L-2025-087, License Amendment Request 25-03, Revise Technical Specifications Bases 3/4.8.1 Ac. Sources - Operating to Align with Regulatory Guide 1.93, Revision 1

From kanterella
(Redirected from ML25143A163)
Jump to navigation Jump to search

License Amendment Request 25-03, Revise Technical Specifications Bases 3/4.8.1 Ac. Sources - Operating to Align with Regulatory Guide 1.93, Revision 1
ML25143A163
Person / Time
Site: Seabrook NextEra Energy icon.png
Issue date: 05/23/2025
From: Mack K
NextEra Energy Seabrook
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
L-2025-087
Download: ML25143A163 (1)
v • d • e


Text

{{#Wiki_filter:NEXTera' EN~ Attn: Document Control Desk U.S. Nuclear Regulatory Commission Washington DC 20555-0001 RE: Seabrook Station Docket No. 50-443 Renewed Facility Operating License No. NPF-86 May 23, 2025 L-2025-087 10 CFR 50.90 License Amendment Request 25-03, Revise Technical Specifications Bases 3/4.8.1 "AC. Sources - Operating" to Align with Regulatory Guide 1.93, Revision 1

Reference:

Regulatory Guide 1.93, Availability of Electric Power Sources, Revision 1, March 2012 (ADAMS Accession No. ML003740292) Pursuant to 10 CFR 50.90, NextEra Energy Seabrook, LLC (NextEra) hereby requests an amendment to Renewed Facility Operating License NPF-86 for Seabrook Station Unit 1 (Seabrook). The proposed license amendment would modify the Seabrook licensing basis by revising Technical Specifications (TS) Bases 3/4.8.1, AC. Sources - Operating, to align with the available AC power source guidelines of Regulatory Guide (RG) 1.93. Specifically, changes are proposed to the applicability of select TS 3.8.1 ACTIONS associated with Unit Auxiliary Transformer (UAT) and Reserve Auxiliary Transformer (RAT) unavailability. The enclosure to this letter provides an evaluation of the proposed change. The Attachment to the enclosure provides the existing TS Bases pages marked up to show the proposed change. The TS Bases markups are provided for information only and will be incorporated in accordance with the Seabrook TS Bases Control Program upon implementation of the approved license amendments. NextEra has determined that the proposed change does not involve a significant hazards consideration pursuant to 10 CFR 50.92(c), and there are no significant environmental impacts associated with the change. The Seabrook Onsite Review Group (ORG) has reviewed the proposed license amendment. In accordance with 10 CFR 50.91, a copy of this application, with attachments, is being provided to the designated New Hampshire official. NextEra requests that the proposed change is processed as a normal license amendment request, with approval within one year of receipt. Once approved, the amendment shall be implemented within 90 days. This letter contains no new or revised regulatory commitments. 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 23rd day of May 2025, Ke~~ Director, Licensing and Regulatory Compliance NextEra Energy Seabrook, LLC P.O. Box 300, Lafayette Road, Seabrook, NH 03874

Seabrook Station Docket No. 50-443

Enclosure:

Seabrook License Amendment Request (LAR) 25-03 Attachments:

1.

Proposed Technical Specification Bases Changes (mark-up) 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 L-2025-087 Page 2 of 2

Seabrook Nuclear Station Docket No. 50-443 Description and Assessment Seabrook Station License Amendment Request 25-03, Revise Technical Specifications Bases 3/4.8.1 "AC. Sources - Operating" to Align with Regulatory Guide 1.93, Revision 1 L-2025-087 Enclosure Page 1 of 12 1.0

SUMMARY

DESCRIPTION................................................................................................................. 2 2.0 DETAILED DESCRIPTION................................................................................................................. 2 2.1 System Design and Operation................................................................................................ 2 2.2 Current Requirements............................................................................................................. 3 2.3 Description of the Proposed Changes..................................................................................4 2.4 Reason for the Proposed Change.......................................................................................... 5

3.0 TECHNICAL EVALUATION

................................................................................................................ 5

4.0 REGULATORY EVALUATION

........................................................................................................... 9 4.1 Applicable Regulatory Requirements Criteria...................................................................... 9 4.2 No Significant Hazards Consideration Analysis................................................................ 10 4.3 Conclusion............................................................................................................................. 11

5.0 ENVIRONMENTAL CONSIDERATION

............................................................................................ 11

6.0 REFERENCES

.................................................................................................................................. 12 ATTACHMENT:

1.

Proposed Technical Specification Bases Changes (marked up)

