Nuclear Fission and Fusion
Text Reading: Giancoli, Physics - Principles with Applications, Chapter 31: Sections 1 to 4
- 31: 1 Nuclear reactions represent transmutation of the elements since the resulting products are different elements from the reacting atoms. Fermi predicted that transmutation could be stimulated by bombarding nuclei with neutrons.
- 31: 2 Hahn and Strassman realized that uranium bombarded by neutrons produced roughly equal nuclei, splitting the atom (fission) rather than stimulating radioactivity. The fission reaction released high energy neutrons which could then split other nuclei, creating a chain reaction if the material was sufficiently dense. Unchecked, a chain reaction produces a nuclear explosion. Held in check by control rods which absorb excess neutrons, the fission reaction can be supported at a long-term controlled rate. Nuclear reactor accidents at Three Mile Island and Chernobyl, as well as difficulties disposing of radioctive waste from reactors, have slowed the spread of reactors as energy sources; however, European dependence on nuclear power is significant.
- 31: 3 Nuclear fusion (putting neutrons and protons together to form larger nuclei) is a cleaner reaction, but more difficult to start, support, and control. Fusion is the source of stellar power. Attempts to create sustained nuclear fusion so far have been unsuccessful, although several theories are under investigation.
- 31: 4 High energy photons and particles emitted by radioactivity can strip electrons from atoms, creating ions and causing cell damage.
- 31: 5 Monitoring exposure to radioactivity involves dosimetry, counting the number if disintegrations per seconds of exposure. Various devices are used by nuclear physicists, HAZMAT workers, or other officials to monitor exposure.
|Q-value or nuclear reaction energy||Reaction: a + X → Y + b|
Q = KEb + KEY - KEa - KEX
Q = (mb + mY - ma - mX)c2
|Q: net energy change|
X: initial nucleus
Y: final nucleus
b: emitted particle
|Uranium Fission (general)||
|U: uranium isotopes|
X1 and X2: fission fragments
γ: gamma radiaton
Read the following weblecture before chat: Fission and Fusion Reactions
Use the FLASH simulation for the proton-proton fusion reaction at the University of Nebraska-Lincoln Astronomy lab to see how the sun uses hydrogen fusion to produce helium.
Chat Preparation Activities
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- The chapter quiz is not yet due.
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