Model study of processes accompanying overheating of fuel elements

In order to simulate mathematically the nonstationary process of heating and melting of fuel elements in BN reactors from the moment that the jacket is dried, we developed the program DYMELT, which also enables calculations of melting of a simulator with direct heating. To model the melting of the experimental sample with a central heating rod, we developed the program MW. In both programs the one-dimensional coupled problem of heat conduction for two and three regions, respectively, in the presence of phase transitions is solved. The initial state is chosen as the state at the moment the jacket of the fuel element is dried out or gas ceases to flow into the simulator. The starting temperature distribution is calculated based on stationary dependences, while the subsequent nonstationary temperature field and the motion of the phase boundaries accompanying melting of a cylindrical element are calculated up to the moment at which the core melts or the transient process terminates owing to the onset of thermal equilibrium or melting of the tungsten heater heating the simulator