:20:00Diablo CanyonNRC Region 4Westinghouse PWR 4-LoopOn 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.
ENS 4785822 April 2012 02:50:00Diablo CanyonNRC Region 4Westinghouse PWR 4-Loop

On April 21, 2012, at 1615 PDT, Diablo Canyon Power Plant (DCPP) operators identified that an attempted manual transfer of the Unit 1 AC power sources from the normal offsite circuit (500 kv) to the alternate offsite circuit (230 kv) failed. The attempted manual transfer of the offsite power source from the normal 500 kv to the alternate 230 kv was a planned activity to shut down Unit 1 for its 17th refueling outage. The failure to manually transfer was concluded to be caused by an indicated out of phase condition between the 500 kv and 230 kv system. DCPP control transfer systems prevent paralleling and transferring the power supplies from the normal to alternate offsite circuit with an out of phase condition. The offsite AC power sources remain capable of being manually transferred from the normal to the alternate source by way of transferring to diesels as an intermediate step. The 230 kv system ability to perform its accident mitigation safety function following a reactor trip or safety injection was not affected by the inability to perform a direct manual transfer from the 500 kv offsite power system. DCPP staff are currently troubleshooting the out of phase indication and will provide an update when the cause is concluded. The licensee notified the NRC Resident Inspector.

  • * * UPDATE FROM MIKE QUITTER TO HOWIE CROUCH AT 2013 EDT ON 4/25/12 * * *

This is an update to EN #47858 reported on April 22, 2012, where Pacific Gas & Electric Company (PG&E) reported that an attempt to manually transfer the DCPP Unit 1 AC power sources from the normal offsite circuit (500 kV) to the alternate required offsite circuit (230 kV) failed. PG&E determined that the out-of-phase condition between the 500kV system and the 230 kV system resulted from the offsite power system configurations and conditions existing at the time of the attempted transfer. PG&E established alternate operating guidance to allow operators to perform bus transfers between the 500kV source and the 230 kV source in the event that an out-of-phase condition exists when bus transfer is desired. PG&E personnel informed the NRC Resident Inspector. Notified R4DO (Proulx).