L-2025-163, Supplement to RAI Response to Requests for Additional Information (Rais) Regarding Seabrook License Amendment Requests to Adopt TSTF-505, Revision 2, Provide Risk Informed Extended Completion Times - RITSTF Initiative 4b, and 10 CFR 50.69
| ML25262A006 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  (NPF-086) |
| Issue date: | 09/18/2025 |
| From: | Mack K NextEra Energy Seabrook |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2025-163 | |
| Download: ML25262A006 (1) | |
Text
NEXTera'"
EN~
U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington D C 20555-0001 RE: Seabrook Station Docket No. 50-443 Renewed Facility Operating License No. NPF-86 L-2025-163 10 CFR 50.90 September 18, 2025 Supplement to RAI Response to Requests for Additional Information (RAls) Regarding Seabrook License Amendment Requests to Adopt TSTF-505, Revision 2, "Provide Risk Informed Extended Completion Times - RITSTF Initiative 4b", and 10 CFR 50.69, "Risk-informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors"
References:
- 1.
NextEra Energy Seabrook, LLC, letter L-2025-015, License Amendment Request 25-01, Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, "Provide Risk Informed Extended Completion Times - RITSTF Initiative 4b", February 3, 2025 (ADAMS Accession No. ML25034A143)
- 2.
NextEra Energy Seabrook, LLC, letter L-2025-041, Application to Adopt 10 CFR 50.69, "Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors" March 21, 2025 (ADAMS Accession No. ML25080A172)
- 3.
NextEra Energy Seabrook, LLC, letter L-2025-149, Response to Requests for Additional Information Regarding Seabrook License Amendment Requests to Adopt TSTF-505, Revision 2, "Provide Risk Informed Extended Completion Times - RITSTF Initiative 4b", and 10 CFR 50.69, "Risk-informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors" September 5, 2025 (ADAMS Accession No. ML25251A063)
- 4.
U.S. Nuclear Regulatory Commission electronic memorandum dated August 7, 2025, Seabrook Station, Unit 1 - Request for Additional Information re: License Amendment Requests to Adopt TSTF-505 and Provisions of 10 CFR 50.69 (EPID L-2025-LLA-0025, L-2025-LLA-0058) (ADAMS Accession No. ML25219A763)
In References 1 and 2, NextEra Energy Seabrook, LLC (NextEra) requested amendments to Renewed Facility Operating License NPF-86 for Seabrook Station Unit 1 (Seabrook). The proposed amendments would adopt Technical Specifications Task Force Traveler 505 (TSTF-505), Revision 2, "Provide Risk-informed Extended Completion Times, RITSTF Initiative 4b" (ADAMS Accession No. ML18253A085), and the provisions of Title 10 of the Code of Federal Regulations (10 CFR), Section 50.69, "Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors."
In Reference 3, NextEra responded to the NRC requests for additional information (RAls) provided in Reference 4.
Subsequent to the Reference 3 submittal, NextEra identified a need to revise its responses to RAl-18 (EEEB 505-01) and RAl-19 (EEEB 505-02) of Reference 4. The enclosure to this letter provides the revised RAI responses. No changes are proposed to the TS and TS Bases markup pages provided in Reference 1 as supplemented by Reference 3.
The information in this RAI response provides additional information that clarifies the application, does not expand the scope of the application as originally noticed, and should not change the NRC staff's originally proposed notice of determination of no significant hazards as published in the Federal Register.
NextEra Energy Seabrook, LLC P.O. Box 300, Lafayette Road, Seabrook, NH 03874
Seabrook Station Docket No. 50-443 This letter contains no regulatory commitments.
