L-MT-23-038, License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6

License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6

ML23317A122
Person / Time
Site:	Monticello
Issue date:	11/10/2023
From:	Hafen S Northern States Power Company, Minnesota, Xcel Energy
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-MT-23-038
Download: ML23317A122 (1)

Text

fl Xcel Energy 2807 West County Road 75 Monticello, MN 55362 November 10, 2023 L-MT-23-038 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6 In accordance with the provisions of 10 CFR 50.90, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), hereby requests a revision to the Technical Specifications (TS) for the Monticello Nuclear Generating Plant (MNGP). The proposed change would modify TS 3.8.6, "Battery Parameters," Surveillance Requirement (SR) 3.8.6.6 to align the battery capacity acceptance criteria for the 125 VDC batteries with the IEEE-450 standard and the NUREG-1433 Standard Technical Specifications.

The Enclosure provides NSPMs evaluation of the proposed change. Attachment 1 to the Enclosure provides the marked-up MNGP TS page. Attachment 2 to the enclosure provides the existing MNGP TS page re-typed. Attachment 3 to the enclosure provides the existing TS Bases, marked-up to show the proposed changes, which are provided for information only.

NSPM has evaluated the changes proposed in this License Amendment Request in accordance with 10 CFR 50.92 and concluded that they involve no significant hazards consideration.

In accordance with 10 CFR 50.91(b)(1), a copy of this application, with the enclosure, is being provided to the designated Minnesota official.

NSPM requests approval of the proposed amendment within 12 months of acceptance with an implementation period of 60 days.

If there are any questions or if additional information is required, please contact Ron Jacobson at (612) 330-6542 or ronald.g.jacobson@xcelenergy.com.

Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.

Document Control Desk L-MT-23-038 Page 2 I declare under penalty of perjury, that the foregoing is true and correct.

Executed on November lo, 2023.

~

Shawn en Site

• e President, Monticello Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc: Administrator, Region Ill, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC State of Minnesota

ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT, UNIT 1 LICENSE AMENDMENT REQUEST REVISE MONTICELLO TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 3.8.6.6 (9 Pages Follow)

L-MT-23-038 NSPM Enclosure ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT, UNIT 1 EVALUATION OF THE PROPOSED CHANGE License Amendment Request Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6 1.0

SUMMARY

DESCRIPTION 2.0 DETAILED DESCRIPTION 2.1 System Design and Operation 2.2 Current Technical Specifications Requirements 2.3 Reason for Proposed Change 2.4 Description of Proposed Change

3.0 TECHNICAL EVALUATION

3.1 System Description 3.2 Basis for the Proposed Change

4.0 REGULATORY ANALYSIS

4.1 Applicable Regulatory Requirements/Criteria 4.2 No Significant Hazards Consideration Determination 4.3 Conclusions

6.0 REFERENCES

ATTACHMENTS:

1. Technical Specification Pages (Marked Up)

2. Technical Specification Pages (Retyped)

3. Technical Specification Bases Pages (Marked Up - For Information Only)

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L-MT-23-038 NSPM Enclosure License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6 1.0

SUMMARY

DESCRIPTION In accordance with the provisions of 10 CFR 50.90, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), hereby requests a revision to the Technical Specifications (TS) for the Monticello Nuclear Generating Plant (MNGP). The proposed change would modify TS 3.8.6, "Battery Parameters," Surveillance Requirement (SR) 3.8.6.6 to allow the battery capacity acceptance criteria for the 125 VDC batteries with the IEEE-450 standard (Reference 1) and the NUREG-1433 Standard Technical Specifications.

This enclosure provides NSPMs evaluation of the proposed change. Attachment 1 to this enclosure provides the marked-up MNGP TS page. Attachment 2 to this enclosure provides the existing MNGP TS page re-typed. Attachment 3 to this enclosure provides the existing TS Bases, marked-up to show the proposed changes, which are provided for information only.

