Question 1: A nuclear chain reaction occurs when a single nuclear reaction causes an average of more than one subsequent reaction, leading to a self-sustaining process. Explain the role of neutrons in initiating and sustaining a chain reaction in a nuclear reactor.

Answer: Neutrons are released during fission and can collide with other fissile nuclei, causing them to split and release more neutrons, thus sustaining the chain reaction.

Question 1: Describe what is meant by the term 'critical mass' in the context of nuclear chain reactions.

Answer: Critical mass is the minimum amount of fissile material needed to sustain a self-perpetuating chain reaction.

Question 2: Explain why controlling the number of neutrons is essential in a nuclear reactor.

Answer: Controlling neutrons prevents the chain reaction from becoming uncontrollable, ensuring safety and steady energy production.

Question 1: Calculate the number of fission reactions after 5 generations if each reaction causes 1.2 more reactions on average. Assume starting with 1 initial reaction.

Answer: Number of reactions = 1 * (1.2)^5 ≈ 2.49 (~3 reactions)

Question 2: If a fissile material has a mass of 10 kg and each fission releases approximately 200 MeV of energy, calculate the total energy released during complete fission of all nuclei. (Use 1 MeV = 1.602 x 10^-13 Joules)

Answer: Number of nuclei = (mass / molar mass) * Avogadro's number; Energy = number of nuclei * 200 MeV * 1.602 x 10^-13 J/MeV; Total energy approximately 2.2 x 10^15 Joules.

Question 1: List three safety precautions that must be considered when designing a nuclear reactor to prevent accidental runaway chain reactions.

Answer: Use of control rods to absorb excess neutrons, maintaining criticality within safe limits, and proper shielding to contain radiation.

Question 2: Describe a basic experimental setup to observe neutron moderation in a nuclear reactor core scenario (theory only).

Answer: The setup includes a fissile material, a moderator such as water or graphite to slow neutrons, and detectors to measure neutron flux at various points, ensuring the neutrons are sufficiently slowed to sustain reactions efficiently.

Question 1: In a controlled nuclear reactor experiment, the number of neutrons detected per second was recorded over time. The data shows an initial increase in neutron count, stabilising after some time. Explain what this indicates about the chain reaction in the reactor.

Answer: It indicates the reactor reached a steady state or critical condition, where the chain reaction is self-sustaining without increasing or decreasing.

Question 1: Discuss how nuclear chain reactions are utilised in nuclear power plants to generate electricity, including key safety features involved.

Answer: Nuclear power plants use controlled chain reactions in fissile materials like uranium or plutonium to produce heat. This heat generates steam, which drives turbines to produce electricity. Safety features include control rods to regulate neutron flow, cooling systems to remove excess heat, and shielding to protect against radiation.