Seabrook Nuclear Station Docket Nos. 50-443 1.0

SUMMARY

DESCRIPTION L-2025-087 Enclosure Page 2 of 12 NextEra Energy Seabrook, LLC (NextEra) requests an amendment to Renewed Facility Operating License NPF-86 for Seabrook Station Unit 1 (Seabrook). The proposed license amendment would modify the Seabrook licensing basis by revising Technical Specifications (TS) Bases 3/4.8.1, A.C. Sources - Operating, to align with the available AC power source guidelines of Regulatory Guide (RG) 1.93. Specifically, changes are proposed to the applicability of select TS 3.8.1 ACTIONS associated with Unit Auxiliary Transformer (UAT) and Reserve Auxiliary Transformer (RAT) unavailability. 2.0 DETAILED DESCRIPTION 2.1 System Design and Operation The Seabrook switchyard is connected to the transmission grid via three electrically and structurally independent 345 kV transmission lines that are terminated at separate terminating structures. The 345kV switchyard includes two metal-enclosed SFe gas-insulated buses (345kV switchyard buses #5 and #6). A double-breaker scheme connects switchyard bus #6 to the high voltage terminals of the unit generator step-up transformers (GSUs) via a SFe gas-insulated circuit. The GSU transformers are connected to the main generator circuit breaker via isolated phase bus ducts. Two-unit auxiliary transformers (UATs) are tapped off the isolated phase bus ducts. When the generator circuit breaker is tripped, the UATs provide power for all the engineered safety features (ESF) loads of the unit via an immediate access circuit from the preferred offsite power supply, 345kV switchyard bus #6, to the onsite distribution system without additional circuit breaker action. Two reserve auxiliary transformers (RATs) are also available to provide a second immediate access circuit from the 345kV switchyard to the onsite electrical distribution system. A breaker-and-a-half scheme connects the high voltage terminals via a SFe gas-insulated circuit from 345kV switchyard bus #5 to the onsite distribution system, providing available power for all loads including all the engineered safety features loads. Each UAT and each RAT have the capacity to supply the requisite electrical power to all onsite Class 1 E equipment under all plant conditions. UAT-2A 345 KV BUS "#6 OFFSITE TRANSMISSION NETWORK UAT-28 345 KVBUS#5 OFFSITE TRANSMISSION NETWORK RAT-38 r /";c; ;-:;;;;:;; f - - - - - ;S~;: ;;N-; -1 ll tl I I

6)

SAFE,-{, LOADS G) SAFETY LOADS I I EDG-1A EDG-18 I !.. ____.Q.N]!1s £!:J\\2.S_l~l2,_TB!_BQT!Q"i§'!§!§~ ____ J EOG* emergency diesel generator UAT. unit auxiliary transformer RAT* reserve auxiliary transformer The UATs and RATs provide physically independent offsite power circuits to the onsite 13.8 kV electrical circuits and the 4.16 kV electrical circuits, including the Class 1 E engineered safety features (ESF) buses, E5 and E6. Each onsite electrical circuit is normally aligned to receive power via a UAT with its associated

Seabrook Nuclear Station Docket Nos. 50-443 L-2025-087 Enclosure Page 3 of 12 RAT in standby. Since both UATs share a single switchyard connection via preferred offsite power supply, 345kV switchyard bus #6, a single failure in the shared section between the switchyard and the UATs could result in the loss of both UATs. Similarly, both RATs share a single connection to 345kV switchyard bus

  1. 5 such that a single failure in the shared section between the switchyard and the RATs could result in the loss of both RATs. With each onsite circuit normally supplied by its associated UAT, the RAT will automatically align and power the corresponding onsite circuit via a synchronism-checked fast transfer scheme should the incoming breaker of the respective UAT open either manually or automatically. If, however, the RAT is already aligned to supply power to the onsite circuit and the UAT is in standby, there is no fast transfer scheme to re-align the UA T to the affected onsite circuit if the respective RAT becomes unavailable. Instead, control room operator action would be required. The connections from the UAT and RAT transformers to the onsite distribution system are made with separate, nonsegregated phase bus ducts which provide the necessary separation to minimize the likelihood of simultaneous failure to the extent practical. Moreover, redundant protective relaying systems and utilization of a breaker-and-a-half switching station minimize the likelihood of a single failure causing the loss of more than a single circuit.

In Licensee Event Report (LER) 2005-004 (Reference 6.2), NextEra reported in accordance with 10 CFR 50.73(a)(2)(i)(B), the failure to enter TS 3.8.1.1, ACTION (a) for an inoperable RAT. In response to the TS violation, the Seabrook TS Bases was revised to establish operability requirements for the UATs and RA Ts, including operability requirements associated with the fast-transfer capability between the UA Ts and RA Ts. No physical changes to the offsite AC electrical system were undertaken as a result of the TS violation. 2.2 Current Requirements Key descriptions and requirements from the Seabrook current licensing bases (CLB) as applicable to the offsite sources are listed below. TS 3/4.8.1 AC Sources - Operating LIMITING CONDITION FOR OPERATION 3.8.1.1 As a minimum, the following AC. electrical power sources shall be OPERABLE:

a.

Two physically independent circuits between the offsite transmission network and the onsite Class 1 E Distribution System, and... TS Bases 3/4.8.1, AC Sources APPLICABLE SAFETY ANALYSES The OPERABILITY of the AC electrical power sources is consistent with the initial assumptions of the Accident analyses and is based upon meeting the design basis of the unit. This results in maintaining at least one train of the onsite or off site AC sources operable during Accident conditions in the event of: o An assumed loss of all offsite or all onsite AC power and o A worst case single failure. LIMITING CONDITION FOR OPERATION (LCO) Two qualified circuits between the offsite transmission network and the onsite Class 1 E Electrical Power System and separate and independent EDGs for each train ensure availability of the

