IR 05000498/2024004
| ML25029A051 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 01/30/2025 |
| From: | Patricia Vossmar NRC/RGN-IV/DORS/PBA |
| To: | Harshaw K South Texas |
| References | |
| IR 2024004 | |
| Download: ML25029A051 (1) | |
Text
January 30, 2025
SUBJECT:
SOUTH TEXAS PROJECT ELECTRIC GENERATING STATION, UNITS 1 AND 2 - INTEGRATED INSPECTION REPORT 05000498/2024004 AND 05000499/2024004
Dear Kimberly A. Harshaw:
On December 31, 2024, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at South Texas Project Electric Generating Station, Units 1 and 2. On January 16, 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.
Five findings of very low safety significance (Green) are documented in this report. All of these findings involved violations of NRC requirements. We are treating these violations as non-cited violations (NCVs) consistent with Section 2.3.2 of the Enforcement Policy.
If you contest the violations or the significance or severity of the violations documented in this inspection report, you should provide a response within 30 days of the date of this inspection report, with the basis for your denial, to the U.S. Nuclear Regulatory Commission, ATTN:
Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region IV; the Director, Office of Enforcement; and the NRC Resident Inspector at South Texas Project Electric Generating Station, Units 1 and 2.
If you disagree with a cross-cutting aspect assignment in this report, you should provide a response within 30 days of the date of this inspection report, with the basis for your disagreement, to the U.S. Nuclear Regulatory Commission, ATTN: Document Control Desk, Washington, DC 20555-0001; with copies to the Regional Administrator, Region IV; and the NRC Resident Inspector at South Texas Project Electric Generating Station, Units 1 and 2. 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. 05000498; 05000499 License Nos. NPF-76; NPF-80
Enclosure:
As stated
Inspection Report
Docket Nos:
05000498; 05000499
License Nos:
Report Nos:
05000498/2024004; 05000499/2024004
Enterprise Identifier:
I-2024-004-0009
Licensee:
STP Nuclear Operating Company
Facility:
South Texas Project Electric Generating Station, Units 1 and 2
Location:
Wadsworth, TX
Inspection Dates:
October 1, 2024, to December 31, 2024
Inspectors:
R. Bywater, Senior Project Engineer
J. Drake, Senior Reactor Inspector
L. Flores, Resident Inspector
V. Lee, Project Engineer
N. Okonkwo, Reactor Inspector
C. Smith, Senior Reactor Inspector
J. Vera, 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 South Texas Project Electric Generating Station, 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
Improper Storage of Compressed Gas Cylinders Cornerstone Significance Cross-Cutting Aspect Report Section Initiating Events Green NCV 05000498/2024004-01 Open/Closed
[H.9] - Training 71111.08P The inspectors identified a finding of very low safety significance (Green) and associated non-cited violation (NCV) of Technical Specification 6.8.1.d, when the licensee failed to implement procedures to properly secure compressed gas cylinders to prevent movement during a seismic event. Specifically, on multiple occasions the inspectors discovered compressed gas cylinders in the protected area and near safety-related equipment that were not restrained in accordance with plant procedures.
Failure to Take Appropriate Corrective Action for the Essential Chilled Water System while in Maintenance Rule (a)(1) Status Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000498,05000499/2024004-02 Open/Closed
[P.2] -
Evaluation 71111.12 The inspectors identified a finding of very low safety significance (Green) and associated non-cited violation of Title 10 CFR 50.65(a)(1) for the failure to take appropriate corrective actions for the essential chilled water system, while in Maintenance Rule (MR) (a)(1) status, when established goals were not met. Specifically, after implementing corrective actions to address repetitive component failures for Unit 1 train C (1C), Unit 1 train B (1B), and Unit 2 train C (2C), there have been three additional repetitive MR functional failures for the affected chillers.
Failure to Establish Maintenance Procedures for Main Steam Safety Relief Valve Springs Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000498/2024004-03 Open/Closed
[H.12] - Avoid Complacency 71111.15 The inspectors documented a self-revealed, Green finding and associated non-cited violation of Technical Specification 6.8.1.a, for the licensees failure to establish, implement, and maintain procedures associated with safety relief valve maintenance. Specifically, the licensee failed to develop schedules to inspect or replace main steam safety relief valve (MSSV)springs. As a result, on February 28, 2024, a crack was found on the spring of Unit 1, MSSV 7420B, leading to the MSSV being declared inoperable and the licensee entering a Unit 1 forced outage to replace the spring.
Failure to Perform Adequate Design Change for Narrow Range RTDs Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000498/2024004-04 Open/Closed
[H.6] - Design Margins 71111.24 The inspectors documented a self-revealed, Green finding and associated non-cited violation of 10 CFR 50, Appendix B, Criterion III for the licensees failure to perform an adequate design change for Unit 1 new slope and offset values for narrow range resistance temperature detectors (RTD). Specifically, the design change used temperature corrected values instead of raw data to calculate new slope and offset values, which resulted in the slope and offset values for the RTDs to be amplified, causing out-of-range indications. As a result, administrative and technical specification limits were exceeded and the loop 3 delta-T (T) and Tave channel was inoperable for longer than its technical specification (TS) allowed outage time.
Failure to Promptly Correct a Condition Adverse to Quality for the Essential Chilled Water System Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000499/2024004-05 Open/Closed
[H.5] - Work Management 71153 The inspectors identified a finding of very low safety significance (Green) and an associated non-cited violation of Title 10 CFR 50, Appendix B, criterion XVI for the failure to promptly correct a condition adverse to quality in the essential chilled water system. Specifically, the licensee failed to promptly replace the existing Unit 2 train B essential chiller (22B)temperature current module with one that had a locking mechanism incorporated into the potentiometer following a 2021 engineering change for setpoint drift. As a result, essential chiller 22B was declared inoperable due to high outlet water temperature when the existing temperature current module failed.
Additional Tracking Items
Type Issue Number Title Report Section Status LER 05000499/2024-003-00 LER 2024-003-00 for South Texas Project, Unit 2,
Containment Isolation Valve Inoperable Resulting in Condition Prohibited by Technical Specification and Prevention of Fulfillment of Safety Function 71153 Closed
LER 05000499/2024-002-00 LER 2024-002-00 for South Texas Project, Unit 2, Two Control Room Envelope HVAC Trains Inoperable Resulting in a Condition That Could Have Prevented Fulfillment of a Safety Function 71153 Closed LER 05000499/2024-001-01 LER 2024-001-01 for South Texas Project, Unit 2,
Supplement to Automatic Reactor Trip and Actuation of Two of Three Emergency Diesel Generators 71153 Closed LER 05000499/2024-001-00 LER 2024-001-00 for South Texas Project, Unit 2,
Automatic Reactor Trip and Actuation of Two of Three Emergency Diesel Generators 71153 Closed LER 05000499/2023-002-00 LER 2023-002-00 for South Texas Project, Unit 2,
Automatic Actuation of Emergency Diesel Generator due to Lockout of Switchyard Electrical Bus 71153 Closed
PLANT STATUS
Unit 1 began the inspection period at rated thermal power and remained there until October 4, 2024, for the beginning of refueling outage 1RE25. The main generator breaker was closed on November 10, 2024, ending refueling outage 1RE25. The unit returned to rated thermal power on November 12, 2024, and remained there for the remainder of the inspection period.
