Debris Bed Heat Removal Models: Boiling and Dryout with Top and Bottom Cooling

摘要

A one-dimensional deep bed model for incipient dryout is developed which predicts deep bed behavior but not shallow bed behavior. A fluidization criterion results which indicates that a debris bed cannot be fluidized by the vapor flow. However, the maintenance of channels within the bed is predicted. A top-subcooled bed model is presented and evidence (both experimental and calculational) is given that the top-subcooled zone removes heat in series (not in parallel) with the boiling zone for sodium-cooled systems. The Sandia D-2 and D-3 top-subcooled dryout data is expressed in terms of non-subcooled dryout and compared with experimental data and model predictions from the literature. The data agrees with several predictions depending on whether the dryout in the boiling zone is dependent on the overlying subcooled zone thickness. A bottom-subcooled bed model is also presented. A post-dryout model is developed to explain the stable dry zone observed in the D-3 experiment and agreement with the data is found. Finally, the top-subcooled and post-dryout models developed are used to make predictions for the upcoming D-4 experiment. (ERA citation 04:055007)