L-2025-163 Page 2 of2 Should you have any questions regarding this submission, please contact Ms. Maribel Valdez, Fleet Licensing Manager, at 561-904-5164.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on the 181h day of September 2025 Ke~
Director, Licensing and Regulatory Compliance
Enclosure:
Revised Responses to RAl-18 (EEEB 505-01) and RAl-19 (EEEB 505-02) cc:
USNRC Region I Administrator USNRC Project Manager USNRC Senior Resident Inspector Director Homeland Security and Emergency Management New Hampshire Department of Safety Division of Homeland Security and Emergency Management Bureau of Emergency Management 33 Hazen Drive Concord, NH 03305 Kimberly Castle, Technological Hazards Supervisor The Commonwealth of Massachusetts Emergency Management Agency 400 Worcester Road Framingham, MA 01702-5399
Seabrook Station Docket No. 50-443 Revised Responses to RAl-18 (EEEB 505-01) and RAl-19 (EEEB 505-02}
L-2025-163 Enclosure Page 1 of6 In References 1 and 2, NextEra Energy Seabrook, LLC (NextEra) requested amendments to Renewed Facility Operating License NPF-86 for Seabrook Station Unit 1 (Seabrook). The proposed amendments would adopt Technical Specifications Task Force Traveler 505 (TSTF-505), Revision 2, "Provide Risk-informed Extended Completion Times, RITSTF Initiative 4b" (ADAMS Accession No. ML18253A085), and the provisions of Title 10 of the Code of Federal Regulations (10 CFR), Section 50.69, "Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors."
In Reference 3, NextEra responded to the NRC's requests for additional information (RAls) provided in Reference 4.
Subsequent to the Reference 3 submittal, NextEra identified the need to revise its responses to RAl-18 (EEEB 505-01) and RAl-19 (EEEB 505-02) of Reference 4, as indicated below. No changes are proposed to the TS and TS Bases markup pages provided in Reference 1 as supplemented by Reference 3.
RAl-18 (EEEB 505-01) - TS LCO 3.8.2.1, Action a 10 CFR Appendix A, General Design Criterion (GDC) 17 requires, in part, that both offsite and onsite electrical power systems be provided to permit the functioning of systems, structures, and components (SSCs) important to safety. The safety function for each system, assuming other is not functioning, assures fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded, and the core is cooled, and containment integrity and other vital functions are maintained for postulated accidents.
LCO 3.8.2.1.a. and b., indicates there are two trains for direct current (de) electrical sources-Each train, A and B, have two battery banks and two battery chargers with only one battery bank and two chargers per train required to be operable. LCO 3.8.2.1, Action a. is for the inoperability of one of two battery banks in one train.
UFSAR Section 8.3.2.1 reveals that the 125 Vdc power system has battery chargers, station batteries, and the 125 Vdc distribution system. Each battery charger supplies steady-state loads with its battery being for transient loads and the reserve power source for charger failure in some way. There are four batteries (battery banks) for the Seabrook single unit plant. Each battery and thus each charger supplies a Class 1 E de bus which powers: inverter for a singular vital instrument bus; Class 1 E de loads; and controls for Class 1 E systems for Engineered Safety Features (ESF). UFSAR Section 8.3.2.1.d. states each battery, battery charger and their loads comprise a single load group with each train having two load groups. USFAR Section 8.3.1.1.d. indicates that 120V Instrumentation and Control Power System powers four vital uninterruptible power supply (UPS) units to supply nuclear steam supply system (NSSS) instrument channels I, II, Ill, and IV. The inverters, supplied by the four batteries for Seabrook plant, are the same four vital UPS units.
UFSAR Table 8.3-3 shows that channels I and Ill are for train A and channels II and IV are for Train B.
UFSAR Section 7.1.2.3 indicates that there are four separate protection sets (channels) I, II, Ill, and IV.
UFSAR Table 7.3-1 indicates that most ESF elements require two of the four channels to trip for safe shutdown - channels I and Ill or II and IV. Each NSSS instrument channel is powered by a de load group which means that two load groups from one train are necessary for safe shutdown.
