ML25225A229
| ML25225A229 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 08/15/2025 |
| From: | John Lamb NRC/NRR/DORL/LPL2-1 |
| To: | Coleman J Southern Nuclear Operating Co |
| References | |
| EPID L-2025-LLA-0127 | |
| Download: ML25225A229 (24) | |
Text
August 15, 2025 Ms. Jamie M. Coleman Regulatory Affairs Director Southern Nuclear Operating Company, Inc.
3535 Colonnade Parkway, Bin N-274-EC Birmingham, AL 35243
SUBJECT:
VOGTLE ELECTRIC GENERATING PLANT, UNIT 4 - ISSUANCE OF AMENDMENT NO. 202 TO REVISE TECHNICAL SPECIFICATION 3.5.2, CORE MAKEUP TANKS (CMTs) - OPERATING (EMERGENCY CIRCUMSTANCES)
Dear Ms. Coleman:
In response to your application dated August 11, 2025, as supplemented by letter dated August 12, 2025, the U.S. Nuclear Regulatory Commission (NRC) has issued the enclosed Amendment No. 202 to Combined License (COL) No. NPF-92 for Vogtle Electric Generating Plant (Vogtle), Unit 4. The amendment revises Technical Specification (TS) 3.5.2, Core Makeup Tanks (CMTs) - Operating, to add a note to the Limiting Condition for Operation (LCO) and another note in Surveillance Requirement (SR) 3.5.2.4 regarding boron concentration. The proposed amendment temporarily revises the TS 3.5.2 to reduce the minimum allowable CMT A boron concentration and to not require performance of SR 3.5.2.4 until startup from the first Vogtle, Unit 4, refueling outage (RFO), which is scheduled for the fall of 2025. The proposed amendment is a one-time temporary change, and the proposed amendment would be effective until startup from the first Vogtle, Unit 4, RFO.
The amendment was submitted under emergency circumstances as described in the provisions of paragraph 50.91(a)(5) of Title 10 of the Code of Federal Regulations due to the time critical nature of the amendment.
A copy of the related safety evaluation is also enclosed. The safety evaluation describes the emergency circumstances under which the amendment was issued and the final no significant hazards consideration determination. A Notice of Issuance addressing the final no significant hazards consideration determination and opportunity for a hearing associated with the emergency circumstances will be included in the Commissions monthly Federal Register notice.
If you have questions, please contact me at 301-415-3100 or John.Lamb@nrc.gov.
Sincerely,
/RA/
John G. Lamb, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No.: 52-026
Enclosures:
- 1. Amendment No. 202 to Vogtle, Unit 4, COL
- 2. Safety Evaluation cc: Listserv
SOUTHERN NUCLEAR OPERATING COMPANY, INC.
GEORGIA POWER COMPANY OGLETHORPE POWER CORPORATION MEAG POWER SPVM, LLC MEAG POWER SPVJ, LLC MEAG POWER SPVP, LLC CITY OF DALTON, GEORGIA VOGTLE ELECTRIC GENERATING PLANT, UNIT 4 DOCKET NO.52-026 AMENDMENT TO FACILITY COMBINED LICENSE Amendment No. 202 License No. NPF-92
- 1.
The Nuclear Regulatory Commission (the Commission) has found that:
A.
The application for amendment by Southern Nuclear Operating Company (SNC),
dated August 11, 2025, as supplemented by letter dated August 12, 2025, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act) and the Commissions regulations set forth in 10 CFR Chapter I; B.
The facility will be constructed and will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C.
There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D.
The issuance of this amendment will not be inimical to the common defense and security or the health and safety of the public; and E.
The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations, and all applicable requirements have been satisfied.
- 2.
Accordingly, the license is hereby amended by page changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 2.D(8) of Facility Combined Operating License No. NPF-92 is hereby amended to read as follows:
(8) Incorporation The Technical Specifications and Environmental Protection Plan in Appendices A and B, respectively, of this license, as revised through Amendment No. 202, are hereby incorporated into this license.
- 3.
This license amendment is effective as of the date of its issuance and shall be implemented upon issuance with the compensatory measures described in Section 3.2 on page E-8 of the SNC letter dated August 11, 2025.
FOR THE NUCLEAR REGULATORY COMMISSION:
Michael T. Markley, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
Attachment:
Page 4 of the facility Combined License and affected pages of Appendix C of the facility Combined License Date of Issuance: August 15, 2025 MICHAEL MARKLEY Digitally signed by MICHAEL MARKLEY Date: 2025.08.15 10:12:52 -04'00'
ATTACHMENT TO LICENSE AMENDMENT NO. 202 TO FACILITY COMBINED LICENSE NO. NPF-92 DOCKET NO.52-026 Replace the following pages of the facility Combined License No. NPF-92 with the attached revised pages. The revised pages are identified by amendment number and contain marginal lines indicating the areas of change.
Facility Combined License No. NPF-92 REMOVE INSERT 4
4 Appendix A to facility Combined License No. NPF-92 REMOVE INSERT 3.5.2-1 3.5.2-1 3.5.2-2 3.5.2-2 3.5.2-3
D.
