IR 05000275/2024004
| ML25015A030 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/15/2025 |
| From: | Patricia Vossmar NRC/RGN-IV/DORS/PBA |
| To: | Gerfen P Pacific Gas & Electric Co |
| References | |
| IR 2024004 | |
| Download: ML25015A030 (1) | |
Text
January 15, 2025
SUBJECT:
DIABLO CANYON POWER PLANT, UNITS 1 AND 2 - INTEGRATED INSPECTION REPORT 05000275/2024004 AND 05000323/2024004
Dear Paula A. Gerfen:
On December 31, 2024, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Diablo Canyon Power Plant, Units 1 and 2. On January 13, 2025, the NRC inspectors discussed the results of this inspection with you and other members of your staff.
The results of this inspection are documented in the enclosed report.
No findings or violations of more than minor significance were identified during this inspection.
This letter, its enclosure, and your response (if any) will be made available for public inspection and copying at http://www.nrc.gov/reading-rm/adams.html and at the NRC Public Document Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.
Sincerely, Patricia J. Vossmar, Chief Reactor Projects Branch A Division of Operating Reactor Safety Docket Nos. 05000275 and 05000323 License Nos. DPR-80 and DPR-82
Enclosure:
As stated
Inspection Report
Docket Numbers:
05000275 and 05000323
License Numbers:
Report Numbers:
05000275/2024004 and 05000323/2024004
Enterprise Identifier:
I-2024-004-0008
Licensee:
Pacific Gas and Electric Company
Facility:
Diablo Canyon Power Plant, Units 1 and 2
Location:
Avila Beach, CA
Inspection Dates:
October 1, 2024, to December 31, 2024
Inspectors:
E. Garcia, Resident Inspector
M. Hayes, Senior Resident Inspector
D. You, Operations Engineer
Approved By:
Patricia J. Vossmar, Chief
Reactor Projects Branch A
Division of Operating Reactor Safety
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an integrated inspection at Diablo Canyon Power Plant, Units 1 and 2, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for overseeing the safe operation of commercial nuclear power reactors. Refer to https://www.nrc.gov/reactors/operating/oversight.html for more information.
List of Findings and Violations
No findings or violations of more than minor significance were identified.
Additional Tracking Items
Type Issue Number Title Report Section Status URI 05000323/2024001-07 Auxiliary Building Ventilation Inoperable Coincident with Redundant Train Diesel Generator Maintenance Outage 71153 Closed LER 05000323/2024-001-00 LCO 3.0.3 Completion Time Limits 71153 Closed
PLANT STATUS
Unit 1 began the inspection period at rated thermal power. On October 5, 2024, the unit reduced power to 50 percent to support condenser cleaning. The unit returned to full power on October 7, 2024. The unit remained at or near rated thermal power for the remainder of the inspection period.
Unit 2 operated at or near rated thermal power for the entire inspection period.
INSPECTION SCOPES
Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors performed activities described in IMC 2515, Appendix D, Plant Status, observed risk significant activities, and completed on-site portions of IPs. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.
REACTOR SAFETY
71111.04 - Equipment Alignment
Partial Walkdown Sample (IP Section 03.01) (2 Samples)
The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:
- (1) Unit 1 auxiliary saltwater pump 1-1 on October 2, 2024
- (2) Units 1 and 2 auxiliary feedwater cross tie to firewater on November 15, 2024
71111.05 - Fire Protection
Fire Area Walkdown and Inspection Sample (IP Section 03.01) (4 Samples)
The inspectors evaluated the implementation of the fire protection program by conducting a walkdown and performing a review to verify program compliance, equipment functionality, material condition, and operational readiness of the following fire areas:
- (1) Unit 2 radiological control area, 115-foot elevation, on October 2, 2024
- (2) Unit 1 emergency diesel generator rooms 1-1, 1-2, and 1-3 on October 30, 2024
- (3) Unit 2 emergency diesel generator rooms 2-1 and 2-2 on November 15, 2024
- (4) Unit 2 vital 480 V switchgear rooms on December 11, 2024
71111.11A - Licensed Operator Requalification Program and Licensed Operator Performance
Requalification Examination Results (IP Section 03.03) (1 Sample)
- (1) The inspectors reviewed and evaluated the licensed operator examination failure rates for the requalification annual operating exam administered from September 17, 2024, to October 25, 2024.
71111.11Q - Licensed Operator Requalification Program and Licensed Operator Performance
Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
- (1) The inspectors observed and evaluated a crew of licensed operators during simulator training on October 1, 2024.
