Review Exam 2

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Review Exam 2

• Power, Neutron Diffusion, Criticality

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Neutron Interactions
What percentage of a neutron beam can pass
through a lead shield 0.1 cm thick? ss11.4 b
sa0.17 b Nlead 0.03296 x 10 24 per cm3
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Power

• A power plant output is 3300 MWth,
  efficiency30, operating at 75 capacity and is
  shutdown for maintenance 1 month every year.
• What is the electric output for this reactor?

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Example Continued

• What is power plant capable of producing?

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Neutron Movement

• A Cf-252 source emits 1 x1012 thermal neutrons
  per second. What is the thermal flux 1 cm from
  the source?
• Properties of Water
• D0.16 cm
• L2.75 cm
• Macroscopic absorption cross section 0.022/cm

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Neutron movement solution
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Lethargy

• A neutron beam collides with several Li-7 nuclei.
  If the neutron beam has an average energy of 2.0
  eV after 5 collisions, what was the beams initial
  average energy?

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Lethargy
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Lethargy continues

• What was the average angle of scattering for the
  neutron beam?

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Criticality

• Definitions
• keff- effective multiplication factor finite
  sized reactor k1 for criticality
• h- avg of neutrons emitted per neutron absorbed
  in the mix
• n - avg of neutrons (prompt and delayed)
  released per fission
• e- fast fission factor
• p- resonance escape probability
• f- thermal utilization factor

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Criticality

• Determine the atom ratio of Pu-239 to water
  required for criticality.

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Lets make it a long problem

• What is the critical dimension of the Pu/water
  slab reactor assume k1.01

or
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• L2 for the moderator water is 8.1

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Subcritical Multiplication

• How much positive reactivity is required to bring
  a reactor from k.83 to k.95