ONS-2014-003, Response to Request for Additional Information Regarding Response to Bulletin 2012-01, Design Vulnerability in Electric Power System.

Response to Request for Additional Information Regarding Response to Bulletin 2012-01, Design Vulnerability in Electric Power System.

ML14035A453
Person / Time
Site:	Oconee
Issue date:	02/03/2014
From:	Batson S Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ONS-2014-003
Download: ML14035A453 (6)

Text

DUKER ENERGYe Scot L.Batson Vice President Oconee Nuclear Station Duke Energy ONOIVP 17800 Rochester Hwy Seneca, SC 29672 o: 864.873.3274 f, 864.873. 4208 Scott.Betson@duke-energy.com 10 CFR 50.54 (f)

ONS-2014-003 February 3, 2014 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 Duke Energy Carolinas, LLC (Duke Energy)

Oconee Nuclear Station (ONS), Unit Nos. 1, 2, and 3 Docket Nos. 50-269, 50-270, and 50-287 Renewed License Nos. DPR-38, DPR-47, and DPR-55 Response to Request for Additional Information Regarding Response to Bulletin 2012-01, "Design Vulnerability in Electric Power System"

Reference:

1. NRC Letter, Request for Additional Information Regarding Response to Bulletin 2012-01, "Design Vulnerability in Electric Power System, "dated 12/20/2013 (ADAMS ML13351A314).

On July 27, 2012, the Nuclear Regulatory Commission (NRC) issued NRC Bulletin 2012-01, "Design Vulnerability in Electric Power System," to all power reactor licensees and holders of combined licenses for nuclear power reactors. Duke Energy provided its response to Bulletin 2012-01 in a letter dated October 23, 2012 (ADAMS ML12300A426). On December 20, 2013, the NRC issued a request for additional information (RAI) requesting licensees to (1) verify the completion of interim corrective actions and compensatory measures and (2) to report the status of each licensee's long-term corrective actions. The enclosure to this letter contains Duke Energy's response for the Oconee Nuclear Station (ONS).

There are no new regulatory commitments contained in this letter.

Please address any comments or questions regarding this matter to Bob Meixell, Oconee Regulatory Affairs, at (864) 873-3279.

§2f7/

U. S. Nuclear Regulatory Commission February 3, 2014 Page 2 I declare under penalty of perjury that the foregoing is true and correct. Executed on February 3, 2014.

Sincerely, Scott L. Batson Vice President Oconee Nuclear Station Enclosure

,U. S. Nuclear Regulatory Commission February 3, 2014 Page 3 xc (w/enclosure):

Mr. Victor McCree, Regional Administrator U.S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 Mr. Richard Guzman, Project Manager (ONS)

(by electronic mail only)

U.S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop O-8C2 Rockville, MD 20852 Mr. Eddy Crowe NRC Senior Resident Inspector Oconee Nuclear Station

Enclosure Oconee Nuclear Station Units 1, 2, and 3 Response to the NRC Request for Additional Information Bulletin 2012-01

Enclosure - Response to NRC Request for Additional Information February 3, 2014 Page 1 RAI 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 I - Summary of All Interim Corrective Actions Lessons learned from the events at Byron Nuclear Station were reviewed and various interim corrective actions evaluated for safety and efficiency at the Oconee Nuclear Station (ONS).

Based on ONS's offsite power configuration, electrical design details, and lessons learned, the following actions were taken to ensure plant operators can promptly diagnose and respond to open phase conditions (OPC):

Interim Corrective Actions:

1. Revised the ONS Units 1, 2, and 3 alarm response guides, to include appropriate responses during a possible OPC.

2. ONS Operations personnel perform daily rounds of the switchyards. This is a general observation performed on the equipment to note any out of normal conditions and take appropriate actions. The daily switchyard rounds procedure was revised to incorporate specific points to look for areas of degraded off site power vulnerabilities.

3. Completed a review of switchyard equipment Preventive Maintenance (PM) procedures to adequately address inspection for potential degraded connections, insulators, etc.

Procedures have been revised as needed.

4. Preliminary training (Read & Sign Package) has been developed and completed for applicable operations personnel.

5. Developed classroom training for this event: causes, consequences, and response. The training is scheduled to be completed in 2014.

6. ONS Maintenance personnel perform multiple walk downs of the switchyards per month monitoring the system. During the walk downs, maintenance personnel look for any anomalies and initiate a corrective action report and/or Work Request to address the issue.

7. Thermal imaging is performed on a semi-annual frequency in the switchyard to detect any potential connection or equipment problems.

Enclosure - Response to NRC Request for Additional Information

'February 3, 2014 Page 2 Response 2 - Status and schedule for completion of plant design changes and modifications The Duke Energy nuclear fleet is investigating options being researched by several vendors, e.g., PSC2000TM, Electric Power Research Institute (EPRI), Schweitzer, etc., to detect open phase fault conditions. There is currently no proven industry technology available 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 implementation.

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 Nuclear Energy Institute (NEI) Open Phase Condition industry guidance document, as well as development of enhancements to the Electrical Transient Analyzer Program (ETAP) software tool being used to analyze open phase fault conditions.

Duke Energy intends to follow the NEI Industry Initiative document and the generic schedule provided within that document. A provision in the NEI Industry Initiative 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 Industry Initiative exemption process.

The NEI Initiative recommends installing new equipment to disable (i.e., trip) the offsite power source for an Open Phase Condition of the transformer(s) that connect the plant onsite power system to the offsite power source. At ONS, the transformers credited with providing offsite power to the onsite power systems are nuclear safety-related and controlled by the station's Technical Specifications (TSs) as part of both the offsite power source and as part of one of two onsite emergency power sources, namely the Keowee Hydroelectric Station's emergency power overhead path. Installing new equipment to change the operation of this transformer will likely require changes to the ONS TSs as compared to other nuclear stations. As outlined in the NEI Industry Initiative, impacts to ONS TSs are likely to result in changes to the schedule provided in the Initiative, at a minimum, to allow for increased NRC review times.