ML25188A184

Issuance of Amendment No. 284 to Authorize Safety Analysis Report Change

ML25188A184
Person / Time
Site:	Arkansas Nuclear
Issue date:	07/30/2025
From:	Mclatchie H NRC/NRR/DORL/LPL4
To:	Entergy Operations
McLatchie H, NRR/DORL/LPL4
Shared Package
ML25192A193	List: ML25188A184 ML25192A201
References
EPID L-2024-LLA-0092
Download: ML25188A184 (1)

Text

July 30, 2025 ANO Site Vice President Arkansas Nuclear One Entergy Operations, Inc.

N-ADM-8 1448 S.R. 333 Russellville, AR 72802

SUBJECT:

ARKANSAS NUCLEAR ONE, UNIT 1 - ISSUANCE OF AMENDMENT NO. 284 TO AUTHORIZE SAFETY ANALYSIS REPORT CHANGE CORRESPONDING TO RELAXATION OF JANUARY 2, 1980, CONFIRMATORY ORDER (EPID L-2024-LLA-0092)

Dear Sir or Madam:

The U.S. Nuclear Regulatory Commission (the Commission) has issued the enclosed Amendment No. 284 to Renewed Facility Operating License No. DPR-51 for Arkansas Nuclear One, Unit 1 (ANO-1). The amendment authorizes a safety analysis report change corresponding to the relaxation of a January 2, 1980, Confirmatory Order in response to your application dated July 2, 2024, as supplemented by letters dated February 26, 2025, and April 8, 2025.

The amendment authorizes a safety analysis report change corresponding to a concurrently issued relaxation of the Confirmatory Order dated January 2, 1980, for ANO-1 to allow an alternate means of addressing the post Three Mile Island Unit No. 2 recommendation that any changeover of the pressurizer heaters from normal offsite power to emergency onsite power is to be accomplished manually in the control room. The relaxation allows the performance of manual actions at 120-volt alternating current (VAC) instrument panels Y01 and Y02 outside the control room to restore power to the pressurizer low-low level interlock to allow operation of required pressurizer heaters on emergency onsite power for certain loss of offsite power events.

A copy of the related Safety Evaluation is also enclosed. Notice of Issuance will be included in the Commissions monthly Federal Register notice.

Sincerely,

/RA Dennis Galvin for/

Hannah McLatchie, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-313

Enclosures:

1. Amendment No. 284 to DPR-51

2. Safety Evaluation cc: Listserv

ENTERGY OPERATIONS, INC.

DOCKET NO. 50-313 ARKANSAS NUCLEAR ONE, UNIT 1 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 284 Renewed License No. DPR-51

1.

The U.S. Nuclear Regulatory Commission (the Commission) has found that:

A.

The application for amendment by Entergy Operations, Inc. (the licensee) dated July 2, 2024, as supplemented by letters dated February 26, 2025, and April 8, 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, by Amendment No. 284, Renewed Facility Operating License No. DPR-51 is amended to authorize revision to the Safety Analysis Report (SAR), as set forth in the application dated July 2, 2024, as supplemented by letters dated February 26, 2025, and April 8, 2025. The licensee shall update the SAR to incorporate the changes as described in the licensees application dated July 2, 2024, as supplemented by letters dated February 26, 2025, and April 8, 2025, and in the NRC staffs safety evaluation associated with this amendment, and shall submit the revised description authorized by this amendment with the next update of the SAR.

3.

This amendment is effective as of its date of issuance and shall be implemented within 90 days from the date of issuance. The SAR changes shall be included in the next periodic update of the ANO-1 SAR in accordance with 10 CFR 50.71(e).

FOR THE NUCLEAR REGULATORY COMMISSION Tony Nakanishi, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Date of Issuance: July 30, 2025 TONY NAKANISHI Digitally signed by TONY NAKANISHI Date: 2025.07.30 11:27:31 -04'00'

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 284 TO RENEWED FACILITY OPERATING LICENSE NO. DPR-51 ENTERGY OPERATIONS, INC.

