Fission is when a really big atom breaks apart into smaller parts. lighter in other tiny particles. There are two kinds of fission: induced fission, which is used in nuclear technology, and spontaneous fission, which is a kind of radioactive decay. Induced fission is the one that scientists use today.

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What is induced fission?

Induced fission is like a "forced decay". Scientists shoot slow-moving neutrons at heavy radioactive materials like uranium-235 or plutonium-239. These materials are called fissile. When the heavy elements break apart, they create two lighter elements called fission products. The reaction also releases other neutrons and high-energy photons.

Neutron-induced fission

During induced fission, neutrons make heavy nuclei unstable. The reaction produces two or three neutrons that move very fast. A moderator is used to slow them down. The slowed-down neutrons can start another fission reaction in another fissile atom.

This process is called a chain reaction. When uranium-235 accepts another neutron, it turns into uranium-236. The chain reaction of uranium-236 when produces products and neutrons The neutrons are captured other uranium-235 atoms, turning into-236 This process repeats as the new isotopes are unstable.

The energy released during fission is huge. It reaches an average of 200 terajoules per kilogram, which is equivalent to 6.6% of the speed of light in a vacuum. A moderator is used to reduce this energy. It works by slowing down fast-moving neutrons so they can be captured by heavy nuclei. Slow neutrons are necessary for this process.

In many nuclear reactions, fission is present in water or graphite. Fast-moving neutrons collide with the atoms of water or graphite and transfer some of their energy to them. This reduces their speed. Slow neutrons are used because they are more likely to be captured by heavy nuclei. The neutron has to pass close to the nucleus and be attracted to it by the strong nuclear force to be absorbed by the nucleus.

The energy released during the induced fission process

During fission, energy is released in two forms: kinetic energy given to the neutrons and products, and high-energy photons (gamma rays). These photons and products slow down and convert into residual energy, which is used to produce work. In nuclear reactors, the residual energy is heat, which is used to create high temperatures and pressurized steam.

On average, uranium-235 produces 83 terajoules per kilogram after fission, which is equivalent to 23.05 gigawatt-hours per kilogram of fissile material.

Products formed by the fission process

The products released during the fission process vary depending on the reaction, with different velocities and energies. However, it is estimated that the products will split into almost equal masses, resulting in heavy elements and radioactive particles. In some cases, the reaction may produce smaller products, such as radiation and neutrons, as well as alpha particles or tritium.

The products formed will also undergo spontaneous disintegration, releasing further particles and energy. In nuclear reactors, these products are known as nuclear waste.

What is spontaneous fission?

Spontaneous fission is a process where a heavy nucleus disintegrates without absorbing an additional neutron. During this event, the atom splits into two lighter nuclei of almost identical mass and residual energy as photons.

Naturally occurring heavy elements like uranium-235 and uranium-238 undergo spontaneous fission as they are inherently unstable. For example, uranium-235 undergoes spontaneous fission and splits into thorium and an alpha particle (helium nucleus) without capturing a neutron.

The rate of decay in spontaneous fission is related to the half-life of the radioactive element, which is the average time it takes for a certain amount of the radioactive material to decay to half of its original mass.

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Fission and nuclear reactors

The process of nuclear fission is utilized in nuclear reactors to generate electricity, which is also known as nuclear energy. The process involves the high-velocity particles and photons produced by fission, which slow down and transmit heat. The heat is then transferred from the reactor's core to a fluid, usually water, which then moves through a pipe to exchange heat with other fluids. This causes the water to have high pressure and temperature, and it is then converted into steam. The steam is then passed through a system of pipes to a turbine, which rotates at a high speed due to the high-pressure steam. The turbine's kinetic energy is then transferred through a shaft to an electrical generator, which produces electricity. This is how nuclear power plants produce electricity.

The future of nuclear fission

Nuclear fission is a leading technology used for energy production in several countries, including, the UK, Japan, Russia, China, the USA, and Canada. These countries continue to develop new technologies that can make nuclear reactors safer, more efficient, and more advanced. Newer designs improve fission by reducing the amount and risk of nuclear waste and improving the amount of energy produced. Additionally, they are designed to disable the possibility of being used to produce nuclear weapons.

In rare instances, natural reactors have been found, such as the one in Gabon. In a natural reactor, radioactive material starts a fission reaction that self-sustains under specific conditions. However, natural reactors are a very rare occurrence, and so far, only one has been confirmed to have existed.

Induced fission is a forced decay that produces products, neutrons, smaller particles like alpha particles, and high-energy photons (gamma rays). The fission reaction can be controlled using a moderator, and in most cases, water is used as a moderator. Nuclear fission is used in nuclear reactors to produce electrical energy, also known as nuclear energy.

Induced Fission

What is induced fission?

Induced fission happens when heavy radioactive elements are bombarded with neutrons to produce decay, releasing energy and particles.

How does induced fission work?

During an induced fission reaction, neutrons force instability at the heavy nuclei. The disintegration reactions of the fissile materials will produce two of three neutrons with a high velocity. A moderator is used to slow the neutrons. The moderator is necessary for the neutrons released by the breakaway to start another breakaway in another fissile atom. During a fission process, the high-energy photons and the products are then converted into residual energy as they slow down. The residual energy of these reactions and collisions is then used to produce work. In this case, the residual energy is heat used in nuclear reactors to create high temperatures and pressurised steam.

What type of neutron is used to induce fission?

The neutrons used to induce fission are named slow neutrons.

Why can’t fast neutrons induce fission?

Fast neutrons are less likely to induce fission as they might not be captured by the nucleus of the atom.

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