ML25029A006
| ML25029A006 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 01/28/2025 |
| From: | Dennis Galvin NRC/NRR/DORL/LPL4 |
| To: | Keele R Entergy Nuclear Operations |
| References | |
| L-2024-LLA-0092 | |
| Download: ML25029A006 (5) | |
Text
From:
Dennis Galvin Sent:
Tuesday, January 28, 2025 6:37 PM To:
Riley Keele, Jr. (rkeele@entergy.com)
Cc:
Subject:
Arkansas Nuclear 1 - Request for Additional Information - Request for Review and Approval Changes to SAR and to a Confirmatory Order - PZR HTR Emergency Power Supply (EPID L-2024-LLA-0092)
Attachments:
ANO LAR Pressurizer Heater RAIs Issued 2025-01-28.pdf
Dear Mr. Keele,
By application dated July 2, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML24184B775), Entergy Operation, Inc. (Entergy, the licensee) requested an amendment to the Renewed Facility Operating License Number DPR-51 for Arkansas Nuclear One, Unit 1 (ANO-1). The proposed changes would modify the ANO-1 Safety Analysis Report (SAR) and the Confirmatory Order to implement all Category A lessons learned requirements by January 31, 1980, for ANO-1. The proposed changes would add to the SAR and the confirmatory order statements for performing manual actions at 120 VAC instrument panels Y01 and Y02 outside the control room to restore power to the pressurizer low-low level interlock.
The Nuclear Regulatory Commission (NRC) staff has determined that additional information is needed to complete its review. The requests for additional information (RAIs) were transmitted to the licensee in draft form on December 12, 2024. A clarification call was held with your staff on January 15, 2025, and the licensee agreed to provide responses to the RAls by February 27, 2025. The NRC staff agrees with this date.
Sincerely, Dennis Galvin Project Manager U.S Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Division of New and Renewed Licenses New Reactor Licensing Branch 301-415-6256
Hearing Identifier:
NRR_DRMA Email Number:
2712 Mail Envelope Properties (SA1PR09MB81113C2BF62B5010201607E8FBEF2)
Subject:
Arkansas Nuclear 1 - Request for Additional Information - Request for Review and Approval Changes to SAR and to a Confirmatory Order - PZR HTR Emergency Power Supply (EPID L-2024-LLA-0092)
Sent Date:
1/28/2025 6:36:52 PM Received Date:
1/28/2025 6:36:00 PM From:
Dennis Galvin Created By:
Dennis.Galvin@nrc.gov Recipients:
"Tony Nakanishi" <Tony.Nakanishi@nrc.gov>
Tracking Status: None "Riley Keele, Jr. (rkeele@entergy.com)" <rkeele@entergy.com>
Tracking Status: None Post Office:
SA1PR09MB8111.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 1381 1/28/2025 6:36:00 PM ANO LAR Pressurizer Heater RAIs Issued 2025-01-28.pdf 279464 Options Priority:
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1 REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST FOR REVIEW AND APPROVAL CHANGES TO SAR AND TO A CONFIRMATORY ORDER - PRESSURIZER HEATER EMERGENCY POWER SUPPLY ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT 1 DOCKET NO. 05000313
=
Background===
By application dated July 2, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML24184B775 Entergy Operations, Inc. (Entergy, the licensee) requested an amendment to the Renewed Facility Operating License Number DPR-51 for Arkansas Nuclear One, Unit 1 (ANO-1). The proposed changes would modify the ANO-1 Safety Analysis Report (SAR) and the Confirmatory Order to implement all Category A lessons learned requirements by January 31, 1980, for ANO-1. The proposed changes would add to the SAR and the confirmatory order statements for performing manual actions at 120 VAC instrument panels Y01 and Y02 outside the control room to restore power to the pressurizer low-low level interlock.
ANO-1 SAR section 4.2.4.4, Pressurizer Heaters, states Each diesel generator [DG]
emergency bus supplies emergency power to 168 kW [kilowatts] of pressurizer heaters. Two separate sets of heaters totaling 84 kW each are supplied by the diesel generators. The remaining 84 kW is powered from a swing bus which can be supplied by either diesel generator.
This ensures emergency power redundancy to sufficient heater capacity to establish and maintain pressure control at hot standby during a loss of offsite power [LOOP].
ANO-1 SAR, section 8.3.1.1.4, 480-Volt Auxiliary System, states As a result of NUREG-0578, Item 2.1.1, an additional 42 kW of pressurizer heater capacity was added. These heaters are powered from the 480-volt swing bus using a safety grade breaker.
Technical Specification (TS) 3.4.9, Pressurizer, Limiting Condition of Operation (LCO) requires a minimum of 126 kW of Engineered Safeguards (ES) bus powered pressurizer heaters to be operable in Modes 1-3.
Regulatory Basis The staff applied the following NRC regulations to review the license amendment request (LAR):
Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix A, 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 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
2 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.
The staff used the following NRC guidance to review the LAR:
NUREG-0737, Clarification of TMI Action Plan Requirements," section II.E.3.1, Emergency Power Supply for Pressurizer Heaters, provides positions and clarifications to the recommendations in section 2.1.1 of NUREG-0578. The positions and clarifications NUREG-0737, section II.E.3.1 are as follows:
Positions Consistent with satisfying the requirements of General Design Criteria 10 ["Reactor design"], 14
["Reactor coolant pressure boundary"], 15 [Reactor coolant system design"], 17 ["Electric power systems"], and 20 ["Protection systems functions"] of Appendix A to 10 CFR Part 50 for the event of loss of offsite power, the following positions shall be implemented:
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.
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.
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.
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-0737, section II.E.3.1provides the following clarifications to the recommendations in section 2.1.1 of NUREG-0578.
Clarifications:
(1) Redundant heater capacity must be provided, and 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 concurrently with the loads required for loss-of-coolant accident.
3 (4) Any changeover of the heaters from normal offsite power to emergency onsite power is to be accomplished manually in the control room.
(5) In establishing procedure to manually load the pressurizer heaters onto the emergency power sources, careful consideration must be given to:
(a) which ESF loads may be appropriately shed for a given situation.
(b) reset of the safety injection actuation signal to permit the operation of the heaters; and (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 (see also Regulatory Guide 1.75).
(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).
Issue:
In the LAR, the staff notes that the 84-kW of pressurizer heaters on the swing bus, which includes the remaining 42-kW for a redundant group of heaters, and the pressurizer low-low level interlock, which permits the operation of the heaters, have access to both DGs even if its not simultaneously. Also, if the 480-volt swing bus or the 120-volt bus feeding the low-low level interlock fails, the required 126-kW pressurizer heater capacity in each redundant group would not be available. Furthermore, it appears that the safety classification of the circuit breakers used to power the pressurizers from the trains 480-volt buses and the low-low level interlock from the 12-volt bus Y02 are not provided in the SAR.
Question 1
- 1. Explain how a redundant group of pressurizer heaters that consist of 84 kW on a train and 42 KW on the swing bus has access to only one Class 1E division power supply that satisfies NUREG-0737, section II.E.3.1, clarifications (1) and (2).
- 2. 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 480-volt buses and 120-volt Y2 to satisfy NUREG-0737, section II.E.3.1, clarification (6).