Unit 2 began the inspection period at rated thermal power and remained there for the 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) (1 Sample)
The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:
- (1) Unit 1, train A residual heat removal system on October 23, 2024
71111.05 - Fire Protection
Fire Area Walkdown and Inspection Sample (IP Section 03.01) (1 Sample)
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 1 Containment on October 16, 2024
71111.07A - Heat Exchanger/Sink Performance
Annual Review (IP Section 03.01) (1 Sample)
The inspectors evaluated readiness and performance of:
(1)ultimate heat sink walkdown and component cooling water heat exchanger performance monitoring on November 28, 2024
===71111.08P - Inservice Inspection Activities (PWR) The inspectors verified that the reactor coolant system boundary, reactor vessel internals, risk-significant piping system boundaries, and containment boundary are appropriately monitored for degradation and that repairs and replacements were appropriately fabricated, examined, and accepted by reviewing the following activities in South Texas Project Unit 1 during refueling outage 1RE25 from October 14 to October 24, 2024.
PWR Inservice Inspection Activities Sample - Nondestructive Examination and Welding Activities (IP Section 03.01)===
The inspectors verified that the following nondestructive examination and welding activities were performed appropriately:
- (1) Ultrasonic Examination
- residual heat removal, 1-WD-20240, pipe to pipe, 12-RH-1101-BB1 weld 13
- residual heat removal, 1-WD-200160, pipe to pipe, 12-RH-1101-BB1 weld 9
- residual heat removal, 1-WD-200220, pipe to pipe, 12-RH-1101-BB1 weld 12
- reactor coolant, 1-WD-108400, branch connection to bent pipe, 2-RC-1121-BB1 weld 1
- reactor coolant, 1-WD-109000, branch connection to bent pipe, 2-RC-1220-BB1 weld 1
- reactor coolant, 1-WD-110200, branch connection to bent pipe, 2-RC-1418-BB1 weld 1
Dye Penetrant Examination
- residual heat removal, RHARHS-1A-IWA2, integral weld attachment residual heat removal pump 1A Visual 1 Examination
- safety injection/containment spray, compartment sump level element Visual 3 Examination
- safety injection, SI-HCV-0899, accumulator vent backup valve Welding Activities
- gas tungsten arc welding o
Residual heat removal, 8-RH-1106-KB2, pipe to elbow, weld 5 o
Residual heat removal, 8-RH-1106-KB2, "T" to pipe, weld 6 PWR Inservice Inspection Activities Sample - Vessel Upper Head Penetration Inspection Activities (IP Section 03.02)
Although no ASME Code required head inspections were required, boric acid deposits were found on several hold down bolts and the base seal on control rod drive mechanism penetration 46. Additional inspections identified the source of the leak as the Greyloc seal on RVLIS (reactor vessel level indicating system) penetration 26.
PWR Inservice Inspection Activities Sample - Boric Acid Corrosion Control Inspection Activities (IP Section 03.03) (1 Sample)
The inspectors verified the licensee is managing the boric acid corrosion control program through a review of the following evaluations:
(1)
- CR 18-11800, 1-SI-FT-0901, Hi Head Safety Injection Pump 1A Discharge To Loop 1A Cold Leg Flow Transmitter
- CR 20-3181, 1-SI-0034A, Safety Injection Accumulator 1A Fill Valve
- CR 23-5591, 1-CV-0120B, CVCS Mixed Bed Demin 1B Outlet To SRST Upper Isolation Valve
- CR 23-8373, 1-RH-FT-0867, RHR Pump 1A Discharge Flow Transmitter
- CR 24-9622, 1-WL-0046 SIS, Accumulator 1A Drain To RCDT Pump Suction Header Isolation Valve
- CR 24-9796, 1-SI-FV-3973 SI, Accumulator 1AQ Fill Line Isolation Valve
- CR 24-9808, 1-SI-0039A, Safety Injection Accumulator 1A Outlet MOV
- CR 23-0591, Unit 1 CV 0120B, CVCS Mixed Bed Demineralizer 1B Outlet to SRST Upper Isolation Valve PWR Inservice Inspection Activities Sample - Steam Generator Tube Inspection Activities (Section 03.04) (1 Sample)
The inspectors verified that the licensee is monitoring the steam generator tube integrity appropriately through a review of the following examinations:
(1)
- For steam generators A, B, C and D:
- 100 percent full length bobbin coil inspection of all tubes 100 percent +POINT probe inspection of the upper tube support plate hot leg to upper tube support plate cold leg of rows 1 and 2
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 November 11 to December 20, 2024.
71111.11Q - Licensed Operator Requalification Program and Licensed Operator Performance
Licensed Operator Performance in the Actual Plant/Main Control Room (IP Section 03.01) (1 Sample)
- (1) The inspectors observed and evaluated licensed operator performance in the control room during the Unit 1 downpower on October 4, 2024, and during power ascension on November 8, 2024.
Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)
- (1) The inspectors observed and evaluated just-in-time training for the Unit 1 outage on October 1, 2024.
71111.12 - Maintenance Effectiveness
Maintenance Effectiveness (IP Section 03.01) (3 Samples)
The inspectors evaluated the effectiveness of maintenance to ensure the following structures, systems, and components (SSCs) remain capable of performing their intended function:
- (1) Unit 2, component cooling water valve MOV-199 stem to disc separation on December 16, 2024
- (2) Units 1 and 2, FLEX diesel preventive maintenance on October 3, 2024
- (3) Units 1 and 2, essential chiller maintenance effectiveness on December 1, 2024
Quality Control (IP Section 03.02) (1 Sample)
The inspectors evaluated the effectiveness of maintenance and quality control activities to ensure the following SSC remains capable of performing its intended function:
(1)operations quality assurance plan requirement implementation on receipt inspection procedure on December 27, 2024
71111.15 - Operability Determinations and Functionality Assessments
Operability Determination or Functionality Assessment (IP Section 03.01) (7 Samples)
The inspectors evaluated the licensee's justifications and actions associated with the following operability determinations and functionality assessments:
- (1) Unit 2, train C diesel generator overspeed trip due to limit switch misalignment on November 1, 2024
- (2) Unit 1, train C control room envelope HVAC ductwork on November 11, 2024
- (3) Unit 2, train D AFW pump outboard bearing oil leak on November 22, 2024
- (4) Unit 1, cracked spring on safety relief valve MSSV 7420B on December 6, 2024
- (5) Unit 1, local controller erratic on steam generator 1C feedwater inlet outside reactor containment C isolation valve bypass on December 12, 2024
- (6) Unit 2, emergency diesel generator 23 broken lube oil crossover tube on December 17, 2024
- (7) Unit 1, train C residual heat removal pump mechanical seal leakage on December 18, 2024
71111.18 - Plant Modifications
Temporary Modifications and/or Permanent Modifications (IP Section 03.01 and/or 03.02) (2 Samples)
The inspectors evaluated the following temporary or permanent modifications:
- (1) Unit 2, train A high head safety injection pump flow restricting orifice modification on November 21, 2024
- (2) Unit 2, replacement of Class 1E switchgear E2C circuit breakers on November 16, 2024
71111.20 - Refueling and Other Outage Activities
Refueling/Other Outage Sample (IP Section 03.01) (1 Sample)
- (1) The inspectors evaluated refueling outage 1RE25 activities from October 4 to November 10, 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) (4 Samples)
- (1) Unit 1, loop 3 delta T after engineering change on September 9, 2024
- (2) Unit 2, train C emergency diesel generator after limit switch replacement on October 20, 2024
- (3) Unit 1, train C emergency diesel generator ESF actuation test for a loss offsite power on October 20, 2024
- (4) Unit 1, automatic control rod drop timing test on November 9, 2024
Surveillance Testing (IP Section 03.01) (2 Samples)
- (1) Unit 1, low head and high head safety injection surveillance on October 11, 2024
- (2) Unit 1, reactor containment building integrated leakage rate test on October 30, 2024
Containment Isolation Valve (CIV) Testing (IP Section 03.01) (1 Sample)
- (1) Unit 1, M-43 outer containment isolation valve LLRT following repair on November 4, 2024
Reactor Coolant System Leakage Detection Testing (IP Section 03.01) (1 Sample)
- (1) Unit 2, elevated RCS leakage on October 28, 2024
71114.06 - Drill Evaluation
Additional Drill and/or Training Evolution (1 Sample)
The inspectors evaluated:
- (1) The licensee's simulator-based licensed operator training evolution that involved a complete loss of AC power and a general emergency on August 20,
OTHER ACTIVITIES - BASELINE
===71151 - Performance Indicator Verification The inspectors verified licensee performance indicators submittals listed below:
MS09: Residual Heat Removal Systems (IP Section 02.08)===
- (1) Unit 1 (October 1, 2023, through September 30, 2024)
- (2) Unit 2 (October 1, 2023, through September 30, 2024)
MS10: Cooling Water Support Systems (IP Section 02.09) (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) Timeliness of corrective actions for essential chiller temperature current module potentiometer failures on December 15, 2024
- (2) Steam generator 1A power operated relief valve 10-amp fuse failure on December 20, 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 access controls that might be indicative of a more significant safety issue.
