How does nuclear power harm fish?

The greatest harm to fish from nuclear power, in terms of the numbers of fish killed so far, has been due to thermal pollution. The nuclear power produced at plants is only about 35% turned into electrical power. The remainder is called waste heat. When rivers, lakes, or the sea are heated up, it can kill fish. In some cases this has a profound effect on the species in the water.

Nuclear power plants have lost radioactive materials into large bodies of water, harming sea and land life. Possibly the worst such event involved loss of material from the Sellafield plant in the U. K. into the Irish Sea.