L-MT-24-017, Response to Request for Additional Information Regarding License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6 (EPID-L-2023-LLA-0160

Response to Request for Additional Information Regarding License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6 (EPID-L-2023-LLA-0160

ML24157A110
Person / Time
Site:	Monticello
Issue date:	06/04/2024
From:	Haten S Northern States Power Company, Minnesota, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-24-017, EPID-L-2023-LLA-0160
Download: ML24157A110 (1)

Text

2807 West County Road 75 Monticello, MN 55362

June 4, 2024 L-MT-24-017 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

Response to Request for Additional Inform ation Regarding License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6 (EPID-L-2023-LLA-0160)

References:

1) NSPM Letter to NRC, "Licen se Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6," dated November 10, 2023 (ML23317A122)

2) NRC email to NSPM, "Monticello - Final RAI for LAR to Revise TS SR 3.8.6, 'Battery Parameters,' SR 3.8.6.6," dated May 10, 2024 (ML24131A080)

In Reference 1, Northern States Power Com pany, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM") submitt ed a license amendment request (LAR) for the Monticello Nuclear Generating Plant (MNGP) regarding changes to Technical Specification (TS) 3.8.6, "Battery Parameters." Specifically, Reference 1 proposed to revise Surveillance Requirement (SR) 3.8.6.6 to align with the battery capacity acceptance criteria for the 125 VDC batteries with the IEEE-450 standard and the NUREG-1433 Standard TS.

The NRC staff has determined that additional information is needed to complete its review (Reference 2). The enclosure to this letter provides NSPM's response to the questions of Reference 2.

The No Significant Hazards Consideration analysis provided in the original submittal is not altered by the additional information provided in Reference 1.

Summary of Commitments

This letter makes no new commitments and no revisions to existing commitments.

Document Control Desk L-MT-24-017 Page2

If you have further questions or require additional clarification1 contact Ron Jacobson at ronald.g,jacobson@xcelenergy.com or (612) 330-6542.

I declare under penalty of perjury, that the foregoing is true and correct.

Executed on June j_, 2024.

Shawn ~

Site ~;si nt, Monticello Nuclear Generating Plant Northern Sta s Power Company - Minnesota

Enclosure

cc: Administrator, Region 111, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC State of Minnesota L-MT-24-017 NSPM Enclosure

ENCLOSURE

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST TO REVISE MONTICELLO TECHNICAL SPECIFICATION SURVEILLANCE REQUIREMENT 3.8.6.6

1.0 BACKGROUND

In Reference 1, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM") submitted a license amendment request (LAR) for the Monticello Nuclear Generating Plant (MNGP), regarding changes to Technical Specification (TS) 3.8.6, "Battery Parameters." Specifically, the LAR proposes to revise Surveillance Requirement (SR) 3.8.6.6 to align with the battery capacity acceptance criteria for the 125 VDC batteries with the IEEE-450 standard and the NUREG-1433 Standard TS.

The NRC staff has determined that additional information is needed to complete its review (Reference 2).

2.0 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION

The NRC request for additional information from Reference 2 is repeated in italics.

Monticello TS SR 3.8.4.3, Note 1 states: The modified performance discharge test in SR 3.8.6.6 may be performed in lieu of SR 3.8.4.3. Monticello TS SR 3.8.4.3 is to verify battery capacity is adequate to supply, and maintain in an OPERABLE status, the required emergency loads for the design duty cycle when subjected to a battery service test.

According to the LAR, the proposed revised TS SR 3.8.6.6 would state:

Verify battery capacity is:

90% of the manufacturers rating for 250 VDC batteries 80% of the manufacturers rating for 125 VDC batteries when subjected to a performance discharge test or a modified performance discharge test.

The revised TS SR 3.8.6.6 has been proposed because according to the LAR, new 125 VDC batteries (C&D Technology KCR-15 with 59 cells) were installed, and battery calculations have been revised based on assuming a 1.25 battery aging factor.

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RAI-1

Please provide the 125 VDC battery load test profile(s) i.e., load versus time steps which would be considered for (1) battery service test for SR 3.8.4.3, and (2) performance discharge test, or a (3) modified performance discharge test for SR 3.8.6.6. Also, explain how these load test profiles were developed based on the load periods/steps considered in the revised 125 VDC battery sizing calculation(s).

Response to RAI-1

NSPM typically conducts a modified performance discharge test at Monticello vice performance of a service test and performance discharge test as allowed by TS SR 3.8.6.6.

