The multiphase, transient, and three-dimensional interaction of molten corium with water during the premixing phase of a steam explosion is simulated in the QUEOS facility using a large number of small solid spheres at temperatures up to 2300 K. The objective of the experiments is to establish a database for testing the models of heat and momentum transfer in multifluid codes as well as the codes' capability to correctly describe multiphase flows. Three experiments with up to 10 kg of spheres made of molybdenum are discussed. Results from calculations with the IVA-KA code are compared with experimental data. The agreement obtained is encouraging, and the calculations show that the intense multiphase interactions obtained in QUEOS constitute very critical and thus valuable test cases.