2.0 DETAILED DESCRIPTION 2.1 System Design and Operation The 125 VDC System provides a highly reliable and independent source of control power to control boards and switchgear. The system also supplies power to the emergency lights and the Hard Pipe Vent (HPV) loads.

During normal operation, these systems are powered from battery chargers with the batteries floating on the system. In the case of loss of all AC power, the batteries automatically power safety related components until AC power is restored to the battery chargers.

The 125 VDC Battery System is sized to meet the 4-hour station blackout scenario while maintaining system voltage above the minimum required to operate loads supplied by the battery.

The system consists of two 125 VDC batteries, three battery chargers, and four Distribution Panels. The 125 VDC "control" batteries provide control power for the in-plant 13.8k Vac Breakers, 4160 Vac breakers, 480 Vac Load Center breakers, Auxiliary control power for the 1R & 2R transformers, and various control relays, annunciators, etc. The 125 VDC System is capable of continuously providing DC electrical power to the required connected safety related normal and emergency loads, and other operating loads, during all modes of plant operation and for all design basis events. One of the two divisions is required for safe shutdown of the unit. For the two divisions provided, each feeds separate DC buses and each battery system is sized to:

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L-MT-23-038 NSPM Enclosure supply miscellaneous loads for periods suitable to its needs and still possess adequate capacity to operate switchgear for a 4-hour period.

provide adequate voltage at the terminals of connected loads for the duration of a 4-hour SBO event and is capable of meeting power requirements during a Design Basis Event.

2.2 Current Technical Specification Requirements 3.8.6 Battery Parameters SURVEILLANCE FREQUENCY SR 3.8.6.6 --------------------------------NOTE-------------------------------

This Surveillance shall not normally be performed in MODE 1, 2, or 3. However, portions of the Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the plant is maintained or enhanced. Credit may be taken for unplanned events that satisfy this SR.

Verify battery capacity is 90% of the manufacturers rating when subjected to a performance In accordance with discharge test or a modified performance discharge test. the Surveillance Frequency Control Program AND 12 months when battery shows degradation, or has reached 85% of the expected life with capacity < 100% of manufacturers rating AND 24 months when battery has reached 85% of the expected life with capacity 100% of manufacturers rating Page 3 of 9

L-MT-23-038 NSPM Enclosure 2.3 Reason for the Proposed Change The cells for both divisions of the 1E 125 VDC batteries (#11 and #12 Batteries) have been replaced improving capacity and available margin, thus the battery replacement recommendation of IEEE-450 (if its capacity is below 80% of the manufacturer's rating) may be applied for those batteries.

2.4 Description of Proposed Change The proposed license amendment would revise the TS Surveillance Requirement 3.8.6.6 acceptance criteria for the 125 VDC batteries from "Verify battery capacity is 90% of the manufacturers rating when subjected to a performance discharge test or a modified performance discharge test." The new acceptance criteria will separate the 125 VDC batteries from the 250 VDC batteries, which have not changed. The acceptance criteria for the 125 VDC batteries will become 80% of the manufacturer's rating. This change results in aligning the 125 VDC batteries to the NUREG-1433 Standard Technical Specifications and the IEEE-450 recommendations.

The TS SR 3.8.6.6 Frequency will remain unchanged.

Attachment 1 to the Enclosure provides marked-up existing MNGP TS pages. Attachment 2 to the Enclosure provides the existing MNGP TS pages retyped. Attachment 3 to the Enclosure provides existing TS Bases pages marked up to show the proposed changes, which are provided for information only and will be processed in accordance with the MNGP Technical Specifications Bases Control Program (TS Section 5.5.9).

3.0 TECHNICAL EVALUATION

3.1 System Description Two 125 VDC battery systems are provided at MNGP, each of which feeds separate DC buses. Both 125 VDC batteries (#11 and #12) now have 59 cells (previously 58 cells). Each cell is larger (now 7 positive plates in KCR-15 cells rather than the 6 positive plates in the previous KCR-13 cells). The C&D Technologies Type KCR-15 cells are shock absorbent clear plastic cells of the lead calcium acid type.

