Answer: Minimum mass for sustained chain reaction.
- A Minimum mass for sustained chain reaction
- B The total mass of the entire reactor core including shielding
- C The maximum mass legally permitted to be stored at one site
- D Exactly half the total mass of fissile material available
Correct answer: A. Minimum mass for sustained chain reaction
Explanation: Critical mass: minimum amount of fissile material for self-sustaining chain reaction (each fission on average causes exactly one more 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.