AEP-NRC-2014-05, Response to a Request for Additional Information Regarding Bulletin 2012-01, Design Vulnerability in Electric Power Design.

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

ML14035A213
Person / Time
Site:	Cook
Issue date:	01/31/2014
From:	Gebbie J Indiana Michigan Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
AEP-NRC-2014-05, BL-12-001
Download: ML14035A213 (7)

Text

INDIANA Indiana Michigan Power MICHIGAN Cook Nuclear Plant POWERO One Cook Place Bridgman, Ml 49106 A unit ofAmerican Electric Power Indiana MichiganPower.com January 31, 2014 AEP-NRC-2014-05 10 CFR 50.54(f)

Docket Nos.: 50-315 50-316 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Donald C. Cook Nuclear Plant Units 1 and 2 Response to a Request for Additional Information (RAI) Regarding Bulletin 2012-01, "Design Vulnerability in Electric Power Design"

References:

1. U. S. Nuclear Regulatory Commission (NRC) Bulletin 2012-01, "Design Vulnerability in Electric Power System," dated July 27, 2012, ADAMS Accession No. ML12074A115.

2. Letter from J. P. Gebbie, Indiana Michigan Power Company (I&M), to NRC, "Donald C. Cook Nuclear Plant Unit 1 and Unit 2, Response to NRC Bulletin 2012-01, Design Vulnerability in Electric Power System," AEP-NRC-2012-93, dated October 25, 2012, ADAMS Accession No. ML12312A465.

3. Letter from M. G. Evans, NRC, to L. J. Weber, I&M, "Request for Additional Information Regarding Response to Bulletin 2012-01, "Design Vulnerability in Electric Power System," dated December 20, 2013, ADAMS Accession No. ML13351A314.

On July 27, 2012, the U. S. Nuclear Regulatory Commission (NRC) issued Bulletin 2012-01, "Design Vulnerability in Electric Power System" (Reference 1). The objectives of the bulletin were stated as follows:

" To notify the addressees that the NRC staff is requesting information about the facilities' electric power system designs, in light of the recent operating experience that involved the loss of one of the three phases of the offsite power circuit (single-phase open circuit condition) at Byron Station, Unit 2, to determine if further regulatory action is warranted.

• To require that the addressees comprehensively verify their compliance with the regulatory requirements of General Design Criterion (GDC) 17, "Electric Power Systems," in Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50 or the applicable principal design criteria in the updated final safety analysis report; and the design criteria for protection systems under 10 CFR 50.55a(h)(2) and 10 CFR 50.55a(h)(3).

U. S. Nuclear Regulatory Commission AEP-NRC-2014-05 Page 2

• To require that addressees respond to the NRC in writing, in accordance with 10 CFR 50.54(f).

The NRC requested that licensees submit a written response within 90 days of the date of the bulletin. Indiana Michigan Power Company's (l&M's) written response for the Donald C. Cook Nuclear Plant (CNP) was submitted via AEP-NRC-2012-93, dated October 25, 2012 (Reference 2).

On December 20, 2013, the NRC issued a Request for Additional Information "Request for Additional Information Regarding Response to Bulletin 2012-01, "Design Vulnerability in Electric Power System" (Reference 3). This letter was sent to selected power reactor licensees and holders of construction permits regarding plant responses to Reference 2 and calls for a response by February 3, 2014.

This letter provides I&M's, licensee for CNP Unit 1 and Unit 2, response to Reference 3. to this letter provides an affirmation statement. Enclosure 2 Provides I&M's response to Reference 3.

Copies of this letter and its enclosures are being transmitted to the Michigan Public Service Commission and Michigan Department of Environmental Quality, in accordance with the requirements of 10 CFR 50.91. There are no new regulatory commitments associated with this response. Should you have any questions, please contact Mr. Michael K. Scarpello, Regulatory Affairs Manager, at (269) 466-2649.

