ML26009A033

Issuance of Amendment No. 310 for One-Time Change to Technical Specification 3.8.1 Action A.3

ML26009A033
Person / Time
Site:	Davis Besse
Issue date:	01/16/2026
From:	Robert Kuntz NRC/NRR/DORL/LPL3
To:	Craven R FirstEnergy Nuclear Operating Co, Vistra Operations Company
Kuntz R, NRR/DORL/LPL3
References
EPID L-2025-LLA-0159
Download: ML26009A033 (0)

Text

January 16, 2026 Mr. Rob Craven Vistra Operations Company LLC c/o Davis-Besse Nuclear Power Station Mail Stop P-DB-3080 5501 N. State Route 2 Oak Harbor, OH 43449-9760

SUBJECT:

DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 - ISSUANCE OF AMENDMENT NO. 310 ADDING A ONE-TIME CHANGE TO TECHNICAL SPECIFICATION 3.8.1 ACTION A.3 (EPID L-2025-LLA-0159)

Dear Mr. Craven:

In response to your application dated October 22, 2025 (Agencywide Documents Access and Management System Accession No. ML25295A487), as supplemented by letter dated December 22, 2025 (ML25356A382), the U.S. Nuclear Regulatory Commission (NRC) has issued the enclosed Amendment No. 310 to Renewed Facility Operating License (RFOL)

No. NPF-3 for the Davis-Besse Nuclear Power Station, Unit No. 1. The amendment adds a one-time extension to the completion time for Technical Specification (TS) 3.8.1, AC [Alternating Current] Sources-Operating, Action A.3. The changes are to allow for completion of maintenance prior to entering the spring 2026 refueling outage.

A copy of the related safety evaluation is also enclosed. A Notice of Issuance addressing the final no significant hazards consideration determination and opportunity for a hearing will be included in the Commissions monthly Federal Register notice.

If you have questions, please contact me at 301-415-3733 or robert.kuntz@nrc.gov.

Sincerely,

/RA/

Robert Kuntz, Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No.: 50-346

Enclosures:

1. Amendment No. 310 to NPF-3

2. Safety Evaluation cc: Listserv

VISTRA OPERATIONS COMPANY LLC AND ENERGY HARBOR NUCLEAR GENERATION LLC DOCKET NO. 50-346 DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 310 License No. NPF-3

1.

The Nuclear Regulatory Commission (the Commission) has found that:

A.

The application for amendment filed by Vistra Operations Company, LLC (the licensee), dated October 22, 2025, as supplemented by letter dated December 22, 2025, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B.

The facility 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 to 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 amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 2.C.(2) of Renewed Facility Operating License No. NPF-3 is hereby amended to read as follows:

(2)

Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 310, are hereby incorporated in the renewed license. Vistra Operations Company LLC shall operate the facility in accordance with the Technical Specifications

3.

This license amendment is effective as of the date of its issuance and shall be implemented within 30 days.

FOR THE NUCLEAR REGULATORY COMMISSION:

Ilka Berrios, Acting Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Renewed Facility License and Technical Specifications Date of Issuance: January 16, 2026 SCOTT WALL Digitally signed by SCOTT WALL Date: 2026.01.16 12:17:03 -05'00'

ATTACHMENT TO LICENSE AMENDMENT NO. 310 TO RENEWED FACILITY OPERATING LICENSE NO. NPF-3 DOCKET NO. 50-346 Replace the following page of Renewed Facility Operating License No. NPF-3 with the attached revised page. The revised page is identified by amendment number and contains marginal lines indicating the area of change.

REMOVE INSERT L-5 L-5 Replace the following page of Appendix A, Technical Specifications, to Renewed Facility Operating License No. NPF-3 with the attached revised page. The revised page is identified by amendment number and contains marginal lines indicating the areas of change.

Appendix A to Renewed Facility Operating License No. NPF-3 REMOVE INSERT 3.8.1-2 3.8.1-2

L-5 Renewed License No. NPF-3 Amendment No. 310 2.C.

