Nuclear technology facts for kids

A smoke detector is a common example of nuclear technology in our homes.

Nuclear technology uses the powerful reactions that happen inside the center of atoms, called the atomic nuclei. Some well-known nuclear technologies include nuclear reactors (which make electricity), nuclear medicine (used in hospitals), and nuclear weapons. You can also find nuclear technology in everyday items like smoke detectors and special gun sights.

How Nuclear Technology Began
Nuclear Weapons
Peaceful Uses of Nuclear Technology
Nuclear Accidents
Benefits for the Environment
See also

How Nuclear Technology Began

Discovering Radioactivity

Most things we see on Earth, like gravity or electromagnetism, don't involve nuclear reactions. This is because the centers of atoms (nuclei) have positive charges and usually push each other away.

In 1896, a scientist named Henri Becquerel was studying uranium salts. He found something new he called radioactivity. He, along with Pierre Curie and Marie Curie, started to study this amazing discovery. They found an element called radium, which was very radioactive.

They learned that radioactive materials give off strong, invisible rays. They named these rays alpha, beta, and gamma. Some of these rays could pass through objects. They also found that too much of these rays could be harmful. Early researchers sometimes got "radiation burns," like a bad sunburn, but didn't realize how dangerous it was long-term.

At first, some people tried to use radioactivity in fake medicines. But soon, scientists realized that these rays, called ionizing radiation, could be very dangerous even in small amounts over time. Many early scientists who worked with radioactivity sadly got cancer because of their exposure. Fake radioactive medicines disappeared, but some uses remained, like making clock dials glow with radium.

As we learned more about atoms, we understood radioactivity better. Some large atomic nuclei are unstable. This means they "decay" (break down) and release energy or tiny particles. The three types of radiation Becquerel and the Curies found are now understood:

Alpha decay happens when a nucleus releases an alpha particle. This particle is like a helium nucleus, with two protons and two neutrons.
Beta decay is when a nucleus releases a beta particle, which is a high-energy electron.
Gamma decay releases gamma rays. These are not particles but very high-energy electromagnetic radiation. Gamma rays are the most dangerous and hardest to stop.

All three types of radiation happen naturally in some elements. We also know that most energy on Earth comes from nuclear processes. For example, the Sun gets its energy from nuclear reactions. Also, heat inside the Earth (called geothermal energy) comes from radioactive uranium decaying.

Understanding Nuclear Fission

In natural radioactivity, the pieces released are very small. But nuclear fission is different. It's when a large atomic nucleus splits into two roughly equal parts. This process releases a lot of energy and also some neutrons.

If these released neutrons hit other unstable nuclei, they can cause those nuclei to split too. This creates a "chain reaction." If the chain reaction releases more neutrons than it uses, it can keep going on its own. A certain amount of material needed to start a self-sustaining chain reaction is called a "critical mass."

If a nucleus splits right away and causes a fast chain reaction, it can lead to a rapid, uncontrolled energy release, usually an explosion. This is how atomic bombs work.

During World War II, scientists realized this. Many countries started programs to build an atomic bomb. The Manhattan Project in the United States, with help from the United Kingdom and Canada, developed the first fission weapons. These bombs were used against Japan in 1945 in Hiroshima and Nagasaki. During this project, the first nuclear reactors were also built. They were mainly for making weapons materials, not for generating electricity.

In 1951, the first nuclear fission power plant, called EBR-1, produced electricity in Idaho. This marked the start of the "Atomic Age," where humans began to use nuclear energy more intensely.

However, if the chain reaction is controlled, it can be used safely. This is done by adding or removing materials that absorb neutrons. This is how nuclear reactors are built. Fast neutrons are hard to capture, so they are slowed down by a "neutron moderator" before they can be easily captured. Today, this type of fission is commonly used to make electricity.

Exploring Nuclear Fusion

Nuclear fusion happens when two light nuclei are forced to crash into each other and combine. This process can either release or absorb energy. If the new nucleus is lighter than iron, energy is usually released. If it's heavier than iron, energy is usually absorbed.

This fusion process is what powers stars, including our Sun. Stars get their energy by fusing hydrogen and helium. They also create lighter elements (like lithium to calcium) and some heavier ones. Even heavier elements (like nickel to uranium) are made in powerful supernova explosions.

These natural processes in space are not "nuclear technology." It's very hard to make fusion happen in a controlled way on Earth because atomic nuclei strongly push each other away. Hydrogen bombs use uncontrolled fusion for their huge destructive power.

Controlled fusion can be made in special machines called particle accelerators. This is how many new, man-made elements are created. A fusor can also create controlled fusion and is useful for making neutrons. However, these devices use more energy than they produce. Creating controlled, useful fusion power has been very difficult, even though research continues worldwide.

Scientists first thought about nuclear fusion during World War II. They explored it as a way to build a bomb, but realized it would need a fission reaction to start. The first full hydrogen bomb was detonated in 1952. It used reactions between deuterium and tritium. Fusion reactions release much more energy per amount of fuel than fission reactions, but starting a fusion chain reaction is much harder.

