Question 1: Define nuclear fission and briefly explain how it releases energy.

Answer: Nuclear fission is a process where a heavy nucleus splits into two smaller nuclei, releasing a large amount of energy, neutrons, and gamma radiation.

Question 2: Describe the role of a neutron in initiating nuclear fission in uranium-235.

Answer: A neutron collides with a uranium-235 nucleus, causing it to become unstable and split into smaller nuclei, releasing energy and more neutrons.

Question 1: Explain why a critical mass is necessary for a sustained nuclear chain reaction.

Answer: A critical mass ensures enough fissile material is present so that released neutrons can cause further fissions, maintaining a chain reaction.

Question 2: What are the main safety precautions to prevent accidental chain reactions in nuclear reactors?

Answer: Precautions include controlling the neutron flux with control rods, using moderators to slow neutrons, maintaining sub-critical conditions, and employing shielding to prevent radiation exposure.

Question 1: Calculate the energy released when one kilogram of uranium-235 undergoes fission. (Mass of uranium-235: 235 g/mol; energy released per fission: approximately 200 MeV).

Answer: Energy per fission = 200 MeV = 200 x 10^6 x 1.602 x 10^-19 J = 3.204 x 10^-11 J. Number of moles in 1 kg = 1000 g / 235 g/mol ≈ 4.255 mol. Number of atoms = 4.255 mol x 6.022 x 10^23 atoms/mol ≈ 2.56 x 10^24 atoms. Total energy = number of atoms x energy per fission ≈ 2.56 x 10^24 x 3.204 x 10^-11 J ≈ 8.2 x 10^13 Joules.

Question 2: If a nuclear reactor produces 1 GW of power, how long can it operate continuously using 10 kg of uranium-235 assuming 100% efficiency?

Answer: Total energy from 10 kg uranium-235 = 8.2 x 10^14 Joules (from previous calculation scaled for 10 kg). Time = total energy / power = 8.2 x 10^14 J / 10^9 W = 8.2 x 10^5 seconds ≈ 9.5 days.

Question 1: Identify three safety precautions necessary when handling fissile materials in a nuclear power plant.

Answer: Use shielding to protect from radiation, control neutron flux with control rods, and ensure proper containment to prevent leaks and accidents.

Question 2: Describe a basic experimental setup to investigate neutron-induced fission in uranium-235, including variables to control and safety measures.

Answer: An experimental setup would include a source of neutrons (e.g., a neutron generator), a sample of uranium-235, and detectors to measure fission events. Variables include neutron flux, sample mass, and shielding. Safety measures include remote handling, proper shielding, and monitoring radiation levels.

Question 1: A reactor's neutron count rate increases sharply when a control rod is withdrawn. Explain what this indicates about the chain reaction.

Answer: It indicates the chain reaction is becoming super-critical, leading to an increased rate of fission events.

Question 2: Discuss how nuclear fission is used in electricity generation and one advantage and one disadvantage of this technology.

Answer: Nuclear fission in reactors produces heat used to generate steam that drives turbines to generate electricity. Advantages include low greenhouse gas emissions and high energy output. Disadvantages include radioactive waste management and risk of accidents.