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The Nuclear Weapons Complex Management for Health, Safety, and the Environment (1989) / Chapter Skim
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Appendix C: Nuclear Criticality
Pages 113-117

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From page 113...
... Such a system is said to have achieved "prompt criticality," and the power output will rise very rapidly. AN ILLUSTRATION Let us start our illustration with a bare sphere of highly enriched uranium of mass 25 kg.
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From page 114...
... In this illustration we have taken some liberties with precise values in the interest of simplification, but the numbers and results are approximately correct FACTORS AFFECTING CRITICALITY Density The quantity of fissionable material required for criticality (the critical mass) is strongly dependent on the material density.
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From page 115...
... Increases in material density are not a concern in ordinary situations, but they play a significant role in the design of nuclear weapons. Moderation When fissionable material is in solution, or present as finely divided particles, the presence of a "neutron moderator," such as water or a hydrocarbon, can effect a significant reduction in Me amount of Missile material required for criticality.
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From page 116...
... The process supervisor usually has the best feeling for the sort of upset conditions that may occur, and the process designer can provide guidance regarding equipment reliability. The criticality safety specialist, who should be skilled at interpreting critical data and evaluatin calculations, is responsible for evaluating the degree of criticality associated with
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From page 117...
... All eight process accidents occurred with materials in solutions: three involved plutonium solutions and five involved uranium solutions. Many were associated with off-normal process activities.
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Key Terms

  • critical mass
  • fissionable material
  • nuclear criticality
  • fissile material
  • neutron absorbers

  • highly enriched
  • enriched uranium
  • criticality accidents
  • criticality control
  • plutonium solutions

  • critical experiment
  • energy release
  • process designer
  • nuclear reactions
  • fission event

  • safety organizations
  • eight process
  • material required
  • process accidents
  • uranium solutions

  • safety specialist
  • experiment facilities
  • radiative capture
  • bare sphere
  • times characteristic

  • glass cylinder
  • total energy
  • close cooperation
  • unplanned nuclear
  • persistent reaction


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