The staff notes the following for DSC for TS LCO 3.8.2.1, Action a, in Table E1-1 of the LAR:
a) DSC appears inconsistent with UFSAR since DSC indicates that a battery "always" assists its charger during an accident, but the UFSAR states that battery and charger for each redundant load group "may" address an accident together "only" if accident loads exceed charger full amperage output rating.
Please clarify or explain this inconsistency.
Seabrook Station Docket No. 50-443 Revised Responses to RAl-18 (EEEB 505-01) and RAl-19 fEEEB 505-02)
L-2025-163 Enclosure Page 2 of6 b) Table E1-1 provides DSC and PRA success criteria for each LCO Action for the rated OBA for Seabrook which is a concurrent loss of coolant accident (LOCA) and loss of offsite power (LOO ). Please clarify for this DSC whether PRA model assumes a battery operates for that OBA and, if so, under what conditions will that happen?
c)
DSC typically indicates minimum SSCs required to operate for safe shutdown for OBA, The DSC for TS LCO 3.8.2.1, Action a seems only to indicate one de load group of one train for safe shutdown, which corresponds to one NSSS instrument channel while UFSAR indicates that two NSSS channels from one train are required for safe shutdown. Please clarify and explain the discrepancy between the DSC and UFSAR.
NextEra Response to RAl-18 (revised) a) The Design Success Criteria (DSC) for TS LCO 3.8.2.1, ACTIONS a and b, require correction to state, "One available DC electrical train, consisting of one battery bank, two battery chargers and two DC distribution buses". The correction reflects that each DC train consists of two DC load groups, with each load group comprised of one full-capacity battery, one battery charger, and one DC distribution bus. However, only one battery is necessary to carry the required DC loads under all plant conditions should power to either battery charger be lost. A correction to Table E1-1 of Reference 1 revising the DSCs for TS LCO 3.8.2.1, ACTIONS a and b, is provided further below.
Any transient emergency peak DC loads are adequately carried by the charger with assistance from the battery should the transient loads exceed the charger full-load output capability. Any inference in the LAR that the battery must assist the associated charger in fulfilling the DC power requirements during a design basis accident was unintentional.
b) The safety-related portion of the Seabrook 125-volt DC electrical power system consists of four 125 volt batteries, chargers and DC buses separated into two redundant trains, each with two distribution subsystems. The loads supplied from the DC buses include inverters for redundant vital instrument buses, diesel generator controls, and distribution panels for the control and operation of Class 1 E systems including the emergency AC power system and Engineered Safety Features. Each safety-related battery is sized to have sufficient capacity to serve as the source for the two load groups of the same train during the period when the other battery in the train is out of service. With a loss of AC power to the charger, each battery is sized to supply all required DC loads for a minimum of two hours. The two-hour duration is consistent with Regulatory Guide 1.93 guidelines and reflects a reasonable time to assess unit status and effect an orderly shutdown.
The accident analyses summarized in UFSAR Chapter 15 assume restoration of emergency AC power by the standby diesel generators. Upon loss of offsite power, the battery chargers are tripped off and the system batteries carry the DC loads until the diesel generator is successfully started and the emergency power sequence (EPS) cycle is completed. During this time, the batteries provide power for the DC load groups, vital control and instrumentation systems required to maintain equipment operating status, start of the diesel generators, and completion of the automatic sequencing of loads onto the diesel generator. The emergency power sequencing scheme is designed to be completed within two minutes after the undervoltage is sensed, including restoration of AC power to the chargers. Any transient emergency peak loads are adequately carried with assistance from the battery should these loads exceed the charger full-load output capability.
The 125-volt DC electrical power system also provides the power source to cope with and recover from a station blackout (SBO) within a specified time frame. Load shedding is not required to meet the SBO four-hour coping duration criteria for all battery/bus combinations.
c) As stated above, the DSCs for TS LCO 3.8.2.1, ACTIONS a and b, required correction to state, "One available DC electrical train, consisting of one battery bank, two battery chargers and two DC
Seabrook Station Docket No. 50-443 Revised Responses to RAl-18 {EEEB 505-01) and RAl-19 (EEEB 505-02)
L-2025-163 Enclosure Page 3 of6 distribution buses". The correction reflects that each DC train consists of two DC load groups, with each load group comprised of one full-capacity battery, one battery charger, and one DC distribution bus. However, only one battery is necessary to carry the required DC loads under all plant conditions should power to either battery charger be lost. A correction to Table E1-1 of Reference 1 revising the DSCs for TS LCO 3.8.2.1, ACTIONS a and b, is provided further below.