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L-MT-23-038 NSPM Enclosure Parameter Previous KCR-13 batteries Current KCR-15 batteries

(#11 and #12) (#11 and #12)

Number of Cells 58 59 Cell Size 6 positive plates 7 positive plates Type Lead Calcium Acid Lead Calcium Acid Manufacturer's rating of each cell to the (ending terminal voltage of (ending terminal voltage of ending terminal voltage 1.81 V at 77°F) 1.81 V at 77°F) 1minute rate 467 Amperes 1minute rate 569 Amperes 1hour rate 218 Amperes 1hour rate 254 Amperes 4hour rate 97 Amperes 4hour rate 114 Amperes The MNGP 125 VDC battery calculations have been revised to assume a 1.25 battery aging factor.

In the event of a 4-hour station blackout scenario (different than a manufacturers rated discharge), the batteries are each sized sufficiently to maintain system voltage above the minimum required to operate loads. The analysis performed includes the voltage drop from the battery terminals to each of the respective loads.

3.2 Basis for the Proposed Change The 90% capacity acceptance criteria had been put in place due to the reduced margin of the previously installed 125 VDC batteries and the use of a lesser aging factor. Both 125 VDC batteries have been replaced, with the new battery cells possessing increased cell sizes and providing one additional cell in each battery thus increasing battery capacity. Therefore, a lesser aging factor per IEEE-450 is no longer used with the 125 VDC batteries and the IEEE-450 battery replacement threshold of 80% capacity can be applied for the 125 VDC batteries.

4.0 REGULATORY ANALYSIS

4.1 Applicable Regulatory Requirements/Criteria

1. Title 10 Code of Federal Regulations 50.36, "Technical specifications":

10 CFR 50.36(c)(2)(ii), Criterion 3, stipulates the following:

"...structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier."

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L-MT-23-038 NSPM Enclosure

2. General Design Criteria (GDC)

MNGP was designed largely before the publishing of the 70 GDC for Nuclear Power Plant Construction Permits proposed by the Atomic Energy Commission (AEC) for public comment in July 1967, and constructed prior to the 1971 publication of the 10 CFR 50, Appendix A, GDC. As such, MNGP was not licensed to the Appendix A, GDC.

The MNGP Updated Safety Analysis Report (USAR), Section 1.2, lists the Principal Design Criteria (PDC) for the design, construction, and operation of the plant. MNGP USAR Appendix E provides a plant comparative evaluation to the 70 proposed AEC design criteria. It was concluded that the plant conforms to the intent of the GDC.

The applicable AEC GDC are:

General Criteria, PDC 1.2.1.a The plant is designed, fabricated, erected, and operated to produce electrical power in a safe, reliable and efficient manner and in accordance with applicable codes and regulations.

This PDC applies to the 125 VDC System because the 125 VDC System supports the safe and reliable operation of the plant by supporting the mitigation of the consequences of accidents and the normal operation of plant systems.

Plant Electrical Power, PDC 1.2.6 Sufficient normal and standby auxiliary sources of electrical power are provided to attain prompt shutdown and continued maintenance of the plant in a safe condition under all credible circumstances. The capacity of the power sources is adequate to accomplish all required engineered safeguards functions under all postulated design basis accident conditions.

This PDC applies to the 125 VDC System because the 125 VDC System supplies power to systems and components required to achieve and maintain the plant in a safe condition under all credible circumstances.

Separation of Safety Systems, PDC 1.2.10 Systems and equipment provided for the prevention of and the mitigation of the consequences of accidents are provided in such redundancy and physical separation that the accident will not preclude operation of sufficient equipment to effectively control the effects of the accident.

This PDC is applicable to the 125 VDC System because the 125 VDC System supplies power to systems and equipment provided for the prevention of and the mitigation of the consequences of accidents.

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L-MT-23-038 NSPM Enclosure Class I Equipment and Structures, PDC 1.2.11 Class I structures, systems and components are those whose failure could cause significant release of radioactivity or which are vital to a safe shutdown of the plant under normal or accident conditions and to the removal of decay and sensible heat from the reactor.

