ON THE EQUIVALENCE OF BOUNDARY AND BOUNDARY-CONDITION PERTURBATIONS IN TRANSPORT-THEORY AND ITS DIFFUSION-APPROXIMATION

It is shown that a perturbation in the external boundary of a system c an be converted into (treated as) a perturbation in the boundary condi tion of the neutron balance equation. As a result, one may then use ex isting boundary condition perturbation or variational methods to estim ate the change in the parameters of interest. The equivalent perturbat ion in the boundary condition is derived both in transport theory and its diffusion approximation for eigenvalue as well as fixed-source pro blems. Generalized boundary conditions in both diffusion and transport theory are considered. The existence of a solution to the problem wit h the equivalent boundary conditions that are nonstandard is investiga ted through analytic examples. The analysis is limited to first-order perturbation theory.