Abstract
The P sub(N)-spatial expansion method has been used for calculating the one-speed transport utilization factor in heterogeneous slab cells in which neutrons may scatter anisotropically. By considering the P sub(1)-approximation with a two-term scattering kernel in both the fuel and moderator regions. An analytical expression for the disadvantage factor has been derived. The numerical results obtained have been shown to be much better than those calculated by the usual P sub(1)- and P sub(3)-approximations and comparable with those obtained by some exact methods.