How Is Nuclear Energy Used Today?

Spiraling fossil fuel prices and the concern over greenhouse gases has caused many, including even some environmentalists, to take a second look at nuclear power. With new reactor designs, nuclear power is safer than ever, although disposal of the highly toxic waste remains a considerable problem. However, despite the second look at nuclear power, it is still only used for the same two principal roles: ship propulsion and generating electricity for general consumption.

Identification

Nuclear power is generated inside a facility called a nuclear reactor. The plant's source of power is the heat produced by a controlled nuclear fission chain reaction involving either uranium or plutonium. In this reaction uranium or plutonium atoms are struck by a neutron, splitting them apart. The result of the fission of these large and unstable atoms is the creation of new, smaller atoms, radiation, and more neutrons. Those neutrons then speed out and strike other uranium or plutonium atoms, creating a chain reaction. The chain reaction is controlled by neutron moderators, which vary in type depending on the design of the reactor. These can be anything from graphite rods to simple water.

Once the heat has been released, a nuclear reactor produces electricity in exactly the same manner as any other thermal-based power plant. The heat converts water into steam, and the steam is used to turn the blades of a turbine, which in turn runs the generator. In this way, heat energy is converted to mechanical energy, and then into electricity.

Types

There are many different ways to categorize nuclear reactor design. One way is to categorize them by moderator material (the substance used to control the fission chain reaction). Another, less popular way, is to categorize reactors by their use. The two main uses for nuclear power today are electricity and propulsion.

Nuclear Propulsion

Nuclear propulsion is how nuclear power is used to drive ships. These reactors are typically of the pressurized water design, which pipes water that serves as both a coolant and moderator under pressure out of the reactor via a loop. This primary coolant loop travels through another secondary coolant chamber filled with water (the coolant water remains in the piping loop and does not mix with the water in the chamber). Because the coolant water is kept pressurized, it does not boil and vaporize. Instead, it becomes incredibly hot and transfers its heat to the secondary coolant tank, which does boil, vaporize to steam, and then works in the same manner as a conventional reactor.

Reactors of this design are more stable and less likely to suffer a critical meltdown. However, they also do not produce as much power as other designs, and they require strongly-built, expensive components to sustain the pressurized water in the primary coolant loop. Therefore, this design is found mostly on ships such as aircraft carriers and icebreakers or submarines. Stability and safety are much greater issues on these platforms, relative to commercial power generation.

Energy Generation

The other major use of nuclear power is for generating electricity. Sixteen percent of the world's electricity is generated by nuclear power, and 19.4 percent of electricity within the United States comes from nuclear power plants. According to the International Atomic Energy Agency, there were 436 nuclear power plants in operation in 2007. A wide range of reactor designs is used in commercial nuclear power.

Considerations

Nuclear power was proposed as a means of providing propulsion for rockets, but this remains the realm of science fiction. While plausible, a working model has never been built. Small nuclear fission reactors have been used to provide electricity for satellites in the past, but the United States has not done this since the 1960s, and the USSR stopped using nuclear power on satellites in the late 1980s.

Resources

• IAEA