Discrete Ordinate Neutron Transport Equation Equivalent to P_L Approximation

A discrete ordinate transport equation in two dimensions equivalent to the P_L approximation is derived to eliminate the ray effect in the ordinary discrete ordinate equations. The number of the discrete ordinates, or the number of unknown functions of this discrete ordinate equation, is equal to that of the P_L equations. Since it is also possible to obtain boundary conditions equivalent to those of the P_L approximation at the interface of mediums or at the free surface, we can obtain a solution identical to that of the P_L equation.