IR 05000498/2025011
| ML25240A902 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 08/29/2025 |
| From: | Michael Bloodgood NRC/RGN-IV/DORS/EB1 |
| To: | Kharrl C South Texas |
| References | |
| IR 2025011 | |
| Download: ML25240A902 (15) | |
Text
August 29, 2025
SUBJECT:
SOUTH TEXAS PROJECT ELECTRIC GENERATING STATION, UNITS 1 AND 2 - NRC COMPRHENSIVE ENGINEERING TEAM INSPECTION REPORT 05000498/2025011 AND 05000499/2025011
Dear Charles Kharrl:
On July 31, 2025, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at South Texas Project Electric Generating Station, Units 1 and 2 and 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.
One finding of very low safety significance (Green) is documented in this report. This finding involved a violation of NRC requirements. We are treating this violation as a non-cited violation (NCV) consistent with Section 2.3.2 of the Enforcement Policy.
If you contest the violation or the significance or severity of the violation 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.
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 (10 CFR) Part 2.390, Public Inspections, Exemptions, Requests for Withholding.
Sincerely, Michael R. Bloodgood, Chief Engineering Branch 1 Division of Operating Reactor Safety Signed by Bloodgood, Michael on 08/29/25 Docket Nos. 05000498 and 05000499 License Nos. NPF-76 and NPF-80
Enclosure:
As stated
Inspection Report
Docket Numbers:
05000498 and 05000499
License Numbers:
Report Numbers:
05000498/2025011 and 05000499/2025011
Enterprise Identifier:
I-2025-011-0016
Licensee:
STP Nuclear Operating Company
Facility:
South Texas Project Electric Generating Station, Units 1 and 2
Location:
Wadsworth, TX 77483
Inspection Dates:
July 14, 2025 to July 31, 2025
Inspectors:
D. Bryen, Reactor Inspector
K. Chambliss, Senior Resident Inspector
W. Cullum, Senior Reactor Inspector
B. Nwafor, Reactor Inspector
M. Siddiqui, Reactor Inspector
F. Thomas, Reactor Inspector
Approved By:
Michael R. Bloodgood, Chief
Engineering Branch 1
Division of Operating Reactor Safety
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting a NRC 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
Failure to Translate High Head Safety Injection Pump Maximum Shutoff Head into MOV Thrust Calculations Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000498,05000499/2025011-01 Open/Closed None (NPP)71111.21M The inspectors identified a Green finding and associated non-cited violation (NCV) of 10 CFR 50, Appendix B, Criterion III, Design Control, for the licensees failure to correctly translate the maximum high head safety injection (HHSI) pump shutoff head into design basis motor operated valve (MOV) thrust calculations. Specifically, the licensee used non-conservative HHSI pump shutoff head values in the HHSI discharge MOV thrust calculations and failed to verify the valves (i.e. A1SIMOV0004A, C2SIMOV0004C, A2SIMOV0004A, B2SIMOV0004B,
B1SIMOV0004B, C1SIMOV0004C) had adequate closing thrust to perform their containment isolation function.
Additional Tracking Items
None.
