A methodology to reduce the computational cost of transient multiphysics simulations for waste vitrification

Legacy radioactive waste stored in tanks at the Hanford Site is scheduled to undergo vitrification in Joule-heated melters. A carefully calibrated computational fluid dynamics model has been developed to characterize fluid flow, chemistry and heat transfer in the melters. Bubbling is replaced by momentum source terms to approximate forced convection circulation patterns and reduce Courant number restrictions on the resolved liquid–air interface. Void zones in the electrical field compensate for the removal of bubbles. The efficiency of the radiation solver is improved by reducing the update frequency of the discrete ordinates and using lower quadrature. A simple polynomial fit captures the waste-to-glass reactions in the cold cap. These simplifications reduce the turnaround time such that it is possible to simulate hundreds of seconds of physical time per day with the calibrated model versus only several seconds of physical time with the original, higher-fidelity model.