Seabrook Nuclear Station Docket Nos. 50-443 L-2025-087 Enclosure Page 4 of 12 required power to shut down the reactor and maintain it in a safe shutdown condition after an AOO or a postulated OBA [Note: The following TS Bases 3/4.8.1 discussion, added in response to the events described in Licensee Event Report (LER) 2005-004 (Reference 6.2), is proposed for deletion.] One of the required. independent offsite AC sources consists of the circuit from an offsite transmission line through the UA Ts to buses ES and E6. Operability requires both UA T breakers closed, energizing emergency buses. The second required independent off site AC source consists of the circuit from a separate off site transmission line through the RA Ts to buses ES and E6. Operability requires each RAT supply breaker be either (1) closed. or (2) in standby with capability for automatic closure. To meet the TS 3.8.1.1 requirements for two independent offsite sources, each emergency bus must (1) be energized from its UA T. and (2) have its RAT available via fast transfer capability. Otherwise. the appropriate action of TS 3.8.1.1 must be entered. Below are examples of the application of the TS to various configurations of the off site AC sources: o The offsite source via the UA Ts is operable when both buses ES and E6 are powered via the UATs. o The off site source via the RA Ts is operable when the RAT is the standby power supply for both buses ES and E6. and both buses have operable auto-transfer capability to the RAT. o With one emergency bus powered from a UA T with capability for auto transfer to the RAT. and the other bus powered from a RAT. the off site source via the UA T is inoperable. The source through the UA Tis not available via auto transfer on the bus that is energized from the RAT. (TS 3.8.1.1 action a is applicable). o With the UA T powering one emergency bus without auto transfer capability to the RAT coincident with the RAT powering the other emergency bus (no auto transfer from the RAT to the UAT exists). both offsite sources are inoperable. (TS 3.8.1.1 action e is applicable.) o With both emergency buses powered from the RATs, the offsite source via the UATs is inoperable since no auto transfer capability to the UATs exists. (TS 3.8.1.1 action a is applicable). 2.3 Description of the Proposed Changes The proposed change aligns TS Bases 3/4. 8.1 with the available AC power source guidelines of RG 1. 93, Revision 1, by deleting the Bases discussion added in response to the events described in LER 2005-004 (Reference 6.2), and inserting the Bases discussion proposed below: For the offsite AC sources. separation and independence are to the extent practical. A circuit may be connected to more than one ESF bus. with fast transfer capability to the other circuit OPERABLE. and not violate separation criteria. A circuit that is not connected to an ESF bus is required to have OPERABLE fast transfer capability to at least one ESF bus to support OPERABILITY of that circuit. Both offsite power circuits are designed to be connected or available via fast transfer to both ESF buses. As proposed, the operability of two physically independent circuits between the offsite transmission network and the onsite Class 1E Distribution System (i.e., LCO 3.8.1.1.a) is maintained with an inoperable UAT or RAT on one or both onsite electrical circuits provided each onsite electrical circuit is powered by physically independent offsite AC power sources.

Seabrook Nuclear Station Docket Nos. 50-443 2.4 Reason for the Proposed Change L-2025-087 Enclosure Page 5 of 12 The proposed change would provide the operational flexibility to conduct while online, UAT/RAT-related maintenance normally extending beyond the Completion Time (CT) allotted by TS 3/4.8.1, thereby reducing refueling outage work and eliminating future amendment requests for extended transformer outages.

3.0 TECHNICAL EVALUATION

3.1 TS Bases 3/4.8.1 Proposed Change In LER 2005-004, NextEra reported the failure to enter TS 3.8.1.1, ACTION (a) for an inoperable RAT which resulted in exceeding the specified 72-hour CT. NextEra's failure to recognize ACTION (a) applicability derived from a practice since initial plant startup of interpreting LCO 3.8.1.1.a to be satisfied with one offsite AC power source aligned to one Class 1 E onsite circuit and the other offsite AC power source aligned to the other Class 1 E onsite circuit. As a result of the TS violation, changes were made to the Seabrook TS Bases to establish conditions for UAT and RAT operability beyond what was previously understood to be the Seabrook licensing basis. Specifically, the TS Bases were revised to describe conditions of UAT and RAT unavailability that instructed entry into TS 3.8.1.1 ACTION (a) and ACTION (e). The proposed change deletes the Bases discussion added in response to the events described in LER 2005-004, and inserts the Bases discussion described in Section 2.3 of this amendment request, based on the regulatory guidance of RG 1.93, Revision 1 (Reference 6.1 ). RG 1.93, Revision 1 describes guidelines the Nuclear Regulatory Commission (NRC) considers acceptable for licensee response to the number of available electric power sources less than required by the limiting conditions for operation (LCO). Specifically, RG 1.93 establishes recommended TS ACTIONS for seven levels of power system degradation: Degradation-level 1 - The available offsite ac power sources are one less than the LCO. Degradation-level 2 - The available onsite ac power sources are one less than the LCO. Degradation-level 3 - The available offsite ac power sources are two less than the LCO. Degradation-level 4 - The available offsite and onsite ac power sources are each one less than the LCO. Degradation-level 5 - The available onsite ac power sources are two less than the LCO. Degradation-level 6 - The available onsite de power sources are one less than the LCO. Degradation-level 7 - The available inverters are one less than the LCO. RG 1.93 degradation-levels #1 and #3 address the availability of offsite AC power sources, whereby degradation-level #4 would be applied consistent with degradation-level #1. Though the Seabrook TS 3.8.1.1 does not specify requirements for the UATs and RATs explicitly, in the context of UAT and RAT operability, the TS Bases should align with RG 1.93 degradation-levels #1 and #3. The TS Bases discussion added in response to the events described in LER 2005-004 specify TS ACTIONS for varying conditions of UAT and RAT inoperability, including conditions not described by degradation-levels #1 and #3. The proposed change retracts the TS Bases discussion added in response to the events described in LER 2005-004 and inserts the Bases discussion described in Section 2.3 of this amendment request, such that the subject TS ACTIONS apply only if the UAT and/or RAT inoperability results in a level of degradation commensurate with RG 1.93 degradation-levels #1 or #3. RG 1.93 Degradation-Level #1 RG 1.93 states for the degradation level [#1] of the available offsite AC power sources one less than the LCO,...

