ML20244A290

Request for Additional Information (E-mail Dated 8/31/2020) License Amendment Request to Revise Battery Surveillance Requirements

ML20244A290
Person / Time
Site:	Millstone
Issue date:	08/31/2020
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Sinha S Dominion Energy Nuclear Connecticut
Guzman R
References
EPID L-2020-LLR-0094
Download: ML20244A290 (4)

Text

{{#Wiki_filter:From: Guzman, Richard To: Shayan Sinha

Subject:

Millstone Unit 3 - REQUEST FOR ADDITIONAL INFORMATION re: License Amendment Request to Revise Battery Surveillance Requirements (EPID: L-2020-LLA-0094) Date: Monday, August 31, 2020 1:21:31 PM

Shayan, On August 18, 2020, the U.S. Nuclear Regulatory Commission (NRC) staff sent Dominion Energy Nuclear Connecticut, Inc. (DENC) the subject Request for Additional Information (RAI) as a draft (via e-mail shown below).This RAI relates to the license amendment request submitted by DENC dated April 30, 2020, (ADAMS Accession No. ML20121A217), proposing to revise Technical Specifications (TS)

Surveillance Requirement (SR) 4.8.2.1.b and 4.8.2.1.c by adding a new acceptance criterion to verify the total battery connection resistance is within pre-established limits to ensure that the intended design functions are met. On August 27, 2020, the NRC staff conducted a conference call with the licensee staff to clarify the request. Following the discussion, you indicated that DENC will provide a response to this RAI within 30 days from the issuance of the RAI; therefore, the NRC staff expects DENCs formal response by September 30, 2020. Updated below is the official (final) RAI. A publicly available version of this e-mail and RAI will be placed in the NRCs ADAMS system. Please contact me should you have any questions in regard to this request. Sincerely, Rich Guzman Sr. PM, Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov From: Guzman, Richard <Richard.Guzman@nrc.gov> Sent: Tuesday, August 18, 2020 9:56 AM To: Shayan Sinha <Shayan.Sinha@dominionenergy.com>

Subject:

Millstone Unit 3 - DRAFT Request for Additional Information - License Amendment Request to Revise Battery Surveillance Requirements (EPID: L-2020-LLA-0094)

Shayan, By letter dated April 30, 2020, (ADAMS Accession No. ML20121A217), Dominion Energy Nuclear Connecticut, Inc., (the licensee), submitted a license amendment request to Renewed Facility Operating License No. NPF-49 for Millstone Power Station Unit 3 (MPS3). The proposed changes would revise MPS3 Technical Specifications (TS) Surveillance Requirement (SR) 4.8.2.1.b and 4.8.2.1.c by adding a new acceptance criterion to verify the total battery connection resistance is within pre-established limits to ensure that the intended design functions are met.

The NRC staff has determined that additional information is needed to complete its review, as described in the request for additional information (RAI) shown below. This RAI is identified as DRAFT at this time to confirm your understanding of the information needed by the NRC staff to complete its evaluation. If youd like to have a clarification call, please let me know and I will coordinate availabilities w/the NRC technical staff. I intend to send out the questions below as official by August 28th, if possible.