ARKANSAS NUCLEAR ONE, UNIT 1 DOCKET NO. 50-313

1.0 INTRODUCTION

By application dated July 2, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24184B775), as supplemented by letters dated February 26, 2025 (ML25057A318) and April 8, 2025 (ML25098A194), Entergy Operations, Inc. (Entergy, the licensee) submitted a license amendment request (LAR) for Arkansas Nuclear One, Unit 1 (ANO-1). The proposed amendment would authorize an ANO-1 safety analysis report (SAR) change corresponding to a concurrently issued relaxation (ML25192A201) of the U.S. Nuclear Regulatory Commission (NRC, the Commission) Confirmatory Order dated January 2, 1980 (hereafter, the 1980 Order) (ML021220215), for ANO-1 to allow an alternate means of addressing the post Three Mile Island Unit No. 2 (TMI-2) recommendation that any changeover of the pressurizer heaters from normal offsite power to emergency onsite power is to be accomplished manually in the control room. The relaxation would allow the performance of manual actions at 120-volt alternating current (VAC) instrument panels Y01 and Y02 outside the control room to restore power to the pressurizer low-low level interlock to allow operation of required pressurizer heaters on emergency onsite power for certain loss of offsite power (LOOP) events.

The supplemental letters dated February 26, 2025, and April 8, 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 December 23, 2024 (89 FR 104571).

2.0 REGULATORY EVALUATION

2.1

System Description

The licensee described the ANO-1 power supply for the pressurizer heaters in the enclosure to the LAR under the heading Current ANO-1 Configuration as the following:

The design of the ANO-1 power supply for the pressurizer heaters, documented in SAR Section 4.2.4.4, provides the capability to supply, from either the offsite power source or the emergency power source (i.e., the units Emergency Diesel Generators (EDGs), when offsite power is not available) and associated controls necessary to establish and maintain natural circulation at hot standby conditions.

In addition, the Station Blackout (SBO) DG [diesel generator] can be a source of emergency power for the pressurizer heaters from either the Red-or Green-train electrical power distribution system.

The heaters are arranged in 14 groups and are controlled by the pressure controller. Two groups utilize modulating control and will normally operate at partial capacity to replace heat loss, thus maintaining pressure at the setpoint.

On-off control is used for the remaining 12 groups. A low-low level interlock prevents the heaters from being energized with the heaters uncovered (less than 55-inch minimum level requirement).

Two separate sets of heaters are supplied by the EDGs. The remaining heaters required to meet the TS [Technical Specification] required capacity, are powered from a swing bus which can be supplied by either EDG. This ensures emergency power redundancy to sufficient heater capacity to establish and maintain pressure control at hot standby during a LOOP.

ANO-1 SAR section 8.3.1.1.5, 120/208-Volt Instrument AC [Alternating Current] System (ML23180A103), provides the following description for the ANO-1 power supply for panels Y1 and Y2, which supply the low-low level interlock for the pressurizer heaters:

The 120/208-volt instrument AC system is designed to provide power for normal station service reactor auxiliary control instrumentation and the instrument fan cooling power supply. This system includes four independent and physically separated instrument panels for the normal station service and reactor auxiliary control instrumentation. These instrument panels are supplied from separate 480-volt engineered safeguards motor control centers in 480-120/208-volt step-down transformers.

The step-down transformers for panels Y1 and Y2 are rated to carry the full load of both instrument panels. A bus tie with key locked breakers is provided between these instrument panels to supply power to either instrument panel in the event of loss of one source or transformer.

2.2 Requirements Imposed by the 1980 Order for ANO-1 Section IV of the 1980 Order ordered, in part, that [t]he Licensee by January 31, 1980, implement all Category A requirements referred to in Part II of this Order.

Section II of the 1980 Order referred to requirements in the following three documents, which are incorporated by reference into the order:

1.

NUREG-0578, TMI-2 Lessons Learned Task Force Status Report and Short-Term Recommendations, dated July 1979 (ML090060030), set forth measures identified by the NRC TMI-2 lessons learned task force to be taken in the short-term to reduce the likelihood of accidents and to improve emergency preparedness in responding to

accidents. Section 2.1.1, Emergency Power Supply Requirements for the Pressurizer Heaters, Power-Operated Relief and Block Valves, and Pressurizer Level Indicators in PWRs [Pressurized-Water Reactors], of NUREG-0578 provides, in part, the following recommendation for the emergency power supply for the pressurizer heaters:

Provide redundant emergency power for the minimum number of pressurizer heaters required to maintain natural circulation conditions in the event of loss of offsite power.