Sincerely, Joel P. Gebbie Site Vice President JMT/amp

Enclosures:

1. Affirmation

2. Response to Request for Additional Information Regarding Bulletin 2012-01 c: J. T. King, MPSC S. M. Krawec, AEP Ft. Wayne, w/o enclosures MDEQ - RMD/RPS NRC Resident Inspector C. D. Pederson, NRC Region III T. J. Wengert, NRC Washington, D.C.

Enclosure I to AEP-NRC-2014-05 AFFIRMATION I, Joel P. Gebbie, being duly sworn, state that I am Site Vice President of Indiana Michigan Power Company (I&M), that I am authorized to sign and file this request with the Nuclear Regulatory Commission on behalf of I&M, and that the statements made and the matters set forth herein pertaining to I&M are true and correct to the best of my knowledge, information, and belief.

Indiana Michigan Power Company Joel P. Gebbie Site Vice President SWORN TO AND SUBSCRIBED BEFORE ME THIS DAY OF ,2014 DANIELLE BURGOYNE Notary Public, State of Michigan County of Berrien My Commission Expires 04-04-2018 My. Commssio ExNotapires /ic- Acting In the County of'*;;f My Commission Expires (,* ,---*

Enclosure 2 to AEP NRC 2014-05 Donald C. Cook Nuclear Plant Response to Request for Additional Information Regarding Bulletin 2012-01 In order for the U. S. Nuclear Regulatory Commission (NRC) staff to complete its review of Indiana Michigan Power Company's (I&M) response (Reference 2) to Bulletin 2012-01, "Design Vulnerability in Electric Power System", the NRC letter (ADAMS ML13351A314) dated December 20, 2013, requests the following from I&M, licensee for Donald C. Cook Nuclear Plant (CNP) Units 1 and 2:

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-lE 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 Industry Operating Experience for the events at Byron station, related to an Open Phase Condition (OPC), were reviewed and interim corrective actions were implemented at CNP.

Based on CNP's offsite power configuration, electrical design details, and on lessons learned, the following actions were taken to ensure plant operators can promptly diagnose and respond to OPCs:

• Interim Corrective Actions o Periodic walk-downs of the switchyards are on-going to identify OPC vulnerabilities.

The CNP switchyards (34.5kV, 69kV, 345kV and 765kV) have two walkdowns that are performed by American Electric Power (AEP) Transmission personnel under CNP's Preventative Maintenance program. Both are performed per an Inter-Organizational agreement between CNP and AEP Transmission. AEP is the parent company to I&M. One inspection is an in-depth inspection performed on a monthly basis. The other inspection is performed weekly per the requirements in Nuclear Electric Insurance Limited Standards and performs visual inspections of switchyard circuit breakers and batteries.

o Operating instructions and training curriculum were reviewed to ensure operators can diagnose and respond to an OPC.

Familiarization information was promptly provided to the CNP operators when the concern from the Byron open phase event became apparent. Also, to increase awareness of the operators, CNP updated lesson plans to address the concern related to the Byron open phase event, including modifications made to the 34.5kV under voltage (UV) relays to detect open phase.

to AEP-NRC-2014-05 Page 2 o Bus transfer procedures were updated to ensure voltage on the low side of the offsite source, Reserve Auxiliary Transformers (RAT), is checked prior to bus transfers and after transfers are complete.

To provide defense in depth, the bus transfer procedures were updated to visually check the Load Tap Changer (LTC) position when auxiliary buses are manually transferred from Unit Auxiliary Transformers (UATs) to RATs during normal shutdown. The LTC position is expected to indicate high if there was a loss of phase on 34.5kV.

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

Inspections of the transformers (RATs, UATs, and Main Transformers) are performed daily by CNP operators to ensure parameters are within expected limits. These include RAT output voltage, LTC position and operation, backup control power availability, temperature, etc., which would provide early warning of offsite power related anomalies o Infrared inspections of switchyard equipment are being completed as part of routine inspections.

As part of the CNP predictive maintenance program, thermography monitoring of switchyard components is performed on a periodic basis consistent with Electric Power Research Institute (EPRI) Guidelines. If conditions warrant, thermography monitoring is performed more frequently. Thermography is performed as a preventive maintenance task and also is performed following maintenance that requires connection changes. Transformer cooling radiators are also monitored using thermography. Thermography monitoring is performed every 3 months on the UATs and the main transformers. The RATs are normally in standby (energized but not loaded) except during refueling outages, therefore thermography monitoring is performed every 18 months on the RATs.

o UV relays were added to the RATs and operations procedures were revised to ensure appropriate response to OPC alarms.