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 05000499/2023-002-00, "Unit 2, Automatic Actuation of Emergency Diesel Generator due to Lockout of Switchyard Electrical Bus" (ADAMS Accession No.
ML24030A968). 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.
- (2) LER 05000499/2024-003-00, "Unit 2, Containment Isolation Valve Inoperable Resulting in Condition Prohibited by Technical Specification and Prevention of Fulfillment of Safety Functions" (ADAMS Accession No. ML24183A174). 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.
- (3) LER 05000499/2024-002-00 "Unit 2, Two Control Room Envelope HVAC Trains Inoperable Resulting in a Condition That Could Have Prevented Fulfillment of a Safety Function" (ADAMS Accession No. ML24291A284). The inspection conclusions associated with this LER are documented in this report under Inspection Results Section 71153. This LER is Closed.
- (4) LER 05000499/2024-001-00, "Unit 2, Automatic Reactor Trip and Actuation of Two of Three Emergency Diesel Generators" (ADAMS Accession No. ML24184C083) and LER 05000499/2024-001-01, "Unit 2, Supplement to Automatic Reactor Trip and Actuation of Two of Three Emergency Diesel Generators" (ADAMS Accession No.
ML24242A163). The inspection conclusions associated with this LER are documented in Inspection Report 05000498/2024050 and 05000499/2024050, dated November 21, 2024, under Inspection Results Section 93812. This LER is Closed.
INSPECTION RESULTS
Improper Storage of Compressed Gas Cylinders Cornerstone Significance Cross-Cutting Aspect Report Section Initiating Events Green NCV 05000498/2024004-01 Open/Closed
[H.9] - Training 71111.08P The inspectors identified a finding of very low safety significance (Green) and associated non-cited violation (NCV) of Technical Specification 6.8.1.d, when the licensee failed to implement procedures to properly secure compressed gas cylinders to prevent movement during a seismic event. Specifically, on multiple occasions the inspectors discovered compressed gas cylinders in the protected area and near safety-related equipment that were not restrained in accordance with plant procedures.
Description:
On multiple occasions between October 14 and 21, 2024, the inspectors identified various compressed gas cylinders of propane, argon, and nitrogen that were not restrained in the protected area as required by licensee procedure 0PGP03-ZI-0015, Control and Use of Industrial Compressed Air and Gases, revision 7, section 4.3, to reasonably ensure it would not adversely impact plant and personnel safety during a seismic event.
Procedure 0PGP03-ZI-0015, section 4.3, requires that, compressed gas cylinders shall be secured to prevent movement during a seismic event. Section 5.4.1 states in part that each compressed gas cylinder shall be secured with an approved restraining device (e.g., chain, rope, or wire). Section 5.4.2 states in part that compressed gas cylinders are to be secured to a substantial anchorage point (e.g., structural steel, I-beams, etc.). Section 5.4.9 states in part that pre-staged compressed gas cylinders used to support future work activities shall be stored within proper permanent OR temporary gas cylinder racks OR properly secured to a structural member (e.g., an I-beam) away from permanent plant equipment AND capped when not in use. Contrary to these requirements, the inspectors found a propane cylinder not secured by the loading dock and multiple argon and nitrogen bottles not properly restrained in the reactor building on the 60-foot elevation. The inspectors identified the improper control of compressed gas cylinders between October 14 and 21, 2024, and the licensee restored compliance on October 22, 2024.
Corrective Actions: The licensee took actions to properly restrain the cylinders and move them to approved storage locations.
Corrective Action References: Condition report 24-10253
Performance Assessment:
Performance Deficiency: The inspectors determined that the licensees failure to properly restrain compressed gas cylinders of propane, argon, and nitrogen in the protected area per licensee procedure 0PGP03-ZI-0015, "Control and Use of Industrial Compressed Air and Gases," revision 7, was a performance deficiency. Examples included a propane cylinder not secured by the loading dock and multiple argon and nitrogen bottles not properly restrained in the reactor building on the 60-foot elevation.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Protection Against External Factors attribute of the Initiating Events cornerstone and adversely affected the cornerstone objective to limit the likelihood of events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. Specifically, the failure to properly restrain compressed gas cylinders of propane, argon, and nitrogen in the protected area led to reasonable doubt regarding the safety of personnel and the operability of nearby safety-related components.
Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The Significance Determination Process (SDP) for Findings At-Power. The inspectors determined the finding was of very low safety significance (Green) based on answering 'no' to all the questions in Section A of Exhibit 2. Specifically, the licensee performed evaluations and reasonably determined the operability/functionality of equipment would be maintained under worst-case seismic conditions.
Cross-Cutting Aspect: H.9 - Training: The organization provides training and ensures knowledge transfer to maintain a knowledgeable, technically competent workforce and instill nuclear safety values. Specifically, the licensee's current training program did not ensure personnel were adequately trained on procedure 0PGP03-ZI-0015.
Enforcement:
Violation: Technical Specification 6.8.1.d requires that written procedures shall be established, implemented, and maintained covering Fire Protection Program implementation.
Procedure 0PGP03-ZI-0015, Control and Use of Industrial Compressed Air and Gases, revision 7, established requirements to implement the Fire Protection Program associated with the proper control of compressed gas cylinders to prevent movement during a seismic event.
Contrary to the above, between October 14 and 21, 2024, the licensee failed to implement procedure 0PGP03-ZI-0015 requirements to properly control compressed gas cylinders to prevent movement during a seismic event. Specifically, the inspectors found a propane cylinder not secured by the loading dock and multiple argon and nitrogen bottles not properly restrained in the reactor building on the 60-foot elevation.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Failure to Take Appropriate Corrective Action for the Essential Chilled Water System while in Maintenance Rule (a)(1) Status Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000498,05000499/2024004-02 Open/Closed
[P.2] -
Evaluation 71111.12 The inspectors identified a finding of very low safety significance (Green) and associated non-cited violation of Title 10 CFR 50.65(a)(1) for the failure to take appropriate corrective actions for the essential chilled water system, while in Maintenance Rule (MR) (a)(1) status, when established goals were not met. Specifically, after implementing corrective actions to address repetitive component failures for Unit 1 train C (1C), Unit 1 train B (1B), and Unit 2 train C (2C), there have been three additional repetitive MR functional failures for the affected chillers.
Description:
The essential chilled water system provides chilled water to safety-related air handling units (AHU) to provide a suitable environment for personnel and Class 1E equipment located in the Electrical Auxiliaries Building, Mechanical Auxiliaries Building, and the Fuel Handling Building and includes the control room envelope (CRE) heating, ventilation and air conditioning (HVAC) system. It is designed to remain functional during and following design basis accidents and for safe shutdown of the plant following an accident. It consists of three, 50-percent-heat-removal-capacity redundant and independent trains. Two chillers are required to be operating at all times, and the chillers are regularly rotated to support plant operations and maintenance.