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 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
===71111.21M - Comprehensive Engineering Team Inspection The inspectors evaluated the following components and listed applicable attributes, permanent modifications, and operating experience:
Structures, Systems, and Components (SSCs) (IP section 03.01)===
(1)3V152VFN005 - Unit 2 ECW Building Intake Fan 21C
- Logic diagram
- Vendor documentation
- Technical specifications, technical specification bases document and final safety analysis report
- Preventative maintenance history
- Visual inspection of the component
- Room ventilation calculations
- Corrective actions related to the component
- Piping and Instrumentation diagrams
- (2) Z352ZLP103, Unit 2 EDG 2 Control Panel
- Updated final safety analysis report, technical specifications, and technical specifications bases document
- Visual inspection of switchgear for configuration and material condition
- Environmental conditions for equipment
- Vendor manual for conformance with manufacturer instructions for installation and maintenance
- Preventive maintenance and periodic verification testing
- Component maintenance history and corrective action program documents
- Schematic and wiring drawings
- Corrective action program documents (3)2N121XSI0004A, High Head Safety Injection Pump 1A Discharge MOV (ORC)
- Mechanical design calculations and considerations:
o Weak link analysis o
Required thrust (torque)o Stroke time requirements o
Maximum differential pressure
- Test and inspection procedures, acceptance criteria, and recent results:
o Inservice testing o
Diagnostic testing
- Motor power requirements:
o Control logic o
Degraded Voltage
- Operating procedures
- Environmental Qualification (4)3E241EIV1203, Unit 1 10KVA Inverter EIV 1203
- Updated final safety analysis report, technical specifications, and technical specifications bases document
- Visual inspection of switchgear for as-built configuration and material condition
- Environmental conditions for equipment
- One-line diagrams and voltage analysis calculations
- Vendor manual for conformance with manufacturer instructions for installation and maintenance
- Preventive maintenance and periodic verification testing
- Component maintenance history
- Schematic and wiring drawings
- System health report
- Updated final safety analysis report, technical specifications, and technical specifications bases document
- Visual inspection of transformer for configuration and material condition
- Environmental conditions for equipment
- Vendor manual for conformance with manufacturer instructions for installation and maintenance
- Preventive maintenance and periodic verification testing
- Component maintenance history
- Schematic and wiring drawings
- Corrective action program documents and trending data
- Operating procedures
- Operations log data of critical parameters
Modifications (IP section 03.02) (2 Samples)
- (1) EC 19-376-13, U1 Train A ESF Diesel Sequencer Class 1E Output Actuation Timing Modules Upgrade
- (2) EC 25-827-2, Identify Alternate Breaker for Class -1E 125 VDC Panel 15 Ampere Branch Circuit Breaker Westinghouse HFB2015/Modified and Install Alternate Breaker for U1 PL139C Breaker #3
10 CFR 50.59 Evaluations/Screening (IP section 03.03) (7 Samples)
- (1) EC 23-2365-2 - Move Wires on Corroded Terminals on TB-13 in JB-14 on SDG21 to Spare Terminals Free of Corrosion
- (2) EC 19-376-13, U1 Train A ESF Diesel Sequencer Class 1E Output Actuation Timing Modules Upgrade
- (3) EC 24-4884-58, Unit 1 Relay 21/G1 Spurious Trip Mitigation
- (4) EC 24-4212-2, Install Alternate Essential Chilled Water Chiller Pump Motor 3V111VPA012
- (5) EC 12-31926, Replacement of Unit 2 Class IE Switchgear E2A Circuit Breakers During 2RE22 Outage
- (6) EC 24-10459-4, Approve Alternate Potentiometer for 1C Main Steam Outlet Power Operated Relief Valve C1MSZT7431
- (7) EC 20-4781-48, Unit 1 Check Valve RH0032A Replacement
Operating Experience Samples (IP section 03.04) (1 Sample)
- (1) CR 19-13263, NUPIC audit of Curtiss-Wright, Steam & Air Solutions
INSPECTION RESULTS
Failure to Translate High Head Safety Injection Pump Maximum Shutoff Head into MOV Thrust Calculations Cornerstone Significance Cross-Cutting Aspect Report Section Mitigating Systems Green NCV 05000498,05000499/2025011-01 Open/Closed None (NPP)71111.21M The inspectors identified a Green finding and associated Non-Cited Violation (NCV) of 10 CFR 50, Appendix B, Criterion III, Design Control, for the licensees failure to correctly translate the maximum high head safety injection (HHSI) pump shutoff head into design basis motor-operated valve (MOV) thrust calculations. Specifically, the licensee used non-conservative HHSI pump shutoff head values in the HHSI discharge MOV thrust calculations and failed to verify the valves (i.e. A1SIMOV0004A, C2SIMOV0004C, A2SIMOV0004A, B2SIMOV0004B, B1SIMOV0004B, C1SIMOV0004C) had adequate closing thrust to perform their containment isolation function.