RAl-19 tEEEB 505-02) - JS Leo 3,8,3,1, Actjon c.
GDC 17 requires, in part, that both offsite and onsite electrical power systems be provided to permit the functioning of systems, structures, and components (SSCs) important to safety. The safety function for each system, assuming other is not functioning, assures fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded, and the core is cooled, and containment integrity and other vital functions are maintained for postulated accidents.
UFSAR Section 8.3.2.1 reveals that the 125 Vdc power system has two trains with each having two battery chargers, two station batteries, and 125 Vdc distribution systems. Each battery charger supplies steady-state loads with its battery being for transient loads and reserve power source for charger failure. There are four batteries (battery banks) for the Seabrook single unit plant. Each battery and thus each charger supplies a Class 1 E de bus which powers: inverter for a singular vital instrument bus; Class 1 E de loads; and controls for Class 1 E systems for Engineered Safety Features (ESF). UFSAR Section 8.3.2.1.d. states each battery, battery charger, and their loads are a load group with each train having two load groups.
US FAR Section 8.3.1.1.d. indicates that 120V Instrumentation and Control Power System powers four vital uninterruptible power supply (UPS) units which supply NSSS instrument channels I, II, II, and IV. The inverters supplied by the four batteries for Seabrook plant are the same four vital UPS units. UFSAR Table 8.3-3 shows that channels I and Ill are for train A and channels II and IV are for Train B. UFSAR Section 7.1.2.3 indicates that there are four separate protection sets (channels) I, II, Ill, and IV. UFSAR Table 7.3-1 indicates that most ESF trip functions require two of four channels to trip - channels I and Ill or II and IV.
The staff notes the following for DSC for TS LCO 3.8.3.1, Action C, in Table E1-1 of the LAR:
DSC appears inconsistent with the UFSAR which requires two energized de buses to power two NSSS instrument channels from one train for safe shutdown whereas the DSC only requires one energized de bus. Please clarify or explain the inconsistency.
NextEra Response to RAl-19 {revised)
The DSC for TS 3.8.2, ACTION c, required correction to state, "One available DC electrical train, consisting of one battery bank, two battery chargers and two DC distribution buses". The correction reflects that each DC train consists of two DC load groups, with each load group comprised of one full-capacity battery, one battery charger, and one DC distribution bus. However, only one battery is necessary to carry the required DC loads under all plant conditions should power to either battery charger be lost. A correction to Table E1-1 of Reference 1 revising the DSC for TS LCO 3.8.3.1, ACTION c, is provided below.
Seabrook Station Docket No. 50-443 Required ACTION Condition Description Revised Responses to RAl-18 (EEEB 505-01) and RAl-19 <EEEB 505-02)
Table E1 List of Revised Required ACTIONs to Corresponding PRA Functions (revised)
PRA Design Success PRASuccess Applicable SSCs SSC Function(s)
Modeled Criteria Criteria TS 3.8.2.1 D.C. SOURCES - OPERA TING Ensure that:
(1) the facility can be maintained in the QF/9 Felifl,JiFee: sa#e,:;c shutdown or ea,:* aR.J_assee,iate.l Train A:
refueling ie#,4' ea,,aei~, eRa,'f}e1r.
ACTION a 125-volt Battery condition for iR oRe e,leetFiea/ traiR Bank 1A or 1C extended time One available DC One or two required periods and Yes electrical train, Same as DSC battery bank(s) in one Train B:
consisting_ of one train inoperable 125-volt Battery (2) sufficient batte~ bank, two Bank 18 or 1D instrumentation batte~ chargers and control andtwoDC capability is distribution buses available for monitoring and maintaining the unit status.