NUREG-0578, appendix A, NRR [NRC Office of Nuclear Reactor Regulation] Lessons Learned Task Force Short-Term Recommendations, section 3.1, Pressurizer Heater Power Supply, provides several positions for the recommendation in NUREG-0578, section 2.1.1 for the pressurizer heaters:

Consistent with satisfying the requirements of General Design Criteria 10, 14, 15, 17, and 20 of Appendix A to 10 CFR Part 50 for the event of loss of offsite power, the following positions shall be implemented:

1.

The pressurizer heater power supply design shall provide the capability to supply, from either the offsite power source or the emergency power source (when offsite power is not available), a predetermined number of pressurizer heaters and associated controls necessary to establish and maintain natural circulation at hot standby conditions. The required heaters and their controls shall be connected to the emergency buses in a manner that will provide redundant power supply capability.

2.

Procedures and training shall be established to make the operator aware of when and how the required pressurizer heaters shall be connected to the emergency buses. If required, the procedures shall identify under what conditions selected emergency loads can be shed from the emergency power source to provide sufficient capacity for the connection of the pressurizer heaters.

3.

The time required to accomplish the connection of the preselected pressurizer heater to the emergency buses shall be consistent with the timely initiation and maintenance of natural circulation conditions.

4.

Pressurizer heater motive and control power interfaces with the emergency buses shall be accomplished through devices that have been qualified in accordance with safety-grade requirements.

NUREG-0578, appendix B, NRR Lessons Learned Task Force Implementation of Short-term Recommendations, designated the recommendations in section 2.1.1 of NUREG-0578 as Category A.

2.

Generic Letter (GL) 79-40, Followup Actions Resulting from the NRC Staff Reviews Regarding the Three Mile Island Unit 2 Accident, dated September 13, 1979 (ML112990325), transmitted to licensees Category A requirements, which were actions at operating nuclear power plants that required prompt implementation to provide

continued assurance of public health and safety. Specifically, enclosure 6, Implementation Schedule, of GL 79-40 designates the recommendations in section 2.1.1 of NUREG-0578 as Implementation Category A, with an implementation completion date of January 1, 1980.

3.

GL 79-56, Discussion of Lessons Learned Short Term Requirements, dated October 30, 1979 (ML031320403), provided clarifications to the positions in NUREG-0578. Specifically, section 2.1.1 of enclosure 1 of GL 79-56 identified the following clarifications regarding the emergency power supply for the pressurizer heaters:

1.

In order not to compromise independence between the sources of emergency power and still provide redundant capability to provide emergency power to the pressurizer heaters, each redundant heater or group of heaters should have access to only one Class 1E division power supply.

2.

The number of heaters required to have access to each emergency power source is that number required to maintain natural circulation in the hot standby condition.

3.

The power sources need not necessarily have the capacity to provide power to the heaters concurrent with the loads required for LOCA

[loss-of-coolant accident].

4.

Any change-over of the heaters from normal offsite power to emergency onsite power is to be accomplished manually in the control room.

5.

In establishing procedures to manually reload the pressurizer heaters onto the emergency power sources, careful consideration must be given to:

a.

Which ESF [engineered safety feature] loads may be appropriately shed for a given situation.

b.

Reset of the Safety Injection Actuation Signal to permit the operation of the heaters.

c. Instrumentation and criteria for operator use to prevent overloading a diesel generator.

6.

The Class 1E interfaces for main power and control power are to be protected by safety-grade circuit breakers.

7.

Being non-Class 1E loads, the pressurizer heaters must be automatically shed from the emergency power sources upon the occurrence of a safety injection actuation signal. (See item 5.b. above)

In response to GL 79-40, by letter dated October 17, 1979 (ML19275A856), the licensee committed, in part, to provide the capability to power 126 kilowatts (kW) of pressurizer heater capacity from redundant emergency power sources within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> following a LOOP to assure proper control for natural circulation. In response to GL 79-56, by letter dated

November 20, 1979 (ML19250C346), the licensee indicated that in addition to the 84 kW of pressurizer heaters on each emergency power train, the additional 42 kW of required heaters are powered from the swing bus that can be connected to either diesel generator, separately and energized manually from the control room. By letter December 5, 1979 (ML19291B904), the licensee slightly modified its response to GL 79-56.