Seabrook Nuclear Station Docket Nos. 50-443 L-2025-087 Enclosure Page 6 of 12 This degradation level means that one of the required offsite ac sources is not available, and therefore, the off site ac power system has no redundancy... If the available offsite ac power sources are one less than the LCO, power operation may continue for a period that should not exceed 72 hours... RG 1.93 degradation-level #1 recommends a 72-hour CT for the condition of the available offsite AC power sources one less than the LCO requirement of two independent offsite AC power sources. In contrast, Seabrook TS Bases 3/4.8.1 requires entry into TS 3.8.1.1, ACTION (a) and imposes a 72-hour CT for a single inoperable UAT or RAT. In this condition, two independent offsite AC sources remain capable of powering one of the onsite electrical circuits albeit only one offsite AC power source is available for other onsite circuit. However, this condition is less degraded than the level of degradation described by RG 1.93 level #1. Moreover, the capability to supply the power requirements under all plant conditions is retained should either offsite AC power source be lost, so the condition is not vulnerable to single failure. Thereby, a 72-hour CT for the condition of a single inoperable UAT or RAT is overly conservative when compared with the RG 1.93 recommendation for degradation-level #1, which assumes the offsite AC power system has no redundancy. Similarly, in contrast to RG 1.93 degradation-level #1, TS Bases 3/4.8.1 requires entry into TS 3.8.1.1, ACTION (a) and imposes a 72-hour CT for the condition of an onsite electrical circuit powered by a RAT since no fast-transfer capability is available to reconnect the electrical load to the associated UAT in the event power to the RAT is lost. The TS Bases 3/4.8.1 fast-transfer requirement is in response to the RG 1.93 recommendation for offsite AC power source availability in sufficient time following a loss of all onsite AC power and the other offsite AC power source. TS Bases 3/4.8.1 addresses this issue with operability requirements associated with UAT to RAT fast transfer capability and imposes TS 3.8.1.1 ACTIONS whenever the fast-transfer is unavailable. However, RG 1.93 does not impose fast-transfer as a condition for operability for the condition of a Class 1 E on site electrical circuit powered by an RAT since both onsite electrical circuits are already connected to independent offsite AC power sources such that power to the unaffected onsite electrical circuit is immediately available without UA T to RAT fast-transfer. Moreover, the capability to supply the power requirements under all plant conditions is retained should either offsite AC power source be lost, so the condition is not vulnerable to single-failure. Thereby, a 72-hour CT for the condition of an onsite electrical circuit powered by a RAT is overly conservative when compared with the RG 1.93 recommendation for degradation-level #1, which assumes the offsite AC power system has no redundancy. RG 1.93 Degradation-Level #3 RG 1.93 states, in part, for the degradation level [#3] of the available offsite AC power sources two less than the LCO,... This degradation level means that the offsite power system is not available or does not have the capability to achieve a safe shutdown and mitigate the effects of an event when coupled with the predicted loss of generation that occurs along with the unit trip or shutdown. If the available offsite ac power sources are two less than the LCO, power operation may continue for 24 hours or for the time period specified in the plant-specific technical specifications if it appears likely that at least one of the off site sources can be restored within that time. RG 1.93 degradation-level #3 recommends a 24-hour CT for the condition of the available offsite AC power sources two less than the LCO requirement of two independent offsite AC power sources. In contrast, Seabrook TS Bases 3/4.8.1 requires entry into TS 3.8.1.1, ACTION (e) and imposes a 24-hour CT for the condition of an inoperable UA T on one onsite electrical circuit and an inoperable RAT on the other onsite electrical circuit. In this condition, one offsite AC source is available to power an onsite electrical circuit via an operable UA T and the other off site AC source is available to power the other on site electrical circuit via an operable RAT such that each onsite circuit is powered by independent offsite AC sources. Moreover,

Seabrook Nuclear Station Docket Nos. 50-443 L-2025-087 Enclosure Page 7 of 12 the capacity to supply the power requirements under all plant conditions is retained should either offsite AC power source be lost, so the condition is not vulnerable to single failure. Thereby, a 24-hour CT for the condition is overly conservative when compared with the RG 1.93 recommendation for degradation-level

  1. 3, which assumes the unavailability of both offsite AC power sources.