The license is subject to, and SNC shall comply with, the conditions specified and incorporated below:
(1)
Changes during Construction - Removed by Amendment No. 199 (2)
Pre-operational Testing - Removed by Amendment Nos. 194 and 199 (3)
Nuclear Fuel Loading and Pre-critical Testing - Removed by Amendment Nos. 194 and 199 (4)
Initial Criticality and Low-Power Testing - Removed by Amendment No. 199 (5)
Power Ascension Testing - Removed by Amendment No. 199 (6)
Maximum Power Level (7)
(8)
SNC is authorized to operate the facility at steady state reactor core power levels not to exceed 3400 MW thermal (100-percent thermal power), as described in the UFSAR, in accordance with the conditions specified herein.
Reporting Requirements - Removed by Amendment No. 199 Incorporation The Technical Specifications and Environmental Protection Plan in Appendices A and B, respectively, of this license, as revised through Amendment No. 202, are hereby incorporated into this license.
(9)
Technical Specifications - Removed by Amendment No. 199 (10)
Operational Program Implementation - Removed by Amendment No. 199 (11)
Operational Program Implementation Schedule - Removed by Amendment No. 199 (12)
Site-and Unit-specific Conditions - Removed by Amendment No. 199
[Blank Pages 5 through 14 removed by Amendment No. 199.]
4 Amendment No. 202
Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 1 Amendment No. 13 (Unit 3)
Amendment No. 202 (Unit 4) 3.5 PASSIVE CORE COOLING SYSTEM (PXS) 3.5.2 Core Makeup Tanks (CMTs) - Operating LCO 3.5.2 Both CMTs shall be OPERABLE.
- NOTE -
For Unit 4 until entry into TS 3.5.3 Applicability during shutdown for 4R01, CMT A may be considered OPERABLE with boron concentration
< 3400 ppm provided:
- a.
CMT A boron concentration is 3100 ppm and
- b.
Average of CMT A and CMT B boron concentration is 3400 ppm.
APPLICABILITY:
MODES 1, 2, and 3.
MODE 4 with the Reactor Coolant System (RCS) not being cooled by the Normal Residual Heat Removal System (RNS).
ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.
One CMT inoperable due to one CMT outlet isolation valve inoperable.
A.1 Restore outlet isolation valve to OPERABLE status.
72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> B.
One CMT inoperable due to water temperature or boron concentration not within limits.
B.1 Restore water temperature and boron concentration to within limits.
72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> C.
Two CMTs inoperable due to water temperature or boron concentration not within limits.
C.1 Restore water temperature and boron concentration to within limits for one CMT.
1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of LCO 3.5.2 Condition C entry concurrent with LCO 3.5.1 Condition B entry AND 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />
Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 2 Amendment No. 185 (Unit 3)
Amendment No. 202 (Unit 4)
ACTIONS (continued)
CONDITION REQUIRED ACTION COMPLETION TIME D.
One CMT inlet line with noncondensible gas volume not within limit.
D.1 Restore CMT inlet line noncondensible gas volume to within limit.
24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> E.
One CMT inoperable for reasons other than Condition A, B, or D.
E.1 Restore CMT to OPERABLE status.
1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from discovery of LCO 3.5.2 Condition E entry concurrent with LCO 3.5.1 Condition B entry AND 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> F.
Required Action and associated Completion Time of Condition A, B, C, D, or E not met.
OR Two CMTs inoperable for reasons other than Condition C.
F.1 AND F.2 Be in MODE 3.
Be in MODE 5.
6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> 36 hours SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.5.2.1 Verify the temperature of the borated water in each CMT is < 120°F.
24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> SR 3.5.2.2 Verify each CMT inlet isolation valve is fully open.
12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> SR 3.5.2.3 Verify the volume of noncondensible gases in each CMT inlet line has not caused the high-point water level to drop below the sensor.
24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />
Technical Specifications CMTs - Operating 3.5.2 VEGP Units 3 and 4 3.5.2 - 3 Amendment No. 185 (Unit 3)
Amendment No. 202 (Unit 4)
SURVEILLANCE REQUIREMENTS (continued)
SURVEILLANCE FREQUENCY SR 3.5.2.4
- NOTE -
Not required to be performed for Unit 4 until entry into TS 3.5.3 Applicability during startup from 4R01.
Verify the boron concentration in each CMT is 3400 ppm and 4500 ppm.
31 days SR 3.5.2.5 Verify each CMT outlet isolation valve strokes open.
In accordance with the Inservice Testing Program SR 3.5.2.6 Verify each CMT outlet isolation valve actuates to the open position on an actual or simulated actuation signal.
24 months SR 3.5.2.7 Verify system flow performance of each CMT in accordance with the System Level OPERABILITY Testing Program.
10 years
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 202 TO THE COMBINED LICENSE NO. NPF-92 SOUTHERN NUCLEAR OPERATING COMPANY, INC.