71111.13 - Maintenance Risk Assessments and Emergent Work Control
Risk Assessment and Management Sample (IP Section 03.01) (2 Samples)
The inspectors evaluated the accuracy and completeness of risk assessments for the following planned and emergent work activities to ensure configuration changes and appropriate work controls were addressed:
- (1) Yellow risk due to emergency diesel generator 1-3 planned maintenance on October 14, 2024 (2)inadvertent VANS notification made to emergency response organization on November 19, 2024
71111.15 - Operability Determinations and Functionality Assessments
Operability Determination or Functionality Assessment (IP Section 03.01) (4 Samples)
The inspectors evaluated the licensee's justifications and actions associated with the following operability determinations and functionality assessments:
- (1) Unit 1 reliability of support systems necessary for emergency diesel generators 1-1 and 1-2 during the maintenance on emergency diesel generator 1-3 on October 16, 2024
- (2) Unit 1 update to the probability risk assessment model and how it effects risk informed completion time on October 21, 2024
- (3) Unit 1 dual indication on emergency diesel generator 1-3 fuel transfer start circuit on October 29, 2024
71111.18 - Plant Modifications
Temporary Modifications and/or Permanent Modifications (IP Section 03.01 and/or 03.02) (1 Sample)
The inspectors evaluated the following temporary or permanent modifications:
(1)reducing number of protected emergency diesel generators from three to two during an offsite power radial feed on December 9, 2024
71111.24 - Testing and Maintenance of Equipment Important to Risk
The inspectors evaluated the following testing and maintenance activities to verify system operability and/or functionality:
Post-Maintenance Testing (PMT) (IP Section 03.01) (6 Samples)
- (1) Unit 1 auxiliary saltwater pump 1-2 and component cooling water heat exchanger 1-2 return to service following testing on October 1, 2024
- (2) Unit 1 emergency diesel generator 1-3 following overhaul and extended on-line maintenance on October 21, 2024
- (3) Unit 1 and 2 diesel fuel oil transfer pump 0-1 following filter and fuse replacements on October 23, 2024
- (4) Unit 2 centrifugal charging pump 2-1 following maintenance on December 3, 2024
- (5) Unit 2 auxiliary building ventilation supply and exhaust fans following sensor modification on December 11, 2024
- (6) Unit 2 component cooling water pump 2-3 following breaker maintenance on December 18, 2024
Surveillance Testing (IP Section 03.01) (3 Samples)
- (1) Unit 1 Surveillance Test Procedure P-SIP-11, "Routine Surveillance Test of Safety Injection Pump 1-1," on October 8, 2024
- (2) Unit 2 Surveillance Test Procedure P-AFW-23, "Routine Surveillance Test of Motor-Driven Auxiliary Feedwater Pump 2-3," on November 5, 2024
- (3) Unit 1 Surveillance Test Procedure P-CCW-A11, "Comprehensive Pump Test of Component Cooling Water Pump 1-1," on November 6, 2024
71114.06 - Drill Evaluation
Additional Drill and/or Training Evolution (1 Sample)
The inspectors evaluated:
- (1) The inspectors evaluated a tabletop emergency preparedness drill on November 13,
OTHER ACTIVITIES - BASELINE
===71151 - Performance Indicator Verification The inspectors verified licensee performance indicators submittals listed below:
BI01: Reactor Coolant System (RCS) Specific Activity Sample (IP Section 02.10)===
- (1) Unit 1 (October 1, 2023, through September 30, 2024)
- (2) Unit 2 (October 1, 2023, through September 30, 2024)
BI02: RCS Leak Rate Sample (IP Section 02.11) (2 Samples)
- (1) Unit 1 (October 1, 2023, through September 30, 2024)
- (2) Unit 2 (October 1, 2023, through September 30, 2024)
71152A - Annual Follow-up Problem Identification and Resolution Annual Follow-up of Selected Issues (Section 03.03)
The inspectors reviewed the licensees implementation of its corrective action program related to the following issues:
(1)review of oil misting onto safety-related cables in inverter rooms on December 17, 2024
71152S - Semiannual Trend Problem Identification and Resolution Semiannual Trend Review (Section 03.02)
- (1) The inspectors reviewed the licensees corrective action program to identify potential trends in auxiliary building ventilation fans failing to start on demand during periods of high rain that might be indicative of a more significant safety issue. The inspectors reviewed the design change package which modified flow switches associated with the starting circuit of the auxiliary building ventilation fans. The inspectors also reviewed the failures to ensure they were properly documented in the maintenance rule program. Overall, the inspectors determined the licensee properly documented the failures of auxiliary building ventilation fans to start and took appropriate corrective actions.
