Question 1: Nuclear fission is a process in which an unstable nucleus splits into two or more smaller nuclei, releasing a significant amount of energy and additional neutrons. This chain reaction can be controlled or uncontrolled, leading to applications such as nuclear power plants or atomic bombs.

Answer: Nuclear fission is the splitting of a heavy nucleus into smaller nuclei, releasing energy and neutrons.

Question 2: Explain why uranium-235 is commonly used as fuel in nuclear reactors.

Answer: Uranium-235 is fissile, meaning it can sustain a chain reaction, and it has a high probability of undergoing fission when struck by a neutron.

Question 1: Define nuclear fission and describe its significance in energy production.

Answer: Nuclear fission is the splitting of a heavy nucleus into smaller nuclei, releasing energy. It is significant because it provides a large amount of energy used in nuclear power plants for electricity generation.

Question 2: Describe the role of a moderator in a nuclear fission reactor.

Answer: A moderator slows down fast neutrons produced during fission, increasing the likelihood of further fission reactions in the fuel.

Question 1: Calculate the energy released when 1 gram of uranium-235 undergoes fission. (Use E=mc², where c=3 x 10^8 m/s, and 1 atomic mass unit = 1.66 x 10^-27 kg. Uranium-235 has an atomic mass of 235 u, and approximately 200 MeV of energy is released per fission event.)

Answer: Approximately 8.2 x 10^10 Joules.

Question 2: If a control rod absorbs 0.5% of neutrons in a reactor during operation, how does this affect the stability of the chain reaction?

Answer: Absorbing 0.5% of neutrons helps control the chain reaction, preventing it from becoming supercritical and ensuring the reaction remains stable.

Question 1: List three safety precautions necessary when handling fissile materials in a nuclear reactor setting.

Answer: Using shielding to protect from radiation, controlling neutron flux with control rods, and ensuring proper containment of radioactive materials.

Question 2: Describe a basic experimental setup to measure the energy released during fission reactions (theory only).

Answer: The setup would include a fissile sample, neutron source, detectors to measure emitted radiation and neutrons, and a calorimeter or other device to estimate energy release. Safety measures include shielding and remote handling to protect against radiation exposure.

Question 1: A sample of uranium-235 undergoes fission, releasing an average of 200 MeV per event. If 1 kg of uranium-235 completely fissions, how much total energy is released? (Use Avogadro's number: 6.022 x 10^23 atoms per mol, and molar mass of uranium-235 = 235 g/mol.)

Answer: Approximately 2.55 x 10^15 Joules.

Question 2: Given that the energy released per fission is about 200 MeV, explain how chain reactions can lead to a rapid release of energy in nuclear bombs versus controlled energy release in reactors.

Answer: In nuclear bombs, the chain reaction is uncontrolled, causing a rapid, exponential increase in fission events that releases a vast amount of energy in a very short time. In contrast, reactors use control mechanisms like control rods and moderators to slow down or absorb neutrons, maintaining a steady, controlled chain reaction for safe energy production.

Question 1: Describe how nuclear fission is utilised in nuclear power plants to generate electricity.

Answer: Nuclear power plants use controlled fission reactions in reactors to produce heat, which is then used to generate steam that drives turbines connected to electricity generators.

Question 2: Discuss the advantages and disadvantages of using nuclear fission as an energy source.

Answer: Advantages include large energy output, low greenhouse gas emissions during operation, and fuel availability. Disadvantages include radioactive waste management, risk of accidents, and proliferation concerns.