This renewed license shall be deemed to contain and is subject to the conditions specified in the following Commission regulations in 10 CFR Chapter I: Part 20, Section 30.34 of Part 30, Section 40.41 of Part 40, Sections 50.54 and 50.59 of Part 50, and Section 70.32 of Part 70; and is subject to all applicable provisions of the Act and to the rules, regulations, and orders of the Commission now or hereafter in effect; and is subject to the additional conditions specified or incorporated below:

(1)

Maximum Power Level Vistra Operations Company LLC is authorized to operate the facility at steady state reactor core power levels not in excess of 2817 megawatts (thermal). Prior to attaining the power level, Toledo Edison Company shall comply with the conditions identified in Paragraph (3) (o) below and complete the preoperational tests, startup tests and other items identified in Attachment 2 to this license in the sequence specified. Attachment 2 is an integral part of this renewed license.

(2)

Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 310, are hereby incorporated in the renewed license.

Vistra Operations Company LLC shall operate the facility in accordance with the Technical Specifications.

(3)

Additional Conditions The matters specified in the following conditions shall be completed to the satisfaction of the Commission within the stated time periods following the issuance of the renewed license or within the operational restrictions indicated. The removal of these conditions shall be made by an amendment to the renewed license supported by a favorable evaluation by the Commission:

(a) Vistra Operations Company LLC shall not operate the reactor in operational modes 1 and 2 with less than three reactor coolant pumps in operation.

(b) Deleted per Amendment 6 (c) Deleted per Amendment 5

AC Sources - Operating 3.8.1 Davis-Besse 3.8.1-2 Amendment 310 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME A. (continued)

A.3 Restore offsite circuit to OPERABLE status.

72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />s*

B. One EDG inoperable.

B.1 Perform SR 3.8.1.1 for OPERABLE offsite circuit(s).

AND B.2 Declare required feature(s) supported by the inoperable EDG inoperable when its redundant required feature(s) is inoperable.

AND B.3.1 Determine OPERABLE EDG is not inoperable due to common cause failure.

OR B.3.2 Perform SR 3.8.1.2 for OPERABLE EDG.

AND B.4 Restore EDG to OPERABLE status.

1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> AND Once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> from discovery of Condition B concurrent with inoperability of redundant required feature(s) 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 24 hours 7 days A one-time Completion Time (CT) extension for an inoperable offsite circuit allows 15 days to restore the inoperable Startup Transformer X02 to OPERABLE status. Compensatory measures within Vistra Operations Company LLC letter L-25-227 dated 12/22/2025 shall be implemented and shall remain in effect during the extended CT period. The one-time extension shall expire upon completion of the maintenance to restore Startup Transformer X02 to OPERABLE status or by 0600 on March 6, 2026, whichever occurs earliest.

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 310 TO RENEWED FACILITY OPERATING LICENSE NO. NPF-3 VISTRA OPERATIONS COMPANY LLC AND ENERGY HARBOR NUCLEAR GENERATION LLC DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 DOCKET NO. 50-346

1.0 INTRODUCTION

By letter dated October 22, 2025 (Agencywide Documents Access and Management System Accession No. ML25295A487), as supplemented by letter dated December 22, 2025 (ML25356A382), Vistra Operations Company LLC (the licensee) requested that the U.S.

Nuclear Regulatory Commission (NRC, the Commission) amend Davis-Besse Nuclear Power Station (Davis-Besse), Unit No. 1, Renewed Facility Operating License (FOL) No. NPF-3. The license amendment request (LAR) would add a one-time extension to the completion time for technical specification (TS) 3.8.1, [Alternating Current] AC Sources-Operating, required action A.3. The changes are to allow for completion of maintenance prior to entering the spring 2026 refueling outage.

The supplement dated December 22, 2025, provided additional information that clarified the application, did not expand the scope of the application as originally noticed, and did not change the NRC staffs original proposed no significant hazards consideration determination as published in the Federal Register on November 24, 2025 (90 FR 53003).

1.1 Background

During normal power operations in Mode 1, the plant electrical loads are powered from the main generator through the auxiliary transformer (X11) while the startup transformers (X01 and X02) are energized but unloaded. For refueling outages Davis-Besse has three offsite sources available that include the startup transformer X01, startup transformer X02 and main transformer X1 through a backfeed configuration.

1.2 Proposed Change The proposed change would extend the completion time (CT) to restore an inoperable offsite circuit for Davis-Besse TS 3.8.1 AC Sources - Operating, Action A.3 from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 15 days, only applicable during Cycle 24. This change is structured for a single (one-time) use to conduct repairs on startup transformer X02 tap changer immediately prior to commencement of the 2026 spring refueling outage.

