Results of MACE tests M0 and M1

This document discusses the Melt Attack and Coolability Experiment (MACE) Program underway at Argonne National Laboratory under ACE/EPRI sponsorship. The program addresses the efficacy of water to terminate an accident situation if melt progression were to result in a molten core/concrete interaction (MCCI) in the reactor containment. Large-scale experiments are being conducted in parallel with related modeling efforts, involving the addition of water to an MCI already underway. The experiments utilize UO{sub 2}/ZrO{sub 2}/Zr corium mixtures, direct electrical heating for simulation of decay heating, and various types of concrete basemats. Currently the tests involve 430 kg corium mass, 25 cm depth, in a 50 cm square test section. Test MO was a successful scoping test, but the first full size test, Ml, failed to achieve melt-water contact owing to existence of a preexisting bridge crust of corium charge. A heat flux of 3.5 MW/m{sup 2} was measured in MO which removed energy from the corium pool equivalent to its entire heat of solidification prior to abatement by formation of an interfacial crust. The crust subsequently limited heat extraction to 600 kW/m{sup 2} and less. Both tests MO and Ml revealed physical evidence of large pool swelling events which resulted inmore » extrusion (and ejection) of melt into water above the crust, significantly increasing the overall quench and reducing the remaining melt in contact with the concrete. Furthermore, test Ml provided evidence of occasional ``burst mode`` ablation events and one additional important benefit of overlying water -- aerosol capture.« less