A series of integral MCCI tests have been performed at Argonne National Laboratory in the internationally sponsored Advanced Containment Experiment Program (ACE). In the ACE tests, direct electric heating was used in the test to initiate core melt and maintain internal heat generation during the sustained interactions of melt with the concrete crucible. Both fully and partially oxidized core melt material and several types of concrete were studied. The ACE results were used in the present work to assess the impact of different model assumptions on the predictions of MCCI thermal hydraulic responses. The code used in the present analyses was a modified version of CORCON/Mod2.