71153 - Follow Up of Events and Notices of Enforcement Discretion Event Report (IP Section 03.02)
The inspectors evaluated the following licensees event reporting determinations to ensure it complied with reporting requirements.
- (1) LER 05000323/2024-001-00, "LCO 3.0.3 Completion Time Limits" (ADAMS Accession No. ML24141A032). The inspectors determined that the cause of the condition described in the LER was not reasonably within the licensee's ability to foresee and correct, and therefore was not reasonably preventable. No performance deficiency nor violation of NRC requirements was identified. This LER is Closed.
INSPECTION RESULTS
Unresolved Item (Closed)
Auxiliary Building Ventilation Inoperable Coincident with Redundant Train Diesel Generator Maintenance Outage URI 05000323/2024001-07 71153
Description:
On March 18, 2024, during a planned maintenance outage of Unit 2 emergency diesel generator (DG) 2-2, auxiliary building ventilation system (ABVS) fan E-1 tripped off on thermal overload and was declared inoperable. The redundant ABVS fan E-2 started automatically and was supported by DG 2-2, which was inoperable due to the planned maintenance outage. Technical specification (TS) limiting condition for operation (LCO) 3.8.1, condition B, required action B.2 requires declaring equipment supported by the inoperable DG inoperable when the redundant equipment on the other train is inoperable, within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of discovery of the condition. After condition B, required action B.2 was applied, operators declared ABVS fan E-2 inoperable in accordance with TS LCO 3.7.12 (the TS for ABVS).
TS LCO 3.7.12 does not describe a required action for two inoperable ABVS trains.
Therefore, TS LCO 3.0.3 was entered, and the licensee was required to be in Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> of applying TS 3.8.1.B.2.
The licensee stated that after ABVS fan E-1 failed, their troubleshooting investigation identified slight discoloration of the C phase contactor between the breaker and the contactor on the load side downstream of the breaker. Voltage, current, and thermography measurements indicated the cause of the condition was most likely local to the connections between the breaker and the contactor. The licensees immediate corrective actions were to refurbish the copper bus bar between the breaker and the contactor and to replace the fasteners for the bus bar. Additional movable contacts internal to the breaker were replaced with a new contact kit. The equipment was post-maintenance tested, declared operable, and returned to service within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The licensee performed a causal evaluation for the ABVS fan E-1 trip and the circumstances surrounding the request for a Notice of Enforcement Discretion (NOED). It was determined that the cause of the thermal overload condition was due to oxidation buildup in the 480 V breaker cubicle for the E-1 fan. This oxidation buildup occurs over a long period of time through normal breaker operation. The breaker cubicle was last opened and inspected on October 24, 2022, during a Unit 2 refueling outage. The system engineer determined the cubicle to be in acceptable condition after all bolted connections were checked and tightened, loose stab and termination connections were checked SAT, and no signs of overheating or excessive contact wear was discovered. The licensee determined that a NOED was necessary because there was no TS action statement for having two inoperable ABVS trains and it was unlikely that troubleshooting, repair plan development and execution, and returning affected equipment to service could be completed within the 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> prior to declaring redundant equipment inoperable per TS 3.8.1 action B.2.
The inspectors evaluated the licensees immediate corrective actions and causal evaluation of the event, and did not identify any findings or violations of more than minor significance. It was not reasonably within the licensees ability to foresee and correct a thermal overload condition on an ABVS exhaust fan breaker during the coincident redundant train DG maintenance outage prior to the requirements of TS 3.0.3 to be in Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. The licensee took the necessary steps to request and receive a NOED, conducted maintenance on the affected equipment, and returned the required TS equipment to operable status within the 24-hour period of discretion granted by the NOED. The licensee plans to conduct thermography prior to major DG maintenance windows in the future and are updating their procedures to incorporate this action. Enhanced monitoring and thermography of 480 V breakers will be conducted going forward to preemptively identify issues. Training and procedure updates for breaker cubicle inspections will be performed due to this event. This URI is closed.
