Monday, March 24, 2014

The Truth About Nuclear Power - Part Four

Subtitle: Nuclear plants use far more fresh water than other power plants

Nuclear power plants, as currently designed and built, consume prodigious amounts of water for cooling.  Compared to combined-cycle gas turbine plants (CCGT), nuclear plants use 4 times as much water for the same output of electricity.   Some plants use cooling towers, and others use once-through cooling where the water is pumped through the plant once, then sent off usually into a lake, river, or ocean.   
South Texas Nuclear Plant with Cooling Reservoir
source: Texas Water Development Board

For this article, the example of the South Texas Nuclear Project is used.  This power plant is a twin-reactor, pressurized water reactor design built near the mouth of the Colorado River in Texas, USA.  The photo nearby shows the location, just north of the small town of Matagorda, on the Gulf of Mexico.  The plant is roughly 50 miles northeast of Corpus Christi, and 100 miles southwest of Houston.   The photo shows the nuclear power plant in the middle foreground, the 7,000 acre cooling reservoir at center, and the Gulf of Mexico at the top.  The Colorado River can be seen, barely, at the left center. 

The plant, known as STNP, is designed to use approximately 50,000 acre-feet (AF) of river water per year for cooling.  The reservoir receives water pumped from the nearby Colorado River, plus any rain that happens to fall.  Rainfall is important in this case, as it averages 30 inches per year over the long term.  Recently the rainfall has been much less due to a prolonged drought.  However, in an average year, the rainfall provides approximately 17,000 AF per year for the plant.   That then, requires the river to provide 50,000 - 17,000 = 33,000 AF per year.  

The water requirements for various types of power plants are shown below, in AF/yr/1000 MW of electrical output.  These are based on the design where hot water that is discharged from the plant evaporates in the cooling reservoir to lose its heat.  

1.  Nuclear power.........................20,300 AF/y/1000 MW
2.  Gas powered steam plant......12,700
3.  CCGT plant................................5,070

From this, it can be seen that nuclear power requires 4 times as much water (20,300 / 5,070 = 4) compared to a modern CCGT plant.  In areas where fresh water is scarce, this is an important consideration when selecting power plant technology.  

Lake Travis and Mansfield Dam, TX
source: LCRA
For the STNP, the Colorado River water is impounded far upstream by Mansfield Dam and held in Lake Travis, a 1.1 million AF reservoir north of Austin, Texas.  Lake Travis is near historic low levels as this is written (March, 2014) due to an extended drought.  The lack of water could cause the STNP output to be reduced. 

For some perspective, had a CCGT design been used along with the 7,000 acre reservoir, the plant would be more than self-sufficient in water needs.   In fact, a much smaller reservoir could have been constructed, approximately one-third the surface area.  

Conclusion:   Nuclear power plants consume 4 time as much water for cooling compared to a modern CCGT power plant.  

Previous installments in The Truth About Nuclear Power can be found below:

Part One - Nuclear Power Plants Cannot Compete
Part Two - Preposterous Power Pricing if Nuclear Power Proponents Prevail
Part Three - Nuclear Power Plants Cost Far Too Much to Construct
Part Four  -  This article
Part Five - Cannot Simply Turn Off a Nuclear Power Plant
Part Six –  Nuclear Plants are Huge to Reduce Costs

Roger E. Sowell, Esq.
Marina del Rey, California

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