Lesson 2: Reading Lesson

Nuclear Energy

Nuclear power plants supply 20 percent of the electricity generated in the United States.

Since 1982, nuclear energy has been second only to coal as an energy source for the production of electricity in the United States. It surpasses oil, natural gas, and hydroelectric power.

Today, more than 100 nuclear power plants produce about 20 percent of all the electricity generated in the U.S.

Although various new energy technologies hold promise for the future, coal, nuclear energy, and natural gas are the energy sources most capable of meeting the growing needs of the U.S. in the next few decades.

What is nuclear energy?

Nuclear energy is the type of energy produced when atoms of certain elements (like uranium and plutonium) are caused to break apart.

Atoms are the building blocks of matter. A strong energy bond holds particles together inside the nucleus of an atom. In most elements with larger atoms, this bond is so strong the atoms always stay intact. However, in some elements, such as uranium, the bond is not as strong. If, under the right conditions, a small particle called a neutron strikes a uranium atom’s nucleus, the nucleus will split into smaller pieces. This splitting process is called fission.

When the nucleus of a uranium atom splits, it releases a relatively large amount of heat energy and one or two neutrons. These neutrons in turn can cause other uranium atoms to split, releasing more heat and still more neutrons. When this process continues, we call it a nuclear chain reaction.

This graphic shows the fission process-- where a neutron splits the nucleus of a uranium atom, resulting in the release of two or three neutrons and a relatively large amount of energy. When the fission process continues in succession, it is called a nuclear chain reaction.

Using nuclear energy to produce electricity

We use a device called a nuclear reactor to convert nuclear energy to electricity. In a nuclear reactor, uranium is arranged in a way that creates a controlled fission process, which emits heat. The heat boils water, which creates steam. The steam turns a turbine, which is connected to a generator. As the turbine spins, the generator turns, and its magnetic field produces electricity.

A chain reaction is a series of identical events, where each event initiates the next - like when dominoes are lined up, and the first domino falls into the second, into the third, and so on until the last domino falls.

Electricity produced by a nuclear reactor is no different than the electricity produced at other power plants that use natural gas, coal, or oil as fuel.

The fuel used in nuclear reactors is enriched uranium formed into ceramic pellets. Each pellet is about the size of the tip of your little finger. The pellets are stacked and sealed in fuel rods – hollow metal tubes about twice the thickness of a pencil and about 4 meters long. Groups of fuel rods are bolted together to form a fuel assembly. One fuel assembly contains about 200 fuel rods.

After a few years in a reactor, the uranium is no longer efficient for producing electricity and the fuel assembly is removed from use. The assembly (now called spent nuclear fuel) is highly radioactive and requires special disposal.

Compared to other types of power plants, nuclear reactors require very little fuel to generate electricity. In fact, one metric ton of nuclear fuel will provide about 100,000 times as much electrical power as that provided by burning one metric ton of coal.

Containment building at a nuclear power plant. Federal law requires every commercial nuclear power plant in the United States to have such a protective facility to prevent radioactive materials from escaping into the environment in case of an accident.

How safe is a nuclear power plant?

In the late 1950s, U.S. power companies began building nuclear power plants to produce electricity. Since then, nuclear power has been proven to be one of our safest energy technologies.

Safety is a major consideration throughout the design, construction, and operation of a nuclear power plant. Hundreds of systems monitor, control, and support the safe operation of the reactor at each power plant. These systems provide safety and reliability and reduce the chance of an accidental release of radioactivity into the environment.

The fuel used in nuclear power plants becomes intensely radioactive and thermally hot. For this reason, nuclear power plants have many physical barriers to guard against the accidental release of this radioactive material.

These barriers include

• the ceramic form of the fuel pellets;
  
  
• the metal that encases the fuel pellets;
  
  
• thick steel walls around the reactor itself (these walls are about 20 to 25 centimeters thick);
  
  
• a containment building lined with steel 2 centimeters thick and walls of reinforced concrete that are about 1 meter thick.

The containment building is strong enough to withstand earthquakes, violent storms, and even the direct impact of a large aircraft. The design prevents radioactive material from escaping into the environment even if there are serious mechanical failures or operator errors at the plant. Engineered safety systems help prevent reactor accidents and lessen the effects if accidents occur. All crucial safety systems have backup systems that duplicate their jobs. For example, huge stainless steel pipes about 61 centimeters in diameter carry water to the reactor core, where it cools the fuel. Any of several independent emergency cooling systems included in the design of the plant can cool the reactor adequately if the others fail.

Another vital part of nuclear power plant safety is the intensive training and preparedness of the people who operate the power plant.

Reactor operators are trained and tested on the procedures of power plant operation. To train operators, utilities use sophisticated power plant simulators – replicas of the control room of a real power plant.

The simulators are computer controlled, allowing the operators to gain practical experience in managing all types of normal and unusual occurrences without any danger to the public or the environment.

The nuclear industry has rigid safety standards, which the U.S. Nuclear Regulatory Commission sets and regulates. Utilities operating nuclear power plants must prove to the commission that each plant can meet these stringent safety standards.

Periodic inspections also ensure that each facility operates safely. Utilities face severe financial penalties if Nuclear Regulatory Commission inspections show the plant is not operating in full compliance with federal regulations.

Some people think a nuclear reactor can explode like an atomic bomb. This cannot happen. A nuclear explosion would require a very high concentration of fissionable uranium. That is the form of uranium that splits to release energy. Fuel in nuclear power plants has a very low concentration of fissionable uranium – only about 3 percent. It releases energy at a very low rate. An atomic bomb releases tremendous amounts of energy instantaneously, and is typically made of plutonium rather than uranium. There is also not a sufficient concentration of fissionable plutonium in reactor fuel to allow an explosion.

Operators in a nuclear power plant control room.