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| Fig. 1: Aerial photo of Turkey Point Nuclear Generating Station. (Source: Wikimedia Commons) |
Turkey Point Nuclear Generating Station (seen in Fig. 1) is a nuclear power plant located in Homestead, Florida, 25 miles south of Miami. It is adjacent to Biscayne National Park and lies on 11,000 acres. Starting operation in 1972, it is owned and operated by Florida Power and Lighting (FPL). It contains two nuclear power generating units and is part of the larger Turkey Point Power Plant which contains an additional natural-gas powered unit. The two nuclear power units (Units 3 and 4) were initially rated for 728 MW of power production but have since been uprated for an additional 15% in 2012 and 2013. [1] The station provides power for millions of South Florida residents. FPL has also been granted a License for an additional two nuclear-power units to be built at the facility; the expansion being met with some criticism. [2]
Rather than the more conventional use of a cooling tower to provide cooling to discharge heat from the nuclear units, the plant uses an elaborate system of cooling canals (seen in Fig. 2) taking up approximately 6,000 of the 11,000 acres the plant is located on. Before the existence of the cooling canal system, cooling water was drawn from Biscayne Bay and eventually discharged back into the bay by a much shorter series of canals. This led to a variety of negative environmental consequences and eventually the plant was ordered to stop this practice. This was the original purpose for the construction of the cooling canals. The primary means by which the canal system works to cool the water is by heat exchange through evaporation and solar radiation, although understanding the full dynamics is quite complicated. [3]
The system consists of 32 canals each of which is approximately 5 miles long from which water is discharged, flows through the canals, and is eventually taken back to the intake system for the units. The canals, for a number of reasons, remain controversial with some calling for FPL to remove them and the potential for retrofitting the plant with cooling towers. [3] Historically, they have been controversial because of the threat they pose to the Everglades as well as to the Biscayne Aquifer, the primary source for freshwater in South Florida. In recent years, the canals have come under scrutiny for their increasing temperature and salinity. [3]
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| Fig. 2: Photo of Turkey Point Cooling-Canal system taken in 1974. (Source: Wikimedia Commons) |
We first investigate the extent and impact of the temperature increase at the Turkey Point Plant. Using data from 2010-2014, it was shown that the average temperature in the water in the Cooling Canal System (CCS), had increased by 4°F on average. This temperature increase prompted FPL to apply for a license from the NRC to increase the maximum intake water temperature of the two nuclear units from 100°F to 104°F. The temperature increase is thought to have been primarily caused by the aforementioned capacity increase of the two nuclear units. [3]
Additionally, as the temperature in the canal system increases, the plants need to get cooling water from elsewhere, which it has done since 2014, and is not considered an ideal long term solution. The sustainability of the cooling canal system is threatened by this temperature increase and if the issue is not fixed, power-generation at the plant will have to be curtailed. According to one study, this information is strong evidence that the two nuclear units should not be further uprated without an improvement or expansion in the CCS system. [3]
We now investigate the extent and impact of the salinity increase at the Turkey Point Plant. Salinity has been tracked at the CCS since its opening and has been steadily rising for the past 40 years. At its opening (in 1973), the salinity in the CCS was recorded at 26.5%. In 2014, the salinity was reported at a near record high of 95%, providing a stark contrast. As with temperature, there are many processes regulating the salinity of the CCS system, the main ones being rainfall, evaporation, and transfer with the Biscayne Aquifer. [4] The increasing salinity has been largely attributed to the excess evaporation over rainfall in the CCS due to the relatively high temperature of the canals compared to surrounding bodies of water. The 2014 report indicated that it will be necessary to add some sort of control mechanism to the canal system to keep the salinity at acceptable levels for operation of the plant. Additionally, the high salinity levels have led to an increase in the chloride levels in the Biscayne Aquifer as it is an important drinking water source. [5]
The Cooling Canal System for the Turkey Point Station is currently operating, but the totality of the evidence suggests that without needed improvements, it is not be a sustainable solution for providing cooling for the two nuclear units at the station. FPL understands this which is in part why the new units they plan to build will not be cooled using a canal system. In summary, the future of the canals is unclear, and while many environmental issues persist with the canal, and it is generally recognized as not an ideal cooling method, the large amount of power provided by the plant makes any rapid change unlikely. [3]
© L.J. Bonanno. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] T. Elfrink, "Turkey Point Nuclear Plant Is Pumping Polluted Water Into Biscayne Bay," Miami New Times, 8 Mar 16.
[2] J. Ianneli, "State Senator Says FPL Isn't Preparing Miami's Nuclear Plant for Sea-Level Rise," Miami New Times, 5 Oct 17.
[3] "Closed Cycle Cooling Tower Feasibility Assessment for Turkey Point Nuclear Units 3 and 4," Powers Engineering, July 2016.
[4] C. A. Gimenez, "Report on Recent Biscayne Bay Water Quality Observations associated with Florida Power and Light Turkey Point Cooling Canal System Operations - Directive 152884," Miami-Dade County, March 2016.
[5] "Turkey Point Plant," Ecology and Environment, Inc, August 2014.
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