Variational method in two-group transport theory

The two-group integral transport equation in subcritical homogeneous isotropically scattering medium in arbitrary geometry is considered. A functional is constructed which is stationary for the solution to the integral equation. If the determinant of the transfer matrix is positive, then the solution gives the minimum of the functional. The applications to the cylindrical Milne problem is shown and examples of the numerical results of the extrapolation distances are presented