For CNP, the most significant impact from OPC is on the 34.5kV circuit. CNP analysis indicated that a loss of voltage on one of the phases may not have been detected by the RAT instrumentation scheme in place at that time. To supplement the existing detection scheme, UV relays have been added across the 34.5kV phases 2-3 on all four RATs. The addition of these UV relays, combined with the existing instrumentation, now makes it possible to detect loss of voltage on all three phases. The current instrumentation will annunciate a trouble alarm if an open phase did occur on any of the three phases of the 34.5kV circuit. Annunciator response procedures were revised to provide guidance to operators to recognize and respond to an open phase in the 34.5kV circuit that supplies reserve auxiliary transformers.

to AEP-NRC-2014-05 Page 3 o Operations surveillance procedures were revised to include recognition of equipment problems caused by OPC.

Operations surveillance procedures were revised to incorporate the recognition of an OPC. The offsite power sources, via the RATs, are maintained in standby during normal operation. Operators check the availability of offsite power by sensing voltage on one of the three 4 kV phases. Since voltage is checked on only one of the phases, loss of voltage on other phases may not be detected. As an interim action to address lack of detection on the other phases, UV relays were added which will alarm in the control room.

Response 2 - Status and Schedule for Completion of Plant Design Changes

• Status o All holders of operating licenses and combined licenses for nuclear power reactors are investigating options being researched by several vendors (PSC2000, EPRI, Schweitzer, etc.) to detect OPC faults. There is currently no available technology that has been proven to detect all the required open phase fault conditions for all plant and transformer designs.

o All holders of operating licenses and combined licenses for nuclear power reactors are working together on the development of the Nuclear Energy Institute (NEI) OPC Guidance Document, as well as the development of enhancements to software tools. For example, OPC capability was added to Electrical Transient Analyzer Program software which is used at CNP.

o With the goal of ensuring accurate detection without compromising nuclear safety or increasing plant risk, new OPC technology is being thoroughly evaluated, tested, and fully analyzed before installation.

o A detailed study to analyze OPC vulnerability at CNP, in accordance with Reference 4, is currently in progress and is expected to be completed by April 2014.

• Schedule o I&M has adopted the generic schedule provided in the Industry OPC Initiative defined in Reference 4.

" I&M plans to meet the milestones of this schedule; however, deviations may be required to accommodate outage schedules, software and hardware availability, manufacturer's delivery capabilities, licensing delays, etc.

o Based on the preliminary results of the detailed study to analyze OPC vulnerability, CNP expects to meet the generic schedule provided (Reference 4).

Once the analysis is complete, a detailed plan and schedule for corrective actions will be developed. Any deviation, if needed, will be documented through the deviation/exemption process addressed in the NEI OPC Guidance Document.

to AEP-NRC-2014-05 Page 4

REFERENCES:

1. U. S. Nuclear Regulatory Commission (NRC) Bulletin 2012-01, "Design Vulnerability in Electric Power System", dated July 27, 2012, ADAMS Accession No. ML12074A115.

2. Letter from J. P. Gebbie, Indiana Michigan Power Company (I&M), to NRC, "Donald C. Cook Nuclear Plant Unit 1 and Unit 2, Response to NRC Bulletin 2012-01, Design Vulnerability in Electric Power System," AEP NRC-2012-93, dated October 25, 2012, ADAMS Accession No. ML12312A465

3. Letter from M. G. Evans, NRC, to L. J. Weber, I&M, "Request for Additional Information Regarding Response to Bulletin 2012-01, "Design Vulnerability in Electric Power System", dated December 20, 2013, ADAMS Accession No. ML13351A314.

4. Nuclear Energy Institute document NEI 13-12, "Open Phase Condition Industry Guidance Document," Revision 0, dated December 2013.