What is nuclear fission? Give an example. Why is energy released in it? What is a fission chain reaction? Differentiate between uncontrolled and controlled fission chain reactions.

What is Nuclear Fission?

Nuclear fission is the process in which the nucleus of a heavy atom, such as uranium-235 or plutonium-239, splits into two or more smaller nuclei, along with a few neutrons and a large amount of energy. This splitting is caused by the nucleus absorbing a neutron, becoming unstable, and then splitting.

Example of Nuclear Fission:

An example of nuclear fission occurs when a uranium-235 nucleus absorbs a neutron and splits into two smaller nuclei, such as barium-141 and krypton-92, releasing energy, neutrons, and gamma radiation.

Why is Energy Released in Nuclear Fission?

Energy is released during nuclear fission because the total mass of the resulting products (the smaller nuclei, neutrons, and other particles) is less than the original mass of the heavy nucleus. This missing mass has been converted into energy, according to Einstein’s equation E=mc2, where E is energy, m is mass, and c is the speed of light. The energy released is substantial, which is why nuclear fission is used in power generation.

What is a Fission Chain Reaction?

A fission chain reaction occurs when the neutrons released from one fission event cause the fission of additional nuclei, which in turn release more neutrons, continuing the cycle. This process can rapidly multiply the number of fissions and the energy released.

For a chain reaction to sustain itself, there needs to be a sufficient concentration of fissile material and proper conditions (like the right number of neutrons and proper moderation of those neutrons).

Uncontrolled vs. Controlled Fission Chain Reactions:

Uncontrolled Fission Chain Reaction:

  • Example: The explosion of a nuclear bomb.
  • Description: In an uncontrolled chain reaction, the fission events continue rapidly without any regulation. Each fission releases more neutrons, leading to an exponential increase in the number of fissions. This rapid escalation results in a massive release of energy, which in a bomb leads to an explosion.

Controlled Fission Chain Reaction:

  • Example: Nuclear power reactors.
  • Description: In a controlled chain reaction, the fission process is carefully managed. Neutron-absorbing materials (like control rods made of boron or cadmium) are used to regulate the number of free neutrons in the system, ensuring that the reaction proceeds at a steady, manageable rate. This controlled reaction releases a steady amount of energy that can be harnessed for power generation.

Key Differences:

  • Uncontrolled fission is used for explosive purposes (nuclear weapons), where the reaction is allowed to escalate out of control.
  • Controlled fission is used for energy generation (nuclear power plants), where the reaction is carefully managed to produce a steady and controlled release of energy.

Related Questions:

  1. When a uranium nucleus absorbs a slow neutron, it subsequently emits two α-particles. What is the resulting element?
  2. Define atomic number, atomic mass number, and nucleon number. How is an atom represented symbolically? Find the number of protons, neutrons, atomic number, atomic mass number, and nucleon number from X. Which element is this?
  3. Define isotope. What are the different isotopes of hydrogen?
  4. What is meant by background radiation? What are different sources of background radiation?
  5. What is radioactivity? Who discovered it? What do you mean by parent nuclide and daughter nuclide? What are the three basic radioactive decay processes, and how do they differ?
  6. What is nuclear transmutation or nuclear decay? What are three basic radioactive decay processes, and how do they differ? Give examples.
  7. What are radioisotopes? Give two examples. Describe two uses of radioisotopes in medicine, industry, and research.
  8. What is a fusion reaction? Explain in detail.
  9. Numerical Problems of Chapter 18: Radioactivity
  10. What is common in isotopes of an element and what is different in them?
  11. It happens that a nuclear radiation emits from an atom of an element, and it moves one step ahead in the periodic table. Explain.
  12. Why do nuclei of atoms with atomic numbers greater than 82 emit radiation?
  13. β-particle is emitted from the neutron of the nucleus. Write the nuclear equation for this reaction.
  14. Why is the range of β-particles greater than α-particles in air with the same energy?
  15. Why is the ionization power of α-particles greater than β-particles in solids with the same energy?
  16. What fraction of a radioactive element will be left after 4 half-lives have elapsed?
  17. Why is energy released when lighter nuclei fuse with heavier nuclei?
  18. How long will a radioactive element take to decay completely?
  19. What is half-life? Derive the formula for the number of un-decayed atoms. Draw a graph for decaying atoms with time.
  20. Physics 10 MCQ