When initiating a fission chain reaction, which neutron characteristics are preferred_________________?
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Answer: B. slow moving
Explanation
Slow-moving thermal neutrons exhibit a much higher probability of interacting with fissile fuel nuclei to cause fission. Lower neutron velocities maximize the capture cross-section of uranium and plutonium isotopes in nuclear reactors. Moderators are intentionally employed to slow down fast fission neutrons so they can sustain the chain reaction. Thermal neutrons possess kinetic energy corresponding to ambient temperatures of surrounding reactor core materials. Fast neutrons move at much higher velocities and are less likely to trigger fission in standard thermal reactor fuel. Neutron moderation occurs through elastic collisions with light moderator atoms like hydrogen, deuterium, or carbon.
Fast moving neutrons require specialized unmoderated reactor designs because their capture probability is much lower. Critical neutrons describe system criticality states rather than a specific preferred velocity for initiating reactions. Neutrons at rest do not exist as a viable population for sustaining continuous nuclear fission chain reactions.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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