An Inline Burnup Algorithm

Inline algorithms have been proposed for coupling Monte Carlo neutron transport solvers with several other physics, such as xenon and iodine densities and thermal hydraulics. This paper proposes a new inline algorithm that can be applied to burnup calculations. The algorithm is a modification of the predictor-corrector method, where the corrector-step nuclide densities are converged simultaneously with the fission source. This could, in principle, obviate the need for two full neutronics solutions per time-step while still allowing the accuracy of predictor-corrector methods with improved stability. This paper describes the algorithm and demonstrates its stability properties through a Fourier analysis. Although not unconditionally stable, judicious use of batching and relaxation are shown to greatly improve the algorithm’s stability properties in realistic systems.