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The Manhattan Project

Page 14

by Bruce Cameron Reed


  R Decay rate [2.6]; general radius of bomb core during explosion [3.3]

  Rbare Threshold critical radius of untamped bomb core

  Rcore Initial radius of bomb core

  RMBq Decay rate in millions of Becquerels in analysis of radioactivity exposure [6.4]

  Rshut Radius of core at second criticality

  Rtamp Outer radius of tamper

  Rα Rate of alpha-decays

  Rn Rate of emission of neutrons from (α, n) reactions [2.6]

  S Number of stages in gaseous diffusion analysis [4.2]

  T Temperature

  U Energy density

  Vacc Accelerating potential in analysis of electromagnetic enrichment [4.1]

  Vf Final gas volume in adiabatic expansion of gun-bomb triggering [5.2]

  V0 Initial gas volume in adiabatic expansion of gun-bomb triggering [5.2]

  Y Weapon yield or fractional yield

  Z Atomic number

  a Angle in analysis of neutron scattering [6.3]

  aC Coulomb energy parameter [2.1]

  aS Surface area energy parameter [2.1]

  b Brightness in analysis of bomb fireball with subscripts F for fireball and S for Sun [6.1]; angle in analysis of neutron scattering [6.3];

  d Distance; characteristic core dimension [3.1]

  k Boltzmann’s constant

  kt Kiloton (4.2 × 1012 J)

  mheavy Mass of heavy-isotope species in gaseous diffusion analysis [4.2]

  mlight Mass of light-isotope species in gaseous diffusion analysis [4.2]

  n Nuclear number density of core material [3.1]

  nfissile Nuclear number density of fissile material in analysis of (α, n) reactions [2.6]

  nheavy Number density of heavy isotope in gaseous diffusion analysis [4.2]

  nimpurity Nuclear number density of impurity material in analysis of (α, n) reactions [2.6]

  nlight Number density of light isotope in gaseous diffusion analysis [4.2]

  t Time

  tcore Time to complete core assembly following first criticality

  thr Exposure time in hours in analysis of radioactivity exposure [6.4]

  tsec Exposure time in seconds in analysis of radioactivity exposure [6.4]

  t1/2 Half-life

  y Reaction yield; usually in sense of (α, n) reaction [2.6]

  vneut Average neutron speed

  α Parameter in analysis of fission energy [2.1]; parameter in analysis of efficiency [3.4] and pre-detonation probability [5.1]

  β Parameter in analysis of fission energy [2.1]

  ε Parameter in analysis of tamped criticality [3.3]

  γ Adiabatic index in gun-bomb triggering [5.2]

  η Parameter in criticality analysis [3.1]

  Δ Mass excess [2.1]

  λ in analysis of tamped criticality [3.3]

  λfiss Mean free path for neutron fission

  λtrans Also . Transport mean free path for neutrons in fissile material

  Transport mean free path for neutrons in tamper material

  σelas Elastic scattering cross-section

  σfiss Fission cross-section

  σtrans Neutron transport cross-section

  v Number of secondary neutrons per fission

  ρ Mass density

  ρ0 Initial mass density of bomb core; usually the ‘normal’ density of the fissile material

  τ Travel time for neutron to cause fission; atmospheric transmittance in analysis of radiant energy in a nuclear explosion [6.1]

  ω Number of collisions sustained by neutron to be slowed to a specific energy [6.3]

 

 

 


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