The NRC staff notes that NUREG-0737, Clarification of TMI Action Plan Requirements, dated November 1980 (ML102560051), was referenced in the original LAR. NUREG-0737 identifies all post-TMI requirements that had been approved for implementation by the Commission at that time. Most of the items in NUREG-0737 had been previously issued as requirements via prior correspondence, though some new requirements were issued in NUREG-0737. NUREG-0737, Item II.E.3.1, Emergency power for pressurizer heaters, is the designation for the requirements in section 2.1.1 of NUREG-0578. The requirements in NUREG-0737, Item II.E.3.1 are unchanged from the clarification of section 2.1.1 in GL 79-56, including the fourth clarification item. However, as NUREG-0737 was issued after the 1980 Order, the NRC staff notes that it is inappropriate to discuss NUREG-0737 with respect to the 1980 Order. Accordingly, by letter dated April 8, 2025, the licensee replaced the discussion in the LAR of NUREG-0737 with a discussion of the three documents discussed above.

2.3 Proposed Change In the LAR, the licensee proposed to change ANO-1 SAR section 4.2.4.4, Pressurizer Heaters, by adding to it the following:

Upon failure of Green-train electrical power, changeover includes actions performed locally at 120 VAC instrument panels Y01 and Y02 to restore power to the Pressurizer Low-Low Level Interlock. This action is outside the control room.

This change would also amount to a relaxation of the 1980 Order, which required, pursuant to GL 79-56, section 2.1.1, clarification 4, that [a]ny change-over of the heaters from normal offsite power to emergency onsite power is to be accomplished manually in the control room.

2.4 Reason for the Proposed Change In the enclosure to the LAR, the licensee provided the following statements that indicate the reasons for the proposed change:

In 2015 Entergy discovered and documented an issue with providing sufficient pressurizer heater capacity during a postulated LOOP event. The event also includes the failure of the Green-train electrical power resulting in loss of power to the pressurizer low-low level interlock.

The pressurizer low-low level heater interlock prevents the heaters from being damaged due to being uncovered. The setpoint is when the pressurizer level is less than or equal to 55 inches. This interlock is powered by the Green-train electrical power distribution system only. If this interlock is de-energized, it would prevent the ability to utilize the required heaters, even if Red-train power and adequate pressurizer level exists.

In the event of the LOOP with failure of Green-train emergency power, the design of ANO-1 requires manual operator actions outside the control room to restore

power to the pressurizer low-low level heater interlock allowing for minimum TS required pressurizer heater capacity powered by Red-train emergency power.

This is contrary to the requirement of Any change-over of the heaters from normal offsite power to emergency onsite power is to be accomplished manually in the control room.

2.5 Applicable Regulatory Requirements and Guidance The following regulations are applicable to the review of the LAR:

Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, Appendix A, General Design Criteria for Nuclear Power Plants, General Design Criterion (GDC) 17, Electric power systems, states, in part:

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 onsite electric power supplies, including the batteries, and the onsite electric distribution system, shall have sufficient independence, redundancy, and testability to perform their safety functions assuming a single failure.

GDC 19, Control room, states, in part:

A control room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions, including loss-of-coolant accidents.

The NRC staff used the following regulatory guidance to review the LAR:

Regulatory Guide (RG) 1.6, Independence Between Redundant Standby (Onsite) Power Sources and Between their Distribution Systems, dated March 10, 1971 (ML003739924),

provides guidance for an acceptable degree of independence between redundant standby (onsite) power sources and between their distribution systems for compliance with GDC 17.

Chapter 18, Revision 3, Human Factors Engineering, of NUREG-0800, Standard Review Plan

[SRP] for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR [Light Water Reactor] Edition, dated December 2016 (ML16125A114), describes the guidance used by the NRC staff to conduct regulatory reviews of license amendments that address human factors topics. It directs the staff to applicable review criteria such as those included in NUREG-1764, Revision 1, Guidance for the Review of Changes to Human Actions, dated September 2007 (ML072640413).

NUREG-1764, Revision 1, describes how to assess changes to manual operator actions. It provides a risk-informed process to determine the level of NRC review necessary and provides the acceptance criteria for each level of review.

The NRC Enforcement Manual https://www.nrc.gov/about-nrc/regulatory/enforcement/guidance.html#manual), Part I, Enforcement Process, section 2.7.8, Relaxation, Withdrawal, or Rescission of Orders states, in part, that the NRC staff may relax, withdraw, or rescind conditions of an order in response to a licensee request or upon its own initiative based upon a good cause justification. Section 2.7.8 also provides criteria that should be considered when evaluating a licensees good cause justification.