Similarly, in contrast to RG 1.93 degradation-level #3, TS Bases 3/4.8.1 requires entry into TS 3.8.1.1, ACTION ( e) and imposes a 24-hour CT for the condition of an UAT available to power one onsite electrical circuit without auto-transfer capability to its associated RAT coincident with the other RAT powering the other onsite circuit. In this condition, no fast-transfer capability is available to transfer the load to the associated RAT in the event off site power to the UA T is lost and no fast-transfer capability to the UA T on the other onsite circuit is available in the event offsite power to its RAT is lost. The TS Bases 3/4.8.1 fast-transfer requirement is in response to the RG 1.93 recommendation for offsite AC power source availability in sufficient time following a loss of all onsite AC power and the other offsite AC power source. TS Bases 3/4.8.1 addresses this issue with operability requirements associated with UAT to RAT fast transfer capability and imposes TS 3.8.1.1 ACTIONS whenever fast-transfer is unavailable. However, RG 1.93 does not impose fast-transfer as a condition for operability for the condition of an UA T available to power one onsite electrical circuit without auto-transfer capability to its associated RAT coincident with the other onsite circuit being powered by an RAT. For this condition, both onsite electrical circuits are already connected to independent offsite AC power sources such that power to the unaffected onsite electrical circuit is immediately available without UA T to RAT fast-transfer. Moreover, the capability to supply the power requirements under all plant conditions is retained should either offsite AC power source be lost, so the condition is not vulnerable to single failure. Thereby, a 24-hour CT for the condition of a UAT without capability to fast-transfer to the RAT, and the other circuit powered from a RAT is overly conservative when compared with the RG 1.93 recommendation for the condition of degradation-level #3, which assumes the unavailability of both offsite AC power sources. The table below depicts the available pathways from switchyard AC power sources #5 and #6, to the Class 1E onsite circuits (train A and B) for varying conditions of UAT and RAT unavailability. The inoperability of one or both Class 1 E onsite circuits is not addressed in the table since TS 3.8.3.1, Onsite Power Distribution - Operating, would apply rather than TS 3.8.1.1, and is not the subject of this amendment request. TRANSFORMERS IN SERVICE INDEPENDENT OFFSITE PWR OFFSITE AC PWR OFFSITE AC PWR PATH TO TRAIN A PATH TO TRAIN B SOURCE TO SOURCE (#6) SOURCE (#5) EACH CLASS 1 E ONSITE TRAIN? UAT-2A UAT-28 RAT-3A RAT-38 [LCO 3.8.1.1.a] X v v v ALIGN RAT-3A UAT-28 (AND RAT-38 YES VIA FAST-XFER) v X v v UAT-2A (AND RAT-ALIGN RAT-38 YES 3A VIA FAST-XFER) v v X v UAT-2A UAT-28 (AND RAT-38 YES VIA FAST-XFER)) v v v X UAT-2A (AND RAT-UAT-28 YES 3A VIA FAST-XFER) X v v X ALIGN RAT-3A UAT-28 YES v X X v UAT-2A ALIGN RAT-38 YES v v X X UAT-2A UAT-28 NO ENTER 72-HR CT

Seabrook Nuclear Station Docket Nos. 50-443 TRANSFORMERS IN SERVICE OFFSITE AC PWR OFFSITE AC PWR SOURCE (#6) SOURCE (#5) UAT-2A UAT-2B RAT-3A RAT-3B X X .J .J X X X X PATH TO TRAIN A PATH TO TRAIN B ALIGN RAT-3A ALIGN RAT-3B NO PATH NO PATH L-2025-087 Enclosure Page 8 of 12 INDEPENDENT OFFSITE PWR SOURCE TO EACH CLASS 1 E ONSITE TRAIN? [LCO 3.8.1.1.a] NO ENTER 72-HR CT NO ENTER 24-HR CT The above table demonstrates that the 72-hour CT of TS 3.8.1.1, ACTION (a), should only apply for the condition of either both UATs or both RATs inoperable since only one offsite AC source would remain available to power the required onsite Class 1 equipment via the operable UATs [or RATs], consistent with the condition described by RG 1.93 degradation-level #1. The condition of both RATs inoperable would include the loss of fast transfer capability between the UATs and their associated RATs. However, the robustness of the Seabrook electrical system design is such that the capability to supply the onsite AC power requirements under all plant conditions is assured by the unaffected offsite AC power source (and by the onsite emergency AC power system) should one of the offsite AC power sources be lost. Thereby, with regard to TS 3.8.1.1 ACTION (a), deletion of the Bases discussion added in response to the events described in LER 2005-004 and inserting the Bases discussion described in Section 2.3 of this amendment request, would not result in a violation of the Seabrook licensing basis. The above table also demonstrates that the 24-hour CT of TS 3.8.1.1, ACTION (e), should only apply for the condition of both UATs and both RA Ts inoperable since no offsite AC power source would be available to power the required onsite Class 1 equipment via operable UATs or RATs, consistent with the condition described by RG 1.93 degradation-level #3. The condition of both RA Ts inoperable would include the loss of fast-transfer capability between the UATs and their associated RATs. However, the robustness of the Seabrook electrical system design is such that the capability to supply the onsite AC power requirements under all plant conditions is assured by the onsite emergency AC power system should both offsite AC power sources be lost. Thereby, with regard to TS 3.8.1.1 ACTION (e), deletion of the Bases discussion added in response to the events described in LER 2005-004 and inserting the Bases discussion described in Section 2.3 of this amendment request, would not result in a violation of the Seabrook licensing basis. Seabrook TS versus Design In LER 2005-004, NextEra reported in accordance with 10 CFR 50.73(a)(2)(i)(B), the failure to enter TS 3.8.1.1, ACTION (a) for an inoperable RAT which resulted in exceeding the specified 72-hour CT. NextEra's failure to acknowledge the RAT inoperability, and thereby ACTION (a) applicability, derived from a historical practice of interpreting LCO 3.8.1.1.a, whereby two physically independent sources from the offsite power system to the onsite Class 1 E distribution system would be satisfied with one offsite AC power source aligned to one Class 1 E onsite circuit and the other offsite AC power source aligned to the other Class 1 E onsite circuit. The long-standing interpretation was consistent with Seabrook FSAR 8.2.1.5, which states that the minimum requirements of General Design Criteria (GDC) 17 and Reg Guide 1.32 can be met with one UA T and one RAT inoperable provided the operable UA T and RAT are connected to opposite emergency buses. FSAR 8.2.1.5 states this connection is acceptable since there are still two independent circuits from the transmission network to the onsite distribution system. NextEra's historical position was that meeting these minimum design requirements should not subject the condition to a TS 3.8.1 ACTION. Inspection Report (IR) 2005-004 (Reference 6.3), which summarized the events leading to LER 2005-004, cited FSAR Section 8.1.5.2 as the basis for the enforcement action. FSAR Section 8.1.5.2 states that the design of the Seabrook electrical power system is in conformance with IEEE Standard 308-1971 (Reference 6.4). However, the IR noted that Section 5.2.1 (3) of the IEEE standard requires each redundant load group