(1) 125 VDC battery load test profiles for battery service test

The 125 VDC battery sizing calculations, in part, determine each batterys duty cycle for the analyzed scenarios. The batteries duty cycles established in the calculations represent the service test profiles as shown in the tables below:

1. 11 125 VDC Battery Service Test Load Profile Period Load Duration (Amps) (Minutes) 1 150.34 1 2 76.42 1 3 76.28 27 4 81.97 1 5 65.37 29 6 66.05 1 7 65.29 30 8 62.69 29 9 128.98 1 10 62.70 30 11 67.84 1 12 112.06 1 13 62.46 28 14 62.31 30 15 62.15 28 16 105.38 1 17 109.89 1

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1. 12 125 VDC Battery Service Test Load Profile Period Load Duration (Amps) (Minutes) 1 129.04 1 2 60.95 1 3 60.90 27 4 66.28 1 5 60.05 29 6 60.05 1 7 59.99 30 8 59.49 29 9 125.33 1 10 58.70 30 11 63.96 1 12 108.50 1 13 58.63 28 14 58.59 30 15 58.56 15 16 58.53 13 17 63.78 1 18 107.34 1

The #11 and #12 125 VDC batteries consist of 59 C&D model KCR-15 cells.

(2) 125 VDC battery load test profiles for performance discharge test

The performance discharge test for KCR-15 cells would be 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to 1.78 vpc, 119 A at 77°F based upon cell performance ratings credited in the 125 VDC battery sizing calculations.

(3) 125 VDC battery load test profiles for modified performance discharge test

Discussion of the profiles for the #11 and #12 125 VDC batteries' modified performance tests follow.

Monticello TS Bases for SR 3.8.6.6 references IEEE Standard 450-1995 (Reference 4) for initial conditions, acceptance criteria, definition of battery capacity degradation and surveillance frequency. IEEE Standard 450-1995 includes general discussion of a typical modified performance test but does not explicitly define, or restrict, the user to a specific methodology. In the absence of more prescriptive guidance, the methodology presented in IEEE Standard 450-2002 (Reference 3) Annex I is used to construct the modified performance test profile for the #11 and #12 batteries. In IEEE Standard 450-2002, no temperature correction is applied to the performance test discharge current and the correction is applied to the capacity calculation instead. However, section 7.3.1.1 of Reference 3 also states that the previous (i.e., 1995) method is still acceptable. Since Monticello TS Bases reference the 1995

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version which only describes the method to correct the performance test discharge current, this practice is employed to specify the recommended discharge test profile.

The methodology used to construct the modified performance test profiles for the #11 and #12 batteries is a Type 2 test as described in IEEE Standard 450-2002 Annex I.

The battery discharge profiles are determined following the outlined steps of Reference 3, Annex I,Section I.2, Type 2 Modified Performance Test.

Duty Cycle The batteries' duty cycles are reflected in the following two tables. Cell sizing is performed with an aging factor corresponding to 80% rated capacity:

1. 11 125 VDC Battery Duty Cycle Period Load Duration (Amps) (Minutes) 1 150.34 1 2 76.42 1 3 76.28 27 4 81.97 1 5 65.37 29 6 66.05 1 7 65.29 30 8 62.69 29 9 128.98 1 10 62.70 30 11 67.84 1 12 112.06 1 13 62.46 28 14 62.31 30 15 62.15 28 16 105.38 1 17 109.89 1

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1. 12 125 VDC Battery Duty Cycle Period Load Duration (Amps) (Minutes) 1 129.04 1 2 60.95 1 3 60.90 27 4 66.28 1 5 60.05 29 6 60.05 1 7 59.99 30 8 59.49 29 9 125.33 1 10 58.70 30 11 63.96 1 12 108.50 1 13 58.63 28 14 58.59 30 15 58.56 15 16 58.53 13 17 63.78 1 18 107.34 1

Base Time for Test The minimum test duration is the duty cycle multiplied by the aging factor used in the cell sizing. For both the #11 and #12 batteries this minimum time is: 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> x 1.25 = 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. This assures the modified performance test durations envelope the duty cycle.

Discharge Rate for Base Time For #11 battery: 100.8 A to 1.78 vpc @ 5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> rate For #12 battery: 96.9 A to 1.81 vpc @ 5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> rate

Duty Cycle Portions above Discharge Rate The #11 125 VDC battery duty cycle data provided above indicates periods 1, 9, 12, 16 and 17 are above the nominal discharge current. The #12 125 VDC battery duty cycle data provided above indicates periods 1, 9, 12, and 18 are above the nominal discharge current.