GEORGIA POWER COMPANY OGLETHORPE POWER CORPORATION MEAG POWER SPVM, LLC MEAG POWER SPVJ, LLC MEAG POWER SPVP, LLC CITY OF DALTON, GEORGIA VOGTLE ELECTRIC GENERATING PLANT, UNIT 4 DOCKET NO.52-026
1.0 INTRODUCTION
By letter dated August 11, 2025 (Agencywide Documents Access and Management System Accession No. ML25223A334), as supplemented by letter dated August 12, 2025 (ML25224A262), Southern Nuclear Operating Company (SNC, the licensee) requested that the U.S. Nuclear Regulatory Commission (NRC or Commission) amend Vogtle Electric Generating Plant (Vogtle), Unit 4, Combined License (COL) Number NPF-92.
The proposed license amendment request (LAR) revises Technical Specifications (TS) 3.5.2, Core Makeup Tanks (CMTs) - Operating, to add a note to the Limiting Condition for Operation (LCO) and another note in Surveillance Requirement (SR) 3.5.2.4 regarding boron concentration, as well as editorial changes. The proposed LAR temporarily revises the TS 3.5.2 to reduce the minimum allowable CMT A boron concentration and to not require performance of SR 3.5.2.4 until startup from the first Vogtle, Unit 4, refueling outage (RFO), which is scheduled for the fall of 2025. The proposed LAR is a one-time temporary change, and the proposed LAR would be effective until startup from the first Vogtle, Unit 4, RFO.
The proposed LAR was submitted under emergency circumstances as described in the provisions of paragraph 50.91(a)(5) of Title 10 of the Code of Federal Regulations due to the time critical nature of the LAR.
2.0 REGULATORY EVALUATION
2.1 System Design and Operation As described in its submittal dated August 11, 2025, the licensee states, in part, that:
The two redundant CMTs provide sufficient borated water to assure Reactor Coolant System (RCS) reactivity and inventory control for all design basis accidents (DBAs),
including both loss of coolant accident (LOCA) events and non-LOCA events.
The CMT size and injection capability are selected to provide adequate RCS boration and safety injection for the limiting DBA. One CMT is adequate for this function during a small break LOCA where one CMT completely spills via the pipe break. The CMTs also provide reactor coolant system makeup and boration during events not involving loss of coolant when the normal makeup system is unavailable or insufficient. The boration capability of these tanks provides adequate core shutdown margin following a steam line break.
Key design features of the CMTs include:
Full-pressure design matching RCS pressure, Location above the RCS loop piping on the non-pressurizer side, Borated water inventory for emergency injection, and Stainless steel plating for corrosion resistance.
Functional Operation of the CMTs The CMT serves as the primary high-pressure safety injection source during various accident scenarios. Its operation relies entirely on natural forces (gravity, temperature differences, and compressed gas pressure) rather than active components like pumps.
The CMT system functions through:
Pressure Balance Line (PBL): Connects the CMT top to the RCS cold leg, maintaining equal pressure between the CMT and primary system, Direct Vessel Injection (DVI) Lines: Connect the CMT bottom to the reactor vessel for gravity-driven injection, and Isolation Valves: Normally closed valves that open automatically upon safety signals.
CMT Operational Modes During accident scenarios, the CMT operates in two distinct phases:
- 1.
Circulation Mode: Initial phase where coolant circulates between the CMT and RCS through the PBL and DVI lines, and
- 2.
Drain Mode: Subsequent phase where the CMT empties its contents into the reactor vessel.
The transition between these modes is determined by thermal-hydraulic conditions and break size during LOCAs.
CMT Safety Functions The CMT system provides multiple safety functions:
High-Pressure Safety Injection: Delivers borated water to the core during transients where normal makeup is inadequate, Automatic Depressurization System (ADS) Activation: CMT liquid level signals trigger ADS stages to enable lower-pressure injection sources, Small Break LOCA (SBLOCA) Mitigation: Provides the only coolant source during initial phases of SBLOCAs, and Boration Capability: Maintains proper reactor water chemistry during accident scenarios.
The CMT system is designed to maintain core cooling indefinitely following design basis events without operator action or alternating current power.
2.2 Regulations and Guidance In accordance with paragraph C.6. of Section VIII, Processes for Changes and Departures, of Appendix D to Part 52, Design Certification Rule for the AP1000 Design, changes to the plant specific TS will be treated as license amendments under 10 CFR 50.90. Pursuant to 10 CFR 50.90, whenever a COL holder desires to amend the license, application for an amendment must be filed with the Commission fully describing the changes desired, and following as far as applicable, the form prescribed for original applications. Per 10 CFR 52.79(a), an application for a COL must contain a final safety analysis report that describes the facility, presents the design bases and the limits on its operation, and presents a safety analysis of the structures, systems, and components of the facility as a whole.
Per 10 CFR 52.79(a)(30), the application for a COL shall include proposed TSs prepared in accordance with the requirements of 10 CFR 50.36. The regulations in 10 CFR 50.36(c)(2)(i) require that TS include LCOs that are the lowest functional capability or performance levels of equipment required for safe operation of the facility. Further, per 10 CFR 50.36(c)(2)(i), when an LCO is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the TS until the LCO can be met. Per 10 CFR 50.36(c)(3), TS will include SRs that are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the LCOs will be met. Per 10 CFR 52.97(c), a COL shall contain the terms and conditions, including TSs, as the Commission deems necessary and appropriate.
