ML17061A672

Summary of February 15, 2017, Meeting with Tennessee Valley Authority on Updates to the Transmission System Regarding Extended Power Uprate for Browns Ferry Nuclear Plant, Units 1, 2, and 3

ML17061A672
Person / Time
Site:	Browns Ferry
Issue date:	04/06/2017
From:	Farideh Saba Plant Licensing Branch II
To:	James Shea Tennessee Valley Authority
Saba F DORL/LPL2-2 301-415-1447
References
CAC MF6741, CAC MF6742, CAC MF6743
Download: ML17061A672 (7)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 April 6, 2017 LICENSEE: Tennessee Valley Authority FACILITY: Browns Ferry Nuclear Plant, Units 1, 2, and 3

SUMMARY

OF FEBRUARY 15, 2017, MEETING WITH TENNESSEE VALLEY AUTHORITY ON UPDATES TO THE TRANSMISSION SYSTEM REGARDING EXTENDED POWER UPRATE FOR BROWNS FERRY NUCLEAR PLANT, UNITS 1, 2, AND 3 (CAC NOS. MF6741, MF6742, AND MF6743)

On February 15, 2017, a Category 1 public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) staff and representatives of Tennessee Valley Authority (TVA, the licensee) at NRC Headquarters, One White Flint North, 11555 Rockville Pike, Rockville, Maryland. The purpose of the meeting was for TVA to present to the NRC staff changes to the previously proposed modifications associated with the transmission system and impacts of those changes on the safety and environmental assessments regarding the extended power uprate (EPU) license amendment request (LAR) for Browns Ferry Nuclear Plant (Browns Ferry)

Units 1, 2, and 3. The meeting notice and agenda, dated January 13, 2017, are available in the Agencywide Documents Access and Management System (ADAMS) under Accession No. ML17034A472. A list of attendees is provided as Enclosure 1.

The licensee submitted the EPU LAR on September 21, 2015 (ADAMS Accession No. ML15282A152), with numerous supplements. Upon approval of the EPU LAR, the licensee plans to implement the EPU in the spring of 2018 for Unit 3, the fall of 2018 for Unit 1, and the spring of 2019 for Unit 2. The proposed EPU amendment would increase the authorized maximum steady-state reactor core power level for each unit from 3,458 megawatts thermal (MWt) to 3,952 MWt.

The licensee's presentation document, which was provided prior to the meeting and attached to the meeting notice, is available under ADAMS Accession No. ML17034A332. The licensee's presentation began with providing background information regarding the transmission system.

TVA stated that an Interconnection System Impact Study (SIS) was performed for Browns Ferry, Units 1, 2, and 3, at EPU conditions. The SIS determined that main generator stability issues exist for a three-phase fault on one of several transmission lines coincident with certain transmission lines already out of service (N-1-1 event). TVA stated that the main generators would become unstable during the N-1-1 event because the existing main generator's excitation systems could not raise the field voltage fast enough and high enough to prevent the instability.

To mitigate the transient stability issues during an event, TVA had planned to install a new shunt-fed, static excitation system on each of the three Browns Ferry units. However, the licensee identified a legacy error in the generator field parameter values that were provided after stator rewind in 2003, and that were used in the development of the Interconnection SIS. The licensee found that, at EPU power levels, more extensive compensatory measures would be needed for the main generators to remain stable and that the previous stability mitigation plan, addressed in the licensee's Supplement 18, dated May 27, 2016 (ADAMS Accession No. ML16197A563), was no longer viable. The licensee further discussed the differences between the previous mitigation plan and the updated plan. TVA stated that the updated

stability mitigation plan for the N-1-1 event would include (1) modifying the existing excitation system from bus-fed type to self-excited type (instead of the previously proposed static excitation system) on each Browns Ferry unit, and (2) installing a static volt-ampere reactive compensator at the existing Limestone Substation near Browns Ferry. The NRC staff asked whether TVA plans to perform any testing in the future when the modifications are done. TVA responded that there is a requirement by the Federal Energy Regulatory Commission (FERC) to do testing and that the FERG-required testing would be performed in several years.

The licensee, in its letter dated January 20, 2017 (ADAMS Accession No. ML17023A200),

submitted Supplement 36 to the EPU LAR. Enclosures to Supplement 36 provided revisions to the Interconnection SIS, Transmission Stability Study, TVA responses to the NRC staff's request for additional information, probabilistic risk assessment, Power Uprate Safety Analysis Report Section 2.5.1.2.2, and list and status of modifications. The licensee stated that the modifications related to the main generator's excitation systems will be implemented at Browns Ferry during the fall of 2020 at Unit 1, during the spring of 2021 at Unit 2, and during the spring of 2020 at Unit 3. The NRC staff noted that the updated system modifications will be implemented sooner than previously planned modifications. The licensee added that, from the time the EPU is implemented until modifications are complete, TVA will develop and follow operating guidelines and procedures for derating the plant, if needed.

The NRC staff asked clarifying questions throughout the presentation. Specifically, the NRC staff asked the licensee to provide the values (before the error and after correcting the error) of the generator field parameter affected by the identified legacy error. The licensee provided the requested information by an e-mail where the licensee explained that the open circuit transient time constant value was the generator field parameter affected by the identified legacy error. A value of 7.283 seconds was reported after the 2003 Stator rewind versus a 2016 corrected value of 9.273 seconds. Both of these numbers are at the 1,330-million volt-ampere rating.