On December 7, 2022, the licensee placed the essential chilled water system in Maintenance Rule (MR) (a)(1) status due to Unit 1 train C exceeding the MR performance criteria for repetitive MR functional failures (RMRFF) for essential chiller 12C due to auxiliary oil pump seal failures. As required by 10 CFR Part 50.65(a)(1), the licensee established corrective actions and goals for the essential chilled water system and entered a 24-month monitoring period. The following train level goals were established: zero RMRFF, three or less MR functional failures (MRFF) per train and less than 361 unavailability hours.
In June 2023, an additional MRFF for essential chiller 12C occurred due to high outlet temperature, resulting in essential chiller train 1C to exceed the (a)(1) goals for maximum number of MRFFs per train. In June 2024, essential chiller train 1C exceeded the (a)(1) goals for unavailability hours due to multiple MRFFs and RMRFFs.
In July 2023, a MRFF occurred for the essential chiller 12B due to high outlet temperature. In August 2023 and November 2023, essential chiller 12B again had high outlet temperatures, and both events were determined to be RMRFFs. In June 2024, train 1B essential chilled water was placed in MR (a)(1) status due to exceeding goals established for RMRFFs and MRFFs per train.
Licensee procedure SEG-0009, Maintenance Rule Basis Document Guideline, Rev. 6, provides a basis for decisions made regarding MR implementation. Section 7.4 provides guidance for dispositioning systems, structures, and components (SSC) from MR (a)(2) to (a)(1). It states, in part, that the cause determination and corrective action should reinforce achieving the performance criteria or goals that are monitored and determine whether the performance criteria or goal itself should be modified. For each equipment failure, the licensee wrote condition reports and established corrective action to fix the individual issues; however, despite the multiple RMRFFs, the inspectors noted that a review and evaluation of (a)(1) goals were not documented in any of the cause determinations nor (a)(1) system status reports. Additionally, the inspectors attended maintenance rule expert panel meetings and noted that discussions for the essential chilled water system focused on individual corrective actions for the SSC failures and not corrective actions necessary to meet established goals.
On November 21, 2023, the licensee assembled an essential chiller deep dive team to review the multiple failures of essential chillers and establish additional corrective actions to address the failures. Deliverables for the corrective action plan were identified in January 2024. Of the twenty corrective actions identified, twelve of those actions have been completed; however, due dates for the remaining eight corrective actions have been extended between two and six times each.
On February 15, 2024, a MRFF occurred for the essential chiller 22C due to high outlet temperatures and was determined to be a RMRFF due to similar failures on essential chillers 12B and 12C. In March 2024, another MRFF occurred for essential chiller 22C and was also determined to be a RMRFF. The licensee placed essential chiller train 2C in MR (a)(1) status due to exceeding the allowable RMRFFs and established the same goals as essential chilled water trains 1C and 1B. In March 2024, essential chillers 12C and 12B each experienced another RMRFF due to temperature control failures.
The inspectors reviewed the maintenance rule history for the essential chillers and concluded that the licensee failed to take appropriate corrective actions to address the failures for essential chillers 12C, 12B, and 22C on February 15, 2024, when further RMRFFs occurred after implementing the corrective actions established during the deep dive review.
Corrective Actions: The licensee wrote condition reports to correct the equipment issues associated with the failures and initiated a refresh charter for the essential chiller deep dive review.
Corrective Action References: CR 2023-10622, 2023-6338, 2023-6823, 2023-8073, 23-10345, 23-10352, 24-1539, 24-2138, 24-2328, 24-2403
Performance Assessment:
Performance Deficiency: The failure to take appropriate corrective actions for the essential chilled water system, while in Maintenance Rule (a)(1) status, when established goals were not met was a performance deficiency. Specifically, corrective actions to address failures on 12C, 12B, and 22C essential chillers were not adequate and resulted in repetitive maintenance rule functional failures.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Equipment Performance attribute of the Mitigating Systems cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the licensees failure to take appropriate corrective action for repetitive maintenance rule functional failures for essential chillers 12B, 12C, and 22C adversely affected the availability and reliability of the essential chilled water system.
Significance: The inspectors assessed the significance of the finding using IMC 0609, Appendix A, The Significance Determination Process (SDP) for Findings At-Power, Exhibit 2, Mitigating Systems Screening Questions, dated November 30, 2020. The finding was determined to be of very low safety significance (Green) because it
- (1) was not a deficiency affecting design or qualification of a mitigating system,
- (2) does not represent a loss of the probabilistic risk assessment (PRA) function of a single train TS system for greater than allowed outage time,
- (3) does not represent a loss of PRA function of one train of a multi-train TS system for greater than its TS allowed outage time,
- (4) does not represent a loss of the PRA function of two separate TS systems for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />,
- (5) does not represent a loss of PRA system and/or function as defined by the plant risk information e-book or the licensees PRA for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and
- (6) does not result in the loss of a maintenance rule risk-significant, non-TS train for greater than three days. Additionally, the finding did not involve external event mitigating systems, the reactor protection system, fire brigade, or flexible coping strategies.
Cross-Cutting Aspect: P.2 - Evaluation: The organization thoroughly evaluates issues to ensure that resolutions address causes and extent of conditions commensurate with their safety significance. Specifically, the licensee did not thoroughly evaluate RMRFFs with the chillers to ensure that the identified corrective actions addressed the causes of the failures.
Enforcement:
Violation: Title 10 CFR 50.65(a)(1), requires, in part, that the licensee shall monitor the performance or condition of SSCs within the scope of the rule against licensee-established goals in a manner sufficient to provide reasonable assurance that these SSCs are capable of fulfilling their intended functions. Such goals shall be established commensurate with safety.
When the performance or condition of a SSC does not meet established goals, appropriate corrective action shall be taken.
Contrary to the above, from February 15, 2024, the licensee failed to take appropriate corrective action when the performance of the essential chilled water system, a system within the scope of the Maintenance Rule, failed to meet established goals. Specifically, the licensee failed to take appropriate corrective action when essential chillers 12C, 12B, and 22C experienced repetitive maintenance rule functional failures.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Failure to Establish Maintenance Procedures for Main Steam Safety Relief Valve Springs Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000498/2024004-03 Open/Closed
[H.12] - Avoid Complacency 71111.15 The inspectors documented a self-revealed, Green finding and associated non-cited violation of Technical Specification 6.8.1.a, for the licensees failure to establish, implement, and maintain procedures associated with safety relief valve maintenance. Specifically, the licensee failed to develop schedules to inspect or replace main steam safety relief valve (MSSV) springs. As a result, on February 28, 2024, a crack was found on the spring of Unit 1, MSSV 7420B, leading to the MSSV being declared inoperable and the licensee entering a Unit 1 forced outage to replace the spring.
Description:
The main steam safety relief valves (MSSV) are required for decay heat removal and cooldown to safe shutdown conditions. Operation of the MSSVs is assumed in accident analyses for mitigation of main steam line breaks, turbine trips, uncontrolled rod cluster control assembly bank withdrawals at power, concurrent with a loss of offsite power. Per the Unit 1 technical specifications, all safety relief valves are required to be operable in Modes 1 through 3.
On February 28, 2024, while Unit 1 was in Mode 1, during the walkdown prior to performing main steam pressure test, the main steam system engineer identified a cracked spring on MSSV 7420B. At 1403 MSSV 7420B was declared inoperable and the unit entered Technical Specification (TS) 3.7.1.1 for an inoperable MSSV. Although the TS actions do not require a unit shutdown for the condition of one inoperable MSSV, on February 29, 2024, the station commenced a Unit 1 reactor shutdown to facilitate repair of the MSSV, which consisted of replacement of the degraded spring. Upon completion of repairs and successful post maintenance testing, the valve was declared operable at 5:35 p.m. on March 3, 2024.
