Which of the following statements is demonstrably false?
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Answer: D. Fast reactor uses moderator
Explanation
Fast reactors are designed without moderators to keep the kinetic energy of neutrons extremely high. Removing the moderator prevents neutrons from slowing down into the thermal energy spectrum. Therefore, stating that a fast reactor uses a moderator contradicts fundamental reactor physics. Fast neutron reactors utilize high-energy neutrons to fission various transuranic fuel isotopes efficiently. Liquid metal coolants such as liquid sodium are used because they do not moderate neutrons significantly. Thermal reactors contrast with fast reactors by intentionally employing moderators to slow neutrons down.
Fast reactors are valuable for burning actinide waste and breeding new fuel from depleted uranium. Engineers must design cooling systems that handle liquid metals safely without relying on water moderation. Understanding these distinct reactor types is essential for advanced nuclear fuel cycle engineering. Option A is a true statement describing the standard geometric arrangement of solid-fuel reactors. Option B correctly cites the typical thermal energy level of slow neutrons in room temperature systems. Option C accurately defines fast neutrons as possessing energies exceeding one thousand electron-volts.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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