Nuclear plants operate by boiling water into steam which turns turbines to produce electricity. The plants use uranium in the form of ceramic nuclear fuel pellets to produce electricity through a process called fission (splitting the uranium nucleus into two parts). Approximately 20 percent of electricity generated in the United States comes from nuclear reactors.

Commercial nuclear power plants in the United States are either boiling water reactors or pressurized water reactors. Both types of reactors are cooled by ordinary water. Approximately two-thirds of the 96 reactors in the United States are pressurized water reactors, and the remainder are boiling water reactors.

Fish and Wildlife Considerations

Most nuclear power plants are located along lakes, rivers or seacoasts because the facilities use water to cool the reactors. Cooling water discharged from a plant can affect the ambient habitat conditions for aquatic species. Fish, freshwater mussels and aquatic macroinvertebrates such as mayflies may be affected by altered water temperature changes. Water that is too hot or too cold can harm or kill aquatic species, affect their health or impact their habitats. Fish may not swim in rivers with altered temperature that can compromise their spawning activities. Water temperature changes can also affect prey or other food items, reducing prey availability and diversity. Nuclear energy involves mining for uranium ore to use in the reactors. Mining activities may result in impacts to streams and other habitats. Habitat may be lost, disturbed or fragmented. Streams may be crossed or buried. Soil placed in streams may change the water chemistry, affecting aquatic species. Uranium-bearing formations are usually associated with strata containing high concentrations of selenium. Pit lakes formed in open pit uranium mines can contain very high levels of selenium in the water. Waterborne selenium concentrations greater than two micrograms per liter are known to impair the reproduction and survival of aquatic birds. When found, these concentrations are likely caused by selenium concentrating in aquatic organisms higher in the food chain (bioaccumulation). Older mines may be associated with releases of uranium and other radionuclides, metals and other contaminants.

Another concern is the possibility of a radioactive leak into the environment. Most facilities conduct a radiological environmental monitoring before the plant starts producing electricity to establish a baseline survey of background radiation in the local environment. Fixed monitoring stations are established around the plant to sample air, surface and ground water, milk from local dairies and vegetation. Plant operators also send samples to state and federal regulators for independent verification. Even slight exposure to nuclear materials can affect the health, breeding and feeding of aquatic species.

Learn more about nuclear energy projects in the United States.