3.0 TECHNICAL EVALUATION

3.1 Introduction The NRC staff notes that the LAR amounts to a proposed relaxation of the 1980 Order with respect to its requirement, pursuant to GL 79-56, section 2.1.1, clarification 4, that [a]ny change-over of the heaters from normal offsite power to emergency onsite power is to be accomplished manually in the control room, in addition to a proposed corresponding change to the ANO-1 SAR. Accordingly, the NRC staff evaluated whether such relaxation and corresponding change continue to provide reasonable assurance of adequate protection of the public health and safety consistent with the NRCs regulations and whether there is a good cause justification for the relaxation. This safety evaluation discusses both the order relaxation and the SAR change since they are interdependent. However, the NRC approval of the order relaxation is the subject of a separate action (ML25192A201), which is being performed concurrently with the NRC staff action on the SAR change. Similarly, the good cause justification for the relaxation of the 1980 Order is evaluated in this safety evaluation because its basis is the same as that for the SAR change.

The NRC staff also notes that the licensee has identified potential issues with the sufficiency of the ANO-1 TS required pressurizer heater capacity to maintain natural circulation at hot standby conditions when offsite power is not available. The licensee anticipates addressing this issue through a separate licensing action (ML25176A1480). Any discussion of meeting NUREG-0578 with regard to pressurizer heater capacity in this safety evaluation refers to continuing to meet the currently required pressurizer heater capacity as stated in the ANO-1 TSs.

3.2 Evaluation of Impacts to NUREG-0578, Appendix A, Section 3.1 Positions The proposed order relaxation and corresponding SAR change impact NUREG-0578, appendix A, section 3.1, position 1, position 3, and position 4.

NUREG-0578, appendix A, section 3.1, position 1 states:

The pressurizer heater power supply design shall provide the capability to supply, from either the offsite power source or the emergency power source (when offsite power is not available), a predetermined number of pressurizer heaters and associated controls necessary to establish and maintain natural circulation at hot standby conditions. The required heaters and their controls shall be connected to the emergency buses in a manner that will provide redundant power supply capability.

NUREG-0578, appendix A, section 3.1, position 1 is clarified by GL 79-56, section 2.1.1, clarification 1 and clarification 2. GL 79-56, section 2.1.1, clarification 1 states:

In order not to compromise independence between the sources of emergency power and still provide redundant capability to provide emergency power to the pressurizer heaters, each redundant heater or group of heaters should have access to only one Class 1E division power supply.

GL 79-56, section 2.1.1, clarification 2 states:

The number of heaters required to have access to each emergency power source is that number required to maintain natural circulation in the hot standby condition.

ANO-1 SAR section 4.2.4.4, Pressurizer Heaters, states, in part:

Each diesel generator emergency bus supplies emergency power to 168 kW of pressurizer heaters. Two separate sets of heaters totaling 84 kW each are supplied by the diesel generators. The remaining 84 kW is powered by a swing bus which can be supplied by either diesel generator.

ANO-1 SAR section 4.2.4, Pressure Control and Protection, states, in part:

168 kW of pressurizer heaters are supplied with emergency power to ensure a minimum of 126 kW is available.

ANO-1 SAR section 8.3.1.1.4, 480-Volt Auxiliary System, states, in part:

As a result of NUREG-0578, Item 2.1.1, an additional 42 kW of pressurizer heater capacity was added.

The NRC staff noted that the 42 kW of pressurizer heaters on the swing bus have access to both EDGs instead of one EDG even if they are not simultaneously connected to the bus. In its supplemental letter dated February 26, 2025, the licensee provided background to the ANO-1 responses to the NRC requests for the implementation of NUREG-0578, section 2.1.1. The licensee referenced the NRC evaluation dated March 10, 1980 (ML19309B770) that concluded on ANO-1 compliance with the emergency power supply requirements for the pressurizer heaters as outlined in NUREG-0578. The 1980 NRC evaluation focused on the provision of 126 kW pressurizer heater capacity within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> after a LOOP and the combination of the 84 kW on each vital bus and 42 kW pressurizer heaters on the swing bus to achieve 126 kW of redundant pressurizer heaters on each safety bus. The 1980 NRC evaluation did not cover the single pressurizer low-low level interlock and the crosstie breakers.

In its LAR, the licensee stated that the electrical crosstie between the panels Y01 and Y02 for the pressurizer low-low level interlock does not compromise the independence between the EDGs, and the ANO-1 design, and procedures allow for this crosstie with the reactor shutdown.

