Mathematical modeling of compression wave formation in the interaction of melted fuel and coolant

Abstract

Modern requirements on nuclear power station safety made it necessary to consider the complex of thermal and radiation processes concomitant to a severe accident exceeding design limits at a nuclear power installation. An important problem is the formation of areas of high pressure in the fuel channels of the reactor caused by complete or partial loss of coolant, which may result in the destruction of reactor elements followed by the release of the accumulated activity into the environment. The final emergency state of the reactor, involving melting and dispersing of fuel, is considered in this article. We mathematically model the formation and propagation of a compression wave brought about by a sharp increase in the free surface of the dispersed fuel and the intensification of heat exchange in the damaged area resulting from it. A model of the high-temperature fuel dispersion process is proposed. The results of calculations by this model have demonstrated a significant dependence of the sizes of fuel fragments on the initial conditions, as well as on the nature of the mixing process. In this paper, the characteristics of the dispersed fuel are used as input parameters whose values are varied within a range recommended by themore » authors.« less