Under 10 CFR 50.92(a), determinations on whether to grant an applied-for license amendment are to be guided by the considerations that govern the issuance of initial licenses to the extent applicable and
appropriate. Both the common standards for licenses in 10 CFR 50.40(a) (regarding, among other things, consideration of the operating procedures, the facility and equipment, the use of the facility, and other TSs, or the proposals) and those specifically for issuance of combined licenses in 10 CFR 52.97(a)(1)(iii), provide that there must be reasonable assurance that the activities at issue will not endanger the health and safety of the public, and that the applicant will comply with the Commission's regulations.
The regulation in 10 CFR Part 50, Appendix A, General Design Criteria (GDC) 26, Reactivity control system redundancy and capability, states:
Two independent reactivity control systems of different design principles shall be provided. One of the systems shall use control rods, preferably including a positive means for inserting the rods, and shall be capable of reliably controlling reactivity changes to assure that under conditions of normal operation, including anticipated operational occurrences, and with appropriate margin for malfunctions such as stuck rods, specified acceptable fuel design limits are not exceeded. The second reactivity control system shall be capable of reliably controlling the rate of reactivity changes resulting from planned, normal power changes (including xenon burnout) to assure acceptable fuel design limits are not exceeded. One of the systems shall be capable of holding the reactor core subcritical under cold conditions.
The regulation in 10 CFR Part 50, Appendix A, GDC 27, Combined reactivity control systems capability, states:
The reactivity control systems shall be designed to have a combined capability, in conjunction with poison addition by the emergency core cooling system, of reliably controlling reactivity changes to assure that under postulated accident conditions and with appropriate margin for stuck rods the capability to cool the core is maintained.
The regulation in 10 CFR Part 50, Appendix A, GDC 35, Emergency core cooling, states:
A system to provide abundant emergency core cooling shall be provided. The system safety function shall be to transfer heat from the reactor core following any loss of reactor coolant at a rate such that (1) fuel and clad damage that could interfere with continued effective core cooling is prevented and (2) clad metal-water reaction is limited to negligible amounts.
The regulation in 10 CFR Part 50, Appendix A, GDC 37, Testing of emergency core cooling system, states:
The emergency core cooling system shall be designed to permit appropriate periodic pressure and functional testing to assure (1) the structural and leak tight integrity of its components, (2) the operability and performance of the active components of the system, and (3) the operability of the system as a whole and, under conditions as close to design as practical, the performance of the full operational sequence that brings the system into operation, including operation of applicable portions of the protection system, the transfer between normal and emergency power sources, and the operation of the associated cooling water system.
3.0 TECHNICAL EVALUATION
3.1 Current TS 3.5.2, LCO Current TS 3.5.2, LCO does not have a NOTE. It states:
LCO 3.5.2 Both CMTs shall be OPERABLE.
3.2 Proposed TS 3.5.2, LCO NOTE The proposed LCO would add a NOTE to LCO 3.5.2 that states:
LCO 3.5.2 Both CMTs shall be OPERABLE.
- NOTE -
For Unit 4 until entry into TS 3.5.3 Applicability during shutdown for 4R01, CMT A may be considered OPERABLE with boron concentration
< 3400 ppm provided:
a.
CMT A boron concentration is 3100 ppm and b.
Average of CMT A and CMT B boron concentration is 3400 ppm.
3.3 Current SR 3.5.2.4 The current SR 3.5.2.4 states the following:
SURVEILLANCE FREQUENCY SR 3.5.2.4 Verify the boron concentration in each CMT is 3400 ppm and 4500 ppm.
31 days 3.4 Proposed SR 3.5.2.4 The proposed SR 3.5.2.4 would state:
SURVEILLANCE FREQUENCY SR 3.5.2.4
- NOTE -
Not required to be performed for Unit 4 until entry into TS 3.5.3 Applicability during startup from 4R01.
Verify the boron concentration in each CMT is 3400 ppm and 4500 ppm.
31 days
3.5 Evaluation of Editorial Changes SNC is proposing the following editorial changes to the TSs:
Move Condition D of TS 3.5.2 from TS page 3.5.2-1 to page 3.5.2-2, because the added NOTE to LCO 3.5.2 was added to page 3.5.2-1 causing rollover of Condition D, Move Condition E of TS 3.5.2 from TS page 3.5.2-1 to page 3.5.2-2, because the added NOTE to LCO 3.5.2 was added to page 3.5.2-1 causing rollover of Condition E, Move SR 3.5.2.4 from TS page 3.5.2-2 to page 3.5.2-3, because the added NOTE to LCO 3.5.2 was added to page 3.5.2-1 causing rollover of SR 3.5.2.4, Move SR 3.5.2.5 from TS page 3.5.2-2 to page 3.5.2-3, because the added NOTE to LCO 3.5.2 was added to page 3.5.2-1 causing rollover of SR 3.5.2.5, Move SR 3.5.2.6 from TS page 3.5.2-2 to page 3.5.2-3, because the added NOTE to LCO 3.5.2 was added to page 3.5.2-1 causing rollover of SR 3.5.2.6, and Move SR 3.5.2.7 from TS page 3.5.2-2 to page 3.5.2-3, because the added NOTE to LCO 3.5.2 was added to page 3.5.2-1 causing rollover of SR 3.5.2.7.