The inspectors reviewed the preventive maintenance approach for the stations main steam safety relief valves, noting that none of the scheduled maintenance activities for these valves directly involved the valve springs. The inspectors noted that a simple clean/inspect maintenance would have revealed the initiation of the crack. The licensee performed a root cause evaluation, which concluded that the spring had developed environmentally assisted cracking, with the root cause stated as there being no established preventive maintenance strategy for the spring.
Corrective Actions: The licensee replaced the MSSV 7420B spring and declared the valve operable on March 3, 2024. The licensee began instituting a preventive maintenance activity to inspect for cracks on MSSV springs and also initiated an action to evaluate recoating the springs with a corrosion inhibitor and replacement of the springs with springs made of alternate material to eliminate risk of environmentally assisted cracking.
Corrective Action References: CR 2024-1979
Performance Assessment:
Performance Deficiency: The failure to institute a preventive maintenance activity that would identify and correct the condition adverse to quality that led to the crack in the spring of MSSV 7420B was a performance deficiency. Specifically, the licensee failed to institute preventive maintenance that would have identified a crack prior to it rendering the safety relief valve inoperable.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Equipment Performance attribute of the Mitigating Systems cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, a crack was found in the spring of safety relief valve MSSV 7420B rendering it inoperable. The crack was not identified and continued to develop because no preventive maintenance activities existed that would have identified issues with MSSV springs.
Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The Significance Determination Process (SDP) for Findings At-Power. Exhibit 2, Mitigating Systems Screening Questions, dated November 30, 2020. The finding was determined to be of very low safety significance (Green) because it
- (1) was not a deficiency affecting design or qualification of a mitigating system,
- (2) does not represent a loss of the probabilistic risk assessment (PRA) function of a single train TS system for greater than allowed outage time,
- (3) does not represent a loss of PRA function of one train of a multi-train TS system for greater than its TS allowed outage time,
- (4) does not represent a loss of the PRA function of two separate TS systems for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />,
- (5) does not represent a loss of PRA system and/or function as defined by the plant risk information e-book or the licensees PRA for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and
- (6) does not result in the loss of a maintenance rule risk-significant, non-TS train for greater than three days. Additionally, the finding did not involve external event mitigating systems, the reactor protection system, fire brigade, or flexible coping strategies.
Cross-Cutting Aspect: H.12 - Avoid Complacency: Individuals recognize and plan for the possibility of mistakes, latent issues, and inherent risk, even while expecting successful outcomes. Individuals implement appropriate error reduction tools. Specifically, for MSSV 7420B, the station did not include any facet of preventive maintenance on MSSV springs, relying on the expected service life of the component. This led to an undiscovered crack in the valve spring which rendered valve MSSV 7420B inoperable.
Enforcement:
Violation: Technical Specification 6.8.1.a, requires, in part, that written procedures shall be established, implemented, and maintained, among others, for applicable procedures in Appendix A of Regulatory Guide 1.33, Revision 2, February 1978. Among these, Regulatory Guide 1.33, Appendix A, Section 9 Procedures for Performing Maintenance, paragraph b, states Preventive maintenance schedules should be developed to specify lubrication schedules, inspections of equipment, replacement of such items as filters and strainers, and inspection or replacement of parts that have a specific lifetime such as wear rings.
Contrary to the above, on February 28, 2024, the licensee failed to establish, implement, and maintain procedures associated with safety relief valve maintenance. Specifically, the licensee failed to develop schedules to inspect or replace main steam safety relief valve springs. As a result, on February 29, 2024, a crack was found on the spring of MSSV 7420B, leading to the MSSV being declared inoperable and the licensee entering a Unit 1 forced outage to replace the spring.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Failure to Perform Adequate Design Change for Narrow Range RTDs Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000498/2024004-04 Open/Closed
[H.6] - Design Margins 71111.24 The inspectors documented a self-revealed, Green finding and associated non-cited violation of 10 CFR 50, Appendix B, Criterion III for the licensees failure to perform an adequate design change for Unit 1 new slope and offset values for narrow range resistance temperature detectors (RTD). Specifically, the design change used temperature corrected values instead of raw data to calculate new slope and offset values, which resulted in the slope and offset values for the RTDs to be amplified, causing out-of-range indications. As a result, administrative and technical specification limits were exceeded and the loop 3 delta-T (T) and Tave channel was inoperable for longer than its technical specification (TS) allowed outage time.
Description:
Reactor coolant temperatures are measured by RTDs in the hot and cold legs of the reactor coolant system (RCS). The outputs of the narrow-range temperature instrumentation (Th and Tc) are further processed to provide the average temperature (Tavg)and the difference between the hot-leg and cold-leg temperatures (T) for each coolant loop.
These processed signals are used for control room indication, inputs to various control systems, and inputs to the reactor protection system (RPS) for the generation of protection-grade interlocks and reactor trip signals. Periodic surveillances and calibrations of the RTDs are performed to ensure that the output of these instruments remain in allowable tolerances to meet administrative and technical specification limits. Any narrow range Th or Tc RTDs found to have a calibration error of greater than 0.5°F are evaluated to ensure that the RTD will not drift beyond the surveillance acceptance criteria of 1.2°F.
During startup from 1RE24 in April 2023, cross calibration data taken showed that the loop 3 hot leg narrow range RTD, in part, was out of the administrative limit of 0.5°F but was less than the surveillance acceptance criteria of 1.2°F. The licensee performed an evaluation to ensure surveillance acceptance criteria would not be exceeded during the operating cycle and initiated a corrective action to perform an engineering change (EC) 23-8110-23, Unit 1 Narrow Range RTD Composite Slope and Offset Table, to establish new slope and offset values for the RTD. The engineering design change was implemented on September 6, 2024, while the unit was in Mode 1.
On September 16, 2024, while performing weekly channel checks, the licensee noted that the RCS (T) loop 3 power indication point was reading lower than normal and was out of band, indicating 97.2 percent instead of 100 percent. The licensee performed a manual (T)calculation and found that the power indication point still yielded the same 97.2 percent result.
This value was non-conservative and would not have resulted in a trip signal at the appropriate power level. The licensee performed an investigation and found that the engineering change implemented on September 6, 2024, incorrectly used the Mode 3 temperature normalized values that were established during cross-calibration from 1RE24 to calculate slope and offset values instead of the raw data. These normalized values are determined during cross calibration using a spreadsheet tool.
During cross calibration, ohmic values and temperature data are collected at four different temperatures to determine the required correction for each narrow range RTD: 250°F, 330°F, 450°F, and 567°F. At the 250°F and 330°F target plateaus, all the RTDs ohmic values and temperature data are directly and simultaneously measured. The measurement is repeated three more times, and the values for all four recordings are averaged to provide data that is used to determine if the RTD is within the administrative limit. If any RTDs are out of the administrative limit, the data is then used to determine the new slope and offset values for those RTDs.
Between the 330°F and 450°F target plateaus, the plant goes through a mode change from Mode 4 to Mode 3, which requires that three of the four RCS loop instrumentation channels be available for the Engineered Safety Features Actuation System (ESFAS); therefore, a change in the data collection method is required. In Mode 3, each loop is measured independently, four times in rapid succession and averaged. The other loops are measured in the same manner. During the change of data collection equipment between the loops, there is some fluctuation in temperature of the RCS, so correction factors are applied to normalize the data used in the analysis. This normalization of temperatures is not required at 250°F and 350°F because data is taken simultaneously.
The spreadsheet tool used to normalize temperature in Mode 3 added temperature corrections to the collected raw data that were greater than 3°F. The use of those values during the design change process resulted in amplified slope and offset values for the RTDs, causing the loop 3 (T) and Tave channel administrative and technical specification limits to be exceeded once adjustments derived from those temperature corrected inputs were implemented on September 6, 2024. While the temperature-corrected data is acceptable for cross-calibration activities, it led to inaccuracies when that data was used in the design process. The methodology used to calculate slope and offset requires uncorrected data.