Seabrook Nuclear Station Docket Nos. 50-443 L-2025-087 Enclosure Page 9 of 12 (aka train) have access to both a preferred and a standby power supply. The IR referenced Figure 1 of the standard which illustrates two Class IE distribution trains, each with a preferred and standby power source. Though the Seabrook electrical system design satisfies the applicable design requirements, including IEEE 308-1971, RG 1.32 (Reference 6.5), etc., the IR 2005-004 report overlooked the premise that the TS are derived from the plant safety analyses, which do not necessarily credit all the inherent safety and defense-in-depth aspects of the plant design. Specifically, 10 CFR 50.36 states,... The technical specifications wm be derived from the analyses and evaluation included in the safety analysis report, and amendments thereto, submitted pursuant to§ 50.34. [10 CFR 50.36(b)] Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the facility. [10 CFR 50.36(c)(2)] Seabrook's safety analyses do not credit, either explicitly or implicitly, the Class 1 E onsite circuits as each being powered by two independent offsite AC sources at the start of any evaluated accident. Instead, they assume each Class 1 E onsite electrical circuits is powered by a single, independent offsite AC power source and evaluate the applicable design basis accidents based on the availability and non-availability of offsite AC power accounting for worst case single failure. Accordingly, Seabrook LCO 3.8.1.1.a does not specify requirements for UA T or RAT operability because the LCO need only reflect the lowest performance level for offsite AC power system connectivity to the onsite electrical distribution system, consistent with 1 O CFR 50.36(c)(2). For the Seabrook offsite AC power system design, the lowest performance level is the availability of a single offsite AC source supplying a single Class 1 E onsite circuit capable of powering the required Class 1 E electrical loads under all plant conditions. The availability of the single offsite AC source is assured by the operability of two independent offsite AC sources each powering one Class 1 E onsite electrical train. Hence, one UAT or RAT powering one Class 1 E onsite circuit and one UAT or RAT powering the other Class 1 E onsite circuit satisfies the lowest performance level for offsite AC power system connectivity to the onsite electrical distribution system as long as the offsite AC power sources are independent of each other, consistent with FSAR Section 8.1.5.2. In this regard, the operability of the off site AC power sources as specified in LCO 3.8.1.1.a is consistent with the initial conditions of the safety analyses, and as such, the current TS Bases are overly restrictive in specifying requirements for UAT and RAT operability that are beyond the initial conditions of the safety analyses. Thereby, deletion of the Bases discussion added in response to the events described in LER 2005-004 and insertion of the Bases discussion described in Section 2.3 of this amendment request, is appropriate and reasonable.

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements Criteria The Seabrook Current Licensing Basis (CLB) incorporates the following codes and standards, applicable to the plant offsite power:

  • 10 CFR 50, General Design Criteria (GDC) 17 states that electric power from the transmission network to the onsite electric distribution system shall be supplied by two physically independent circuits (not necessarily on separate rights of way) designed and located so as to minimize to the extent practical the likelihood of their simultaneous failure under operating and postulated accident and environmental conditions. Each of these circuits shall be designed to be available in sufficient time following a loss of all onsite alternating current power supplies and the other offsite electric power circuit, to assure that specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded. One of these circuits shall be designed to be available within a few seconds following a loss-of-coolant accident to assure that core cooling, containment integrity, and other vital safety functions are maintained.

Seabrook Nuclear Station Docket Nos. 50-443 L-2025-087 Enclosure Page 10 of 12

  • 10 CFR 50, GDC 18 states that electric power systems important to safety shall be designed to permit appropriate periodic inspection and testing of important areas and features, such as wiring, insulation, connections, and switchboards, to assess the continuity of the systems and the condition of their components.
  • IEEE Std. 308-1974 "Standard Criteria for Class 1E Electric Systems for Nuclear Power Generating Stations," states that a minimum of one circuit from the transmission network normally shall be available during operation. If only one circuit from the transmission network is normally available, the design shall include a provision for alternate access to the transmission network. The circuit that is normally available shall be designed to be available within an acceptable time following a loss-of-coolant accident.
  • NRC Regulatory Guide (RG) 1.32, Revision 2, "Criteria for Safety-Related Electric Power Systems for Nuclear Plant", describes a method acceptable to the NRC staff of complying with GDC Criteria 17 and 18 with respect to the design, operation, and testing of safety-related electric power systems, with specified exceptions. The RG endorses IEEE Std. 308-1974, with exceptions, and states, in part, that "within an acceptable time" in IEEE Std 308-174, Section 5.2.3(4), should be construed to mean "within a few seconds", a preferred design would include two immediate access circuits from the transmission network, and an acceptable design would substitute a delayed access circuit for one of the immediate access circuits provided the availability of the delayed access circuit conforms to

[GDC] Criterion 17.

