The type of reactions in which the “identity of an atomic nucleus is changed by bombarding of energetic particles i.e. alpha particle, gamma rays, neutrons or protons, etc.” are known as nuclear reactions. There are four different types of nuclear reactions known to humans. Each nuclear reaction is different from one another in the context of characteristics and applications. The four types of nuclear reactions are as follows:
- Nuclear fusion
- Nuclear fission
- Nuclear decay
- Nuclear transmutation
In this type of reaction, two or more small nuclei collide with each other and result in a single heavier nucleus. Nuclear fusion occurs in the elements with a low atomic number such as hydrogen and helium etc. It is the exact counter reaction of nuclear fission in which heavier nucleus breaks down into lighter nuclei. These reactions result in a large amount of energy emission. Energy in the universe is a cause of nuclear fusion reactions. The pressure at the center of the star is very high so this reaction takes place. Its best example is the nuclear fusion reaction in the sun where the temperature of the core is 15 million degrees Celsius. At this high temperature and high pressure of core, two isotopes of hydrogen named deuterium and tritium collide and form helium with the release of a tremendous amount of energy in heat form. According to a rough estimation, about 600 million tons of hydrogen are converted into helium every second in the sun.
The process in which an atomic nucleus splits down into two or lighter nuclei is known as a nuclear fission reaction. A massive amount of energy is released as the result of a fission reaction and the reaction is exothermic type. Most fission reactions produce two charged fragments so-known as binary fission. Three positively charged fragments may also produce occasionally and are called ternary fission. Fission reaction takes place in nuclei of higher atomic numbers. It is exactly the opposite of a nuclear fusion reaction except energy is released in both reactions. In a fission reaction, unstable heavy nuclei split into two or smaller pieces that are more stable than the parent nucleus. Energy and extra neutrons are released in a nuclear fission reaction. These emitted neutrons further split other atoms of heavier nucleus present in the reaction medium, the reaction carries on in a chain fashion. Atomic bomb works on the principle of nuclear fission reaction, in which uranium is used to produce that much of energy.
“Nucleus of an unstable atom decays spontaneously with the emission of radiations,” this type of process is called nuclear decay. Radioactive decay is another name of the same process. The unstable nucleus carries on decay process until a stable nucleus is produced, under a sequence of reaction series like Uranium series, Thorium series, Actinium series, etc. There are six types of nuclear decay:
- Alpha decay
- Electron capture
- Gamma emission
- Positron emission
- Spontaneous fission
1. Alpha decay:
This type of decay is observed in atomic nuclei with atomic masses of 200 or greater. An alpha particle (helium atom) is formed as a product.
2. Beta decay:
In this type of nuclear reaction a beta particle produces. It is observed in nuclei having a large number of neutrons. A neutron splits into a proton and a beta particle (high energy electron). A beta particle may seep down in the living body and damage cells.
3. Electron capture:
An electron of the inner shell of nuclei combines with a proton and generates neutron. X-rays are produced as a result of the movement of the second inner shell electron to a lower energy level.
4. Gamma emission:
When gamma rays have been produced the nuclei of the parent atom do not change into another element, but a large amount of energy is released. This is the peculiarity of this reaction.
5. Positron emission:
A proton breaks down into a neutron and positron. This reaction is the opposite of beta decay. Positron emission tomography (PET) found its application in the pharmaceutical field.
6. Spontaneous fission:
In this type of reaction, a nucleus breaks down completely and produce two different fragments with different atomic numbers and mass numbers. This reaction takes place on its own as the name showed. A massive amount of energy is also released as a product.
It’s so far is the conversion of one element or an isotope into any other element. A transmutation is completed either by nuclear reactions (in which an out-of-doors particle reacts with a nucleus) or with the help of decay, where no outdoor reason is needed. Most stars perform transmutation through fusion reactions concerning hydrogen and helium, at identical times. Traditional fission power reactors additionally purpose artificial transmutation, now not from the energy of the device, however using exposing elements to neutrons produced by fission from an artificially produced nuclear chain response. Artificial nuclear transmutation has been taken into consideration as a probable mechanism for decreasing the number and threat of radioactive material. Most natural transmutation on this planet nowadays is mediated employing cosmic rays (inclusive of production of carbon-14) and with the help of the nuclear reaction of radioactive primordial nuclides leftover from the initial formation of the solar system (such as potassium-forty, uranium, and thorium), plus the nuclear reaction of products of these nuclides (radium, radon, polonium, etc.)