2.0 REGULATORY EVALUATION

The NRC staff considered the LAR against the following regulatory requirements and design basis.

2.1 Requirements Under Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Section 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 technical specifications, or the proposals) and those specifically for issuance of operating licenses in 10 CFR 50.57(a)(3), 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 Commissions regulations.

The regulation at 10 CFR 50.36, Technical specifications, requires, in part, that the operating license of a nuclear production facility include TS. Paragraph 50.36(c)(2)(i) of 10 CFR requires that the TS include limiting conditions for operation (LCOs), which are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When an LCO of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the TSs until the condition can be met. The remedial actions specified in the TS must provide the requisite reasonable assurance of public health and safety described in 10 CFR 50.40 and 50.57. As part of the LAR, the licensee proposed additional remedial actions as part of its proposed extension to the restoration time.

Appendix A General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50, General Design Criterion (GDC) 17, Electric power systems, requires, in part, that an onsite electric power system and an offsite electric power system shall be provided to permit the functioning of structures, systems, and components important to safety. The safety function for each system (assuming the other system is not functioning) shall be to provide sufficient capacity and capability to assure that (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as a result of anticipated operational occurrences and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents.

The regulation at 10 CFR 50.63, Loss of all alternating current power, requires, in part, that a nuclear power plant shall be able to withstand for a specified duration and recover from a complete loss of offsite and onsite AC sources (i.e., a station blackout (SBO)).

The regulation at 10 CFR 50.65, Requirements for monitoring the effectiveness of maintenance at nuclear power plants, requires, in part, that the licensee shall monitor the performance or

Appendix A General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50, GDC 17, Electric power systems, requires, in part, that an onsite electric power system and an offsite electric power system shall be provided to permit the functioning of structures, systems, and components important to safety. The safety function for each system (assuming the other system is not functioning) shall be to provide sufficient capacity and capability to assure that (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as a result of anticipated operational occurrences and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents.

2.2 Guidance The NRC staff applied the following regulatory guidance to the evaluation of the LAR:

Regulatory Guide (RG) 1.93, Availability of Electric Power Sources, (ML090550661) provides guidance with respect to operating restrictions or completion time if the number of available AC sources is less than that required by the TS LCO. This guide recommends a maximum completion time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for an inoperable onsite or offsite AC source.

RG 1.155, Station Blackout, (ML003740034) provides guidance for complying with the requirement in 10 CFR 50.63 that nuclear power plants be capable of coping with an SBO event for a specified duration.

RG 1.177, Plant-Specific, Risk-Informed Decision-making: Technical Specifications, January 2021, Revision 2 (ML20164A034), describes an acceptable risk-informed approach for assessing proposed changes to TS Allowable Outage Times (AOTs), also known as Completion Times (CTs).

RG 1.200, Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities, December 2020, Revision 3 (ML20238B871), describes one acceptable approach for determining whether the technical adequacy of the probabilistic risk assessment (PRA), in total or the parts that are used to support an application, is sufficient to provide confidence in the results such that the PRA can be used in regulatory decisionmaking for light-water reactors.

NUREG-0800 Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR [Light Water Reactor] Edition, Branch Technical Position (BTP) 8-8 Onsite (Emergency Diesel Generators) and Offsite Power Sources Allowed Outage Time Extensions (ML113640138), provides guidance to the NRC staff in reviewing LARs for licensees proposing a one-time or permanent TS change to extend an offsite power source outage time beyond 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

2.3 Description of Offsite Power System The Davis-Besse Updated Final Safety Analysis Report (UFSAR) (ML24269A054)

Section 1.2.5.1 states that:

Two startup transformers supply offsite power to station auxiliaries during startup, shutdown, and loss of normal power source. The station distribution system

consists of essential (safety related) and nonessential (station auxiliaries) supplied by: 13.8kV buses, 4.16kV buses, 480V unit substations, 480 VAC motor control centers, DC motor control centers, DC to AC power supply systems and regulated AC power supply systems. The station distribution system is described in [UFSAR] Section 8.3.1 and depicted in electrical one line diagrams as listed in

[UFSAR] Section 1.5.3.1. On-site standby power is provided by two redundant emergency diesel generators [EDGs] each connected to its respective 4.16kV essential bus and one non-class 1E diesel generator which can be aligned to power either 4.16kV essential bus in the event of a station blackout.