The inspectors reviewed the licensees engineering change and noted that it did not specify whether to use raw or temperature normalized data to calculate the new slope and offset values. Additionally, the inspectors questioned the post modification testing performed after implementation of the engineering change. While the licensees post modification testing verified that the output of the loop 3 hot leg narrow range RTD was within the hot leg operating band, it did not compare the temperature values against the average of all the RTDs, which is a critical step that would identify slope and offset calibration issues and ensure that the value was within TS limits.
Corrective Actions: The licensee issued a revision to EC 23-8110-23 to use Mode 3 raw collected data as an input to calculate slope and offset values. Additionally, the licensee is implementing changes to their procedures to specifically identify that raw data shall be used when performing design changes to calculate new slope and offset values for narrow range RTDs.
Corrective Action References: 2024-8943, 2024-8966
Performance Assessment:
Performance Deficiency: The failure to perform an adequate design change and post modification testing for Unit 1 new slope and offset values for narrow range RTDs was a performance deficiency. Specifically, temperature corrected values were used instead of raw data to calculate new slope and offset values, which resulted in the slope and offset values for the RTDs to be amplified, and the error was not identified during post-modification testing.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Design Control attribute of the Mitigating Systems cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the design change inappropriately used temperature-corrected values for the RTDs, resulting in administrative and TS limits to be exceeded and a non-conservative RTD input to RPS.
Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The Significance Determination Process (SDP) for Findings At-Power. The finding was determined to be of very low safety significance (Green) because the finding resulted in a minor functional degradation of RPS and not a significant functional degradation, in that the finding affected the accuracy of a single channel of an RPS trip function while other redundant instrumentation remained available to enable the affected safety functions to actuate as designed.
Cross-Cutting Aspect: H.6 - Design Margins: The organization operates and maintains equipment within design margins. Margins are carefully guarded and changed only through a systematic and rigorous process. Special attention is placed on maintaining fission product barriers, defense-in-depth, and safety-related equipment. Specifically, the design change to establish new slope and offset values for the loop 3 (T) and Tave channel did not adequately evaluate the use of temperature corrected values vice raw data, resulting in the erroneous setpoints.
Enforcement:
Violation: Title 10 CFR 50, appendix B, criterion III, requires, in part, that measures shall be established to assure that applicable regulatory requirements and the design basis are correctly translated into specifications, drawings, procedures, and instructions. The design control measures shall include provisions to assure that appropriate quality standards are specified and included in design documents and that deviations from such standards are controlled. The design control measures shall provide for verifying or checking the adequacy of design, such as by the performance of design reviews, by the use of alternate or simplified calculational methods, or by the performance of a suitable testing program.
Technical Specification 3.3.1 states, in part, in Mode 1 and Mode 2, Reactor Trip System instrumentation channels and interlocks of Table 3.3-1 shall be operable with response times as shown in Chapter 16 in the Updated Final Safety Analysis Report (UFSAR). Table 3.3-1, functional unit item 8, Overtemperature T, and functional unit item 9, Overpower T, require, in part that with the number of operable channels one less than the total number of channels, startup and/or power operation may proceed provided that for functional units with installed bypass test capability, the inoperable channel may be placed in bypass, and must be placed in the tripped condition within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Technical Specification 3.3.2, Engineered Safety Features Actuation System Instrumentation, requires, in part, in Modes 1-3, that the Engineered Safety Features Actuation System (ESFAS) instrumentation channels and interlocks shown in Table 3.3-3 shall be operable with their Trip Setpoints set consistent with the values shown in the Trip Setpoint column of Table 3.3-4 and with response times as shown in Chapter 16 in the UFSAR. TS 3.3.2 action statement
- (c) requires, in part, that in Modes 1-3, with an ESFAS instrumentation channel or interlock inoperable, take the action shown in Table 3.3-3. Table 3.3-3, functional unit item 5.f, Turbine Trip and Feedwater Isolation Tave-low coincident with reactor trip (P-4), action 20, requires that with the number of operable channels one less than the total number of channels, startup and/or power operation may proceed provided that for functional units with installed bypass test capability, the inoperable channel may be placed in bypass, and must be placed in the tripped condition within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Contrary to the above, from September 9 to September 16, 2024, the licensee failed to establish measures to assure that applicable regulatory requirements and the design basis were correctly translated into specifications, drawings, procedures, and instructions, failed to assure that appropriate quality standards were specified and included in design documents, and failed to verify or check the adequacy of design by the performance of a suitable testing program. Specifically, the licensee failed to ensure that instructions or procedures for performing EC 23-8110-13 to establish Unit 1 new slope and offset values for narrow range RTDs specified the use of raw data to calculate new slope and offset values, and temperature corrected values were inappropriately used. Additionally, the licensee failed to verify or check the adequacy of the design by performance of a suitable testing program when post modification testing failed to compare the temperature values against the average of all the RTDs, and the error was not identified. The slope and offset values for the RTDs were amplified, and administrative and technical specification limits were exceeded. As a result, the number of operable channels was one less than the total number of channels as required by TS 3.3.1, Table 3.3-1 functional unit items 8 and 9 and TS 3.3.2 action (c), Table 3.3-3 functional unit item 5f, and the inoperable channel was not placed in bypass and was not placed in the tripped condition within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Failure to Promptly Correct a Condition Adverse to Quality for the Essential Chilled Water System Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000499/2024004-05 Open/Closed
[H.5] - Work Management 71153 The inspectors identified a finding of very low safety significance (Green) and an associated non-cited violation of Title 10 CFR 50, Appendix B, criterion XVI for the failure to promptly correct a condition adverse to quality in the essential chilled water system. Specifically, the licensee failed to promptly replace the existing Unit 2 train B essential chiller (22B)temperature current module with one that had a locking mechanism incorporated into the potentiometer following a 2021 engineering change for setpoint drift. As a result, essential chiller 22B was declared inoperable due to high outlet water temperature when the existing temperature current module failed.
Description:
The essential chilled water system provides chilled water to safety-related air handling units (AHU) to provide a suitable environment for personnel and Class 1E equipment located in the Electrical Auxiliaries Building, Mechanical Auxiliaries Building and the Fuel Handling Building and includes the control room envelope (CRE) heating, ventilation and air conditioning (HVAC) system. It is designed to remain functional during and following design basis accidents and for safe shutdown of the plant following an accident. It consists of three 50-percent heat-removal-capacity redundant and independent trains. Two chillers are required to be operating at all times and the chillers are regularly rotated to support plant operations and maintenance.
The chiller contains, in part, a temperature current module (TCM) that operates in conjunction with a chilled water temperature sensor, pre-rotation vane motor, and hot gas bypass valve in a servo-type system to control the leaving water temperature by modulating chiller unit capacity. Potentiometers are used in the TCM to calibrate the input and output to verify controller operation at the appropriate setpoints.
On August 20, 2024, at 4:00 a.m., train C CRE HVAC system was declared inoperable for planned maintenance. At 8:10 p.m. on August 20, 2024, essential chiller 22B was declared inoperable due to outlet temperatures of the chiller swinging between 43-55 degrees. The essential chiller is considered inoperable when outlet temperature exceeds 52 degrees. This condition also resulted in train B CRE HVAC being declared inoperable, resulting in a condition that could have prevented fulfillment of the CRE HVAC systems safety function.
The licensee performed troubleshooting to determine the cause of the temperature swings identified on essential chiller 22B. The licensee had previously installed additional monitoring equipment to assist with troubleshooting efforts for the essential chillers and noted that there was erratic output of the load and unload signals as well as a high level of electrical noise internal to the TCM, indicating that there were vibration-induced potentiometer value changes that affect controlling setpoints of the chiller.
