Adjoint and Generalized Adjoint Flux Calculations Using the Collision Probability Technique

Computation of adjoint and generalized adjoint fluxes may present some difficulties, especially when relying on the collision probability technique in transport theory. This paper proposes a simple method to compute those adjoint flux and generalized adjoint fluxes associated with homogenized and condensed cross sections. By defining a pseudo adjoint flux, one can apply an algorithm, similar to that required for the evaluation of the direct neutron flux, to adjoint flux calculations. Because of the presence of the scattering source, a multigroup iterative procedure is used in DRAGON for the direct flux solution. We show that this procedure can be easily modified in such a way that the performance of the solution algorithm is preserved for the adjoint problem. Finally, a generic adjoint algorithm is presented to deal with generalized adjoint fluxes' computation.