In addition, the licensee stated that when the panels are cross tied, the source of emergency power remains the red-train EDG until the green-train EDG is restored, the crosstie between panels Y01 and Y02 has been disconnected, and the normal power source for panels Y01 and Y02 has been restored. ANO-1 SAR, section 8.3.1.4, Independence of Redundant Systems, describes the independence of redundant systems stating that the redundant systems are

designed to be physically independent of each other so that failure of one train or channel will not jeopardize safe shutdown of the reactor; and that the independence of the redundant system is consistent with RG 1.6. RG 1.6 recommends that [i]f means exist for manually connecting redundant load groups together, at least one interlock should be provided to prevent an operator error that would parallel their standby power sources. ANO-1 SAR section 8.3.1.1.8.1, Interlocks Against Interconnection of Redundant Emergency Buses, states that to insure against interconnections of redundant emergency buses and meet the intent of RG 1.6, the crosstie breakers between the panels Y01 and Y02 are normally open and are provided with keyed locks.

The NRC staff reviewed the single line diagrams for the ANO-1 electrical distribution system in LAR enclosure, attachment 5, Single line description of the ANO-1 Electrical Distribution System, the ANO-1 SAR, and related information and finds that the crosstie between 120 VAC panels Y01 and Y02 does not impact the independence of the redundant train EDGs, because (1) the reactor is already shut down when the Green-train panel Y02 is connected to the Red-train panel Y01 through the crosstie so that the crosstie will not jeopardize safe shutdown, and (2) keyed locks are provided for the crosstie breakers to ensure that the EDGs are not paralleled through the crosstie, as recommended in RG 1.6.

The NRC staff noted that if the Green-train panel Y02 supplying the pressurizer low-low level interlock or the crosstie between the panels Y01 and Y02 fails, the required minimum pressurizer heater capacity (126 kW) to maintain natural circulation in the hot standby condition would not be available even if the Red-train EDG is operable. The staff requested the licensee to explain how the connection of the 126 kW of pressurizer heaters to an EDG satisfies GL 79-56, section 2.1.1, clarifications 1 and 2. In its supplemental letter dated February 26, 2025, the licensee stated that existing ANO-1 TS 3.4.9, Pressurizer, Action C covers the condition when less than two of the three required heater groups (on both 480-VAC vital bus and the swing bus) are operable. Existing ANO-1 TS 3.4.9 Action C requires restoring the engineered safeguards (ES) bus powered pressurizer heater capacity within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> when this capacity is less than limit (126 kW). The staff finds that the licensee adequately addressed the issue of the failure of the panel Y02 or the crosstie between panels Y01 and Y02 since TS 3.4.9 Action C provides adequate remedial actions for restoring the required minimum pressurizer heater capacity for each EDG to meet NUREG-0578, Appendix A, section 3.1, position 1.

NUREG-0578, Appendix A, section 3.1, position 3 states:

The time required to accomplish the connection of the preselected pressurizer heater to the emergency buses shall be consistent with the timely initiation and maintenance of natural circulation conditions.

In the LAR, the licensee stated that ANO-1 previously committed to having the TS required heater capacity (126 kW) restored within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> following a LOOP to assure proper control for natural circulation in the hot standby condition (Mode 3). If panel Y02 is de-energized during a LOOP concurrent with the loss of the Green-train EDG, the licensee stated that it would restore power to the pressurizer low-low level interlock within approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> by manually cross-tying the Green-train 120-VAC panel Y02 to the Red-train 120-VAC panel Y01 outside the control room. The licensee estimated the 1-hour time by adding an estimated time of 30-45 minutes for performing all the actions in the ANO emergency operating procedure for degraded power up to the step of re-energizing panel Y02 and an average time of 12.6 minutes for completing actions in the ANO Job Performance Measure to power Y02 from Y01 without paralleling sources. The NRC staff finds that since the 1-hour time for manually re-energizing

the pressurizer low-low level interlock outside the control room is within the 2-hour committed time for having the required minimum heater capacity (126 kW) following a LOOP and failure of the Green-train EDG, the licensee continues to meet NUREG-0578, Appendix A, section 3.1, position 3. This manual action is further evaluated in section 3.3 of this safety evaluation.

NUREG-0578, Appendix A, section 3.1, position 4 states:

Pressurizer heater motive and control power interfaces with the emergency buses shall be accomplished through devices that have been qualified in accordance with safety-grade requirements.

