Nuclear Power Career Field Structure
Nuclear power is energy released in large amounts by the splitting or formation of atomic nuclei. The light and heat of the sun and other stars is an example of naturally occurring nuclear energy. Artificially produced nuclear energy can be released in a steady, controllable manner in devices called nuclear reactors.
In non-nuclear electrical power plants, a fuel of some kind is used to convert water into steam in a steam boiler. The steam from the boiler flows under high pressure through pipes and into a turbine, causing it to rotate. The turbine drives an electric generator that produces the electricity. In nuclear plants, the fuel is uranium, which undergoes a fission reaction, or atom-splitting, that produces tremendous quantities of heat. Water circulated through the reactor carries the heat away, in the form of steam under very high pressure, through pipes to drive the turbines that produce electricity in the same way as in a conventional power plant.
A nuclear reactor is a structure loaded with pellets of nuclear fuel, usually uranium with about 2 percent of the radioactive isotope uranium-235. The pellets are lined up in thin metal tubes called fuel rods. The more fuel rods packed in a given space, the more fission reactions that take place in the reactor. When fission reactions occur, neutrons (tiny particles of radiation energy traveling at great speed) are released and cause other fission reactions to occur in what is called a chain reaction.
The reactor also includes channels through which cooling water circulates and other empty spaces where control rods can be inserted. A control rod contains material that absorbs the released neutrons, thus preventing some fission reactions from occurring. When control rods are inserted into the reactor, they reduce the number of atoms being split, causing the reactor to cool down and generate less heat. When the control rods are withdrawn, the reaction rate speeds up and the reactor gets hot and generates more heat. Thus, the power in a nuclear-fueled electrical power plant is controlled by moving the control rods in and out of the reactor.
The area of the reactor where the fission takes place is called the core, and it is contained within the reactor vessel, lined by a thick inner shell of steel to keep the heat in the system and under control. This internal shield is surrounded in turn by several feet of concrete insulation that serves as a nuclear radiation shield to protect personnel and the surrounding area from radiation. The radiation is very harmful to the human body when absorbed in sufficient quantities.
In addition to the immediate radiation produced by fission, the fission process and the bombardment of materials by neutrons create a variety of both gaseous and solid radioactive materials. Some of these materials emit intense radiation, and some remain radioactive for a very long time. Most reactors are housed in a steel-lined concrete structure called the containment building, whose purpose is to contain radioactive materials should an accident release them from the reactor.
A serious problem associated with the use of nuclear energy is the handling, treatment, and disposal of the solid, liquid, and gaseous radioactive waste products it creates. Several methods for the long-term disposal of highly radioactive wastes have been developed and studied. The most widely accepted plan consists of binding the wastes in a glasslike or ceramic substance that is resistant to corrosion. This waste material would be placed deep underground in stable geological formations where it would remain undisturbed. Meanwhile, until long-term plans are agreed upon, radioactive wastes are being held in temporary storage, typically in containers held in pools of water near nuclear plants. The water carries away the heat produced by radioactive decay and serves as a shield against the radiation they emit. The Nuclear Regulatory Commission, an independent agency of the federal government, is responsible for the regulation and safety of nuclear power in the United States.