UFSAR Section 8.2.1 states that three 345 kV overhead lines connect the switchyard to the onsite distribution system, one line to each of the two startup transformers (X01 and X02) and a third line to the main transformer (X1). UFSAR Figure 8.2-2 provides the 345 kV switchyard one-line diagram, depicting the 345 kV connections to the Bayshore Substation, Lemoyne Substation, Beaver Substation and Hayes Substation.

LAR section 2.1 states that:

An offsite to onsite circuit consists of one 345 - 13.8 kV startup transformer, one 13.8 kV bus, one 13.8 - 4.16 kV tie transformer, and the respective circuit paths, including the nonessential bus and feeder breakers, to one 4.16 kV essential bus.

3.0 TECHNICAL EVALUATION

The NRC staff evaluates AOT extension requests from licensees for offsite power sources to allow online maintenance of offsite power source(s) such as a transformer or bus. (Note: The staff uses the terms AOT and CT interchangeably to denote the time allowed in TS to restore a system, structure, or component.) The NRC staff reviewed the proposed LAR, as supplemented, from a deterministic, as well as a probabilistic risk assessment (PRA) perspective. Section 3.1 of this safety evaluation (SE) provides the staffs deterministic evaluation of the proposed changes. Specifically, the NRC staff evaluated defense-in-depth aspects for electric power sources in accordance with the guidance provided in BTP 8-8.

Section 3.2 of this SE contains the staffs evaluation of the licensees risk insights.

3.1 Deterministic Evaluation Regulation in 10 CFR 50.63 requires that each light water-cooled nuclear power plant be able to withstand and recover from a loss of all AC power, referred to as an SBO. Davis-Besses SBO coping duration is 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> per UFSAR Section 15.2.9.2.4. Davis-Besse has a non-safety SBO diesel generator (SBODG), which is credited as an alternate AC source (AAC), connecting to 4.16 kV Bus D2. UFSAR section 8.3.1.1.4.2 states that the SBODG has a continuous rating of 2865 kW. UFSAR section 8.3.1.1.4 states that each EDG has a continuous rating of 2600 kW and thus, the SBODG has a greater capacity than the EDGs. UFSAR Section 8.3.1.1.4.2 states that the SBODG has a continuous rating of 2865 kW and meets the criteria specified in Appendix B to NUMARC 87-00, Guidelines and Technical Bases for NUMARC Initiative Addressing Station Blackout at Light Water Reactors and in Regulatory Guide 1.155, Station Blackout. As such, the SBODG will continue to adequately supply the necessary equipment to mitigate an SBO event. The NRC finds that Davis-Besse will continue to meet the requirements of 10 CFR 50.63 and RG 1.155 under the proposed 15-day CT.

3.1.1 Conformance to BTP 8-8 Supplemental Power Source Capacity BTP 8-8 provides guidance from a deterministic perspective, including defense-in-depth aspects, for one-time or permanent CT extensions for the EDGs and offsite power sources from the current AOT up to 14 days. BTP 8-8, in section B, states that:

A supplemental power source should be available as a backup to the inoperable EDG or offsite power source, to maintain the defense-in-depth design philosophy of the electrical system to meet its intended safety function. The supplemental source must have capacity to bring a unit to safe shutdown (cold shutdown) in case of a loss of offsite power (LOOP) concurrent with a single failure during plant operation (Mode 1)..

The permanent or temporary power source can be either a diesel generator, gas or combustion turbine, or power from nearby hydro units.

In the letter dated December 22, 2025, the licensee stated that that the SBODG is credited as a supplemental power source in accordance with BTP 8-8. UFSAR section 8.3.1.1.4.2 states that the SBODG has a continuous rating of 2865 kW and meets the criteria specified in Appendix B to NUMARC 87-00, Guidelines and Technical Bases for NUMARC Initiative Addressing Station Blackout at Light Water Reactors and in Regulatory Guide 1.155, Station Blackout.