  • NRC Regulatory Guide 1.93, Revision 1, "Availability of Electric Power Sources", states that whenever the technical specifications 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 following considerations:

the reliability, availability, and capability of the remaining sources; the required maintenance activities do not further degrade the power system or in any way jeopardize plant safety; and continued compliance with the required actions stipulated for each LCO specified in the plant-specific technical specifications. 4.2 No Significant Hazards Consideration Analysis NextEra Energy Seabrook, LLC (NextEra) requests an amendment to Renewed Facility Operating License NPF-86 for Seabrook Station Unit 1 (Seabrook). The proposed license amendment modifies the Seabrook licensing basis by revising Technical Specifications {TS) Bases 3/4.8.1, AC. Sources - Operating, to align with the available AC power source guidelines of Regulatory Guide (RG) 1.93. Specifically, changes are proposed to the applicability of select TS 3.8.1 ACTIONS associated with Unit Auxiliary Transformer (UAT) and Reserve Auxiliary Transformer (RAT) unavailability. NextEra has evaluated if a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below: ( 1) Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated? Response: No The proposed change removes select TS Bases restrictions on UA T and RAT operability within the guidelines of the applicable design basis requirements. The proposed change neither alters plant equipment nor the way in which plant equipment is operated or maintained, and thereby cannot increase the probability of any previously evaluated accident. The proposed change cannot affect

Seabrook Nuclear Station Docket Nos. 50-443 L-2025-087 Enclosure Page 11 of 12 the type or amount of effluent that could be released off-site or increase individual or cumulative occupational exposures, and thereby cannot increase the consequences of any evaluated accident. Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated. (2) Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated? Response: No The proposed change removes select TS Bases restrictions on UAT and RAT operability within the guidelines of the applicable design basis requirements. The proposed change neither installs new nor modifies existing plant equipment and thereby cannot introduce new equipment failure modes. The proposed change does not alter safety analysis assumptions, or create new accident initiators or precursors, and thereby cannot introduce a new or different type of accident. Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated. (3) Does the proposed amendment involve a significant reduction in a margin of safety? Response: No The proposed change removes select TS Bases restrictions on UA T and RAT operability within the guidelines of the applicable design basis requirements. The proposed change does not modify any safety limits, limiting safety system settings, or safety analysis assumptions or inputs, and thereby cannot affect plant operating margins. The proposed change does not modify equipment credited in safety analyses, and thereby cannot affect the integrity of any radiological barrier. Therefore, the proposed change does not involve a significant reduction in a margin of safety. Based on the above, NextEra concludes that the proposed change presents no significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a finding of "no significant hazards consideration" is justified. 4.3 Conclusion Based on the considerations discussed above, ( 1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's 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.

5.0 ENVIRONMENTAL CONSIDERATION

A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or would change an inspection or surveillance requirement. However, the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or a significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

Seabrook Nuclear Station Docket Nos. 50-443

6.0 REFERENCES

L-2025-087 Enclosure Page 12 of 12 6.1 Regulatory Guide 1.93, Revision 1, Availability of Electric Power Sources, March 2012 (ADAMS Accession No. ML003740292) 6.2 Seabrook Licensee Event Report (LER) 2005-004-00, "Noncompliance with Technical Specification for Offsite AC Sources," May 19, 2005 (ADAMS Accession Number ML051440423) 6.3 U.S. Nuclear Regulatory Commission letter dated May 10, 2005, Seabrook Station - NRC Integrated Inspection Report 05000443/2005004 (ADAMS Accession Number ML051300636) 6.4 IEEE Std 308-1974, Standard Criteria for Class 1 E Electric Systems for Nuclear Power Generating Stations, February 1974 6.5 NRC Regulatory Guide 1.32, Revision 2, Criteria for Safety-Related Electric Power Systems for Nuclear Power Plants, February 1977 (ADAMS Accession Number ML003739990)

Seabrook Station Docket No. 50-443 ATTACHMENT PROPOSED TECHNICAL SPECIFICATION BASES CHANGES (MARK-UP) (3 pages follow) L-2025-087

ELECTRICAL POWER SYSTEMS BASES 3/4.8.1 AC SOURCES (Continued) To reduce the risk of performing extended EOG maintenance activities of up to 14 days while on-line a non-safety related supplemental emergency power system (SEPS) may be relied on when available. The SEPS is designed to provide back up power to either emergency bus whenever one of the emergency diesel generators (EOG) is out of service, particularly during Modes 1 through 4 operation. The SEPS is verified available and an operational readiness status check is performed when it is anticipated that one of the EDGs will be inoperable for longer than the allowable outage time of 72 hours. The design of the SEPS is capable of providing the required safety and non-safety related loads in the event of a total loss of offsite power and if one or both emergency diesel generators fail to start and load. During these events it is assumed that there is no seismic event or an event that requires SEPS to support safeguards actuation, e.g., safety injection, containment building spray, etc. APPLICABLE SAFETY ANALYSES The initial conditions of OBA and transient analyses in the UFSAR, Chapter 6 (Ref. 4) and Chapter 15 (Ref. 5), assume ESF systems are OPERABLE. The AC electrical power sources are designed to provide sufficient capacity, capability, redundancy, and reliability to ensure the availability of necessary power to ESF systems so that the fuel, Reactor Coolant System (RCS), and containment design limits are not exceeded. A discussion of these limits may be found in the Bases for Section 3/4.2, Power Distribution Limits; Section 3/4.4, Reactor Coolant System; and Section 3/4.6, Containment Systems. The OPERABILITY of the AC electrical power sources is consistent with the initial assumptions of the Accident analyses and is based upon meeting the design basis of the unit. This results in maintaining at least one train of the onsite or offsite AC sources OPERABLE during Accident conditions in the event of:

a.

