A nuclear reactor core reaches its critical size when_________________?
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Answer: A. chain reaction can be initiated
Explanation
A reactor core reaches critical size when neutron production balances losses allowing chain reactions to begin. At this critical threshold every fission event triggers exactly one subsequent fission event on average. Reaching this size is the fundamental prerequisite for initiating stable power generation inside a core. Criticality depends on core geometry, fuel enrichment, moderator selection, and neutron reflector placement. The effective multiplication factor equals exactly one when a reactor operates in a steady critical state. Subcritical cores absorb or leak more neutrons than they produce causing reactions to die out.
Reactor operators carefully manipulate control rods to guide the core smoothly up to its critical size. Understanding criticality ensures that operators maintain safe operating margins during startup procedures. Uncontrolled reactivity excursions can lead to severe core damage if critical parameters are mismanaged. Claiming the core becomes uncontrollable confuses normal criticality with a prompt supercritical accident. Exploding is a characteristic of unconstrained nuclear weapons rather than regulated power reactor cores. Producing no power describes a subcritical state where the chain reaction cannot sustain itself.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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