Capacity Removed by Portions above Nominal Discharge Rate The capacity removed by each period of the duty cycle whose current is above the nominal discharge rate is identified in the following tables. For the #11 battery, the currents of periods 16 and 17 are within 5 amps and are combined to simplify the test profile. Duty cycle current values are rounded up to the nearest one-tenth ampere and capacity removed is rounded down.

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1. 11 Battery Period Duration Load Capacity (Minutes) (Amps) Removed (AH) 1 1 150.4 2.5 9 1 129.0 2.1 12 1 112.1 1.8 16+17 2 109.9 3.6 Totals 5 min 10.0

1. 12 Battery Period Duration Load Capacity (Minutes) (Amps) Removed (AH) 1 1 129.1 2.1 9 1 125.4 2.0 12 1 108.5 1.8 18 1 107.4 1.7 Totals 4 min 7.6

Capacity Delivered at Specified Discharge Rate For #11 battery: 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> x 100.8 A = 504 AH For #12 battery: 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> x 96.9 A = 484.5 AH

Percent of Rated Capacity to Discharge during Service Test Portion For #11 battery: 504 AH x 0.80 = 403.2 AH For #12 battery: 484.5 AH x 0.80 = 387.6 AH

Capacity Required to Discharge above Service Test Peaks For #11 Battery: 403.2 AH - 10.0 AH = 393.2 AH For #12 Battery: 387.6 AH - 7.6 AH = 380.0 AH

New Baseline Discharge Current The adjusted baseline current is determined (rounding up).

For #11 Battery: 393.2 AH / (4.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> - 5 / 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br />) = 100.4 A. There are no periods with a current of 100.4 A to 100.8 A.

For #12 Battery: 380.0 AH / (4.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> - 4 /60 hours) = 96.7 A. There are no periods with a current of 96.7 A to 96.9 A.

Minimum Required Terminal Voltage For the #11 and #12 batteries, the terminal voltage required to satisfy the service test portion of the modified performance test is included with the specified profile. The final (performance test) voltage corresponds to the final cell voltage for the selected 5-hour discharge rate.

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The modified performance test profiles are detailed below. The corresponding minimum required voltage for each test step is included. To demonstrate the service test portion has been satisfied, the battery terminal voltage is to be recorded at the lowest reading for each step. Load bank control band and M&TE accuracy are not included in the profile and must be addressed in accordance with established station practices.

1. 11, 125 VDC Battery Modified Performance Test Profile Step Rate Duration Minimum Temp.

(Amperes) (Minutes) Test Voltage Correction Allowed 1 150.4 1 105 No 2 100.4 118 105 Yes 3 129.0 1 105 No 4 100.4 31 105 Yes 5 112.1 1 105 No 6 100.4 86 105 Yes 7 109.9 2 105 No 8 100.8 Until End* 105 Yes Total (ts) 300

• 60 minutes for 100% rated capacity

1. 12, 125 VDC Battery Modified Performance Test Profile Step Rate Duration Minimum Temp.

(Amperes) (Minutes) Test Voltage Correction Allowed 1 129.1 1 109.1 No 2 96.7 118 109.1 Yes 3 125.4 1 109.1 No 4 96.7 31 107.2 Yes 5 108.5 1 107.2 No 6 96.7 87 107.2 Yes 7 107.4 1 106.8 No 8 96.9 Until End 106.8 Yes Total (ts) 300 Terminal voltage required to satisfy the service test is 105.455 volts.

60 minutes for 100% rated capacity

For both of the modified performance test profile tables, tested capacity is calculated per Reference 4, Section 6.5, as follows:

% capacity at 77F = (Ta /Ts) x 100, where Ta is actual time of test to specified terminal voltage Ts is rated time to specified terminal voltage

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3.0 REFERENCES

1. NSPM Letter to NRC, "License Amendment Request to Revise Monticello Technical Specification Surveillance Requirement 3.8.6.6," dated November 10, 2023 (ML23317A122)

2. NRC email to NSPM, "Monticello - Final RAI for LAR to Revise TS SR 3.8.6, 'Battery Parameters,' SR 3.8.6.6," dated May 10, 2024

3. IEEE Std. 450-2002 IEEE Recommended Practice for Maintenance, Testing and Replacement of Vented Lead-Acid Batteries for Stationary Applications

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

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