Train A:
Ensure that:
One full-capacity
( 1) the facility QRe Fefif.;iFee: sa#e,:;,
battery charger on can be saR~~ aR.l_asse@iate.l Bus #11A, and maintained in the f:el,~( ea,aaeii~~ eRe,'§e1r; ACTIONb One full-capacity shutdown or IR eRe s/eek:feal F:caiR One or two full capacity battery charger on refueling One available DC Bus#11C.
Yes electrical train, Same as DSC charger(s) in one train condition for consisting_ of one inoperable extended time Train B:
periods and batte~ bank, two One full-capacity batte~ chargers battery charger on
- 2) sufficient andtwoDC Bus #11 B, and instrumentation distribution buses One full-capacity and control L-2025-163 Enclosure Page 4 of6 Comments
Seabrook Station Docket No. 50-443 Required ACTION Condition Description Revised Responses to RAl-18 (EEEB 505-01) and RAl-19 lEEEB 505-02}
Table E1 List of Revised Required ACTIONs to Corresponding PRA Functions (revised)
PRA Design Success PRASuccess Applicable SSCs SSC Function(s)
Modeled Criteria Criteria battery charger on capability is Bus #11 D available for monitoring and maintaining the unit status.
TS 3.8.3.1 ONSITE POWER DISTRIBUTION - OPERA TING Train A, 125-volt D.C.
Busses consisting of:
- 1) 125-volt D.C. Bus
- 11A energized from Battery Bank 1A or 1C QRe lJ. S. Bl:#6
- 2) 125-volt D.C. Bus 9R9~~9EJ. °ffelfi i~
- 11 C energized Provide asseeiateEI Ba~e.,,
ACTION c from Battery Bank instrument and BaRlf 1C or 1A.
One available DC One D.C. bus not control power Yes electrical train, Same as DSC energized from an Train B, 125-volt D.C.
supplies to SSCs consisting_ of one OPERABLE battery bank Susses consisting of:
important to batte!)!. bank, two safety batte!)!. charg_ers
- 1) 125-volt D.C. Bus andtwoDC
- 11 B energized distribution buses from Battery Bank 1B or 1D 125-volt D.C. Bus
- 11 D energized from Battery Bank 1D or 1B.
L-2025-163 Enclosure Page 5 of 6 Comments
Seabrook Station Docket No. 50-443 Revised Responses to RAl-18 (EEEB 505-01) and RAl-19 fEEEB 505-02}
References:
L-2025-163 Enclosure Page 6 of6
- 1.
NextEra Energy Seabrook, LLC, letter L-2025-015, License Amendment Request 25-01, Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, "Provide Risk Informed Extended Completion Times - RITSTF Initiative 4b", February 3, 2025 (ADAMS Accession No. ML25034A143)
- 2.
NextEra Energy Seabrook, LLC, letter L-2025-041, Application to Adopt 10 CFR 50.69, "Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors" March 21, 2025 (ADAMS Accession No. ML25080A172)
- 3.
NextEra Energy Seabrook, LLC, letter L-2025-149, Response to Requests for Additional Information Regarding Seabrook License Amendment Requests to Adopt TSTF-505, Revision 2, "Provide Risk Informed Extended Completion Times - RITSTF Initiative 4b", and 10 CFR 50.69, "Risk-informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors" September 5, 2025 (ADAMS Accession No. ML25251A063)
- 4.
U.S. Nuclear Regulatory Commission electronic memorandum dated August 7, 2025, Seabrook Station, Unit 1 - Request for Additional Information re: License Amendment Requests to Adopt TSTF-505 and Provisions of 10 CFR 50.69 (EPID L-2025-LLA-0025, L-2025-LLA-0058) (ADAMS Accession No. ML25219A763)