Description:
The emergency core cooling system at South Texas Project consists of three independent trains, and each train consists of one high-head safety injection pump and one low-head safety injection pump. The HHSI pumps (i.e. PA101A, B, C) are 100-percent capacity centrifugal pumps, and each pump has a discharge MOV (SIMOV0004A, B, C)which serve as the outside containment isolation valves.
The licensee established Calculation MC 6460 Rev. 0, Minimum Thrust for GL 89-10 Gate MOVs, to calculate the minimum required open and closing thrust for motor-operated gate valves. For the HHSI discharge MOVs, the calculation listed the maximum expected differential pressure (MEDP) in the closing direction as 1582 psig. The closing MEDP value was based on calculation ST400088-00054CWN, Motor Operated Valve Evaluation -GNL 89-10 for 6GM77FHA, and translated into the MOV database calculation for each valve.
The licensee established calculation ST400088-00054CWN Rev. 1, to verify the valves would perform their intended functions under the maximum operating conditions (i.e. maximum differential pressures).Section III, Calculation Methodology/Introduction, states, in part, the methodology throughout is to assess the maximum opening and closing differential pressure for each operating modethe calculated maximum differential pressures and maximum flow rates are not necessarily representative of actual operating conditions in that they may be conservative/bounding conditions for design purposes. The inspectors reviewed Section III.B.1, Safety Injection and Recirculation for Accident Mitigation, and noted the MEDP in the closing direction was based on the maximum pump shutoff head at the time of demand closure. The calculation used a maximum pump shutoff head of 3700 ft, resulting in a closing MEDP of 1582 psig.
On July 14, 2025, the inspectors requested the vendor high head safety injection pump curve and questioned the maximum pump shutoff head used in ST400088-00054CWN. After reviewing the calculation, the licensee found that the minimum pump shutoff head was used instead of the maximum pump shutoff head. The licensee documented the use of a non-conservative pump shutoff head in a condition report.
Corrective Actions: The licensee generated CR 25-6307 and performed an operability evaluation under CR 25-6307-1. The licensee demonstrated the MOVs had sufficient closing thrust to perform their design basis functions.
Corrective Action References: CR 25-6307
Performance Assessment:
Performance Deficiency: The licensees failure to correctly translate the maximum HHSI pump design shutoff head into MOV thrust calculations was a performance deficiency, and contrary to 10 CFR 50, Appendix B, Criterion III, Design Control.
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 site used non-conservative maximum pump shutoff head values to perform the thrust calculations for the HHSI MOVs and failed to ensure the valves had sufficient closing thrust to perform their design basis containment isolation functions. Additionally, the licensee did not have adequate closing thrust margin and had to remove conservatisms in the calculation to regain the additional margin.
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 that this finding is of very low safety significance (Green) because although the finding was a deficiency affecting the design or qualification of a mitigating SSC, the SSC maintained its operability and PRA functionality.
Cross-Cutting Aspect: Not Present Performance. No cross-cutting aspect was assigned to this finding because the inspectors determined the finding did not reflect present licensee performance. Specifically, the error of using the wrong pump shutoff head occurred outside of the nominal 3-year period and, therefore, does not reflect current performance.
Enforcement:
Violation: Title 10, CFR Part 50, Appendix B, Criterion III, Design Control, requires, in part, that measures be established to assure that applicable regulatory requirements and the design basis are correctly translated into specifications, drawings, procedures, and instructions.
Contrary to the above, as of July 16, 2025, the licensee failed to assure that applicable regulatory requirements and the design basis were correctly translated into specifications, drawings, procedures, and instructions. Specifically, the licensee failed to translate HHSI pump maximum shutoff head design basis into the design thrust calculations/specifications for HHSI discharge MOVs: A1SIMOV0004A, C2SIMOV0004C, A2SIMOV0004A, B2SIMOV0004B, B1SIMOV0004B, C1SIMOV0004C.
Enforcement Action: This violation is being treated as a non-cited violation, consistent with Section 2.3.2 of the Enforcement Policy.
