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 and each power plant. These systems provide maximum safety and reliability, and reduce the chance of an accidental release of radioactivity into the environment.  (Read more about radiation in the “Things You Thought You Knew” section.)

Environmental Safety

Nuclear energy is the largest producer of electric power without emitting any significant pollution or greenhouse gases.  The second-largest is hydroelectric power (about 7 percent), followed by wind and solar power (about 2 percent). Since nothing is burned in the generation of nuclear electricity, nothing harmful is vented into the atmosphere. This is why nuclear power plants do not have smokestacks common to fossil fuel generation facilities. Some nuclear power plants use large cooling towers to remove excess heat from cooling water before it is returned to the waterways; the discharge is water vapor, not smoke or radioactive matter.

Power Plant Safety

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 encasing the fuel pins; the reactor vessel with 8- to 10-inch-thick walls of steel; and a containment building with a lining of ¾-inch steel and walls of reinforced concrete three or more feet thick. This 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.

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.

Some people think a nuclear reactor can explode like an atomic bomb. This cannot happen! A nuclear explosion requires a very high concentration of fissionable uranium. That is the form 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.

Utilities in the United States have operated commercial nuclear power plants since 1957. During this time, no one in the United States has died or been injured as a result of operations at a commercial nuclear power plant. Efforts to ensure that nuclear power plants maintain this safety record are constantly emphasized, and the record compares favorably with all other ways of making electricity.

What about Nuclear Waste?

In the process of day-to-day living, people produce waste. Consider the amount of food scraps, used paper, and other trash that you and your family throw into the trash every day. Just think of how much waste one visit to a fast food restaurant creates—leftover food and drinks, bags, straws, cups, and containers.

Industries also generate trash as a result of doing or making something. The leftovers of an industrial process are called waste.

Like all industries, nuclear power plants produce waste. But nuclear waste is not like normal garbage. The problem with nuclear power plants is not the amount of waste they make, which is quite small compared with the amount of waste produced by many other industries. The problem is that some nuclear power plant wastes are radioactive. This means that disposing of the waste requires special care to protect workers and the public. The way it is disposed of depends on how radioactive the waste is.

All nuclear waste is radioactive. It gives off invisible energy rays that can make people sick and even die if they’re exposed to it. Nuclear waste will stay radioactive for hundreds of thousands of years.

Waste that is only slightly radioactive is called low-level waste. Low-level radioactive waste from a nuclear power plant includes such things as filters, cleaning rags, lab supplies, and discarded protective clothing. Hospitals, research labs, and agriculture also generate low-level waste.

Power plant waste that is very radioactive is called high-level waste. Most high-level waste from a nuclear power plant comes from spent (used) fuel. Spent fuel is fuel that has been removed from the reactor. Not only is it highly radioactive, but it produces a great deal of heat.

Disposing of Nuclear Waste

Because it emits only small amounts of radiation, low-level waste is usually sealed in strong cartons or steel drums and placed in shallow burial sites that are regulated. States that produce low-level waste are responsible for disposing of it. As time passes, the waste becomes less radioactive as a result of radioactive decay.

Nuclear power plants store spent fuel near the reactor in a deep pool of water called the spent fuel pool. During storage, the spent fuel cools down and also begins to lose its radioactivity through radioactive decay. In three months, the used fuel loses about 50 percent of its radiation. In one year, it loses about 80 percent, and in 10 years it loses 90 percent. Nevertheless, because some radioactivity remains for thousands of years, the waste must be carefully and permanently isolated from the environment.

Currently, spent nuclear fuel and high-level radioactive waste are stored in temporary facilities at some 125 sites in 39 states. These storage sites are located in a mixture of cities, suburbs, and rural areas. Most are located near large bodies of water.

In the United States today, more than 161 million people reside within 75 miles of temporarily stored nuclear waste.

> View Nuclear Waste Locations by State

Transporting the Nuclear Waste

When the time comes to ship nuclear waste to a permanent disposal location, the spent fuel will be carefully loaded into shipping containers, which are called spent fuel casks.

If you own a musical instrument, it probably has a case that you keep it in. The case prevents damage that could happen while you take your violin or saxophone to music class.

A spent fuel cask is similar to an instrument case in that both are specially made to protect their contents. In addition, a spent fuel cask must also protect people and the environment from the fuel it holds.

As a result, spent fuel casks are designed with heavy shielding that protects people from radiation, as well as with thick walls that prevent radioactive substances in the spent fuel assemblies from getting into the environment.

A typical spent nuclear fuel cask sitting on a railcar

A spent fuel cask is designed to withstand the worst sorts of disasters and accidents, and a series of tests is conducted on sample casks to ensure that the casks really work. These tests include:

• being dropped from 30 feet onto reinforced concrete;
• being dropped from 40 inches onto a thick steel bar;
• being burned in a 1,475o F fire for 30 minutes, and’
• being put under 3 feet of water for 30 minutes.

These tests are carefully monitored and measured with high-speed cameras that help engineers and scientists study these containers under conditions that simulate an accident.

In one test, a spent fuel cask was even mounted on a tractor trailer that was hit broadside by a train engine moving at 80 miles per hour. The impact demolished the train engine, but did not damage the cask. Afterward, the cask was put into a fire for two hours. Scientists carefully examined the cask for any damage and found that the cask’s contents had remained intact.

> See videos of radioactive cask crash test simulations

In addition to all the requirements that casks must meet in order to be shipped by truck or train, the truck driver and train operator must be trained in the hazards of radioactive materials, transportation regulations, and emergency procedures. The route that the cask takes is also given careful consideration in order to avoid large cities and undesirable road conditions.