Symbol
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Meaning
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Comments
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Position vector (i.e. x,y,z)
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Energy
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Unit vector (solid angle) in direction of motion
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Time
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Neutron velocity vector
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Angular neutron flux Amount of neutron track length in a differential volume about , associated with particles of a differential energy in about , moving in a differential solid angle in about , at time .
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Note integrating over all angles yields scalar neutron flux
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Scalar neutron flux Amount of neutron track length in a differential volume about , associated with particles of a differential energy in about , at time .
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Average number of neutrons produced per fission (e.g., 2.43 for U-235).[1]
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Probability density function for neutrons of exit energy from all neutrons produced by fission
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Probability density function for neutrons of exit energy from all neutrons produced by delayed neutron precursors
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Macroscopic total cross section, which includes all possible interactions
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Macroscopic fission cross section, which includes all fission interactions in about
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Double differential scattering cross section Characterizes scattering of a neutron from an incident energy in and direction in to a final energy and direction .
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Number of delayed neutron precursors
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Decay constant for precursor i
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Total number of precursor i in at time
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Source term
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