Nuclear Weapons

A nuclear weapon is an explosive device that gets its destructive power from nuclear reactions, either fission or a mix of fission and fusion. Both reactions release huge amounts of energy from very small amounts of material. Even small nuclear devices can destroy a city with their blast, fire, and radiation. Nuclear weapons are called weapons of mass destruction. Their use and control have been a major part of international politics since they first appeared.

Designing a nuclear weapon is complex. It needs to hold special materials in a safe state, then quickly make them "critical" (start a chain reaction) for an explosion. It's also hard to make sure the reaction uses a lot of the fuel before the device breaks apart. Getting the right nuclear fuel is also difficult, as the necessary unstable materials don't exist naturally in large enough amounts on Earth.

One type of uranium, called uranium-235, is naturally unstable enough. But it's always mixed with a more stable type, uranium-238, which makes up over 99% of natural uranium. So, uranium-235 must be separated or "enriched."

Another element, plutonium, also has an unstable type that can be used. But natural plutonium isn't found in enough amounts, so it must be made in a nuclear reactor.

The Manhattan Project created nuclear weapons using both uranium and plutonium. They tested the first nuclear weapon, code-named "Trinity," in New Mexico on July 16, 1945. This test proved that the weapon's design would work. A uranium bomb, called Little Boy, was dropped on Hiroshima, Japan, on August 6, 1945. Three days later, a plutonium bomb, called Fat Man, was dropped on Nagasaki. After this terrible destruction and loss of life, the Japanese government surrendered, ending World War II.

Since these bombings, no nuclear weapons have been used in war. However, they led to an "arms race" where countries built more and more powerful bombs to act as a nuclear deterrent (to stop others from attacking). The Soviet Union detonated its first fission weapon on August 29, 1949. Other countries like the United Kingdom, France, and China also developed nuclear weapons.

About half of the deaths from Hiroshima and Nagasaki happened two to five years later due to radiation exposure. A radiological weapon (sometimes called a "dirty bomb") is designed to spread dangerous radioactive material. It wouldn't explode like a nuclear bomb, but it could kill many people and contaminate a large area. No radiological weapon has ever been used. While not useful for a traditional military, they are a concern for nuclear terrorism.

There have been over 2,000 nuclear tests since 1945. In 1963, many countries signed the Limited Test Ban Treaty. This treaty stopped nuclear weapons testing in the atmosphere, underwater, or in space. It still allowed underground nuclear testing. Most countries have now pledged to stop all nuclear testing.

Nuclear weapons are the most destructive weapons known. During the Cold War, opposing powers had huge nuclear arsenals, enough to kill hundreds of millions of people. Many generations grew up worried about nuclear war.

However, the huge energy released by nuclear weapons also showed the possibility of a new energy source for peaceful uses.

Peaceful Uses of Nuclear Technology

Nuclear Power for Electricity

Nuclear power uses controlled nuclear fission to release energy. This energy can be used for things like powering ships, providing heat, or generating electricity. In a nuclear power plant, a controlled nuclear chain reaction creates heat. This heat boils water, makes steam, and turns a turbine. The turbine then generates electricity.

Today, nuclear power provides about 15.7% of the world's electricity (as of 2004). It also powers aircraft carriers, icebreakers, and submarines. All working nuclear power plants use fission. No man-made fusion reaction has yet created a useful source of electricity.

Medical Uses of Nuclear Technology

Nuclear technology in medicine is used for finding diseases (diagnostics) and treating them (radiation treatment).

Imaging: The biggest use of radiation in medicine is in medical radiography. This uses X-rays to create images of the inside of the human body. This is the largest source of man-made radiation exposure for people. Medical and dental X-ray machines use X-ray sources. Special radioactive substances, called radiopharmaceuticals, are used as tracers or contrast agents in the body. For example, Positron emission tomography (PET) uses these to create detailed images.
Radiation Treatment: Radiation is also used to treat diseases, especially cancer, in a process called radiation therapy.

Industrial Applications

Since some radiation can pass through materials, it's used for various measurements. X-rays and gamma rays are used in industrial radiography to see inside solid products. This helps check for flaws without damaging the product. The item is placed between the radiation source and a special film. After exposure, the film shows any internal defects.

Gauges: These use how gamma rays are absorbed by materials.
- Level indicators: A source and detector are placed on opposite sides of a container. They show if material is present at that level. This is used for liquids or grainy substances.
- Thickness gauges: If a material has a constant density, the radiation detector can measure its thickness. This is useful for making things like paper or rubber continuously.
Controlling Static Electricity: To stop static electricity from building up in factories (for paper, plastics, etc.), a small strip of radioactive americium-241 can be placed near the material. This source ionizes the air, which removes the electric charges.
Radioactive tracers: Radioactive versions of elements act chemically like their non-radioactive forms. So, scientists can "trace" a substance by following its radioactivity.
- For example, adding a gamma tracer to a gas or liquid in a pipe can help find a hole.
- Adding a tracer to a motor part can help measure how much it wears down by checking the radioactivity in the lubricating oil.
Oil and Gas Exploration: Nuclear well logging helps find out if new or existing oil and gas wells will be profitable. This technology uses a neutron or gamma-ray source and a detector lowered into boreholes to learn about the surrounding rock.
Road Construction: Nuclear gauges are used to measure the density of soils, asphalt, and concrete for road building.