In 2021, the licensee created a plan of action to address outlet temperature drift for the essential chillers, which included, in part, a corrective action to document and approve an engineering change for the TCM that changed the temperature control point potentiometers to a more robust 10-turn potentiometer with a locking device that would prevent vibration-induced setpoint changes. The engineering change was approved in August 2023. The licensee scheduled the existing TCMs to be changed out with those with the more robust potentiometers during subsequent planned work week windows. Essential chiller 22B was scheduled to have the engineering change implemented in May 2024; however, it was deferred to December 2024 due to only having one available spare at the time. The licensee received additional spares in July and August but did not implement the engineering change during the next available train B work window beginning August 5, 2024. The TCM subsequently failed on August 20, 2024.
Corrective Actions: The licensee changed out the installed TCM with one that had the more robust potentiometer with the locking device to prevent vibration-induced setpoint drift.
Corrective Action References: CR 2024-8068, 2021-8518
Performance Assessment:
Performance Deficiency: The failure to promptly correct a condition adverse to quality within the essential chilled water system was a performance deficiency. Specifically, the licensee failed to promptly replace the existing essential chiller 22B temperature current module with one that had a locking mechanism incorporated into the potentiometer following a 2021 engineering change for setpoint drift when maintenance was deferred from May 2024 to December 2024.
Screening: The inspectors determined the performance deficiency was more than minor because it was associated with the Equipment Performance attribute of the Mitigating Systems cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, essential chiller 22B was declared inoperable due to erratic outlet temperature swings that resulted in temperatures exceeding 52 degrees. These temperature swings were caused by vibration induced changes in potentiometer values that affected the chiller temperature setpoints.
Significance: The inspectors assessed the significance of the finding using IMC 0609 Appendix A, The Significance Determination Process (SDP) for Findings At-Power. Exhibit 2, Mitigating Systems Screening Questions, dated November 30, 2020. The finding was determined to be of very low safety significance (Green) because it
- (1) was not a deficiency affecting design or qualification of a mitigating system,
- (2) does not represent a loss of the probabilistic risk assessment (PRA) function of a single train TS system for greater than allowed outage time,
- (3) does not represent a loss of PRA function of one train of a multi-train TS system for greater than its TS allowed outage time,
- (4) does not represent a loss of the PRA function of two separate TS systems for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />,
- (5) does not represent a loss of PRA system and/or function as defined by the plant risk information e-book or the licensees PRA for greater than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and
- (6) does not result in the loss of a maintenance rule risk-significant, non-TS train for greater than three days. Additionally, the finding did not involve external event mitigating systems, the reactor protection system, fire brigade, or flexible coping strategies.
Cross-Cutting Aspect: H.5 - Work Management: The organization implements a process of planning, controlling, and executing work activities such that nuclear safety is the overriding priority. The work process includes the identification and management of risk commensurate to the work and the need for coordination with different groups or job activities. Specifically, the licensee had experienced multiple failures of TCMs for the essential chillers and had deferred replacement of the essential chiller 22B TCM in May 2024 due to parts availability.
However, they received spare replacement TCMs during July and August 2024 and failed to appropriately revisit their deferral plans before the TCM failed.
Enforcement:
Violation: Title 10 CFR Part 50, Appendix B, Criterion XVI, "Corrective Action," requires, in part, that measures shall be established to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and nonconformances are promptly identified and corrected.
Contrary to the above, from August 5, 2024, the licensee failed to assure that conditions adverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and nonconformances were promptly identified and corrected. Specifically, the licensee failed to promptly replace a deficient essential chiller 22B TCM, and the necessary maintenance was deferred to December 2024. The TCM for essential chiller 22B subsequently failed on August 20, 2024.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
Observation: Semi-Annual Trend Review - Individuals disregarding or bypassing access controls 71152S The inspectors reviewed the licensees corrective action program, performance indicators, condition reports (CRs), and other documentation available to help identify performance trends that might indicate the existence of a more significant safety issue. The inspectors verified that the licensee was taking corrective actions to address the identified adverse trends. The inspectors did not review any cross-cutting themes because none existed at the site. The inspectors noted a negative trend in access controls, including two instances of tailgating into a control room.
CR 24-2297: On March 8, 2024, an individual gained access into the Unit 1 mechanical electrical auxiliary building by tailgating. The individual did have authorized access.
CR 24-2876: On March 26, 2024, an individual working in the Unit 2 containment building exited through the elevator, walked towards the personnel airlock and walked under a suspended load.
CR 24-3246: On April 2, 2024, a worker exited the Unit 2 radiologically controlled area via the emergency exit bypass door. The door is posted Radiological Controlled Area Boundary - Emergency Exit Only - Contact Health Physics.
CR 24-3410: On April 5, 2024, a worker entered a radiologically controlled area without being logged into a radiation work permit.
CR 24-3659: On April 11, 2024, individuals were provided access via the west elevator on the turbine generator building 2 into a restricted area during a heavy lift. Individuals crossed no danger barriers to gain access to the restricted area.
CR 24-5395: On May 23, 2024, an individual that works for plant engineering tailgated into the Unit 2 control room and did not have authorized access to the control room.
CR 24-10251: On October 17, 2024, an individual gained access to the control room that did not have the appropriate access level.
The licensee has corrected each of the conditions at the time of discovery. However, some of the corrective actions included coaching the individuals, which would not reach a wider audience. This could be a factor in the repetitive nature of this trend. Not correcting these behaviors could lead to a lapse where an individual with malevolent intent could access unauthorized areas. The inspectors noted that most of these issues have occurred during timeframes when outages were ongoing.
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
- On October 23, 2024, the inspectors presented the inservice inspection for Unit 1 results to Kimberly A. Harshaw, Acting President, Chief Executive Officer and Chief Nuclear Officer, and other members of the licensee staff.
