Note to readers: The following analysis of the Browns Ferry Nuclear Plant extended power uprate amendment comes directly from the beta version of Everstar's Gordian Research platform and was edited only for web formatting and to remove internal Gordian links. It was generated in about two minutes using this prompt: "for the browns ferry epu, produce a detailed summary of this application and all RAIs, RAI responses, and supplements. produce a table of the RAIs including the branch asking them and create a graphical timeline of the correspondence." For more insights, see related posts on uprates or contact hello@everstar.ai to get on the waiting list for an account.

Browns Ferry Nuclear Plant Extended Power Uprate: Comprehensive Analysis of Application, RAIs, and Regulatory Process

Executive Summary

The Browns Ferry Nuclear Plant (BFN) Extended Power Uprate (EPU) represents a significant licensing action undertaken by Tennessee Valley Authority (TVA) to increase the maximum authorized core thermal power level from 3,458 megawatts thermal (MWt) to 3,952 MWt, representing a 14.3% increase. This comprehensive analysis examines the EPU application submitted on September 21, 2015, the extensive Request for Additional Information (RAI) process that followed, and the ultimate approval granted by the Nuclear Regulatory Commission (NRC) on August 14, 2017. The EPU implementation was staggered across the three units during refueling outages in 2018-2019, adding approximately 465 MWe of generation capacity to TVA's portfolio. The review process involved multiple technical branches of the NRC, with over 200 RAIs addressed across areas including reactor systems, electrical engineering, mechanical components, and human factors. [0] [1] [2]

Technical Analysis

EPU Application Overview

The EPU application submitted by TVA on September 21, 2015, consisted of several key components that formed the technical basis for the power uprate request. The Power Uprate Safety Analysis Report (PUSAR), designated as NEDC-33860P, provided a comprehensive summary of safety analyses and evaluations performed to support the proposed increase in thermal power. This report followed the NRC-approved licensing topical report methodology NEDC-33304P-A, "Constant Pressure Power Uprate," Revision 4, also known as the Constant Pressure Power Uprate Licensing Topical Report (CLTR). For topics outside the CLTR approved applicability, such as the use of AREVA ATRIUM 10XM fuel, the technical evaluations were based on a series of NRC-approved AREVA methods. [0] [3]

The application also included the Fuel Uprate Safety Analysis Report (FUSAR), ANP-3403P, which addressed fuel-specific considerations for the EPU. Additional supporting documents included ANP-3404 (Browns Ferry Unit 3 Cycle 19 Representative Reload Analysis at Extended Power Uprate), ANP-3343 (Nuclear Fuel Design Report), and various mechanical design reports for the ATRIUM 10XM and ATRIUM 10 fuel assemblies. These evaluations concluded that all plant components, as modified, would continue to be capable of performing their design functions at the proposed uprated core thermal power level. [3] [4]

Major Technical Areas and Modifications

The EPU implementation required significant modifications to major balance-of-plant equipment. Key modifications included:

Replacement Steam Dryers: New steam dryers with increased structural design margin to accommodate EPU operation. These were curved hood six-bank dryers analyzed for fatigue resulting from flow-induced vibration and hydrodynamic loads.

Main Turbine Upgrades: Replacement of the High Pressure Turbine rotors with GE's Advanced Design Steam Path, designed specifically for the increased flow associated with EPU.

Condensate and Feedwater Systems: Installation of higher capacity condensate booster pumps and motors, modifications to the condensate demineralizer system, and replacement of reactor feedwater pumps.

Electrical System Modifications: Changes to the main generator excitation system and upgrades to various electrical components to handle the increased power output.

