Simulation of sodium boiling experiments with THERMIT sodium version

Abstract

Natural and forced convection experiments(SBTF and French) are simulated with the sodium version of the thermal-hydraulic computer code THERMIT. Simulation is done for the test secti- -on with the pressure-velocity boundary condition and subsequ- -ently extended to the whole loop. For the test section simu- -lation, a s.teady-state and transient calculations are perform- -ed and compared with experimental data. For the loop simula- -tion, two methods are used, a simulated 1-D loop and an actual 1-D loop. In the simulated 1-D loop analysis, the vapor densi- -ty is increased by one hundred and two hundred times to avoid the code failure and the results still showed some of the impor- -tant characteristics of the two-phase flow oscillation in a loop. A mathematical model is suggested for the two-phase flow oscillation. In the actual 1-D loop, only the single phase calculation was performed and turned out to be nearly the same as the simulated 1-D loop single phase results.

In the process of simulation, it is discovered that the energy conservation equations of THERMIT fails to conserve energy by a small amount due to interfacial mass transfer and frictional dissipation of mechanical into thermal energy. The problems and applicability of the THERMIT physical models are also discussed.