Corrective Action References: Notification 51229398, 51229466, and
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
- On January 13, 2025, the inspectors presented the integrated inspection results to Paula Gerfen, Senior Vice President, Generation and Chief Nuclear Officer, and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
106717-7
Intake Structure for Unit 1
216
106717-7A
Intake Structure for Unit 2
216
Drawings
106717-8
Unit 1 Intake Discharge to Condenser Outlet Flow Diagram
2
EOP FR-C.1
Unit 1 Response to Inadequate Core Cooling
26C
Procedures
EOP FR-C.1
Unit 2 Response to Inadequate Core Cooling
19D
Corrective Action
Documents
Notifications
256348
111805-12
Unit 1 & 2 Radiological Control Area (RCA) Elev. 100
111805-22
Unit 2 Radiological Control Area (RCA) Elev. 115'
111805-49
Unit 1 Turbine Building Elev. 85'
111805-60
Unit 2 Turbine Building Elev. 85'
111805-61
Unit 2 Turbine Building Elev. 85'
111906-11
Unit 2 Turbine Building Elev. 85'
111906-12
Unit 2 Turbine Building Elev. 104'
Drawings
111906-6
Unit 1 Turbine Building Elev. 85'
Miscellaneous
M-824
Controlled Combustion Loading Tracking Calculation
Miscellaneous
71111.11A Table 03.03-1 Examination Results
TQ2.DC3
Licensed Operator Continuing Training Program
TQ2.DC15
Licensed Operator Annual/Biennial Exam Development and
Administration
Procedures
TQ2.ID4
Training Program Implementation
Corrective Action
Documents
Notifications
226912, 51251460, 51262272
OP J-6B:IX
Diesel Generator Extended On-Line Maintenance
STP M-21-ENG.1
Diesel Engine Generator Inspection (Every Refueling
Outage)
STP M-21-ENG.2
Diesel Engine Generator Inspection (Every Second
Refueling Outage)
Procedures
STP M-9B
Overspeed Trip Test of Diesel Generators
Work Orders
Corrective Action
Documents
Notifications
256523, 51258615, 51258637, 51262776
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Drawing
437657
Diesel Fuel Transfer Pumps
AD7.DC6
On-Line Maintenance Risk Management
Procedures
OP1.DC44
Risk Informed Completion Time Program
Work Orders
Corrective Action
Documents
Notifications
51192270, 51212195
OP J-2:VIII
Guidelines for Reliable Transmission Service for DCPP
40, 41
Procedures
OP O-36
Protected Equipment Postings
Corrective Action
Documents
Notifications
235081, 51258835
Miscellaneous
DCN 2000002061
Design Change Package for Fan S-45 Flow Switch
Relocation
OP D-1:I
Auxiliary Feedwater System - Make Available
OP E-5:II
Auxiliary Saltwater System Two CCW Heat Exchanger
Operation
STP M-21-RTS.1
Return Diesel Engine to Service Following Outage
Maintenance
STP M-26
ASW System Flow Monitoring
STP M-9A3
Diesel Engine Generator 1-3 Routine Surveillance Test
STP P-AFW-23
Routine Surveillance Test of Motor-Driven Auxiliary
Feedwater Pump 2-3
STP P-ASW-12
Routine Surveillance Test of Auxiliary Saltwater Pump 1-2
STP P-CCP-21
Routine Surveillance Test of Centrifugal Charging Pump 2-1
STP P-CCW-23
Routine Surveillance Test of Component Cooling Water
Pump 2-3
STP P-CCW-A11
Comprehensive Pump Test of Component Cooling Water
Pump 1-1
STP P-DFO-01
Routine Surveillance Test of Diesel Fuel Oil Transfer
Pump 0-1
14A
Procedures
STP P-SIP-11
Routine Surveillance Test of Safety Injection Pump 1-1
Work Orders
WO 60167055, 64099427, 64175161, 64211275, 64285874,
286806, 64286807, 64287981, 64295489, 64309105
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
ESOMS Logs
DCPP Form 69-
11506
Dose Equivalent I-131 and Corrected I-131 Calculation Data
Sheet
2/26/2017
71151
Miscellaneous
DCPP Form 69-
297
RCS Dose Equivalent Iodine Performance Indicator
2/08/2022
Corrective Action
Documents
Notifications
50077678, 50307520, 50539359, 50541988, 51161487,
51162301, 51205737
Corrective Action
Documents
Notifications
225585, 51226017, 51226892
107723-12
Auxiliary Building: Condenser Unit Room, Cable Spreading
Room, 480V Switchgear Room Supply & Exhaust
114
107723-13
Auxiliary Building: 480V AC Switchgear, Battery, Inverter,
and Reactor Rod Drive Control Rooms
Drawings
494432-1
Auxiliary Building Switchgear Room Supply Fans S-43 & 44
Corrective Action
Documents
Notifications
223636, 51229398, 51229452, 51229453, 51229466,
229578, 51230229, 51247028, 51260708, 51260860
OM7.ID1
Problem Identification and Resolution
OM7.ID3
Root Cause Evaluation
Procedures
OM7.ID4
Cause Evaluations
44