Instrumentation Upgrades: Recalibration of instruments, setpoint changes, and software modifications to accommodate the new operating parameters. [4] [5] [6]

The EPU resulted in a higher main steam flow rate achieved by increasing the reactor power along slightly modified rod and core flow control lines. It also increased reactor vessel dome pressure by less than 3% to help provide sufficient pressure control and turbine flow capabilities. [4]

Regulatory Considerations

RAI Process and Technical Review

The NRC's review of the Browns Ferry EPU application was extensive, involving multiple technical branches that issued over 200 RAIs. These RAIs covered a wide range of technical areas, reflecting the comprehensive nature of the regulatory review process. The major NRC technical branches involved in the review included:

Reactor Systems Branch (SRXB): Issued RAIs related to core performance, thermal-hydraulics, and safety analyses. These included questions about peak bundle power, stability characteristics, and various operational scenarios. [7] [8] [10]

Nuclear Performance and Code Review Branch (SNPB): Focused on nuclear performance and analytical methods, including questions about the MICROBURN-B2 code and fuel design considerations. [9]

Electrical Engineering Branch (EEEB): Addressed questions related to electrical power systems, including grid stability and the ability of electrical systems to support EPU operation. [10]

Mechanical and Civil Engineering Branch (EMCB): Concentrated on mechanical components, particularly the replacement steam dryers, which were a critical component of the EPU. [11] [12] [13]

Human Factors Engineering Branch (APHB): Examined operator actions, procedures, and training for EPU conditions. [14] [12] [11]

Accident Dose Branch (ARCB): Reviewed radiological consequences analyses under EPU conditions. [15] [16]

Spent Fuel Pool Branch (SFP): Evaluated spent fuel pool criticality safety analysis for EPU conditions. [17] [18] [11]

TVA responded to these RAIs through numerous supplements to the original application, with the response process extending from early 2016 through mid-2017. [11] [25] [18]

Approval and Implementation Timeline

The NRC issued the amendments approving the EPU on August 14, 2017, following a thorough review process that included evaluation by the Advisory Committee on Reactor Safeguards (ACRS). The ACRS completed its review and recommended approval on June 19, 2017. The implementation of the EPU was staggered across the three units during scheduled refueling outages:

Unit 3: Spring 2018 (completed in July 2018)

Unit 1: Fall 2018 (completed in January 2019)

Unit 2: Spring 2019

This staggered implementation approach allowed TVA to manage the significant modifications required for each unit while maintaining operational flexibility. [19] [4] [2] [20]

RAI Table and Correspondence Timeline

Table of RAIs by Branch

Graphical Timeline of EPU Correspondence

Uncertainties and Limitations

Despite the comprehensive nature of the EPU application and review process, several areas of uncertainty required special attention. One significant area was the replacement steam dryers, which were subject to extensive analysis to ensure structural integrity under EPU conditions. The NRC issued multiple RAIs related to the steam dryer design and analysis, reflecting the importance of this component to the safe operation of the plant at uprated conditions. [11] [12]

Another area of uncertainty involved the electrical grid stability under EPU conditions. TVA performed an Interconnection System Impact Study (SIS) for the EPU, which initially identified the need for a new 500 kV transmission line. However, subsequent analysis determined that this could be addressed through other modifications, including replacing six 500 kV breaker failure relays, installing capacitor banks in five locations throughout the TVA transmission system, and modifying the excitation system of all three BFN main generators. [11]

The elimination of containment accident pressure credit represented a significant safety enhancement included in the EPU application. This involved improving the thermal performance of the Residual Heat Removal (RHR) heat exchangers, which required extensive testing and analysis to demonstrate adequate performance under EPU conditions. [11] [17]

Recommendations and Next Steps

The successful implementation of the Browns Ferry EPU demonstrates the value of a thorough, systematic approach to major plant modifications and licensing actions. For utilities considering similar power uprates, several key recommendations emerge:

Comprehensive Application Development: Develop a thorough application that addresses all technical areas potentially affected by the power uprate, following established regulatory guidance such as the Constant Pressure Power Uprate Licensing Topical Report.

Proactive RAI Management: Anticipate areas of regulatory concern and be prepared to respond promptly to RAIs. The Browns Ferry experience shows that RAIs will likely focus on areas such as steam dryers, electrical systems, and safety analyses.

Phased Implementation Approach: Consider a staggered implementation approach across multiple units, as TVA did with Browns Ferry, to manage the significant modifications required and incorporate lessons learned from earlier implementations.

Post-Implementation Monitoring: Establish robust monitoring programs to verify that plant performance meets expectations under uprated conditions, particularly for components such as steam dryers that are susceptible to flow-induced vibration.

