Answer: Slow down neutrons (for thermal fission).
- A Slow down neutrons (for thermal fission)
- B Speed up and accelerate fission neutrons to higher energy
- C Absorb gamma rays emitted during the fission process
- D Generate electricity directly from the heat produced
Correct answer: A. Slow down neutrons (for thermal fission)
Explanation: Moderator (heavy water, graphite) slows fast neutrons to thermal speeds. Slow neutrons are better captured by U-235 for fission.
Binding energy per nucleon rises sharply for light nuclei, peaks around iron-56 (the most stable nucleus), then slowly declines for heavier nuclei - which is exactly why fusing light nuclei or splitting heavy nuclei both release energy: each moves the products toward this stability peak.
Concept context
Radioactivity, nuclear reactions, fission, fusion, and binding energy.