EXIT MEETINGS AND DEBRIEFS
The inspectors verified no proprietary information was retained or documented in this report.
- On July 31, 2025, the inspectors presented the NRC inspection results to Chuck Karrl and other members of the licensee staff.
DOCUMENTS REVIEWED
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
5Ql59MB1023
STANDBY DIESEL GENERATOR SYSTEM
Class 1E DC System Scenario, Battery / Charger / Inverter
Sizing & System Voltage Calculation
Switchgear 4.16kV E2A - Design Basis Operation
Minimum Thrust For GL 89-10 Gate MOVs
ST400088-
00054CWN
Motor Operated Valve (MOV) GNL 89-10 for 6GM77FHA
01/25/1991
Calculations
STI-94-009559-11
GL 89-10 Program Design Basis Review A1SIMOV0004A
11/23/1993
Corrective Action
Documents
2-355, 22-9270, 23-10287, 22-2555, 19-13263, 21-11988,
21-12444, 21-12889, 22-10673, 22-11838, 22-12881, 22-
00032, 23-09709, 24-11973, 25-00015, 25-00705, 24-
10459, 24-11655, 24-10685, 24-04879, 24-11285, 23-2365
Corrective Action
Documents
Resulting from
Inspection
25-6287, 25-6292,
25-6294, 25-6253,
25-6307, 25-6305,
25-6712, 25-6713,
25-5086, 25-6253,
25-6375
00009E0AAAA#1,
Sheet 01
Single Line Diagram, Main Generator Unit & Standby XFMR
Protection & Metering
00009E0GM02#1,
Sheet 01
Elementary Diagram, Main Generator DC Circuits
00009E0PB01#1,
Sheet 02
Elementary Diagram, Main Transformer & 345KV Line
Protection
00009E0PC03
Sheet 01
Electrical Diagram 13.8 KV BUS 2F, 2G, 2H, FDR BKR
E2A, E2B, E2C TO AUX XFMR E2A, E2B, E2C
00009E0PK04
Sheet 2
Elementary Diagram ESF Transformer & 4.16kV Bus E2A,
E2B, and E2C Protection and Metering
00009E0SI13#1
Elementary Diagram HHSI Pumps 1A, 1B, & 1C Discharge
MOV's 0004A, 0004B, & 0004C
10162D40
Inch 1525 LB Valve Assembly Drawing
Drawings
108, Sheet No. 46
I-06, SSPS Schematic Diagram, AC Power Distribution
06/08/2000
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
Train "R"
1084H13, Sheet
No. 47
I-06, SSPS Schematic Diagram, AC Power Distribution
Train S
06/08/2000
5N129F05013#1
Piping and Instrumentation Diagram Safety Injection System
9E0CV26 Sheet 1
Electrical Diagram Centrifugal Charging Pumps 2A & 2B
20-4781-48
Unit 1 Check Valve RH0032A Replacement
23-2365-2
Move Wires on Corroded Terminals on TB-13 in JB-14 on
SDG21 to Spare Terminals Free of Corrosion
2300178
Document change notice
24-4212-2
Install Alternate Essential Chilled Water Chiller Pump Motor
3V111VPA012
24-4884-58
Unit 1 Relay 21/G1 Spurious Trip Mitigation
25-827-2
Identify Alternate Breaker for Class -1E 125 VDC Panel 15
Ampere Branch Circuit Breaker Westinghouse
HFB2015/Modified and Install Alternate Breaker for U1
PL139C Breaker #3
DCP# 01-13109-8
Include Stroke Time Limits for Applicable MOVs in MOV
Database
09/13/2007
EC 12-31926-363
Replace ESF Bus 2A ABB HK Class 1E Circuit Breakers
With Siemens NTS Vacuum Circuit Breakers
Engineering
Changes
EC 12-31926-43
Class 1E 4.16 KV Circuit Breaker Replacements
Control of Vendor Technical Information
0960L
SI Accumulator Pressure Loop Calibration
Emergency Diesel Generator 12(22)
4E519EB01108
Design Basis Document 4.16kV AC Power System
5N129MB01045
Design Basis Document Safety Injection (SI) System
5V150VQ1004
Essential Cooling Water Intake Structure Ventilation System
7E139ES0006
Specification Change Notice 5000 KVA Auxiliary ESF &
BOP Transformers
F
MOV Database
Actuator: A1SIMOV0004A
OPGP04-ZE-0312
U1 Train A ESF Diesel Sequencer Class 1E Output
Actuation Timing Modules Upgrade
Miscellaneous
PRA-NB-25
Essential Cooling Water System Includes Top Events
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
ECWS, WA, WB, and WC
PRA-NB-34
South Texas Project Electric Generating Station
Probabilistic Risk Assessment - Safety Injection System
STI-35552509
ESF SBDG Output Timing Module Upgrade Factory
Acceptance Test Data Report.