Time to Make AAC Source Available BTP 8-8 further states that for plants using the AAC, the time to make the AAC available, including accomplishing the cross-connection, should be approximately one hour. UFSAR section 15.2.9.2.4 states that the SBODG is available within 10 minutes of the onset of an SBO event and has a capacity greater than the EDGs. Therefore, the SBODG availability conforms to BTP 8-8 since the SBODG is available within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

Verification of Availability of AAC Source BTP 8-8 states that the availability of the AAC should be verified within the last 30 days before entering extended AOT by operating or bringing the power source to its rated voltage and frequency for 5 minutes and ensuring all its auxiliary support systems are available or operational. The licensee stated in the letter dated December 22, 2025, that the SBODG monthly test is performed every 30 days. The licensee further stated that this monthly test verifies the proper frequency and voltage, verifies the support systems are operating properly, parallels the SBODG to the grid, maintains the SBODG peak load for at least 5 minutes, and runs the SBODG for at least 60 minutes. In addition, the licensee included a compensatory measure that the SBODG will be demonstrated functional by verifying its periodic test is current prior to start of the extended 15-day CT. Thus, the staff finds that since the SBODG is verified to be available within 30 days of entering the proposed 15-day CT, the SBODG conforms to the availability criteria in BTP 8-8.

BTP 8-8 states that the plant should have formal engineering calculations for equipment sizing and protection and have approved procedures for connecting the AAC or supplemental power sources to safety buses. In the letter dated December 22, 2025, the licensee stated that Davis-Besse has abnormal and emergency procedures which direct restoring power to essential

power buses via the SBODG and included the relevant portion of the procedure to restore power to Bus C1 or D1 from the SBODG in Attachment 4. The licensee further stated that the SBODG capacity satisfies the NUMARC 87-00 capacity attribute and has approximately the same capacity as one of the existing EDGs. UFSAR section 8.3.1.1.4.2 discusses the protection, including the circuit breakers connecting the SBODG to 4.16 kV nonessential bus D2. Therefore, since the SBODG has been sized to provide power to the necessary loads, is electrically isolated, and has protective features and procedures to start and load the SBODG, the staff finds the licensee conforms to BTP 8-8 with regard to calculations for equipment sizing and protection and procedures for connecting the SBODG.

Verification of Availability of AAC Source BTP 8-8 states that the extended AOT will be used no more than once in a 24-month period (or refueling period) for major maintenance on an offsite power transformer or bus. 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 condition can be met. In the letter dated December 22, 2025, the licensee proposed to add a footnote to the 72-hour CT for TS 3.8.1.A.3 that states the following:

A one-time Completion Time (CT) extension for an inoperable offsite circuit allows 15 days to restore the inoperable Startup Transformer X02 to OPERABLE status. Compensatory measures within Vistra Operations Company LLC letter L-25-227 dated 12/22/2025 shall be implemented and shall remain in effect during the extended CT period. The one-time extension shall expire upon completion of the maintenance to restore Startup Transformer X02 to OPERABLE status or by 0600 on March 6, 2026, whichever occurs earliest.

The proposed TS footnote states that it is a one-time CT extension, references the letter that lists the compensatory measures required when applying the 15-day CT, specifies the applicable equipment and the conditions when the extension is applicable (i.e., restore inoperable startup transformer X02 to operable), and includes an expiration date. The staff finds that the proposed footnote would provide definitive requirements in the TS to support the maintenance activity. The staff concludes that the proposed TS change is in compliance with the requirements in 10 CFR 50.36(c)(2)(i) and in conformance to BTP 8-8 because it would provide sufficient remedial actions during the startup transformer X02 maintenance activities until LCO 3.8.1 can be met.

Justification of 15-Day Completion Time BTP 8-8 states that the AOT should be limited to 14 days and the licensee must provide justification for the duration of the requested AOT (actual hours plus margin based on plant-specific past operating experience). LAR section 2.3 states that the 13 days provides the duration necessary to restore the X02 transformer tap changer, including 2 days for replacement of the transformer bushings, for a total of 15 days. In the letter dated December 22, 2025, the licensee provided a detailed outline of work activities for the tap changer repair and bushing and anticipates the duration of 315 hours0.00365 days <br />0.0875 hours <br />5.208333e-4 weeks <br />1.198575e-4 months <br /> to complete the work. The licensee further stated that the remaining 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br />, for a total of 360 hours0.00417 days <br />0.1 hours <br />5.952381e-4 weeks <br />1.3698e-4 months <br /> or 15 days, would accommodate unexpected maintenance or weather delays. Staff reviewed the detailed outline of activities and the actual hours plus margin. The staff finds that the 15-day AOT duration is reasonable and conforms to the guidance in BTP 8-8.

