MNS-14-045, Responses to Request for Additional Information Related to License Amendment Request for One-Time Change to Technical Specification 3.8.4, DC Sources-Operating for Battery Replacement Dated October 28, 2013

Responses to Request for Additional Information Related to License Amendment Request for One-Time Change to Technical Specification 3.8.4, DC Sources-Operating for Battery Replacement Dated October 28, 2013

ML14164A028
Person / Time
Site:	Mcguire, McGuire
Issue date:	06/03/2014
From:	Capps S Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
MNS-14-045, TAC MF2983, TAC MF2984
Download: ML14164A028 (4)

Text

I. . 41 Steven D. Capps Vice President ENERGY McGuire Nuclear Station Duke Energy MG01VP 1 12700 Hagers Ferry Road Huntersville, NC 28078 o: 980.875.4805 f: 980.875.4809 Steven. Ca pps@du ke-energy.com Serial No.: MNS-14-045 June 3, 2014 10 CFR 50.90 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION: Document Control Desk

Subject:

Duke Energy Carolinas, LLC McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369 and 50-370 License Amendment Request for One-Time Change to Technical Specification 3.8.4, "DC Sources-Operating" for Battery Replacement dated October 28, 2013 (TAC Nos. MF2983 and MF2984)

Responses to Request for Additional Information Related to the License Amendment Request (LAR)

This letter provides the responses to the request for additional information (RAI) regarding the referenced LAR dated October 28, 2013 (ADAMS No. ML13304B445). This request was received from the NRC staff by letter dated May 12, 2014. The NRC staff's questions and Duke Energy's responses are provided in Attachment 1.

The conclusions reached in the original determination that the LAR contains No Significant Hazards Considerations and the basis for the categorical exclusion from performing an Environmental/Impact Statement have not changed as a result of this request for additional information. This letter contains no new regulatory commitments.

Please direct any questions you may have in this matter to Lee A. Hentz at (980) 875-4187.

I declare under penalty of perjury that the foregoing is true and correct. Executed on June 6, 2014.

Sincerely, Steven D. Capps Attachment www.duke-energy.com

" p, US Nuclear Regulatory Commission June 3, 2014 Page 2 cc w/

Attachment:

V. M. McCree Regional Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 J. Zeiler NRC Senior Resident Inspector McGuire Nuclear Station G. Edward Miller (addressee only)

Project Manager (McGuire)

U.S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, MD 20852-2738 W. L. Cox Ill, Section Chief North Carolina Department of Environment and Natural Resources Division of Environmental Health Radiation Protection Section 1645 Mail Service Center Raleigh, NC 27699-1645

ATTACHMENT 1 REQUEST FOR ADDITIONAL INFORMATION MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 PROPOSED CHANGES TO TECHNICAL SPECIFICATION 3.8.4 TIME-EXTENSION OF REQUIRED ACTION A.2.2 COMPLETION TIME DOCKET NOS. 50-369 AND 50-370 By letter dated October 28, 2013, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13304B445), Duke Energy Carolinas (Duke Energy) submitted a license amendment request (LAR) to amend the Technical Specifications (TS) 3.8.4, "DC Sources - Operating," for McGuire Nuclear Station, Units 1 and 2, in support of plant modifications to replace existing shared vital batteries while at power. In order for the NRC staff to complete its review of the LAR, the following additional information is requested.

1. On page 2 of Attachment 1 of the LAR, the licensee stated that about 50% of the vital batteries cells are affected by positive post seal nut and jar lid cracking. Please discuss available mitigation strategies/further maintenance that will be used on the new batteries to prevent this potential failure mechanism.

Duke Energy Response:

The post seal nut and jar lid cracking are caused by nodular corrosion between the post seal and the lead post. This phenomena is a characteristic of all lead acid batteries and is not preventable by the licensee.

Nodular corrosion occurs at a molecular level between the Lead Oxide and water under the post seal. Due to imperfections in the lead post created during the manufacturing process, microscopic capillary tubes are created along the surface of the lead posts. These tubes channel electrolyte under the post seal which results in lead ions bonding with the electrolyte creating lead compounds that occupy a larger volume than the lead alone. This causes the lead compounds to push out against the post seal. No maintenance practices can prevent the chemical reactions since the reactants involved are native to the cell and the post seal is a non-replaceable part of the cell.

Inspections for cell cracking is part of the normal weekly and quarterly vital battery preventative maintenance. All cracks are documented on a vital battery log sheet, which is updated by Engineering and kept by Document Control Management.

From discussions regarding the nodular corrosion phenomenon with battery vendors, other nuclear stations, and industry experts there is currently no permanent solution to prevent nodular corrosion as the battery ages. Different vendors have mitigating strategies however, none are able to guarantee their cells will not experience cracking as the cell ages. As indicated by the performance tests, the McGuire NCN-27 batteries have shown minimal capacity loss for their age.

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ATTACHMENT I

2. On page 8 of Attachment 1 of the LAR, the licensee stated that the new vital batteries are essentially the same as the existing batteries with the exception of the new ones being rated 1944 ampere hours instead of 1945 ampere hours at the 8-hour discharge.

Please explain why reducing the ampere hours (AH) rating does not impact the existing design/licensing basis margins for the DC power system.

Duke Energy Response:

The 1944AH/1 945AH rated capacity is for the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> discharge test to 1.75V per cell. McGuire does take credit for discharging the vital batteries for eight hours at the eight hour rate. The existing licensing basis states the battery shall be able to meet its defined duty cycle for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

While the published 8-hour rate has changed by 1 AH, the 1 min (1840A), 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> (975A) and 30 min (1327A) discharge rates have not changed. These are the data points that are used in the battery sizing calculation per IEEE-485-1983 to determine the required duty cycle for the vital batteries. Since the inputs to the sizing calculation have not changed, the existing design/licensing basis margins remain bounding for the Vital DC power system.

3. On page 10 of Attachment 1 of the LAR, the licensee stated that a temporary charger will be installed to maintain the temporary battery at 132 volts DC. The temporary charger will have a disconnect to electrically isolate it from the temporary battery and the DC bus. Describe the design and capability of the temporary battery charger, including how it will be connected to a Class 1 E supply, if needed. Also, please explain whether the temporary battery charger will impact the emergency diesel generator loading.

Duke Energy Response:

The temporary charger is a commercial grade charger powered from a non-safety source.

Connecting the charger to non-safety power will not affect the emergency diesel generator loading. The temporary charger shall be capable of maintaining the battery on float charge which is the normal configuration for the replacement evolution. The charger is not intended to carry any load other than the one to two amps required to maintain the temporary battery on float charge.

The temporary charger will remain isolated from the Class 1 E DC electrical system by the temporary battery disconnect switch and the open breakers on EVDS distribution center.

In the event that the temporary battery is required, the temporary charger will be isolated procedurally by opening the temporary charger's DC output via the breaker or disconnect switch. After the charger is disconnected from the temporary battery, alignments can be made to close the temporary battery disconnect switch and make the appropriate breaker alignments on EVDS to tie the temporary battery to recover a lost DC channel. As discussed in the LAR, this alignment is only for defense-in-depth recovery efforts to stabilize the plant in the event that the cross-tied battery is lost.

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