MNS-14-017, Response to Request for Additional Information Regarding Response to NRC Bulletin 2012-01

Response to Request for Additional Information Regarding Response to NRC Bulletin 2012-01

ML14043A112
Person / Time
Site:	Mcguire, McGuire
Issue date:	01/30/2014
From:	Capps S Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
MNS-14-017
Download: ML14043A112 (4)

Text

DUKESteven DUKE Vice D. Capps President ENERGY, McGuire Nuclear Station Duke Energy MG01VP 12700 Hagers Ferry Road Huntersville, NC 28078 o: 980.875.4805 f: 980.875.4809 January 30, 2014 Steven.Capps@duke-energy.com Serial No: MNS-14-017 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Duke Energy Carolinas, LLC (Duke Energy)

McGuire Nuclear Station, Units 1 and 2 Docket Numbers 50-369 and 50-370 Response to Request for Additional Information Regarding Response to NRC Bulletin 2012-01 On July 27, 2012, the Nuclear Regulatory Commission (NRC) issued NRC Bulletin 2012-01 "Design Vulnerability in Electric Power System." By letter dated October 25, 2012, Duke Energy submitted McGuire Nuclear Station's response to this bulletin.

By letter dated December 20, 2013, the NRC requested additional information from licensees to verify that interim corrective actions have been completed and to determine the status of long-term corrective actions. The enclosure provides Duke Energy's response to this request and contains no new regulatory commitments.

If there are any questions or if additional information is needed, please contact Brian Richards of McGuire Regulatory Affairs at (980) 875-5171.

I declare under penalty of perjury that the foregoing is true and correct. Executed on January 30, 2014.

Sincerely Steven D. Capps Enclosure www.duke-energy.com

U.S. Nuclear Regulatory Commission January 30, 2014 Page 2 xc:

V. M. McCree, Regional Administrator U. S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave. NE, Suite 1200 Atlanta, GA 30303-1257 J. C. Paige, Project Manager (CNS & MNS)

U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, MD 20852-2738 J. Zeiler NRC Senior Resident Inspector McGuire Nuclear Station

Enclosure McGuire Units 1 and 2 Response to the NRC Request for Additional Information Bulletin 2012-01 NRC letter (ADAMS ML13351A314) dated December 20, 2013 requests the following:

"In order for the NRC staff to complete its review of responses to the bulletin, the following additional information is requested:

1. Provide a summary of all interim corrective actions that have been taken since the January 30, 2012, event at Byron Station, Unit 2, to ensure that plant operators can promptly diagnose and respond to open phase conditions on the offsite power circuits for Class-i E vital buses until permanent corrective actions are completed.

2. Provide a status and schedule for completion of plant design changes and modifications to resolve issues with an open phase of electric power."

Response 1 - Summary of All Interim Corrective Actions Lessons learned from the events at Byron station were reviewed and various interim corrective actions evaluated for effectiveness based on McGuire Nuclear Station and transformer design.

Based on lessons learned, the following actions have been taken to ensure plant operators can promptly diagnose and respond to an open phase condition:

• A walkdown of the switchyard to identify open phase vulnerabilities.

• Bi-annual infrared inspections of switchyard and transformer yard equipment are being completed as part of existing preventive maintenance inspections.

• An alarm was added to the operator aid computer based on switchyard busline current data points.

• Revised operations procedures to include appropriate response to the OAC alarm.

" Transformer yard rounds have been performed daily and include general and detailed inspections of the transformers to ensure parameters are within expected limits.

• The 4kV essential bus is monitored for a Loss-of-Voltage (LOV) condition by three undervoltage relays. There is one LOV relay for each phase of the bus.

• The 4kV essential bus is also monitored for degraded voltage conditions by three additional undervoltage relays. There is one degraded voltage relay for each phase of the bus.

Page 1

Enclosure McGuire Units 1 and 2 Response to the NRC Request for Additional Information Bulletin 2012-01 Response 2 - Status and Schedule for Completion of Plant Design Changes The Duke Energy fleet is investigating options being researched by several vendors (PSC2000, EPRI, Schweitzer, etc.) to detect open phase fault conditions. There is currently no industry technology that has been proven to detect all the required open phase fault conditions for all plant and transformer designs. With the goal of ensuring accurate detection without compromising nuclear safety or increasing plant risk, it is paramount that this new technology being evaluated be tested and fully analyzed before installation. These research investigations are progressing faster than anticipated.

Design studies of the single open phase fault conditions have been started for the Duke Energy nuclear fleet. The Duke Energy nuclear fleet is fully engaged in the development of the NEI Open Phase Condition Industry Guidance Document, as well as development of enhancements to the ETAP software tool being used to analyze open phase fault conditions.

McGuire Nuclear Station intends to follow the schedule provided in the NEI Industry Initiative Document. A provision in the schedule has already been identified for any deviations required for items such as the accommodation of outage schedules or technology availability and will be documented through the NEI exemption process.

Page 2