Reactions are endless around us and they are occurring at every moment. However, there are specific reactions that may have adverse effects on human beings if they come in close contact. Chemical reactions are such occurrences which can be both useful and harmful, especially if they are not controlled.
Students often ask what is nuclear fission, which is an integral part of studying Physics as a subject in high school. This topic, interesting as it is, also involves a great deal of concepts which must be learnt in-depth.
Nevertheless, nuclear reactions such as fission reactions are considered to be highly energetic in nature. It means the process emits a huge amount of energy while taking place.
What Do You Mean By a Nuclear Reaction?
To understand what is fission, students need to get a detailed background of the same. So, let us understand a nuclear reaction first. Here, the word nuclear indicates and relates to the nucleus of an atom.
So, when the atom is bombarded with another particle with high energy, the reaction that takes place is called a nuclear reaction. Students should note here that the reaction causes an irreversible change in the characteristics of the atom.
Also, the high energy particle can be either an alpha particle, a proton, a heavy ion or a gamma-ray photon, etc. Do remember, an external particle for bombarding is necessary whenever you ask for what is nuclear fission and nuclear fusion.
Both these reactions require an external agent to initiate the reaction. Hence, students should be aware of the names of such agents too.
What is the Meaning of Nuclear Fission?
The nuclear fission definition states that on a nuclear reaction the particle or atom splits into two smaller and lighter nuclei. You must also note, on the splitting of an atom, its two daughter nuclei weigh lighter than the parent nucleus.
Here, in the picture above, as you can see, an atom has split into two. The nuclear fission meaning is that it will keep on splitting the atoms one after another. Furthermore, it also releases a huge amount of energy.
Therefore, this kind of reaction is usually explosive in nature. You may take help of an example of nuclear fission reaction for better understanding. Uranium is such an element that undergoes nuclear reaction.
Nuclear Energy - A Brief Explanation
The mass of an atom is concentrated in its nucleus. As already mentioned while explaining what is nuclear fission, it releases a large amount of energy while going through fission. This energy is called nuclear energy.
You should note that there is another kind of nuclear reaction called nuclear fusion. In this process, the atoms get together and release energy. Both these processes release a massive amount of energy which is termed as nuclear energy.
Another vital aspect related to this discussion is that of the nuclear fission equation, which should be taken into account while studying.
Nuclear Reactors in Power Plants
The real-life application of nuclear fission is in producing electricity. You might have heard about nuclear power plants. It is one of the most convenient options for mass production of electricity. The reaction releases high energy which is then processed through multiple layers to produce electric power.
To know about the nuclear fission process in a more detailed manner, you can look into our website. You can also download our Vedantu app for enhanced and ease of learning.
FAQs on Nuclear Fission
1. What is the definition of nuclear fission with an example?
Nuclear fission is a nuclear reaction where the nucleus of a heavy atom, like uranium, splits into two or more lighter nuclei when struck by a neutron. This process releases a significant amount of energy. A classic example is the fission of Uranium-235:
- ¹n + ²³⁵U → ²³⁶U* → ¹⁴¹Ba + ⁹²Kr + 3¹n + Energy
Here, a neutron hits a U-235 nucleus, forming an unstable U-236 nucleus, which then splits into Barium, Krypton, and three more neutrons.
2. What are the typical products released during a nuclear fission reaction?
During a typical nuclear fission event, several products are released. The primary products are:
- Two smaller nuclei: These are often called fission fragments, such as Barium and Krypton in the case of Uranium-235 fission.
- Neutrons: Usually two or three free neutrons are ejected, which can go on to initiate further fission events.
- Energy: A tremendous amount of energy is released, primarily in the form of kinetic energy of the fission fragments and gamma radiation.
3. Can you provide the general equation for a nuclear fission reaction?
The general equation representing a nuclear fission reaction, as per the CBSE Class 12 Physics syllabus for 2025-26, can be written as:
X + n → X* → Y + Z + neutrons + Q (Energy)
In this equation:
- X is the initial heavy, fissile nucleus (e.g., ²³⁵U).
- n is the incident neutron that initiates the fission.
- X* is the unstable, excited compound nucleus formed temporarily.
- Y and Z are the fission fragments (the two smaller nuclei).
- Q represents the large amount of energy released in the reaction.
4. Why is a chain reaction essential for a sustained nuclear fission process?
A chain reaction is essential because it allows the fission process to be self-sustaining and produce a continuous, large-scale release of energy. When one nucleus fissions, it releases multiple neutrons. For a sustained reaction, at least one of these newly released neutrons must successfully strike another fissile nucleus, causing it to fission. If this process repeats, it creates a cascade effect or a 'chain', leading to an exponential increase in fission events and energy output, which is the fundamental principle behind nuclear reactors.
5. What is the main difference between nuclear fission and nuclear fusion?
The main difference between nuclear fission and fusion lies in the process and the atoms involved:
- Process: Nuclear fission is the splitting of a single heavy, unstable nucleus into two or more lighter nuclei. In contrast, nuclear fusion is the process of combining two light nuclei to form a single, heavier nucleus.
- Energy Release: Both processes release enormous amounts of energy, but the energy released per nucleon is generally greater in fusion than in fission.
- Conditions: Fission can be initiated by a low-energy neutron, while fusion requires extremely high temperatures and pressures to overcome the electrostatic repulsion between positively charged nuclei.
6. Why is Uranium-235 a preferred fuel for nuclear fission over Uranium-238?
Uranium-235 is preferred over the more abundant Uranium-238 primarily because it is a fissile material, whereas U-238 is fertile. This means U-235 can sustain a chain reaction with slow-moving (thermal) neutrons. When a U-235 nucleus absorbs a slow neutron, it becomes highly unstable and has a high probability of undergoing fission. In contrast, U-238 tends to absorb slow neutrons without splitting and instead transmutes into Plutonium-239. It can only undergo fission with very high-energy (fast) neutrons, making it unsuitable for sustaining the kind of chain reaction needed in most common nuclear reactors.
7. How is the massive energy release in nuclear fission explained by the concept of mass defect?
The massive energy release in nuclear fission is explained by the concept of mass defect and Einstein's mass-energy equivalence principle, E = mc². The total mass of the fission products (the smaller nuclei and neutrons) is slightly less than the total mass of the original heavy nucleus and the incident neutron. This 'missing' mass, known as the mass defect (Δm), is not actually lost but is converted into a tremendous amount of energy (E) according to the formula, where 'c' is the speed of light. Because c² is a very large number, even a tiny amount of lost mass results in a huge release of energy.
8. What are some real-world applications of nuclear fission?
Nuclear fission has several significant real-world applications, primarily focused on energy generation and scientific research. The most important applications include:
- Nuclear Power Plants: Controlled nuclear fission chain reactions are used in nuclear reactors to generate heat. This heat is used to produce steam, which drives turbines to generate electricity for millions of homes and industries.
- Medical Isotopes: Fission byproducts are used to produce radioisotopes essential for medical diagnostics and cancer therapy.
- Scientific Research: Fission reactions are used in research reactors to produce neutron beams for studying materials and in various physics experiments.
