FORWARD-ADJOINT MONTE-CARLO COUPLING WITH NO STATISTICAL ERROR PROPAGATION

Methods for coupling multiple forward and adjoint radiation transport Monte Carlo calculations with no statistical error propagation are pre sented. Correlated forward and adjoint particle histories are uniforml y initialized on arbitrarily placed intermediate source boundaries thr oughout the calculational system. In applying the method to multilegge d duct streaming problems, these source boundaries are placed at the d uct leg intersections. The necessary forward and adjoint fluxes for th e coupling procedure are each computed from an opposite-mode calculati on. The no-error-propagation feature is the result of an exact correla tion of all phase-space variables for coupled forward-adjoint particle histories at each boundary. For ducts of more than two legs, next-eve nt estimation between forward and adjoint collision sires across arbit rarily placed intermediate scoring boundaries is necessary to achieve the variable cor relation. Comparison of calculational results between the coupled and standard methods for two- and three-legged ducts are presented.