Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Nuclear power, as with all power sources, has an effect on the environment through the nuclear fuel cycle, through operation, and potentially through the disposal of waste. As with any thermal power station, nuclear plants exchange 60 to 70% of their thermal energy by cycling with a body of water or by evaporating water through a cooling tower. This thermal efficiency is slightly greater than that of coal fired power plants.The cooling options are typically once-through cooling with river or sea water, pond cooling, or cooling towers. Many plants have an artificial lake like the Shearon Harris Nuclear Power Plant or the South Texas Nuclear Generating Station. Shearon Harris uses a cooling tower but South Texas does not and discharges back into the lake.