This PDC applies to the 125 VDC System because the 125 VDC System supports the safe shutdown of the plant and decay and sensible heat removal from the reactor by providing power to equipment required to perform this function.

3. 10 CFR 50.63, Loss of All Alternating Current Power 10 CFR 50.63(a)(2): The reactor core and associated coolant, control, and protection systems, including station batteries and any other necessary support systems, must provide sufficient capacity and capability to ensure that the core is cooled and appropriate containment integrity is maintained in the event of a SBO for the specified duration. The capability for coping with a SBO of specified duration shall be determined by an appropriate coping analysis. Utilities are expected to have the baseline assumptions, analyses, and related information used in their coping evaluations available for NRC review.

NSPM has evaluated the proposed change against the applicable regulatory requirements and acceptance criteria. The technical analysis concludes that the proposed TS changes will continue to assure that the design requirements and acceptance criteria for MNGP are met.

Based on the considerations discussed above, (i) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (ii) such activities will be conducted in compliance with the Commissions regulations, and (iii) the approval of the proposed change will not be inimical to the common defense and security or to the health and safety of the public.

4.2 No Significant Hazards Consideration Determination Analysis In accordance with the provisions of 10 CFR 50.90, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), hereby requests a revision to the Technical Specifications (TS) for the Monticello Nuclear Generating Plant (MNGP). The proposed change would modify the TS "Battery Parameters," Surveillance Requirement (SR) to align the battery capacity acceptance criteria for the 125 VDC batteries with the IEEE-450 standard and the NUREG-1433 Standard Technical Specifications.

NSPM has evaluated whether or not 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:

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L-MT-23-038 NSPM Enclosure

1. Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No.

The proposed change revises the Battery Parameters SR acceptance criteria for verifying battery capacity following a performance test discharge or a modified performance test discharge for the 125 VDC batteries to align with the IEEE-450 recommended battery replacement criteria. Both 125 VDC batteries were replaced in the most recent two refueling outages; the new installed batteries have a larger overall capacity compared to the previous batteries, allowing the replacement of the plant-specific acceptance criteria and use of the IEEE-450 recommendation. The 125 VDC batteries are not assumed to be initiators of any previously analyzed accident.

Therefore, the proposed change does not increase the probability of any accident previously evaluated. The batteries are used in the accident analyses to mitigate design basis accidents. The revised SR acceptance criteria does not affect the ability of the 125 VDC batteries to provide the required response in a 4-hour station blackout scenario or other previously analyzed accident scenarios. Since the system will still be able to perform its accident mitigation function, the consequences of accidents previously evaluated are not increased.

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 previously evaluated?

Response: No.

The proposed change revises the Monticello TS battery parameter surveillance requirement (SR) acceptance criteria for the 125 VDC batteries to adopt the IEEE-450 recommended replacement criteria following battery replacement that raised overall capacity. The change does not introduce a new mode of plant operation. The change will not introduce new accident initiators or impact the assumptions made in the safety analysis.

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 revises the Battery Parameters Surveillance Requirement acceptance criteria for the 125 VDC batteries to adopt the IEEE-450 recommended battery replacement criteria. Both 125 VDC batteries were replaced in the most recent Page 8 of 9

L-MT-23-038 NSPM Enclosure two refueling outages; the new installed batteries have a larger overall capacity compared to the previous batteries, allowing the replacement of the plant-specific acceptance criteria and use of the IEEE-450 recommendation. The 125 VDC battery criteria is changed from verify battery capacity is 90% of the manufacturer's rating when subjected to a performance discharge test or a modified performance discharge test, to a verify capacity is 80% of the manufacturer's rating. The 125 VDC batteries will continue to supply loads for the required accident analyses 4-hour duration (unchanged). The change in SR acceptance criteria does not alter a design basis or safety limit.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

4.3 Conclusions In 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 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.

5.0 ENVIRONMENTAL CONSIDERATION

The proposed change 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 change does not involve (i) a significant hazards consideration, (ii) a significant change in the types or 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 change 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 change.