Additionally, during the presentation, the NRC staff asked TVA to provide a block diagram of the existing generator exciter system and the proposed modified generator exciter system. The licensee, in another e-mail, provided the requested diagrams as shown in Enclosure 2 of this meeting summary.

The licensee continued its presentation (starting from slide 14) by discussing environmental aspects of the transmission system update. TVA explained that instead of installing capacitor banks at the Wilson Substation in Wilson County, Tennessee, TVA would install a static volt-ampere reactive compensator at the existing Limestone Substation in Limestone County, Alabama, near Browns Ferry. TVA submitted LAR Supplement 37 on February 3, 2017 (ADAMS Accession No. ML17034A562), which included updated TVA responses to the staff's request for additional information associated with environmental reviews, Revision 2 of the supplemental environmental report, and updated draft environmental assessment and finding of no significant impact. TVA did not identify any significant environmental impact from the updated transmission system.

There was one member of the public in attendance by telephone. Public Meeting Feedback forms were not received. At the end of the meeting, following questions and answers between the NRC staff and TVA representatives, the member of the public stated his concerns about the possibility of flooding of the Tennessee River and malfunction of the nearby dams, and the impact on operations of the Browns Ferry units. The NRC staff responded that the issues regarding the flooding and functionality of dams were not relevant to the subject of this meeting.

However, the NRC staff informed the member of the public that the NRC staff in the Office of Nuclear Reactor Regulation, Division of Japan Lessons Learned (JLD), has been evaluating

flooding hazards for all the nuclear power plants and that the majority of the JLD reports are publicly available in ADAMS.

Please direct any inquiries to me at 301-415-1447 or Farideh.Saba@nrc.gov.

~~~t1 ' b ~~ ~(_

Farideh E. Saba, Senior Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-259, 50-260, and 50-296

Enclosures:

1. List of Attendees

2. Charts - Existing Voltage Regulation and New Voltage Regulation cc w/enclosures: Distribution via Listserv

LIST OF ATTENDEES FEBRUARY 15. 2017. MEETING WITH TENNESSEE VALLEY AUTHORITY ON UPDATES TO THE TRANSMISSION SYSTEM REGARDING EXTENDED POWER UPRATE FOR BROWNS FERRY NUCLEAR PLANT. UNITS 1. 2. AND 3 Name Oraanization Farideh Saba U.S. Nuclear Reaulatorv Commission (NRC)

Benjamin Beasley NRC Russell Haskell NRC Vijay Goel NRC Adakou Foli NRC Todd Hilsmeier NRC Jeffrey Rikhoff NRC Kevin Folk NRC William Rautzen NRC Ami Patel NRC Briana Granae* NRC Gerard Dovie Tennessee Vallev Authority <TVA)

Pete Donahue TVA Dan Green TVA Ashley Michael TVA Joe Bashore TVA William Baker TVA Gordon Williams TVA Marvin Lewis* Public

• By telephone Enclosure 1

Transformer 480/135 Vac uuuu Existing Voltage Regulation nnnn AC Voltage I Current Input Gen Field Breaker

(

I Rectifier Assembly

( A .I.JC DC Generator 3<1> Output Turbine t

Exciter t

Generator Collector Rings Collector Rings 112 Enclosure 2

.i New Voltage Regulation AC \b1tag~ I Current Input Gen Ftelct ere Roct1f1or Assembty DC Goncrato l Output TUrbine Excit1 CoUectorR

SUBJECT:

SUMMARY

OF FEBRUARY 15, 2017, MEETING WITH TENNESSEE VALLEY AUTHORITY ON UPDATES TO THE TRANSMISSION SYSTEM REGARDING EXTENDED POWER UPRATE FOR BROWNS FERRY NUCLEAR PLANT, UNITS 1, 2, AND 3 (CAC NOS. MF6741, MF6742, AND MF6743) DATED APRIL 6, 2017 DISTRIBUTION:

Public BGrange, NRR LPL2-2 Reading File APatel, NRR RidsNrrLABClayton Resource WRautzen, NRR RidsRgn2MailCenter Resource JBowen, OEDO RidsACRS_MailCTR Resource TClark, OEDO RidsNrrPMBrownsFerry Resource TWertz, NRR RidsNrrDorlLpl2-2 Resource VGoel, NRR RHaskell, NRR KFolk, NRR THilsmeier, NRR JRikhoff, NRR RidsNrrDra Resource AFoli, NRR RidsNrrDe Resource RidsNrrDorl Resource ADAMS Access1on No.: ML17061A672 *b1y e-mar OFFICE NRR/DORL/LPL2-2/PM NRR/DORL/LPL2-2/LA NRR/DLR/RERP/BC(A)*

NAME FSaba BClayton (LRonewicz for) JRikhoff DATE 04/06/2017 04/06/2017 04/03/2017 OFFICE NRR/DE/EEEB/BC* NRR/DORL/LPL2-2/BC NRR/DORL/LPL2-2/PM NAME JZimmerman (RMathew for) BBeasley FSaba DATE 03/29/2017 04/06/2017 04/06/2017 OFFICIAL RECORD COPY