VTD P025-0004
Test Performance Curve No. 37752-A4
2/08/1978
VTD-A363-0021
Vendor Technical Document for Instruction and Operating
Manual, 10 KVA Inverter, VTD-A363-0021
VTD-B455-0094
Vendor Technical Document Liquid Insulated Primary And
Secondary Unit Substation Transformers
VTD-S637-0009
ESF Load Sequencer for South Texas Project Electric
Generating Station
VTD-W120-0678
AB DE-ION Circuit Breakers Time Current Characteristic
Curves For Standard and Mark 75 Thermal Magnetic Circuit
Breakers
25-6307-1
CR Action 25-6307-1, Unit 1 and 2, 3Q
07/18/2025
Operability
Evaluations
CR 02-5929
Engineering Evaluation of SDG Operability without Standby
Lube Oil or Standby Jacket Water Pumps
MOV Diagnostic Testing Error Analysis and Acceptance
Criteria
Inservice Testing Program
Inservice Testing Program for Valves
Motor Operated Valve Program
Preventative Maintenance Program
Operator Time Critical Action Program
10CFR50.59 Evaluations
Steam Generator P.O.R.V. Maintenance
am Generator PORV Hydraulic Actuator Maintenance
Auxiliary ESF Transformer Test
20 VAC NSSS Vital 10 KVA Inverter/Rectifier Maintenance
20 VAC NSSS Vital Inverter/Rectifier (10 KVA)
Performance Test
Procedures
Calibration of KD-10 and KD-11 Relays
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
MOV Performance and Degradation Trending
MOV Diagnostic Testing (VOTES) - Rising Stem Valves
Paul Munroe PORV EQ Replacement
AC Electrical Distribution Breaker Lineup
Transformer Normal Breaker and Switch Lineup
Emergency Diesel Generator 11(21)
0001
Essential Cooling Water Operations
Safety Injection System Initial Lineup
Plant Startup to 100%
26
Plant Shutdown From 100% to Hot Standby
Loss Of 120 VAC Class Vital Distribution
Transfer to Cold Leg Recirculation
Switchgear E1A(E2A) Bus Outage
Essential Cooling Water Pump 1C(2C) Reference Values
Measurement
Essential Cooling Water System Train C Testing
Safety Injection System Miscellaneous and Train 1A(2A)
Valve Operability Test
Local Leakage Rate Test Calculations, Guidelines, and
Program
MOV IST Margin and Test Frequency Determination
ENG-0007
Predictive Maintenance Administrative Guideline
MG-0006
Work Execution and Closeout Guideline
WCG-0001
Work Screening and Processing
Work Orders
96020332,
96029921,
409421, 580708,
659112, 685895,
674806, 648785,
616773, 700957,
501868, 636905,
641528, 641529,
641623, 665883,
Inspection
Procedure
Type
Designation
Description or Title
Revision or
Date
680597, 716333,
716412, 519318,
519319, 519320,
519321, 519323,
519325, 519327,
519329, 51930,
346395, 711515,
716538
EM-2-05000456
ECW PUMP BLDG TRN C VENT FAN 21C 2-HZ-FN-005
EM-2-95002552,
EM-2-95002553,
PT-2-93002897
ECW INTAKE BUILDING VENT FAN 21C
06