Commercial Products

Tritium illumination: Tritium is used with a glowing material in rifle sights to help with accuracy at night. Some runway markers and exit signs also use this technology to stay lit during power outages.
Smoke detector: An ionization smoke detector has a tiny bit of radioactive americium-241, which gives off alpha radiation. Inside, there are two chambers. Both have a small source of Americium-241 that creates a small electric current. One chamber is closed for comparison. The other is open to the air. When smoke enters the open chamber, the current is disrupted because smoke particles attach to the charged ions. This reduces the current. When the current drops low enough, the alarm goes off.

Food Processing and Agriculture

In biology and agriculture, radiation is used to cause changes (mutations) in plants to create new or better species. This is sometimes called atomic gardening. Another use is in insect control through the sterile insect technique. Here, male insects are sterilized with radiation and released. They can't have offspring, which helps reduce the insect population.

In industry and food, radiation is used to sterilize tools and equipment. A benefit is that items can be sealed in plastic before sterilization. A growing use in food production is food irradiation.

The Radura logo shows that food has been treated with radiation.

Food irradiation is when food is exposed to ionizing radiation to destroy microorganisms, bacteria, viruses, or insects. The radiation sources can be gamma rays from radioactive materials, X-ray generators, or electron accelerators. Other uses include stopping sprouts from growing, delaying ripening, increasing juice yield, and improving how dry foods re-hydrate.

The main effect of irradiating food is that it damages the DNA of living things. This stops microorganisms from growing and causing spoilage or disease. Insects can't survive or reproduce. Plants stop ripening or aging. All these effects are good for consumers and the food industry.

The amount of energy used for food irradiation is small, much less than cooking. Even at a typical dose, most food would only warm up by about 2.5°C (4.5°F).

Irradiation is special because it delivers a lot of energy at the atomic level. It can break molecules and cause ionization, which simply heating cannot do. This leads to new benefits but also new concerns. Treating solid food with radiation can have a similar effect to heat pasteurization for liquids like milk. However, calling irradiated foods "cold pasteurization" is debated because the processes are very different, even if the results can be similar.

Some people worry about the health risks of "induced radioactivity" from food irradiation. However, experts say that the types of radiation sources approved for food treatment have energy levels too low to make any element in food radioactive. Food that has been irradiated does not become more radioactive than luggage going through an airport X-ray scanner or teeth that have been X-rayed.

Food irradiation is allowed in over 40 countries. More than 500,000 metric tons of food are irradiated worldwide each year.

Food irradiation is mostly a non-nuclear technology. It uses ionizing radiation, which can come from accelerators or gamma rays from nuclear decay. The worldwide industry for processing with ionizing radiation is huge. Most of it uses accelerators for things like medical supplies, plastics, and cables, not just food.

Nuclear Accidents

Nuclear accidents can be very dangerous because of the powerful forces involved. Early incidents often led to deadly radiation exposure. Marie Curie died from a blood disorder caused by her high exposure. Two scientists, Harry Daghlian and Louis Slotin, died after accidentally mishandling the same piece of plutonium. Unlike regular weapons, the intense light, heat, and explosive force are not the only deadly parts of a nuclear weapon. About half of the deaths from Hiroshima and Nagasaki happened two to five years later due to radiation exposure.

Civilian nuclear and radiological accidents mainly involve nuclear power plants. Most common are leaks that expose workers to dangerous material. A nuclear meltdown is a more serious danger where nuclear material is released into the environment. The most significant meltdowns happened at Three Mile Island in Pennsylvania and Chernobyl in the Soviet Ukraine. The earthquake and tsunami in Japan on March 11, 2011, caused serious damage to the Fukushima Daiichi nuclear power plant.

Military accidents usually involve losing nuclear weapons or them exploding unexpectedly. The Castle Bravo test in 1954 was much more powerful than expected. It contaminated nearby islands and a Japanese fishing boat, causing one death. In the 1950s to 1970s, several nuclear bombs were lost from submarines and aircraft. Some have never been found. In recent decades, such accidents have become much less common.

Benefits for the Environment

Supporters of nuclear energy point out that nuclear-generated electricity reduces carbon dioxide emissions by 470 million metric tons each year. This is carbon dioxide that would otherwise come from burning fossil fuels. Also, the small amount of waste that nuclear energy creates is safely stored or recycled for other energy uses.

Supporters also highlight the risks of other electricity sources. For example, the Environmental Protection Agency estimates that coal causes 30,000 deaths a year due to its environmental impact. In comparison, 60 people died in the Chernobyl disaster. A real-world example of nuclear energy's impact is that carbon emissions increased by 650,000 tons in just two months after the Vermont Yankee nuclear plant closed.