Neutron radiation

Tiny bits fly through the air. They are called neutrons. These bits can come from big machines. They can also come from space.

Sometimes, these bits hit other tiny parts. This can make new things. It can even start a chain of events.

These bits can be very strong. They can pass through many things. This makes them hard to stop.

We use water to stop them. Water helps slow the bits down. This keeps people safe.

Scientists use these bits for many jobs. They can help look inside parts. They can even help treat sick cells.

Neutrons are tiny parts of atoms. They are a type of radiation. Unlike other radiation, neutrons have no charge. This helps them pass through many things. They are very strong and can be dangerous.

Neutrons come from many places. They can come from space. They can also come from big machines. Some neutrons come from nuclear fission. This is when an atom splits apart. This split lets out more neutrons. These neutrons can hit other atoms. This can start a chain reaction.

In nuclear reactors, neutrons move at different speeds. Some are fast. Others are slow. We call slow neutrons thermal neutrons. To make a reaction work, we must slow them down. We use a moderator to do this. Graphite and water are common moderators.

Neutrons can also change things. They can make atoms radioactive. This is called neutron activation. Because of this, neutrons can damage tools and bodies. To stay safe, we use shields. Materials with lots of hydrogen work best. Water and wax are good shields. Boron is also a great way to stop them.

Neutron radiation is a special type of energy. It is made of free neutrons, which are tiny particles. Unlike other types of radiation, neutrons have no electric charge. This makes them very good at passing through many materials. They can be quite dangerous to living things. This is because they can cause biological damage to cells. They are even ten times more effective at this than gamma radiation.

Neutrons are released through several different ways. One way is through nuclear fission, where an atom splits apart. This split releases more neutrons, which can start a chain reaction. Another way is through nuclear fusion, where atoms join together. They also come from cosmic rays in space. These are called cosmogenic neutrons. They hit our atmosphere and can even change nitrogen into carbon-14.

Scientists discovered neutron radiation by watching particles collide. They saw an alpha particle hit a beryllium nucleus. This collision turned the beryllium into a carbon nucleus. During this event, a neutron was released. This discovery helped us understand how these particles work. Today, we use large machines like particle accelerators to study them. Some machines, like the Spallation Neutron Source, create many neutrons at once.

In nuclear reactors, neutrons move at different speeds. Fast neutrons have a lot of energy. However, they are hard for atoms to catch. To fix this, we use a moderator to slow them down. A moderator is a material that helps neutrons reach a slower state. We call these slow neutrons thermal neutrons. Common moderators include graphite, light water, or heavy water.

Neutrons can also change the very nature of objects. This is called neutron activation. It happens when an atom captures a neutron and becomes radioactive. This can make metal tools or even body tissues radioactive. To stay safe, we use shields made of hydrogen-rich materials. Water, wax, and concrete are all good shields. Boron is also an excellent material to stop neutrons.

Neutron radiation is a form of ionizing radiation consisting of free neutrons. Unlike alpha or beta radiation, neutrons carry no electric charge. This lack of charge makes them highly penetrating through many types of matter. They are often called indirectly ionizing radiation. This is because they do not excite electrons directly like charged particles do. Instead, they cause ionization through secondary effects. For example, a neutron might be absorbed by a nucleus, causing the emission of a gamma ray. This gamma ray then removes an electron from an atom.

Neutrons are released through several powerful nuclear processes. In nuclear fission, a heavy nucleus splits and releases free neutrons. In nuclear fusion, lighter nuclei join together to release neutrons. These neutrons can then react with other nuclei to form new nuclides. This process can trigger further radiation in a chain reaction. Neutrons also come from cosmic radiation hitting the Earth's atmosphere. These are known as cosmogenic neutrons. They often possess higher energy levels than neutrons found in reactors.

Scientists discovered neutron radiation through specific particle collisions. They observed an alpha particle colliding with a beryllium nucleus. This interaction transformed the beryllium into a carbon nucleus. During this specific process, a neutron was emitted. This is described by the notation Be(α, n)C. Today, large devices like particle accelerators produce neutrons. One notable example is the Spallation Neutron Source. These machines allow researchers to study particle interactions in controlled environments.

In nuclear reactors, neutrons are categorized by their energy levels. Fast neutrons move with high kinetic energy. However, most fissionable nuclei have a low cross section for absorbing fast neutrons. This means they are unlikely to capture them. To fix this, engineers use a neutron moderator. A moderator slows fast neutrons down to thermal velocities. Thermal neutrons have an energy distribution similar to a gas in equilibrium. Common moderators include graphite, light water, and heavy water.

Neutron radiation has many important scientific and medical uses. In medicine, Boron Neutron Capture Therapy treats cancerous tumors. This works because neutrons are highly penetrating and damage cellular structures. Scientists also use neutron radiation for scattering and diffraction experiments. This helps them study the structure of materials in biology and chemistry. In industry, neutron radiography and tomography create images of parts. These tools are vital for the nuclear, aerospace, and explosives industries.

Despite these uses, neutron radiation presents serious health hazards. A major danger is neutron activation. This occurs when a neutron is captured by an atomic nucleus. This transformation can turn stable substances into radioactive radionuclides. This process can make bodily tissues and industrial equipment radioactive. Because neutrons are uncharged, they are very dangerous to the whole body. In living tissue, they are roughly ten times more effective at causing damage than gamma radiation.

Effective protection requires specific types of radiation shielding. Because neutrons have high kinetic energy, they must be slowed down first. Hydrogen-rich materials are the most effective at this task. Light atoms like hydrogen use elastic scattering to slow neutrons. Materials like water, paraffin wax, and polyethylene are excellent shields. Concrete and gravel are also used because they are inexpensive. Boron is another great absorber because it decays into carbon or helium without producing much gamma radiation.

Finally, neutron radiation can physically degrade solid materials over time. High-energy neutrons cause a process called a collision cascade. When a neutron hits a lattice atom, it creates a primary knock-on atom. This atom then hits others, creating many more defects. This can lead to metal embrittlement or neutron-induced swelling. In graphite, this can cause the Wigner effect. This buildup of energy and defects can even lead to accidents, such as the Windscale fire.