The USGS Water Science School
Here is the Beaver Valley Electricity Power Station in Pennsylvania. What stands out are the huge towers–cooling towers. When electricity is generated, the water used becomes very hot. The hot water is sprayed inside these large towers and the water cools as it evaporates in the air.
And the "clouds" you see? Those are like any other clouds, which are caused by the water vapor gas (that was evaporated) turning back into tiny liquid cloud particles (condensation).
Credit: U.S. Nuclear Regulatory Commission