Nuclear Science and Engineering / Volume 150 / Number 3 / July 2005 / Pages 257-266
Technical Paper / dx.doi.org/10.13182/NSE05-1
A set of interface conditions is derived rigorously for the general spherical harmonics solution of the Boltzmann transport equation in three-dimensional Cartesian geometry. The derivation builds upon earlier work of Davidson and Rumyantsev to arrive at sets of interface conditions applicable to both even- and odd-order N spherical harmonics approximations. The exact set of conditions is compared to the approximate set currently employed in the odd-order N variational nodal code VARIANT, and the differences in accuracy and computational effort are summarized. The exact interface conditions are necessary for first-order implementations of spherical harmonics methods.