The proposed editorial changes do not alter the intent, scope, or requirements in the TS, but do serve to improve its presentation and usability. Therefore, the NRC staff finds the proposed editorial changes acceptable.
3.6 Technical Evaluation of the Proposed Changes 3.6.1 NRC Staff Evaluation of Minimum Boron Concentration The current minimum boron concentration is 3400 ppm to meet the CMT safety analysis minimum reactivity control requirements. The maximum boron concentration allowed within each CMT at any time is 4500 ppm to prevent overboration.
Because the CMTs are in open communication with the RCS via the balance line, whenever the CMT is sampled for surveillance purposes, the volume of removed water is replaced by RCS water via the balance line. The RCS water is typically at a lower boron concentration; therefore, each sample dilutes the CMT. Depending on the starting boron concentration in the CMT, there is the possibility that the sampling activity could cause the CMT boron concentration to fall to a point which would require borated makeup. Borated makeup at power is not desirable because it forces the displaced water back into the RCS via the balance line. This causes additional thermal transients on the balance line and also causes the potential for a reactivity excursion in the reactor if the boron concentration of the RCS is affected.
CMT A The Vogtle, Unit 4, CMT A has been experiencing CMT in-leakage both from sampling activities and due to leak-by of the CMT discharge isolation valves (PXS-V014A and PXS-V015A).
Vogtle, Unit 4, is at the end of its first operating cycle with approximately one month remaining before entering the fall RFO.
Using a mass balance equation, infinite dilution equation, and the boron dilution effects of the RCS, SNC determined the leak rate from CMT A into the RCS, and the impact of that leak rate on the boron concentration of CMT A.
Utilizing the most recent boron concentration sample result of 3479 ppm taken on August 9, 2025, and the current calculated leakage rate of 46.9 gallons per day (gpd), SNC calculates the boron concentration in CMT A will remain greater than the proposed limit of 3100 ppm through the end of the current operating cycle.
SNC is going to continue performing RCS monitoring to confirm the concentration in CMT A remains above the proposed TS limit of 3100 ppm until entry into first RFO for Vogtle, Unit 4.
Based on the above, the NRC staff finds that there is reasonable assurance that the CMT A boron concentration will remain above the proposed TS limit of 3100 ppm and the average of the CMT A and CMT B boron concentration will remain 3400 ppm; therefore, the NRC staff finds the proposed NOTE to LCO 3.5.2 is acceptable.
CMT B CMT B sampling will be required to be performed prior to the upcoming Vogtle, Unit 4, RFO and will result in a lowering its boron concentration as discussed above.
The SNC letter dated August 11, 2025, states:
CMT B does not show indications of RCS in-leakage via outlet valve leak-by. The boron concentration of the last sample on July 25, 2025, was 4052 ppm. Currently, the only dilution mechanisms in CMT B are via taking samples and diffusion due to the concentration gradient between the CMT and the RCS. To support an average of 3400 ppm, assuming CMT A is at the proposed minimum limit of 3100 ppm, CMT B must remain greater than 3700 ppm. If CMT B started to leak it would also cause an increase in boron in the RCS and would be detected in the RCS samples being taken to monitor CMT A leakage. Therefore, there is reasonable assurance that CMT B will remain greater than 3700 ppm until the LCO 3.5.2 applicability is exited in 4R01 [first RFO for Vogtle, Unit 4] and this value is bounding.
SNC performed analysis, based on available plant data, shows that (1) the known leakage from CMT A bounds leakage from CMT B with a boron concentration of greater than 3700 ppm, (2)
CMT B does not show indications of RCS in-leakage via outlet valve leak-by, (3) at present, the only dilution mechanisms in CMT B are via taking samples and diffusion due to the concentration gradient between the CMT and the RCS, and (4) historical trends show the maximum dilution to be less than 200 ppm.
To support an average of 3400 ppm, assuming CMT A is at the proposed minimum limit of 3100 ppm, CMT B must remain greater than 3700 ppm. If CMT B started to leak, it would also cause an increase in boron in the RCS and would be detected in the RCS samples being taken to monitor CMT A leakage. Based on the above, NRC staff concludes that there is reasonable assurance that CMT B will remain greater than 3700 ppm until the LCO 3.5.2 applicability is exited in the first RFO
for Vogtle, Unit 4, and this value is, therefore, bounding. Therefore, the NRC staff finds the NOTE to SR 3.5.2.4 acceptable.
3.6.2 NRC Staff Evaluation of Design Basis Accidents at Minimum Boron Concentration The CMT stores borated water and serves as a passive makeup source to the RCS during accident scenarios. It supports core cooling and boron concentration management by providing makeup water to the RCS when natural circulation and passive cooling trains provide cooling/heating paths (e.g., during station blackout (SBO) or SBLOCA-like events), helping to maintain subcriticality and core cooling without active pumps. In AP1000, CMT makeup is part of the passive safety system design, complementing the passive core cooling system, Passive Residual Heat Removal, and other passive makeup paths.