6.0 REFERENCES

1. IEEE Std 450-1995, "IEEE Recommended Practice for Maintenance, Testing, and Replacement of Vented Lead-Acid Batteries for Stationary Applications."

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ENCLOSURE, ATTACHMENT 1 MONTICELLO NUCLEAR GENERATING PLANT, UNIT 1 LICENSE AMENDMENT REQUEST REVISE MONTICELLO TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 3.8.6.6 TECHNICAL SPECIFICATIONS PAGES (MARKUP)

(1 Page Follows)

Battery Parameters 3.8.6 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.6.6 --------------------------------NOTE-------------------------------

This Surveillance shall not normally be performed in MODE 1, 2, or 3. However, portions of the Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the plant is maintained or enhanced.

Credit may be taken for unplanned events that satisfy this SR.

Verify battery capacity is 90% of the In accordance with manufacturers rating when subjected to a the Surveillance performance discharge test or a modified Frequency Control performance discharge test. Program AND 12 months when battery shows degradation, or has reached 85%

of the expected life with capacity Verify battery capacity is: < 100% of manufacturers

• 90% of the manufacturer's rating for rating 250 VDC batteries AND

• 80% of the manufacturer's rating for 24 months when 125 VDC batteries battery has reached 85% of when subjected to a performance the expected life discharge test or a modified performance with capacity discharge test. 100% of manufacturers rating Monticello 3.8.6-5 Amendment No. 200 TBD

ENCLOSURE, ATTACHMENT 2 MONTICELLO NUCLEAR GENERATING PLANT, UNIT 1 LICENSE AMENDMENT REQUEST REVISE MONTICELLO TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 3.8.6.6 TECHNICAL SPECIFICATIONS PAGES (RETYPED)

(1 Page Follows)

Battery Parameters 3.8.6 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.6.6 --------------------------------NOTE-------------------------------

This Surveillance shall not normally be performed in MODE 1, 2, or 3. However, portions of the Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the plant is maintained or enhanced.

Credit may be taken for unplanned events that satisfy this SR.

Verify battery capacity is: In accordance with the Surveillance 90% of the manufacturers rating for 250 VDC Frequency Control batteries Program 80% of the manufacturer's rating for 125 VDC AND batteries 12 months when when subjected to a performance discharge test or a battery shows modified performance discharge test. degradation, or has reached 85%

of the expected life with capacity

< 100% of manufacturers rating AND 24 months when battery has reached 85% of the expected life with capacity 100% of manufacturers rating Monticello 3.8.6-5 Amendment No. 200 TBD

ENCLOSURE, ATTACHMENT 3 MONTICELLO NUCLEAR GENERATING PLANT, UNIT 1 LICENSE AMENDMENT REQUEST REVISE MONTICELLO TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 3.8.6.6 TECHNICAL SPECIFICATIONS BASES (MARKUP)

(Provided for Information Only)

(2 Pages Follow)

DC Sources - Operating B 3.8.4 BASES BACKGROUND (continued)

During normal operation, the DC loads are powered from the battery chargers with the batteries floating on the system. In case of loss of normal power to the battery charger, the DC loads are automatically powered from the station batteries.

The DC power distribution system is described in more detail in Bases for LCO 3.8.7, "Distribution System - Operating," and LCO 3.8.8, "Distribution System - Shutdown."

Each DC battery subsystem is separately housed in a ventilated room.

The common standby 125 VDC battery charger is located in a room separate from the other 125 VDC battery chargers electrical power subsystems. Each subsystem is located in an area separated physically for the 250 VDC and electrically from the other subsystems to ensure that a single failure batteries and >80% in one subsystem does not cause a failure in a redundant subsystem.

There is no sharing between redundant Class 1E subsystems such as for the 125 VDC batteries, battery chargers, or distribution panels, except the common batteries standby 125 VDC battery charger may be shared between the Division 1 and Division 2 125 VDC electrical power subsystems.

