Nuclear Reactor Water Usage and the Implications of Limited Water Availability

Safiyyah Abdul-Khabir
March 22, 2013

Submitted as coursework for PH241, Stanford University, Winter 2013

Nuclear Reactor Water Usage and Consumption

Nuclear is known as the thirstiest power source. Due to high water withdrawals, nuclear power plants are usually located near lakes, rivers, or the ocean. The vast amounts of water are for cooling purposes typically through the use of a direct cooling or closed cycle cooling system. In a direct cooling system, the steam used to turn the turbines is cooled by water that is pumped through the condensers from an outside source and then discharged back into the environment. This differs from the closed cycle cooling system where the water used for cooling is pumped from the steam condenser to a cooling tower or pond and then recycled back to the condenser. While the direct cooling system has a relatively high amount of water usage from the environment, the closed cycle cooling system has higher amounts of water consumption due to losses from evaporation. [1] In both cases, the water usage and consumption for a conventional nuclear power plant is higher than for the average fossil fuel power plant (Table 1). Nuclear power plants require more cooling water because they operate at thermodynamically lower steam conditions which results in a lower cycle efficiency. Thus a greater steam recirculation rate which contributes to a greater flow of cooling water is needed to produce a given amount of electricity compared to an average fossil fuel plant. [2]

Plant and Cooling System Type Water Usage (gal/MWh) Typical Water Consumption (gal/MWh)
Fossil/biomass/waste-fueled steam, once-through cooling 20,000 to 50,000 ~300
Fossil/biomass/waste-fueled steam, pond cooling 300 to 600 380-480
Fossil/biomass/waste-fueled steam, cooling towers 500 to 600 ~480
Nuclear steam, once-through cooling 25,000 to 60,000 ~400
Nuclear steam, pond cooling 500 to 1100 400-720
Nuclear steam, cooling towers 800 to 1100 ~720
Table 1: Comparison of water requirements for fossil fuel and nuclear power plants. Source: EPRI

Implications of Limited Water Availability

As freshwater resources become scarcer, the nexus between water and energy becomes magnified. Thermoelectric power plants, including nuclear plants, make up 40% of freshwater usage in the US. The high water requirements mean that the operations of these power plants are susceptible to heat waves and droughts. If the temperature of a water body is already high, environmental regulations do not allow for further discharges of high temperature water above a certain threshold. Furthermore, if water levels in a body of water drop too low, the power plant may not be able to intake enough water. [3] In the hot, dry summer of 2006, several nuclear plants across Europe stopped operations due to restricted water availability. [4] In August 2012, a nuclear reactor at Millstone Nuclear Power Station in Connecticut shut down after the seawater used for cooling became too warm. Other nuclear plants, including the Braidwood Generating Station in Chicago, were only able to continue operations with a high temperature cooling water after receiving special permission from the Nuclear Regulatory Commission. [5]

Climate change is predicted to have significant impacts on freshwater river flow levels and temperature. Under future climate scenarios for 2031-2060, nuclear and coal power generating capacities during summers are predicted to decrease by 4.4%-16% in the U.S. and 6.3%-19% in Europe due to a lack of cooling water. [3] To adapt to a warmer climate and scarcer freshwater resources, strategies could focus on siting plants near coasts and increasing the thermal efficiency of power plants.

© Safiyyah Abdul-Khabir. 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] E. V. Giusti and E.L. Meyer, "Water Consumption by Nuclear Powerplants and Some Hydrological Implications," U.S. Department of the Interior, Geological Survey Circular 745, 1977.

[2] "Water & Sustainability (Volume 3): U.S. Water Consumption for Power Production - The Next Half Century," Electric Power Research Institute, Technical Report 1006786, March 2002.

[3] M. T. H. van Vliet et al. "Vulnerability of US and European Electricity Supply to Climate Change," Nature Climate Change 2, 676 (2012).

[4] J. Jowit and J. Espinoza, "Heatwave Shuts down Nuclear Power Plants," The Guardian, 29 Jul 06.

[5] J. Eaton, "Record Heat, Drought Pose Problems for U.S. Electric Power," National Geographic, 17 Aug 12.