In a thermal nuclear reactor, the control of the fission rate and the moderation of neutron speeds are vital for safe and stable power generation.
Which statement is correct?
The primary function of the moderator is to absorb the kinetic energy of the fission fragments to heat the surrounding coolant.
Control rods are made of materials with a high neutron-capture cross-section, such as boron, and are inserted further into the core to decrease the power output.
Thermal neutrons have kinetic energies of several mega-electronvolts (MeV{\text{MeV}}MeV), which is necessary to overcome the electrostatic repulsion of the uranium nucleus.
An effective moderator material should consist of heavy nuclei, such as lead, to ensure neutrons undergo many small-energy-loss collisions.
128 exam-style questions on AQA A Level Physics Radioactivity (A-level only), covering Rutherford scattering (A-level only), $\alpha$ , $\beta$ and $\gamma$ radiation (A-level only), Radioactive decay (A-level only), Nuclear instability (A-level only), Nuclear radius (A-level only), Mass and energy (A-level only), Induced fission (A-level only), and Safety aspects (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.