Compensatory Measures BTP 8-8 provides guidance that 1) the availability of the AAC shall be checked every 8-12 hours (once per shift), 2) if the AAC becomes unavailable any time during the extended AOT, the unit shall enter the LCO and start shutting down within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, 3) preplanned maintenance will not be scheduled if severe weather conditions are anticipated, and 4) no discretionary switchyard maintenance will be performed. In the letter dated December 22, 2025, the licensee added compensatory measures related to once-per-shift checks of the SBODG, actions in response to severe weather, and actions to restrict discretionary switchyard maintenance, as listed in Section 3.5 of this evaluation. These compensatory measures address the availability of the SBODG checked once per shift, preplanned maintenance not scheduled if severe weather is anticipated, and no discretionary switchyard maintenance, as discussed in BTP 8-8. For when the AAC or SBODG becomes unavailable during the extended AOT and commencing shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the licensee stated in the letter dated December 22, 2025, that BTP 8-8 provides this guidance for extended AOT and that both EDGs are available to power essential buses. The NRC staff notes that regarding the compensatory measure regarding the unavailability of the SBODG and start shutdown, BTP 8-8 states that the 24-hour period will only be allowed only once withing any given extended EDG AOT and therefore, would not apply to offsite source AOT amendments. Based on the above, the staff finds that the compensatory measures related to once-per-shift checks of the SBODG, actions in response to severe weather, and actions to restrict discretionary switchyard maintenance, conform to BTP 8-8.

In addition, BTP 8-8 provides guidance for pressurized water reactors that steam-driven emergency feed water (EFW) pumps are controlled as protected equipment. LAR section 3.2 lists the protected equipment, including EFW system. Regarding the compensatory measure for protected equipment, in the letter dated December 22, 2025, the licensee states that Plant administrative procedures governing protected equipment postings will be utilized to protect risk significant plant equipment. This includes the EDGs, SBODG, EFW System and startup transformer X01. UFSAR section 8.2.1 states that three 345 kV overhead lines connect the switchyard to the onsite distribution system, one line to each of the two startup transformers (X01 and X02). During the proposed extended 15-day AOT, the NRC staff notes that the license stated that the remaining operable offsite circuit will be via startup transformer X01 and is included as protected equipment. The staff compared the protected equipment to the guidance in BTP 8-8 and finds that the protected equipment conforms to BTP 8-8.

Based on the above, the staff finds that the SBODG: 1) is an adequate alternate power source,

2) has sufficient capacity and capability, 3) can be connected to the Class 1E bus within an hour, and 4) verified to available prior to and during the proposed 15-day CT; it is consistent with the guidance in BTP 8-8.

3.1.2 Conformance to RG 1.93 RG 1.93 section B states that in order to provide a reasonable level of confidence in safety, the period of continued operation is based on 1) the necessary time to perform corrective maintenance, 2) the capacity and capability of the remaining electric power sources, and 3) the low probability of a design basis accident occurring during this period. RG 1.93 section C states that whenever the TS allow power operation to continue during a specific degradation level, such continued power operation should be contingent upon the plant-specific technical specification requirements and the reliability, availability, and capability of the remaining sources and the required maintenance activities do not further degrade the power system or in any way jeopardize plant safety. The discussion in SE section 3.1.1 provides the staffs evaluation on

time to perform the maintenance, and the capacity and capability of the remaining power sources and the supplemental power source. SE Section 3.2 provides a risk insight discussion.

Based on the staffs evaluation above on the time to perform the maintenance and capacity and capability of the remaining sources, the staff finds the licensee continues to comply with RG 1.93.

3.1.3 Evaluation of Compensatory Measures In letter dated December 22, 2025, the licensee described compensatory measures that will be implemented and are listed as follows:

Any emergent work will be assessed and managed in accordance with 10 CFR 50.65(a)(4) and the applicable TS.