The key accident categories where CMT is credited include:
SBLOCA scenarios with delayed or failed active makeup: CMT provides additional RCS inventory and borated water to help keep RCS level, control boron concentration, and support continued cooldown, SBO or events where active equipment is unavailable: CMT can contribute to maintaining core cooling via natural circulation paths and passive makeup to the RCS, and Non-LOCA events where maintaining RCS inventory and boron concentration is important for subcriticality and cooling, and where the CMT might be a contributor to makeup requirements in the analysis.
CMT A and CMT B are assumed to be operable to provide emergency boration and core makeup when the chemical and volume control is unavailable or insufficient, and to mitigate the consequences of any DBA which requires the safety injection of borated water.
In its letter dated August 11, 2025, the licensee stated:
The non-DBA ATWS [Anticipated Transient Without a SCRAM] scenario discussed in UFSAR [Updated Final Safety Analysis Report] Section 15.8 associated with demonstrating compliance to 10 CFR 50.62 (ATWS Rule) and the non-DBA SSD/SST
[Safe Shutdown Duration/ Safe Shutdown Temperature] analyses are performed with better estimate conditions, including the assumption that both CMTs inject at a boron concentration of 3500 ppm. The minimum average boron concentration of 3400 ppm allowed by this change is offset by conservatisms in these evaluations, namely:
For both ATWS and SSD/SST, maintaining the Unit 4 CMT A and B average boron concentration at or above 3400 ppm is sufficient to bound the impacts of a CMT A boron concentration as low as 3100 ppm. This will ensure that the nominal boron concentration assumption remains valid for these analyses.
For the ATWS analysis, the end-of-life/cycle (EOL) moderator temperature coefficient (MTC) is more negative than the beginning of cycle and the ability of the EOL MTC to mitigate an ATWS event is increased significantly. Use of the EOL MTC would also more than offset the 100 ppm difference in CMT boron concentration for the ATWS events.
For the SSD/SST analysis, the steam generator trip masses modeled in the evaluation, which are based on the UFSAR Chapter 15 LONF [loss of normal feedwater] safety analysis, are conservatively low.
For the SSD/SST analysis, additional conservatisms associated with RCS and PRHR HX [passive residual heat removal heat exchanger] heat transfer that would significantly impact the analyses are provided in NF-GP-25-082 and are considered Westinghouse Proprietary Class 2.
CMT boration is not credited in the Steam Generator Tube Rupture (SGTR) event as the control and shutdown rods are assumed to trip and provide adequate shutdown margin.
With the proposed NOTE to LCO 3.5.2, there is no adverse impact on the LONF event, and there is no adverse impact on shutdown margin for SBLOCA.
With the proposed NOTE to LCO 3.5.2, there is greater than 800 ppm shutdown margin for the Double Ended Direct Vessel Injection (DEDVI) accident. The DEDVI is the limiting Large-Break Loss-of-Coolant Accident (LBLOCA).
The NRC finds the margins in the ATWS, SGTR, LONF, SBLOCA, LBLOCA, and DEDVI analyses are sufficient to bound the impacts of a CMT A boron concentration as low as 3100 ppm provided the boron concentration from CMT A and CMT B combined are on average 3400 ppm.
Based on the above, the NRC staff finds the NOTE to LCO 3.5.2 acceptable.
3.6.3 NRC Staff Evaluation of Compensatory Measures In its letter dated August 11, 2025, the licensee stated:
During the period(s) of operation with the proposed TS effective, an Adverse Condition Monitoring Plan (ACMP) will be implemented as a defense-in-depth effort. The ACMP will be built around the daily RCS boron samples with the following features:
Utilize changes in boron concentration with the Operability Determination Support Basis (ODSB) methodology for calculating CMT leak-by and projected boron concentration.
Periodically recalculate the projected time at which the CMT A boron concentration will fall below the requested 3100 ppm minimum limit or the current 3400 ppm minimum limit.
Apply trigger points based on rising CMT leakage and projected times for going below 3100 ppm boron or 3400 ppm boron, including actions to:
o Re-evaluate station plans, including potentially de-rating the Unit to support a CMT boration.
o Evaluate the need and timing of confirmatory CMT samples.
The above compensatory measures provide reasonable assurance that CMT A will remain operable while the requested LAR is in effect and being implemented.
The NRC staff finds that the compensatory measures provide defense-in-depth.
3.6.4 NRC Staff Evaluation of Proposed NOTE for LCO 3.5.2 The NRC staff has determined that Vogtle, Unit 4, may operate until it begins its first RFO as described in this safety evaluation (SE). The proposed NOTE allows CMT A to maintain a boron concentration less than the current TS limit, but 3100 ppm. The compensatory actions proposed by the licensee provide reasonable assurance that the average CMT boron concentration for Vogtle, Unit 4, will be maintained greater than the TS required CMT boron concentration of 3400 ppm. The NRC staff determined that there is reasonable assurance that the assumptions in the analyses will be met both by ongoing evaluations performed by SNC and by the licensees monitoring and trending that assure that the CMT boron levels will be within the assumed temporary ranges and revised TS.