Procedure Updates and Training: Ensure that all procedures are updated and operators are thoroughly trained on the changes associated with EPU operation before implementation. [19] [4]

The Browns Ferry EPU represents a significant achievement in maximizing the value of existing nuclear assets while maintaining safety margins. The additional 465 MWe of generation capacity provides substantial benefits in terms of low-carbon electricity production and economic value. The lessons learned from this project can inform future power uprates and other major modifications at nuclear power plants across the industry.

[1] Browns Ferry, Units 1, 2 and 3 - Submits Proposed Technical Specifications Change TS-505 - Request for License Amendments - Extended Power Uprate.: ML15282A152

[2] Browns Ferry, Unit 1 - Response to NRC's Request for Additional Information Related to Technical Specifications (TS) Change No. TS - 431 - Request For License Amendment Extended Power Uprate (EPU) Operation.: ML051580249

[3] Browns Ferry Units 1, 2 & 3, Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Upgrade (EPU) - Supplement 28, Responses to Requests for Additional Information.: ML16217A144

[4] Browns Ferry, Units 1, 2 & 3, Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 9, Responses to Requests for Additional Information.: ML16095A293

[5] Browns Ferry Nuclear Plant, Units 1, 2, and 3 - Responses to Requests for Additional Information Regarding License Amendment, Extended Power Update, Supplement 16: Letter, Enclosure 2, Enclosure 3: ML16141B248

[6] Browns Ferry, Units 1, 2, and 3 - Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 20, Responses to Requests for Additional Information.: ML16166A151

[7] Browns Ferry Nuclear Plant, Units 1, 2 & 3, Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate - Supplement 19, Responses to Requests for Additional Information.: ML16169A332

[8] Browns Ferry Nuclear Plant, Units 1, 2, and 3 - Non-Proprietary Issuance of Amendments Regarding Extended Power Uprate (CAC Nos. MF6741, MF6742, and MF6743).: ML17032A120

[9] Browns Ferry, Units 1, 2, and 3 - Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 11, Responses to Requests for Additional Information.: ML16106A072

[10] Browns Ferry Nuclear Plant - Wikipedia: https://en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Plant

[10] Browns Ferry Nuclear Plant, Units 1, 2, and 3 - Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 23, Miscellaneous Updates.: ML16195A510

[11] Browns Ferry, Units 1, 2, and 3 - Proposed Technical Specifications Change TS-505 - Request for License Amendments - Extended Power Uprate - Supplement 12, Responses to Requests for Additional Information.: ML16113A393

[12] Browns Ferry, Units 1, 2 & 3, Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Corrected Pages for the Final Environmental Assessment and Finding of No Significant Impact.: ML17163A423

[13] Browns Ferry Nuclear Plant, Units 1, 2, and 3 - Response to Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 25.: ML16210A501

[14] Browns Ferry Nuclear Plant, Units 1, 2, and 3 - Transmittal of Response to Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 33, Revised Response to Request for Additional....: ML16288A546

[15] Brown Ferry, Units 1, 2 & 3, Responses to Requests for Additional Information and Updates Associated with Interconnection System Impact Study Modifications on Proposed Technical Specifications Change TS-505 - Request for License Amendments - Extended...: ML16197A563

[16] Browns Ferry, Units 1, 2, and 3 - Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 8, Response to Request for Additional Information.: ML16089A054f

[17] Browns Ferry Nuclear Plant, Units 1,2, and 3 - Response to Request for Additional Information on Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 27.: ML16211A393

[18] Browns Ferry, Units 1, 2 and 3 - Proposed Technical Specifications Change TS-505 - Request for License Amendments - Extended Power Uprate(EPU) - Supplement 38, Spent Fuel Pool Criticality Safety Analysis - Updated Information.: ML17062A998

[19] Browns Ferry Nuclear Plant, Units 1, 2, and 3 - Transmittal of Response to Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 36, Transmission System Update -Safety Aspects.: ML17023A200

[20] Browns Ferry Nuclear Plant, Units 1, 2 & 3, Proposed Technical Specification Change TS-505 - Request for License Amendments - Extended Power Uprate - Supplement 10, Response to Request for Additional Information.: ML16096A411

[25] Federal Register/Vol. 82, No. 175/Tuesday, September 12, ...: https://www.govinfo.gov/content/pkg/FR-2017-09-12/pdf/2017-19216.pdf

Photo courtesy of NRC.