  Muons interact with matter via two major interaction mechanisms: ionization
and radioactive process, and multiple Coulomb scattering leading to energy loss
and trajectory deflection, respectively. For a monoenergetic muon beam crossing
an object, the scattering angle follows a Gaussian distribution with a zero
mean value and a variance that depends on the atomic number of the material
object it traversed. Thus, the measured scattering angle may be used to
reconstruct the geometrical and material information of the contents inside the
dry storage cask.
  In traditional X-ray computed tomography, the projection information used to
reconstruct the attenuation map of the imaged objects is the negative natural
logarithm of the transmission rate of the X-rays, which is equal to the linear
summation of the X-ray attenuation coefficients along the incident path.
Similarly, the variance of the muon scattering angle is also the linear
integral of the scattering density of the objects crossed by the muons. Thus, a
muon CT image can be built by equating scattering density with attenuation
coefficient. However, muon CT faces some unique challenges including: 1) long
measurement times due to low cosmic muon flux, 2) insufficiently accurate muon
path models, and 3) the inability to precisely measuring muon momentum.
  In this work, three different muon path models, two different projection
methods, and two different reconstruction methods were investigated for use in
muon CT of dry storage casks. The investigation was conducted in a validated
Geant4 workspace, both in an ideal case and with relevant engineering
restrictions considered. The results of these investigations and the expected
benefits for fuel cask monitoring are reported herein.