Thanks,

~~~~~~~~~~~ Rich Guzman Sr. PM, Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov

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REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO REVISE BATTERY SURVEILLANCE REQUIREMENTS MILLSTONE POWER STATION, UNIT NO. 3 DOCKET NO. 50-423 (EPID: L-2020-LLA-0094) By letter dated April 30, 2020, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20121A217), Dominion Energy Nuclear Connecticut, Inc. (the licensee) submitted a license amendment request (LAR) to Renewed Facility Operating License No. NPF-49 for Millstone Power Station Unit 3 (MPS3). The proposed changes would revise MPS3 Technical Specifications (TS) Surveillance Requirement (SR) 4.8.2.1.b and 4.8.2.1.c by adding a new acceptance criterion to verify the total battery connection resistance is within pre-established limits to ensure that the intended design functions are met. The Nuclear Regulatory Commission (NRC) staff has reviewed the information provided in the submittal and has determined that additional information as requested below is needed to complete its review. Regulatory Basis The following NRC requirements are applicable to the NRC staffs review of the LAR: Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix A, General Design Criterion (GDC) 17, General Design Criteria for Nuclear Power Plants, requires, in part, that nuclear power plants have onsite and offsite electric power systems to permit the functioning of structures, systems, and components that are important to safety. The onsite system is required to have sufficient independence, redundancy, and testability to perform its safety function, assuming a single failure. 10 CFR 50, Appendix A, GDC-18, Inspection and testing of electric power systems, requires that electric power systems that are important to safety must be designed to permit appropriate periodic inspection and testing. 10 CFR 50.36(c)(3), Technical Specifications, requires that TSs include SRs, which are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met. Additionally, the following guidance document as referenced by the licensee is applicable for conformance to the regulatory requirements: Institute of Electrical and Electronics Engineers (IEEE) Standard 450-1980 and IEEE Standard 450-1975 IEEE Recommended Practice for Maintenance, Testing, and Replacement of Large Lead Storage Batteries for Generating Stations and Substations. The NRC staff also applied the 2002 edition of IEEE Standard 450 as it illustrates methods for measuring battery connection resistance.

Request for Additional Information (RAI) The licensee proposed adding new acceptance criterion to TS SR 4.8.2.1.b and 4.8.2.1.c to verify that the total battery connection resistance is within pre-established limits, which ensures that the batteries can perform their specified safety functions by maintaining required battery terminal voltage under design-basis load conditions. Section 3.2.1, Battery Resistance Evaluation, of the LAR states that Batteries 301A-1 and 301B-1 are model number NCN-27 and Batteries 301A-2 and 301B-2 are model number NCN-11. The LAR further states: However, because surveillance procedure C SP 760, "Battery Discharge Test" (Reference 6.7) monitors only the plate-to-post and inter-cell connections and does not include the resistance from the inter-tier and inter-rack cabling (which have a total calculated impedance of 870 micro-ohm), the new calculated bounding acceptance criteria value is 3894 micro-ohm. To determine the acceptability of the proposed TS total battery connection resistance limits, the NRC staff requests the following additional information:

RAI-1

The manufacturers data sheets indicate that NCN 11 battery cells have two posts per cell and NCN 27 cells have four posts per cell. Therefore, there are differences in the type and number of intercell connections. Section 3.2.1 of the LAR states that resistance sources in the MPS3 battery setup include plate-to-post connections, inter-cell connections, and cabling connections. The LAR also states that because MPS3 surveillance procedure for the battery discharge test monitors only the plate-to-post and inter-cell connections, the conductor resistance for inter-tier and inter-rack cables is not included in the bounding resistance value of 3894 micro-ohm. The NRC staff notes that in addition to plate to post intercell connections, there are cabling connections, such as external/terminal cable lug to battery post and inter-tier or inter-rack cable lug to cell post. These cabling connections are also subjected to resistance changes due to acid related corrosion, loose connection fittings, improper mating surfaces, or material degradation. The LAR does not differentiate between the allowable resistance values for the different types of cell connections for the NCN-11 and NCN-27 cells. Annex F of IEEE Standard 450-2002 provides examples of methods for performing connection resistance measurements for various cell configurations. Please provide a discussion on any differences between industry accepted guidance (e.g. Annex F of IEEE 450-2002) for measuring intercell connections for the different types of batteries and methods used at MPS3. In the discussion, confirm that the resistance of the cabling connections (i.e., connections between inter-tier cable lugs, inter-rack cable lugs, terminal cable lugs, multiple posts and battery posts) is included in the bounding resistance value of 3894 micro-ohm.

RAI-2

Section 3.1.2, Class 1E Batteries, of the LAR discusses the ampere-hour capacity of the battery systems and the 2-hour sizing criterion. Section 3.2.1, Battery Resistance Evaluation, states: To ensure full functionality of the battery and associated loads with the new total allowable battery inter-cell impedance of 4764 micro-ohm, the most conservative battery draw and associated voltage drop was verified against the load profiles to ensure all battery minimum voltage requirements would be met. The primary bounding event for batteries is Loss of Onsite Power (LOP), but the calculations supporting the technical evaluation (Reference 6.6) also reviewed the normal and emergency operation loading

as part of the sizing verification. Please provide a discussion on the calculation which demonstrates that LOP event is the bounding event for the proposed TS total connection resistance of 3700 micro-ohm. In the discussion please provide:

a. A summary of assumptions, design basis and margins considered for total circuit resistances (battery internal resistance, battery system connection resistance, external conductor and conductor connection resistance, etc.) when evaluating battery load profiles for postulated operational conditions such as LOP. Please include a summary of load profile for other events such as station blackout and LOP coupled with an accident.

b. Examples of equipment with limiting (minimum) terminal voltage and current conditions required to operate, as the battery terminal voltage approaches 1.75V per cell at the end of 2 hours.

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