Daily communication will be held with the grid operator to monitor grid conditions and ensure no significant grid perturbations are expected during the extended completion time period.

Plant administrative procedures governing protected equipment postings will be utilized to protect risk significant plant equipment. This includes the EDGs, SBODG, EFW System and startup transformer X01.

There will be no scheduled work that would result in more than GREEN (low) PRA risk impact.

All scheduled work reviewed to ensure no work is performed that could threaten offsite and onsite power sources. Switchyard work will be limited to activities involving startup transformer X02 only.

Emergent issues resulting in unplanned inoperability of risk significant systems will be addressed in a timely manner.

The SBODG will be demonstrated functional by verifying its periodic test is current prior to start of the extended 15 day CT. In addition, plant operators will perform routine shiftly walkdowns of the SBODG and document in the electronic logging system (eSOMS).

Both EDGs will be demonstrated OPERABLE by verifying their respective surveillance are current prior to the start of the extended 15 day CT.

Reserve Source Selector Switches (RSSS) will both be aligned to the startup transformer X01 Prior to removing startup transformer X02 from service, review the weather forecast for severe weather in the immediate future. In the event of severe weather, all work associated with startup transformer X02 will be suspended and the station procedures for severe weather will be used to control work processes.

Around the clock staffing will occur in the Outage Control Center to address issues affecting compensatory measure equipment without undue delay. Any subsequent limiting condition required actions will be entered, and followed as appropriate, for an off-site circuit inoperable.

The NRC staff reviewed the above compensatory measures with respect to the defense-in-depth aspects. Based on its review, the NRC staff finds that these compensatory measures will provide reasonable assurance for the duration of the extended CT interval such that (1) the risk of the plant transients is reduced, (2) operation, testing, and maintenance of the plant equipment will be minimized to avoid an adverse impact on plant operations, (3) systems and components significant to this LAR and its supplements will be protected and only critical non-discretionary work will be performed on those systems and components in accordance with

overall safety considerations, and (4) main control room operators will be specifically alerted to the ongoing maintenances.

3.2 Risk Insight Evaluation The licensee provided risk insights related to the proposed change in section 3.3 of to the LAR. The licensee stated that the proposed one-time CT extension to TS 3.8.1 would result in an Incremental Conditional Core Damage Probability (ICCDP) of 8.32E-07 for the requested 15 days, which is less than the ICCDP acceptance criterion of 1.0E-06 as described in RG 1.177. Similarly, the Incremental Conditional Large Early Release Probability (ICLERP) for the requested 15 days is 2.14E-08, which is less than the ICLERP acceptance criterion of 1.0E-07 described in RG 1.177. The licensee also stated that cables for MCCs E31A

& F31A were not traced for the fire PRA model and are therefore considered failed in all fire scenarios. Since this is not a risk-informed LAR, the above-mentioned PRA models used by the licensee to derive risk insights were not reviewed by the NRC staff to determine their technical acceptability to support this SE.

In its review of the LAR, as supplemented, the NRC staff confirmed that the licensee-provided qualitative risk insights associated with the proposed one-time TS change support the assertion of minimal risk increase to the plant. The NRC staff also considered the associated compensatory measures to aid the deterministic review of the proposed change, which are discussed in section 3.1.3 of this SE. The proposed compensatory measures further limit the risk impact and provide adequate defense-in-depth related to system redundancy, independence, and diversity to maintain safe shutdown capability. The NRC staff also concluded that the risk insights supported the traditional engineering conclusions associated with the proposed change.

Based on the information provided by the licensee and the evaluation above, the NRC staff concludes that the submitted risk insights and compensatory measures demonstrate minimal increase in risk during the extended 15-day CT. The NRC staff also concludes that risk insights are acceptable for the purposes of supporting the deterministic SE.

3.3 Technical Evaluation Conclusion

Based on the results of the deterministic evaluation described above in section 3.1 and the PRA evaluation described above in section 3.2, the NRC staff concludes that the proposed one-time change to TS 3.8.1, AC Sources -Operating, to extend the allowable CT for Required Action A.3 from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 15 days to complete repairs is acceptable and will not impact the licensees continuous compliance with the requirements of 10 CFR 50.36, 50.63, and 10 CFR 50 Appendix A, GDC 17. The existing CT of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> will be restored after the modification is complete.

