The results of studies on the extension of methodological capabilities of determining physico-chemical conditions of lead-based liquid-metal coolants

Abstract

The authors consider examples of using the thermal cycling method for heavy lead- and lead-bismuth-based coolants with simultaneous measurement of the thermodynamic activity (TDA) parameter of oxygen impurities. In these experiments, structural EI852 and EP823 ferritic-martensitic steels as well as EP302 austenitic steel were used as sources of iron impurities. As a result of the experiments, it was found that iron oxides previously formed in the coolant, as such or in the form of an oxide film on the structural steels, are not inert phases in heavy coolants, but can exchange iron and oxygen with the melt. The nature of this exchange depends both on the actual coolant impurity state and on external conditions, including, first of all, temperature. The experimental data obtained by thermal cycling of lead- and lead-bismuth coolants were analyzed both in the region of relatively high oxygen TDA values close to the oxygen saturation concentration and in the region of sufficiently low values of this parameter close to the saturation concentration of iron impurities. It is concluded that the proposed coolant thermal cycling method is informationally significant and can be recommended for further use, for example, to obtain quantitative data on the content of iron impurities in the coolant.