- On January 16, 2025, the inspectors presented the integrated inspection results to Kimberly A. Harshaw, Acting President, Chief Executive Officer and Chief Nuclear Officer, and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Drawings
5R169F20000#1
Residual Heat Removal System
Procedures
Residual Heat Removal System Operation
Fire Preplan Reactor Containment Building Central Reactor
Area (Upper)
Fire Preplan Reactor Containment Building SW Peripheral
Area
Fire Preplan Reactor Containment Building NW Peripheral
Area
Fire Preplan Reactor Containment Building SW Peripheral
Area
Fire Preplan Reactor Containment Building NW Peripheral
Area
Fire Preplan Reactor Containment Building NE Peripheral
Area
Fire Plans
Fire Preplan Reactor Containment Building Central Reactor
Area (Lower)
Miscellaneous
FHAR
STP Fire Hazards Analysis Report
Amendment
Work Orders
Work
Authorization
Number
647112
Corrective Action
Documents
CR
18-3993, 24-0217, 23-5591, 23-5769, 23-8373, 23-9271,
24-3804, 24-0711, 24-8521, 24-8535, 24-8536, 24-8537,
24-8538, 24-8539, 24-8540, 24-7245, 24-8542, 24-8664,
24-8665, 24-8666, 24-8870, 24-8866, 24-8670, 24-8542,
24-8540, 24-8538, 24-8539, 24-8537, 24-8536, 24-8533,
24-8535, 24-8518, 24-8515, 24-8202, 24-4975, 24-4697,
24-4943
Corrective Action
Documents
Resulting from
Inspection
CR
24-9605, 24-10252, 24-10253, 24-10254, 24-10255
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Steam Generator Management Program: Pressurized Water
Reactor Steam Generator Examination Guidelines
Inservice Inspection Program Plan For The South Texas
Project Electric Generating Station Units 1 And 2
Assessment
INPO's Pressurized Water Reactor (PWR) Materials Review
Visit At South Texas Project
2/15/2016
SG-CDMP-19-21
South Texas 1RE22 Steam Generator Degradation
Assessment
SG-CDMP-20-10
South Texas Project Unit 1 Steam Generator Cycle 22
Condition Monitoring and Cycles 23, 24, and 25 Final
Operational Assessment
Miscellaneous
SG-CDMP-24-9
South Texas 1RE25 Steam Generator Degradation
Assessment
General Ultrasonic Examination
Ultrasonic Thickness Examination
Recording Data From Direct Visual, Liquid Penetrant, and
Magnetic Particle Examinations
Liquid Penetrant Examination (Color Contrast Solvent
Removable)
Magnetic Particle Examination (Dry Powder Yoke Method)
Visual Examination of Component Supports for ASME
Section XI Inservice Inspection
ASME XI Examination for VT-1 and VT-3
ASME Section XI Visual Examination for Containment Metal
Liner Inspections
Visual Examination of Welds and Base Metal
Visual VT-2 Examinations
ASME Section XI VE Visual Examinations
System Pressure Testing Program
RCS Pressure Boundary Inspection for Boric Acid Leaks
Boric Acid Corrosion Control Program
Station Self-Assessment Program
Procedures
0001
General Welding Requirements
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
0001A
ASME Repair/Replacement Welding Requirements
0001B
ASME/ANSI B31.1 Welding Requirements
0001C
AWS/HVAC Welding Requirements
0001D
Welding Documentation Requirements
0002
Welding Procedure Specification Preparation and
Qualification
0003
Welder Qualification and Certification
0004
Control of Filler Materials
0005
Control of Post Weld Heat Treatment
0006
Arc Wire Thermal Spray Coatings
PDI-UT-1
PDI Generic Procedure for the Ultrasonic Examination of
Ferritic Pipe Welds
G
PDI-UT-2
PDI Generic Procedure for the Ultrasonic Examination of
Austenitic Pipe Welds
J
PDI-UT-3
PDI Generic Procedure for the Ultrasonic Through-Wall
Sizing of Planar Flaws in Similar Metal Piping Welds
G
Miscellaneous
Training Plan
Just-in-time Training Presentation
Plant Startup to 100%
26
Procedures
Plant Shutdown From 100% to Hot Standby
Corrective Action
Documents
CR
24-6338, 2023-6823, 2023-8073, 2023-10345, 2023-
10352, 2023-10622, 2024-1539, 2024-2138, 2024-2403,
24-8155
Drawings
3NC2001
Consolidated Maxiflow Safety Valve
Miscellaneous
2CC03 -
Component
Cooling Water
Startup Work Request
03/23/1988
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
2L529TS0103
Specification for ASME Section III Butterfly Valves
Operations Quality Assurance Plan, Chapter 10.0
"Inspection"
RIP #4146
Receiving Inspection Planning for Permanent Plant Items
08/17/1984
VTD-C568-0004
Instructions for Installation and Maintenance Consolidated
Safety Valves Nuclear Type 3700
VTD-S407-0001
Stewart & Stevenson Technical Manual
FLEX Equipment Functionality Program
Receipt Inspection
FLEX-0001
Diverse and Flexible Coping Strategies (FLEX) Program
Document
FLEX-0002
Final Integrated Plan Beyond Design Basis FLLEX
Mitigating Strategies
Procedures
SEG-0009
Maintenance Rule Basis Document Guideline
Work Orders
Work
Authorization
Numbers
713593, 710242, 711987, 713015, 666746, 670867,
675330, 679754, 658637
Corrective Action
Documents
CR
24-9013, 2024-6981, 2024-9711, 2024-10415, 2024-
10928, 2024-2158, 2024-1883, 2024-1979
5Q159F22545#2
Piping & Instrumentation Diagram Standby Diesel Shutdown
System
5V119V250041#1
PIPING & INSTRUMENTATION DIAGRAM HVAC
CONTROL ROOM ENVELOPE SYSTEM
8041--01197CE
Control Schematic (Starting Sequence Control)
2/17/2020
8041--01198CE
Control Schematic (Starting Sequence Control)
2/04/2001
8041--01199-HCE
Control Schematic (Starting Sequence Control)
2/13/1993
8041--01207CE
Control Schematic (Shutdown and Alarm System)
07/12/2001
Drawings
5V119V0143
HVAC ELECTRICAL AUXILIARY BUILDING PARTIAL
PLAN EL. 60' AREA 7
5Q159MB1023
Standby Diesel Generator System Design Basis Document
Miscellaneous
Root Cause
Evaluation
Main Steam Safety Relief Valve had a cracked spring
06/20/2024
Fluid Leak Management Program
Procedures
Electrical Auxiliary Building HVAC System
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Control Room Emergency Air Cleanup System Function
Test
677359
Inspect, repair, and preserve control room ductwork
upstream of the outside air
11/05/2024
Work Orders
715578
Residual Heat Removal Pump 1C Replace Mechanical Seal
2-31926-381
Replacement of Unit 2 Class 1E Switchgear E2C Circuit
Breakers During 2RE23 Outage
Engineering
Changes
21-4916-2
Change Hole Size of Conical Flow Restricting Orifice for
HHSI Pump 2A to Raise Flow Rate
Notification of Field Work Complete for EC 21-4916-2
04/06/2024
Miscellaneous
Return-To-Service Checklist for EC-21-4196-2
05/14/2024
Procedures
10CFR50.59 Evaluations
Work Orders
669255
High Head Safety Injection Pump 1A(2A) Comprehensive
Pump Test
Corrective Action
Documents
CR
24-9013, 2024-10682, 2024-5415, 2024-10637,
24-8966, 2024-8943
2-355-46
ESI Recommend Limit Switch Replacement for Standby
Diesel Generator Overspeed Switch
Engineering
Changes
EC 23-8110-23
Unit 1 Narrow Range RTD Composite Slope and Offset
Table
AMS Fact Sheet: RTD Cross Calibration Method
Standard Design Process Interface Procedure
Miscellaneous
VTD-E945-0002
Engine Systems, Inc. Seismic Qualification of Limit Switch
and Bracket
RCS Leakage Monitoring
0010
Standby Diesel Generator Overspeed Shutdown Butterfly
Valve Maintenance
Standby Diesel 13(23) LOOP Test
Standby Diesel 13(23) LOOP - ESF Actuation Test
Standby Diesel Generator 6 Year Inspection
Automatic Multiple Rod Drop Time Measurement
LLRT M-43 Supplementary Containment Purge Supply
Procedures
Reactor Containment Building Integrated Leakage Rate Test
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Work Orders
Work
Authorization
Numbers
698928, 693203, 703859, 703867, 703869, 660437,
631984, 631986
Corrective Action
Documents
CR
24-7476
Miscellaneous
Licensed Operator Requal Cycle 242 & 243 E-plan Scenario
Evaluation Report, July 23 - September 10, 2024
10/08/2024
Corrective Action
Documents
CR
21-8518, 2024-0750
Procedures
WCG-0008
Prevent Recurring Equipment Problems (PREP)
Work Orders
Work
Authorization
Numbers
615485, 701742
Corrective Action
Documents
CR
24-2297, 2024-2876, 2024-3246, 2024-3410, 2024-3659,
24-5395, 2024-10251
Corrective Action
Documents
CR
24-8068, 2024-8943, 2024-8942, 2023-10850
Engineering
Changes
21-8518-8
Upgrade Temperature Control Point and Max Load
Adjustment Potentiometers of the UCI-TCM-1A Temperature
Current Modules for Chillers
Condition Report Engineering Evaluation 24-8342-1
08/30/2024
Engineering
Evaluations
Prompt Equipment Performance Checklist, Standby
Transformer 2 Trip
Procedures
Switchyard Management
Work Orders
Work
Authorization
Numbers
701459, 552052, 642813