SNC proposed to add a NOTE to LCO 3.5.2 that would allow the CMT A boron concentration to temporarily go below the TS established limit of 3400 ppm as long as the average of CMT A and B boron concentrations remain 3400 ppm. The compensatory measures proposed to be taken during the period provide reasonable assurance that the design basis and beyond design bases analyses affected by CMT boron concentration remain valid for the plant specific conditions during the proposed LAR implementation period. Therefore, 10 CFR 50.36(c)(2) will be met because, during the temporary period, LCO 3.5.2 continues to assure that the CMTs lowest functional capability to assure safe operation of the facility is maintained. The TS requirements to exit the applicability of the LCO by shutting down the reactor if the proposed requirements are not met remain in place and are acceptable because they are not changed and maintain adequate safety.
3.6.5 NRC Staff Evaluation of Proposed NOTE for SR 3.5.2.4 SNC also proposed to add a NOTE to SR 3.5.2.4 that allows its performance for Vogtle, Unit 4, to be suspended until startup from the pending RFO. This change affects only CMT B because the CMT A SR is not due until the after Vogtle, Unit 4, is scheduled for shutdown for refueling in fall 2025. Even with this change, the licensee continues to meet 10 CFR 50.36(c)(3) because the NRC staff determined that the temporary suspension of the SR will not adversely affect the verification that the necessary boron concentration of the CMTs is maintained such that the LCO will continue to be met. The licensee proposed compensatory measures provide additional assurance that the LCO will be met during the applicable period LAR implementation period.
Based on the above, the NRC staff determined that the requirements of 10 CFR 50.36 will continue to be met for the duration that the proposed temporary TS changes are in effect. The permanent TS requirements will be restored when Vogtle, Unit 4 returns to power following refueling outage R401.
3.6.6 Technical Conclusion The NRC staff finds the proposed editorial changes to the TSs acceptable, because the proposed editorial changes do not alter the intent, scope, or requirements in the TS, but the editorial changes do serve to improve its presentation and usability.
The NRC staff concludes the changes to LCO 3.5.2 and SR 3.5.2.4 are acceptable and would continue to meet the requirements of 10 CFR 50.36. The NRC staff also concludes that the added NOTE to LCO 3.5.2 and SR 3.5.2.4 would continue to meet GDCs 26, 27, 25, and 37. Based on the above, the NRC staff finds the changes to TS LCO 3.5.2 and SR 3.5.2.4 are acceptable.
4.0 EMERGENCY CIRCUMSTANCE Regulation 10 CFR 50.91(a)(5) states the following:
Where the Commission finds that an emergency situation exists, in that failure to act in a timely way would result in derating or shutdown of a nuclear power plant, or in prevention of either resumption of operation or of increase in power output up to the plant's licensed power level, it may issue a license amendment involving no significant hazards consideration without prior notice and opportunity for a hearing or for public comment. In such a situation, the Commission will not publish a notice of proposed determination on no significant hazards consideration, but will publish a notice of issuance under § 2.106 of this chapter, providing for opportunity for a hearing and for public comment after issuance. The Commission expects its licensees to apply for license amendments in timely fashion. It will decline to dispense with notice and comment on the determination of no significant hazards consideration if it determines that the licensee has abused the emergency provision by failing to make timely application for the amendment and thus itself creating the emergency. Whenever an emergency situation exists, a licensee requesting an amendment must explain why this emergency situation occurred and why it could not avoid this situation, and the Commission will assess the licensee's reasons for failing to file an application sufficiently in advance of that event.
The NRCs regulations in 10 CFR 50.91(a)(5) state where the NRC finds that an emergency situation exists, in that failure to act in a timely way would result in derating or shutdown of a nuclear power plant, or in prevention of either resumption of operation or of increase in power output up to the plants licensed power level, the NRC may issue a license amendment involving no significant hazards consideration without prior notice and opportunity for a hearing or for public comment. In such a situation, the NRC will publish a notice of issuance under 10 CFR 2.106, providing for opportunity for a hearing and for public comment after issuance.
As discussed in Section 2.5 of SNCs submittal dated August 11, 2025, as well as the SNC letter dated August 12, 2025, SNC requested that the proposed LAR be reviewed by the NRC on an emergency basis, because of the following:
SNC said that it used its best effort to make a timely application, as the need for the LAR only became apparent when CMT A boron concentration was projected to fall below the TS limit on August 17, 2025.
SNC said that the repair of the outlet valves which would adjudicate the issue could only be performed during an outage.
SNC said that repair of the valves was not previously completed during a planned maintenance.
outage, because the valves had been planned for repair during the RFO, and SNC had a strategy based on plant conditions at that point in time for maintaining CMT A boron levels in TS limits. In addition, SNC stated that the site did not have all the parts needed to be able to repair both of the valves at the time of the maintenance outage.
SNC said that conditions have emerged despite reasonable planning and reliance on prior Vogtle, Unit 3, operating experience.
SNC stated that it could not have reasonably avoided the situation, since the valve repairs require outage conditions and the minimum boron concentration in CMT A would be breached without an LAR, and increasing the boron concentration in the CMT A would provide an unnecessary complication in SNCs shutdown plan given end-of-cycle core characteristics.
SNC stated that it could not reasonably foresee challenges to maintaining TS limits and steady-state operation over the final few weeks of the Unit 4 cycle. SNC provided boron concentration readings.