Each Division 1 and Division 2 250 VDC battery has adequate storage capacity to meet the duty cycle(s) discussed in USAR, Section 8.5.1.1 (Ref 4). Each Division 1 and Division 2 125 VDC battery has adequate storage capacity to meet the duty cycle(s) discussed in USAR, Section 8.5.2.1 (Ref. 5). The battery is designed with additional capacity above that required by the design duty cycle to allow for temperature variations and other factors.

The batteries for DC electrical power subsystems are sized to produce capacity greater than required for a design basis accident and monitored to ensure battery capacity will remain > 90% during the operating cycle.

The minimum design voltage limit is 105/210 V.

The battery cells are of flooded lead acid construction with a nominal specific gravity of 1.215. The open circuit voltage is the voltage maintained when there is no charging or discharging. Once fully charged, the battery cell will maintain 98% capacity for 30 days without further charging per manufacturer's instructions. Optimal long term performance however, is obtained by maintaining a float voltage 2.20 to 2.25 Vpc. This provides adequate over-potential, which limits the formation of lead sulfate and self discharge.

Each battery charger of DC electrical power subsystem has ample power output capacity for the steady state operation of connected loads required during normal operation, while at the same time maintaining its battery Monticello B 3.8.4-2 Revision No. 63 TBD

Battery Parameters B 3.8.6 A capacity of 80% shows that the battery rate of deterioriation is BASES increasing, even if there is ample capacity to meet the load requirements.

SURVEILLANCE REQUIREMENTS (continued) discharge test must remain above the minimum battery terminal voltage specified in the battery service test for the duration of time equal to that of the service test.

The 125 VDC The acceptance criteria for this Surveillance are consistent with IEEE-450 batteries were sized (Ref. 1). This reference recommends that the battery be replaced if its to meet the assumed capacity is below 80% of the manufacturer's rating if the battery was sized duty cycle loads using a 1.25 aging factor. If a lesser aging factor was used, battery replacement will be required before 80% capacity is reached to ensure when the battery that the load can be served. The 250 VDC batteries were sized using a design capacity 1.11 aging factor, therefore a 90% capacity limit was chosen. While the reaches this 80% 125 VDC batteries were sized using a 1.25 aging factor, a similar 90%

limit using a 1.25 capacity limit was chosen for conservatism. Furthermore, the 125 VDC aging factor. and 250 VDC batteries are sized to meet the assumed duty cycle loads when the battery design capacity reaches this 90% limit.

and they lesser The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

If the battery shows degradation, or if the battery has reached 85% of its expected life and capacity is < 100% of the manufacturer's rating, the Surveillance Frequency is reduced to 12 months. However, if the battery shows no degradation but has reached 85% of its expected life, the Surveillance Frequency is only reduced to 24 months for batteries that retain capacity 100% of the manufacturer's rating. Degradation is indicated, according to IEEE-450 (Ref. 1), when the battery capacity drops by more than 10% relative to its capacity on the previous performance test or when it is below 90% of the manufacturer's rating.

The 12 month Frequency is consistent with the recommendations in IEEE-450 (Ref. 1). The 24 month Frequency is derived from the recommendations of IEEE-450 (Ref. 1).

This SR is modified by a Note. The reason for the Note is that performing the Surveillance would remove a required DC electrical power subsystem from service, perturb the electrical distribution system, and challenge safety systems. This restriction from normally performing the Surveillance in MODE 1, 2, or 3 is further amplified to allow portions of the Surveillance to be performed for the purpose of reestablishing OPERABILITY (e.g., post work testing following corrective maintenance, corrective modification, deficient or incomplete surveillance testing, and other unanticipated OPERABILITY concerns) provided an assessment determines plant safety is maintained or enhanced. This assessment shall, as a minimum, consider the potential outcomes and transients associated with a failed partial Surveillance, a successful partial Surveillance, and a perturbation of the offsite or onsite system when they are tied together or operated independently for the partial Surveillance; as Monticello B 3.8.6-7 Revision No. 63 TBD