A fast breeder reactor employs which type of moderator material__________________?
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Answer: E. no moderator is used
Explanation
Fast breeder reactors operate entirely without a moderator to maintain a chain reaction using fast neutrons. Eliminating the moderator preserves high neutron energies necessary for breeding fissile plutonium from uranium-238. Fast neutron spectra favor fertile captures rather than thermal neutron slowing and parasitic absorptions. Fast reactors use liquid metals like sodium as coolants because they remove heat without moderating neutrons. The fission cross-section is smaller at high energies requiring higher fissile enrichment to sustain operations. Breeding ratios greater than one allow these reactors to produce more fuel than they consume over time.
Fast breeder technology significantly extends global uranium resources by utilizing plentiful uranium-238 isotopes. Managing unmoderated fast neutron fluxes requires advanced materials engineering to withstand radiation damage. These specialized reactors play a crucial role in closing the nuclear fuel cycle and reducing waste. Demineralized water acts as a strong moderator and coolant in standard thermal light water reactors. Heavy water contains deuterium and serves as an efficient moderator in pressurized heavy water reactor designs. Graphite is a classic solid moderator utilized extensively in gas-cooled and early graphite-moderated reactors.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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