SNCs letter dated August 12, 2025, states:
Adding sufficient boric acid to maintain CMT A boron concentration above the minimum Technical Specification (TS) limit of 3400 ppm is not possible due to the characteristics of an end-of-life core combined with the observed valve leakage. The negative reactivity that results from adding boric acid is unable to be counteracted by diluting the Reactor Coolant System (RCS) due to the low boron concentration without performing a significant derate [emphasis added].
NRC Staff Conclusion regarding Emergency Circumstance The NRC staff reviewed the licensees basis for processing the proposed LAR as an emergency amendment, as discussed above, and has determined that an emergency situation will exist consistent with the provisions in 10 CFR 50.91(a)(5). Furthermore, the NRC staff determined that: (1) the licensee used its reasonable efforts to make a timely application; (2) the licensee could not reasonably have avoided the situation; and (3) the licensee has not abused the provisions of 10 CFR 50.91(a)(5). Based on these findings, and the determination that the LAR involves no significant hazards consideration as discussed below, the NRC staff has determined that a valid need exists for issuance of the LAR using the emergency provisions of 10 CFR 50.91(a)(5).
5.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The NRCs regulation in 10 CFR 50.92(c) states that the NRC may make a final determination, under the procedures in 10 CFR 50.91, that a license amendment involves no significant hazards consideration if operation of the facility, in accordance with the amendment, would not: (1) involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.
The licensees evaluation of the issue of no significant hazards consideration is presented below:
- 1)
Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?
Response: No.
The proposed changes do not adversely affect the operation of any structures, systems, or components (SSCs) associated with an accident initiator or initiating sequence of events. The proposed changes do not affect the design of the passive core cooling system.
The proposed amendment does not affect accident initiators or precursors nor adversely alter the design assumptions, conditions, or configuration of the facility. The proposed amendment does not alter any plant equipment or operating practices with respect to such initiators or precursors in a manner that the probability of an accident is increased.
The proposed amendment to temporarily reduce the minimum allowable Unit 4 CMT A boron concentration and to not require Unit 4 core makeup tank (CMT) boron concentration to be verified again until startup from the first Unit 4 refueling outage does not adversely affect the operation of the assumed mitigation systems or the containment fission product barrier assumptions. As demonstrated in the SNC request, the temporary reduction in minimum allowable Unit 4 CMT A boron concentration is more than offset by existing margins in the safety analyses. As such, the proposed change will not alter assumptions relative to the mitigation of an accident or transient event. The proposed amendment does not increase the likelihood of the malfunction of an SSC or adversely impact analyzed accidents.
Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
- 2)
Does the proposed change create the possibility of a new or different accident from any accident previously evaluated?
Response: No.
The proposed changes do not change the design function of the CMTs. These proposed changes do not introduce any new equipment or components that would result in a new failure mode, malfunction or sequence of events that could adversely affect safety-related or nonsafety-related equipment. This activity will not allow for a new fission product release path, result in a new fission product barrier failure mode, or create a new sequence of events that would result in significant fuel cladding failures.
Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
- 3)
Does the proposed change involve a significant reduction in a margin of safety?
Response: No.
The margin of safety is related to the ability of the CMTs to provide adequate shutdown margin throughout the duration of the temporary change. Evaluation of the impact of
allowing the Unit 4 CMT A boron concentration to be less than the required limit on the capability of the passive core cooling system to perform its design function has confirmed that margins in these analyses are sufficient to bound the impacts of a CMT A boron concentration as low as the proposed lower limit provided the average boron concentration from both CMTs is greater than the proposed combined average limit. The change to the frequency of boron concentration surveillance doesnt change the validation of the CMTs to support safety analysis initial conditions. No safety analysis or design basis acceptance limit/criterion is challenged or exceeded by the requested change, thus no margin of safety is reduced.
Therefore, the proposed change does not involve a significant reduction in a margin of safety.
For the reasons noted above, there is no significant reduction in a margin of safety. Based on the above evaluation, the NRC staff concludes that the three standards of 10 CFR 50.92(c) are satisfied.
Therefore, the NRC staff has made a final determination that no significant hazards consideration is involved for the proposed amendment and that the amendment should be issued as allowed by the criteria contained in 10 CFR 50.91.
6.0 STATE CONSULTATION
In accordance with the Commissions regulations, the Georgia State official was notified of the proposed issuance of the amendments on August 12, 2025. On August 12, 2025, the State of Georgia official had no comments.
7.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements.
The NRC staff has determined that the amendment involves no significant increase in the amounts and no significant change in the types of any effluents that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
8.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) there is reasonable assurance that such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors: S. Smith, NRR F. Forsaty, NRR J. Lamb, NRR Date: August 15, 2025.
ML25225A229 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DSS/SCPB/BC NRR/DSS/STSB/BC NAME JLamb KZelenock (ABaxter for)
MValentin SMehta DATE 08/13/2025 08/14/2025 08/14/2025 08/14/2025 OFFICE NRR/DSS/SNSB/BC NRR/DORL/LPL2-1/BC NRR/DORL/LPL2-1/PM NAME NDifrancesco (ASallman for)
MMarkley JLamb DATE 08/14/2025 08/15/2025 08/15/2025