Adjoint weighting for continuous-energy Monte Carlo radiation transport.

摘要

Methods are developed for importance or adjoint weighting of individual tally scores within a continuous-energy k-eigenvalue Monte Carlo calculation. These adjoint-weighted tallies allow for the calculation of certain quantities important to understanding the physics of a nuclear reactor.;The methods, unlike traditional approaches to computing adjoint-weighted quantities, do not attempt to invert the random walk. Rather, they are based upon the iterated fission probability interpretation of the adjoint flux, which is the steady state population in a critical nuclear reactor caused by a neutron introduced at that point in phase space. This can be calculated in a strictly forward calculation, and this factor can be applied to previously computed tally scores.;These methods are implemented in a production Monte Carlo code and are used to calculate parameters requiring adjoint weighting, the point reactor kinetics parameters and reactivity changes based upon first-order perturbation theory. The results of these calculations are compared against experimental measurements, equivalent discrete ordinates calculations, or other Monte Carlo based techniques.