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Ch.21 - Nuclear Chemistry
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Brown 14th EditionCh.21 - Nuclear Chemistry문제 58
21장, 문제 58

Which of the following statements about the uranium used in nuclear reactors is or are true? (i) Natural uranium has too little 235U to be used as a fuel. (ii) 238U cannot be used as a fuel because it forms a supercritical mass too easily. (iii) To be used as fuel, uranium must be enriched so that it is more than 50% 235U in composition. (iv) The neutron-induced fission of 235U releases more neutrons per nucleus than the fission of 238U.

검증된 단계별 안내
1
Step 1: Understand the composition of natural uranium. Natural uranium consists mostly of two isotopes: 238U and 235U. The isotope 235U is fissile, meaning it can sustain a nuclear chain reaction, but it is only about 0.7% of natural uranium.
Step 2: Evaluate statement (i). Natural uranium has too little 235U to be used as a fuel. This statement is true because the concentration of 235U in natural uranium is too low to sustain a chain reaction in most nuclear reactors without enrichment.
Step 3: Evaluate statement (ii). 238U cannot be used as a fuel because it forms a supercritical mass too easily. This statement is false. 238U is not fissile and does not form a supercritical mass easily. Instead, it is fertile, meaning it can be converted into a fissile material (239Pu) in a reactor.
Step 4: Evaluate statement (iii). To be used as fuel, uranium must be enriched so that it is more than 50% 235U in composition. This statement is false. For most nuclear reactors, uranium is enriched to about 3-5% 235U, not more than 50%.
Step 5: Evaluate statement (iv). The neutron-induced fission of 235U releases more neutrons per nucleus than the fission of 238U. This statement is true. The fission of 235U typically releases more neutrons, which is crucial for sustaining a chain reaction.

주요 개념

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Uranium Isotopes

Uranium exists primarily in two isotopes: U-235 and U-238. U-235 is fissile, meaning it can sustain a nuclear chain reaction, while U-238 is not directly usable as fuel in most reactors. Natural uranium contains about 0.7% U-235, which is insufficient for most nuclear reactors, necessitating enrichment to increase the proportion of U-235.
추천 영상:
가이드 코스
04:36
Isotopes

Nuclear Enrichment

Nuclear enrichment is the process of increasing the percentage of U-235 in uranium. For most reactors, uranium must be enriched to about 3-5% U-235, not over 50% as stated in the question. Enrichment allows for a more efficient fission reaction, enabling the uranium to be used effectively as fuel in nuclear reactors.
추천 영상:
가이드 코스
02:06
Nuclear Binding Energy

Neutron-Induced Fission

Neutron-induced fission occurs when a neutron collides with a nucleus, causing it to split and release energy, along with additional neutrons. U-235 releases more neutrons per fission event compared to U-238, which is crucial for sustaining a chain reaction in nuclear reactors. This property makes U-235 a preferred fuel for nuclear energy production.
추천 영상:
가이드 코스
03:29
Band of Stability: Nuclear Fission
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