ANO-1 SAR figure No. 8-1, Station Single Line Diagram, and LAR enclosure, attachment 5 figure 32.02B, Electrical Distribution One Line Diagram, show two crosstie breakers between panels Y01 and Y02. The NRC staff requested the licensee to provide the safety classification of the circuit breakers that are used to power the pressurizer heaters and the low-low level interlock from the Class 1E buses. In its supplemental letter dated February 26, 2025, the licensee stated that the crosstie breakers between panels Y01 and Y02, the breakers supplying the panels Y01 and Y02, and all the breakers used to power the pressurizer heaters on the 480-VAC vital buses and the swing bus are safety-related. The staff finds that since all the circuit breakers used to supply power to the pressurizer heaters and their interlock from the emergency buses are safety-related, the licensee continues to meet NUREG-0578, Appendix A, section 3.1, position 4.

Based on the above evaluation, the NRC staff finds that the licensee continues to meet NUREG-0578, Appendix A, section 3.1, positions 1, 3, and 4 when the pressurizer low-low level interlock is manually reenergized by cross-tying panels Y01 and Y02 using safety-related breakers outside the control room because the Red-train EDG can supply the required minimum heater capacity and the associated controls necessary to establish and maintain natural circulation at hot standby conditions within an acceptable time. Therefore, the staff finds that the proposed relaxation of the 1980 Order with respect to GL 79-56, section 2.1.1, clarification 4 and the proposed corresponding change to the ANO-1 SAR are acceptable.

3.3 Evaluation of Manual Action 3.3.1 Description of Manual Action The proposed relaxation of the 1980 Order with respect to GL 79-56, section 2.1.1, clarification 4 and the proposed corresponding change to the ANO-1 SAR include the manual action of changing over the power supply of pressurizer heaters from normal offsite power to emergency onsite power. Specifically, upon failure of Green-train electrical power, operators will be required to manually re-energize the 120 VAC instrument AC distribution panel Y02 (Green-train) from the 120 VAC instrument AC distribution panel Y01 (Red-train). This manual action would be performed locally (i.e., outside the control room) to restore power to the Pressurizer Low-Low Level Interlock.

The manual action does not replace an automatic system or component actuation. The action required for the changeover of the onsite electrical power supply for the pressurizer low-low level interlock is currently contained in ANO-1 procedures. No new actions are being proposed.

Currently, in the event of the LOOP with failure of Green-train emergency power, the design of

ANO-1 requires a manual action outside the control room to restore power to the pressurizer low-low level heater interlock allowing for minimum TS required pressurizer heater capacity powered by Red-train emergency power.

The proposed change does not present potentially harsh or inhospitable environmental conditions where the manual action is to be performed or along the pathway to the remote location. The licensee described the training program, which addresses the manual action affected by the proposed change. There are no proposed changes to the emergency operating procedures associated with this LAR.

3.3.2 Credited Manual Action The licensee credits the manual action associated with the proposed relaxation of the 1980 Order with respect to GL 79-56, section 2.1.1, clarification 4 and the proposed corresponding change to the ANO-1 SAR to be performed within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to restore heater capacity in accordance with ANO-1 TS 3.4.9 to assure proper control for natural circulation in the hot standby condition. The licensee reviewed 2022 performances of the job performance measures included in the training program and determined an average completion time for these activities of 12.6 minutes from the time the cue was provided until the evolution was completed. The estimated time to perform all the actions in the emergency operating procedure condition up to the step to re-energize panel Y02 is approximately 30 to 45 minutes. Therefore, the total time to complete the set of actions is approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. This time would not change with the proposed amendment. The pressurizer heaters are not credited in Chapter 15 safety analyses or in the probabilistic risk assessment.

3.3.3 Risk Assessment to Determine Level of Review The NRC staff reviewed the proposed change and verified that the manual action is in the low-risk category by assessing it against table A.2, Generic PWR Human Actions That Are Risk Important, in appendix A of NUREG-1764 and verified that no actions from that table are included in the submittal. The NRC staff finds the proposed change presents a minimal change in risk. Therefore, the staff applied the criteria for a Level 3 review.

3.3.4 NRC Staff Evaluation The licensee described the manual action associated with the proposed change. The NRC staff reviewed the LAR and verified that the manual action is in the low-risk category by assessing it against the applicable tables in NUREG-1764. The NRC staff also considered the proposed relaxation of the 1980 Order and the basis for requiring the heaters to be operated from the control room.