4.0 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.

An 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 startup transformers are standby equipment that are not normally used during power operations until after the initiation of an accident scenario, so extending the time the startup transformer X02 is allowed to be out of service does not increase the probability of an accident previously evaluated in the Updated Final Safety Analysis Report (UFSAR).

There is no significant increase in the consequences of an accident during the repairs to startup transformer X02. A risk assessment has been performed for plant configuration during the proposed CT change.

The Probabilistic Risk Assessment (PRA) analysis supports this CT change to TS 3.8.1. The Incremental Conditional Core Damage Probability and the Incremental Conditional Large Early Release Probability both remain below the acceptance criterion described in Regulatory Guide 1.177. The increase in risk can be mitigated by the measures described in section 3.2 above, specifically protecting important equipment such as the Emergency Diesel Generators (EDGs), Station Blackout Diesel Generator (SBODG), and Emergency Feedwater System (EFW). The risk assessment recommends that these systems be maintained available and protected throughout the duration of the extended CT to mitigate the increased risk of a loss of offsite power and to mitigate the increased fire and seismic risk.

There is no change in the station response to a Loss of Offsite Power (LOOP) or Station Blackout (SBO) as a result of the CT change because X02 is not included in the designated equipment used in the LOOP and SBO coping strategies.

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 amendment involves repairs to startup transformer X02.

This work is to be performed with the plant online. During normal online operations, startup transformer X02 is in a standby condition with plant loads being provided by auxiliary transformer X11. The proposed change does not alter the design, physical configuration, or mode of operation of any other plant structure, system, or component. The proposed extended X02 inoperability is bounded by the LOOP analysis. No physical changes are being made to any other portion of the plant (i.e., no new or different

type of equipment will be installed) or a change in the method governing normal plant operation; therefore, no new accident scenarios, failure mechanisms, or limiting single failures are introduced as a result of this change. The proposed change to the CT to allow repairs of startup transformer X02 does not result in any new mechanisms that could initiate damage to the reactor or its principal safety barriers since all design and performance criteria will continue to be met and DBNPS will continue to be operated within the limits of its licensing basis.

Therefore, the proposed amendment does not create the possibility of a new or different kind of accident from any previously evaluated.

3.

Does the proposed change involve a significant reduction in a margin of safety?

Response: No.

The proposed amendment to extend the TS 3.8.1 Action A.3 CT does not significantly reduce the margin of safety for accident mitigation. During the proposed maintenance, both trains of emergency power will be supplied by auxiliary transformer X11 which is the normal configuration when the main generator is in service. Both EDGs will be maintained operable and the SBODG will be maintained functional and protected in the event of a LOOP. Compensatory measures will be implemented to minimize nuclear safety and generation risk.

To support a scheduled 13 day maintenance period, Vistra OpCo requests a CT of 15 days. PRA analysis (Attachment 5) has determined a CT of 18 days remains within the Regulatory Guide 1.177 criterion.

Therefore, the proposed amendment does not involve a 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.

5.0 STATE CONSULTATION

In accordance with the Commissions regulations, the Ohio State official was notified of the proposed issuance of the amendment on January 9, 2026. There were no comments received from the State of Ohio official.

6.0 ENVIRONMENTAL CONSIDERATION

The amendment changes requirements with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. 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. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration as published in the Federal Register on November 24, 2025 (90 FR 53003), and there has been no public comment on such finding. Further, the NRC staff has found that the amendment involves no significant hazards consideration. 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.

6.0 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 amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributors: S. Ray, NRR K. West, NRR C. Ng, NRR Date: January 16, 2026

ML26009A033 NRR-058 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DEX/EEEB/BC NAME RKuntz SLent WMorton DATE 1/9/2026 1/9/2026 1/12/2026 OFFICE NRR/DSS/SCPB/BC NRR/DRA/APLA/BC (A)

NRR/DSS/STSB/BC NAME MValentin MGonzalez SMehta DATE 1/9/2026 1/5/2026 1/12/2026 OFFICE NRR/DORL/LPL3/BC (A)

NRR/DORL/LPL3/PM NAME IBerrios (SWall for)

RKuntz DATE 1/16/2026 1/16/2026