PHENOMENOLOGICAL MODELING APPROACH TO ANISOTROPIC ABLATION IN MOLTEN CORE CONCRETE INTERACTIONS

摘要

As a result of recent molten core-concrete interaction (MCCI) experiments, CCI tests, the trend of concrete ablation consistently depends on the type of concrete. Specifically, tests with LCS concrete yields isotropic concrete ablation in comparison to anisotropic ablation with siliceous concrete. Isotropic ablation means vertical and horizontal ablations depths are similar in each experiment, while anisotropic ablation means ablation into a vertical wall is much greater than ablation to bottom wall. This is an interesting result, since MCCI simulant experiments indicate that there should be only isotropic ablation. Simulation results of CCI tests by the CORQUENCH code, a well-known MCCI computer model, shows good agreement with the cases with isotropic ablation but not with the cases with anisotropic ablation. Thus, the goal of this work is to better understand the reasons for anisotropic ablation in cases with siliceous concrete. One empirically observes a clear separation between melt and concrete, with no solid gravel in the solidified corium for MCCI tests with LCS concrete, while there is solid gravel observed in the solidified corium in cases with siliceous concrete. Given this consistent observation, two physical effects are expected: delayed gas release by the silica gravel and surface area enhancement at the concrete-corium interface. These effects can cause anisotropic ablation in cases with siliceous concrete. This phenomenological approach is modeled and implemented into the CORQUENCH code in this work. Comparison of simulation result of the modified and existing CORQUENCH model for CCI tests for cases with siliceous concrete shows that the modified code has better agreement to test data.