Physico-chemical analyses and solidification path reconstruction of multi-component oxidic spread melts

In the case of a hypothetical severe core melt accident lin a nuclear power plant, scenarios in which a mixture of core materials could melt and mix w ith the vessel metallic structures and part of the basemat concrete, cannot be fully excluded. In order to study the behavior of this mixture called c erium, experiments have been performed in which highly refractory materials have been melted and spread onto a ceramic substrate. This paper describes the physico-chemical analyses made on the cerium experimentally obtained f rom these experiments after cooling. The results show that even if the chem ical composition of the cerium is homogeneous, variations of crystalline ph ases are detected along the sample height. These variations are linked to t he solidification conditions. The solidification paths followed by the diff erent cerium layers are then calculated using a thermodynamic database and software dedicated to cerium studies. Finally, a methodology for the estima tion of cerium physical properties is presented and applied to the differen t layers of these spreads. (C) 2001 Elsevier Science B.V. All rights reserv ed.