TO THE QUESTION ABOUT THE INFLUENCE OF DISPERSED IRON OXIDES ON THERMODYNAMIC STATE OF HLMC UNDER NON-ISOTHERMAL CONDITIONS

Abstract

In the initial period of HLMT development, it was shown that ensuring the corrosion resistance of structural steels is associated with ensuring a certain oxygen regime of the coolant. To control it, oxygen TDA sensors were created later. It was assumed that the oxygen activity in HLMC in different temperature zones of the circulation loop obeys the so-called "isoconcentration" distribution, which, when formally recalculated the measured oxygen TDA values, gives a constant concentration value at different temperatures. However, later it turned out that such a distribution of TDA is not always realized. The observed character of deviations could be explained by the influence of iron impurity. At the same time, quantitative estimates of this effect were carried out under the assumption of the formation of stoichiometric magnetite under conditions of its thermodynamic stability in the entire range of temperatures and concentrations of the initial components. The limitation of this approach lies, first of all, in the fact that it does not take into account the processes of dissociation of solid-phase iron oxides, which can occur in the hot zone when appropriate conditions are created, which can be realized with a decrease in the content of dispersed iron oxides. The importance of taking this factor into account is due to the fact that, during corrosion testing of steels in HLMC, the processes of dissociation of magnetite are actually observed in practice. Within the framework of this work, a computational method for assessing the effect of filtration processes on the thermodynamic state of HLMC has been developed. Quantitative estimates of the effect of the content of dispersed oxides in HLMC on the thermodynamic state of the coolant under non-isothermal conditions in iso-concentration and non-iso-concentration modes have been obtained and which can be used in calculation codes and comparison of experimental results with calculations.