The U.S. Nuclear Regulatory Commission will announce in the Dec. 1 Federal Register that it is taking comments on an environmental review related to power uprates planned by the Tennessee Valley Authority for Browns Ferry Units 1-3 in Alabama.
The NRC is considering issuance of amendments to Renewed Facility Operating Licenses for Browns Ferry Nuclear (BFN) Units 1-3, located in Limestone County, Alabama. The proposed amendments would increase the maximum licensed thermal power level for each reactor from 3,458 megawatts thermal (MWt) to 3,952 MWt. This change, referred to as an extended power uprate (EPU), represents an increase of approximately 14.3% above the current licensed thermal power limit.
The NRC is issuing a draft environmental assessment (EA) and draft finding of no significant impact (FONSI) for public comment associated with the proposed EPU. Comments will be taken for 30 days from Dec. 1. Based on the results of the draft EA, the NRC said it did not identify any significant environmental impacts associated with the proposed amendments and has, therefore, prepared a FONSI.
Each of BFN’s three nuclear units is a General Electric boiling-water reactor. The BFN uses a once-through (open-cycle) condenser circulating water system with seven helper cooling towers to dissipate waste heat. Four of the original six cooling towers that serve BFN have undergone replacement, and TVA plans to replace the remaining two towers in fiscal years 2018 and 2019. Additionally, TVA constructed a seventh cooling tower in May 2012.
An EPU usually requires significant modifications to major balance-of-plant equipment. The proposed EPU for BFN would include replacement of the steam dryers, replacement of the high pressure turbine rotors, replacement of reactor feedwater pumps, installation of higher capacity condensate booster pumps and motors, modifications to the condensate demineralizer system, modifications to the feedwater heaters, and upgrade of miscellaneous instrumentation, setpoint changes, and software modifications.
TVA anticipates no changes in existing onsite land uses or disturbance of previously undisturbed onsite land. According to TVA’s current schedule, modifications and upgrades related to the proposed EPU would be completed at Unit 1 during the fall 2018 refueling outage, at Unit 2 during the spring 2019 outage, and at Unit 3 during the spring 2018 outage. If the NRC approves the proposed EPU, TVA would begin operating each unit at the uprated power level following these outages.
These uprates would increase the heat generated by the plant’s steam turbines, which would in turn increase the amount of waste heat that must be dissipated. TVA would increase its use of the cooling towers (i.e., operate in helper mode) to dissipate some of this additional heat; the remaining heat would be discharged to Wheeler Reservoir. If helper mode operation were to be insufficient to keep the reservoir temperatures within BFN’s water permit limits, TVA would reduce (i.e., derate) the thermal power of one or more of the units to maintain regulatory compliance, a practice which TVA currently employs at BFN as necessary.
The licensee predicts that it would operate the cooling towers in helper mode an additional 22 days per year on average (88 days total) and that the most extreme years could result in an additional 39 days per year of cooling tower helper mode operation (121 days total).
The EPU would require several upgrades to the transmission system and the BFN main generator excitation system to ensure transmission system stability at EPU power levels. TVA performed a Revised Interconnection System Impact Study in May 2016, which determined that the EPU would require the following transmission upgrades:
- replacement of six 500-kV breaker failure relays;
- installation of 764 megavolt-ampere reactive (MVAR) capacitor banks in five locations throughout the TVA transmission system; and
- modification of the excitation system of all three BFN main generators.
The proposed action would allow TVA to meet the increasing power demand forecasted in TVA service area. The licensee estimates that energy consumption in this area will increase at a compound annual growth rate of 1.2% until 2020 with additional moderate growth continuing after 2020.
Said TVA about the Browns Ferry project in its Nov. 15 annual Form 10-K report: “Because the license amendment requests (‘LARs’) submitted by TVA to the NRC at the beginning of this project have been under review for an extended time due to uprate-related technical issues, the original amendment request was withdrawn and resubmitted in September 2015. If approved, the license amendment would allow all three units at Browns Ferry to increase capacity by 20 percent over original power levels, inclusive of projects previously completed on Units 1, 2, and 3 which resulted in a five percent increase in capacity.
“TVA expects to begin implementing the EPU project starting in the spring of 2018 for Unit 3, the fall of 2018 for Unit 1, and the spring of 2019 for Unit 2, and TVA expects to complete the project in 2024. The project involves engineering analyses and modification and replacement of certain existing plant components to enable the units to produce the additional power requested by the license amendments. These improvements will be ongoing in parallel with the NRC’s license amendment review process. The project is estimated to cost approximately $475 million and expected to add 465 MW of generating capacity.”