Regarding the 1980 Order, NUREG-0578 states designs should be upgraded to provide the operator with the capability to maintain natural circulation at hot standby through the use of pressurizer heaters when offsite power is not available. NUREG-0578 also points to Reactor Systems Branch (RSB) Technical Position 5-1, Design Requirements of the Residual Heat Removal System, Revision 1, dated March 1979 (ML19221B105)1, and RG 1.139, Guidance for Residual Heat Removal, dated May 1978 (ML040750334), for a description of requirements 1 RSB Technical Position 5-1 was an attachment to SRP 5.4.7, Residual Heat Removal System, through Revision 3. The guidance in RSB Technical Position 5-1 was merged into SRP 5.4.7 in Revision 4 and is no longer a separate attachment.

concerning the design capability for taking the reactor plant from normal operating conditions to cold shutdown conditions, assuming a LOOP. The requirement for emergency power supply to the pressurizer heaters is consistent with these requirements. Both RSB Technical Position 5-1 and RG 1.1392 state that limited operator action outside of the control room would be considered acceptable if suitably justified.

The licensee provided justification for the action outside the control room by providing the following:

a description of the manual action providing the complexity of the tasks involved, which demonstrates how limited the manual action outside of the control room is; a description of the environmental conditions expected; a discussion of the ingress/egress paths taken by the operators to complete the manual action; a description of the existing procedures and training associated with the manual action; and the information required by the control room staff to determine whether such operator action is required.

The NRC staff finds the justifications suitable, consistent with RSB Technical Position 5-1 and RG 1.139, and thus acceptable.

3.3.5 Evaluation of Manual Action Conclusion The NRC staff reviewed the manual action included in the LAR. The staff confirmed that the manual action is low-risk, and therefore the staff conducted a Level 3 review, which focused on the proposed relaxation of the 1980 Order requiring that the action be taken within the control room. The staff found the justifications acceptable, and therefore, the staff concluded that there is no significant degradation in safety as a result of approving the LAR regarding human factors engineering.

3.4 Technical Evaluation Summary The NRC staff reviewed the licensees proposed relaxation of the 1980 Order for ANO-1 and proposed corresponding change to section 4.2.4.4 of the ANO-1 SAR to allow manual actions outside the control room to restore emergency power to the pressurizer heaters. The staff finds that the proposed change satisfies the applicable positions of NUREG-0578, Appendix A, section 3.1 and that there is no significant degradation in safety as a result of the proposed change regarding human factors engineering. Therefore, the staff concludes that the proposed change does not impact the licensees continued compliance with 10 CFR Part 50, Appendix A, GDCs 17 and 19.

3.5 Good Cause Evaluation By supplemental letter dated April 8, 2025, the licensee provided its good cause justification by referring to and summarizing the justification for the proposed change in the LAR. As the NRC staff has found the LAR acceptable as described in sections 3.2 through 3.4 of this safety 2 RG 1.139 was withdrawn by Federal Register notice (FRN) dated June 10, 2008 (73 FR 32750). The notice states, in part, The withdrawal of Regulatory Guide 1.139 does not, in and of itself, alter any prior or existing licensing commitments based on its use.

evaluation, the NRC staff similarly finds that the licensee has shown good cause for the relaxation of the 1980 Order as described in the LAR, as supplemented by letters dated February 26, 2025, and April 8, 2025.

4.0 STATE CONSULTATION

In accordance with the Commissions regulations, the Arkansas State official was notified of the proposed issuance of the amendment on July 9, 2025. The State official had no comments.

5.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to the 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 amendment involves no significant hazards consideration published in the Federal Register on December 23, 2024 (89 FR 104571), and there has been no public comment on such finding. 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 needs to 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: Adakou Foli, NRR Kamishan Martin, NRR Date: July 30, 2025

Package: ML25192A193 Relaxation Letter: ML25192A201 Amendment: ML25188A184

• via eConcurrence NRR-058 OFFICE NRR/DORL/LPL2-2/PM*

NRR/DORL/LPL4/LA*

NRR/DEX/EEEB/BC NAME DGalvin PBlechman WMorton DATE 7/7/2025 7/10/2025 5/14/2025 OFFICE NRR/DRO/IOLB/HFT/TL OGC - NLO*

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NAME ADAgostino JWachutka TNakanishi DATE 5/14/2025 7/21/2025 7/30/2025 OFFICE NRR/DORL/LPL4/PM*

NAME HMcLatchie (DGalvin for)

DATE 7/30/2025