An assumed loss of all offsite power or all onsite AC power and

b.

A worst case single failure. The AC sources satisfy Criterion 3 of 10 CFR 50.36. The SEPS is not designed for OBA loads and is not credited in the accident analyses. LIMITING CONDITION FOR OPERATION (LCO) Two qualified circuits between the offsite transmission network and the onsite Class 1 E Electrical Power System and separate and independent EDGs for each train ensure availability lei~ of the required power to shutdown the reactor and maintain it in a safe shutdown condition after an anticipated operational occurrence (AOO) or a postulated OBA. One ef the requirefJ, independent offsite AC souroes oonsists of the oirouit from an offsite transmission line through the UATs to buses E5 and ES. Operability of this circuit requires that both UAT supply brealmrs be elosed, energizing the emergency buses. The second required independent offsite AG source consists of the circuit from a separate effsite transmission line through the RATs to buses E5 and ES. For this cireuit to be operable, each emergenoy bus RI\\T supply breaker must be either (1) closed, er (2) in standby with capability for automatic closure. Each offsite circuit must be capable of maintaining rated frequency and voltage, and accepting required loads during an accident, while connected to the ESF buses. SEABROOK-UNIT 1 B 3/4 8-2 Amendment No. 80, 97, BC Oa-W 4tMtt

ELECTRICAL POWER SYSTEMS BASES 3/4.8.1 AC SOURCES (Continued) LIMITING CONDITION FOR OPERATION (LCO) (continued) The offsite circuits receive power from three 34S,OOO volt transmission lines which terminate in a common termination yard, which is then fed to the switchyard. The switchyard is arranged through circuit breakers and transformers to form the two qualified circuits. Each ESF bus is capable of being supplied by the offsite circuits either through the unit auxiliary transformer (UAT) or reserve auxiliary transformer (RAT). The UAT is the preferred power supply and the RAT is the alternate power supply. Each EOG must be capable of starting, accelerating to rated speed and voltage, and connecting to its respective ESF bus on detection of bus undervoltage. This will be accomplished within 10 to 12 seconds, depending on the type of event (12 seconds for loss of power only event, and 10 seconds for events requiring safety injection). Each EOG must also be capable of accepting required loads within the assumed loading sequence intervals, and continue to operate until offsite power can be restored to the ESF buses. These capabilities are required to be met from a variety of initial conditions such as EOG in standby with the engine hot and EOG in standby with the engine at ambient (keep-warm temperature) conditions. Additional EOG capabilities must be demonstrated as well to other required surveillances, e.g., capability of the EOG to revert to standby status on an ECCS signal while operating in parallel test mode. In addition, though not specifically mentioned in the LCO, one required emergency power sequencer timer per train must be OPERABLE as well. The sequencer is an essential support system to the EOG associated with a given ESF bus. Furthermore, the sequencer is on the primary success path for most major AC electrically powered safety systems powered from the associated ESF bus. Therefore, loss of an ESF bus sequencer affects every major ESF system in the train. Thus, the proper sequencing of loads, including tripping of nonessential loads is a required support function for EOG OPERABILITY. The AC sources in one train must be separate and independent (to the extent possible) of the AC sources in the other train Ref. 1. For the EOGs separation and inder:>endence are complete. To meet the TS 3.8.1.1 requirement for two indepen ent offsite sources, each emergency bus must (1) be energized from its UAT, and (2) have its RAT supply available via fast transfer capability. Otherwise, the appropriate action of TS 3.8.1.1 must be entered. Below are examples of the application of the TS to various configurations of the offsite AC sources: The offsite source via the UATs is operable when both buses ES and E6 are powered via the UATs. The offsite source via the RATs is operable when the RAT is the standby power supply for both buses ES and E6, and both buses have operable auto transfer capability to the RAT. With one emergency bus powered from a UAT with capability for auto transfer to the RAT, and the other bus powered from a RAT, the offsite source via the UAT is inoperable. The source through the UAT is not available via auto transfer on the bus that is energized from the RAT, (TS 3.8.1.1 action a is applicable). With the UAT powering one emergency bus without auto transfer capability to the RAT coincident with the RAT powering the other emergency bus (no auto transfer from the RAT to the UAT exists), both offsite sources are inoperable. (TS 3.8.1.1 action e is applicable.) With both emergency buses powered from the RATs, the offsite source via the UATs is inoperable since no auto transfer capability to the UATs exists. (TS 3.8.1.1 action a is applicable.) SEABROOK - UNIT 1 B 3/4 8-3 Amendment No. 80, 97, BG 06 03 Replace with INSERT next page.

INSERT For the offsite AC sources, separation and independence are to the extent practical. A circuit may be connected to more than one ESF bus, with fast-transfer capability to the other circuit OPERABLE, and not violate separation criteria. A circuit that is not connected to an ESF bus is required to have OPERABLE fast transfer capability to at least one ESF bus to support OPERABILITY of that circuit. Both offsite power circuits are designed to be connected or available via fast transfer to both ESF buses.}}

Retrieved from "https://kanterella.com/w/index.php?title=L-2025-087,_License_Amendment_Request_25-03,_Revise_Technical_Specifications_Bases_3/4.8.1_Ac._Sources_-_Operating_to_Align_with_Regulatory_Guide_1.93,_Revision_1&oldid=5513855"