Investigations on fuel-coolant interaction with the RCN code VS-4

A set of partial differential equations describing the conservation of mass, energy and momentum in a coolant channel as a function of axial coordinate and time are solved with the RCN Code VS-4, using the method of characteristics. The viscosity and turbulence of coolant are taken into account in the usual manner of technical thermodynamics by the introduction of a friction coefficient in the momentum equation. The heat transported by the axial mass flow in the subassembly is assumed to be so large that the heat transport by axial conduction may be neglected. The heat transport by conduction in the radial direction is assumed to be perfect. The calculation results are discussed and concluded as follows. (1) The method of characteristics was proved to be applicable not only to the one phase but also to the description of the honogeneous equilibrium two phase part of a thermohydraulic process. (2) To investigate the reactor safety aspects of FCI (fuel-coolant interaction) process and to evaluate the experimental research on FCI, it is indispensable to take the axial dependence effects into account. To this end, the axially dependent code VS-4 based on the method of characteristics is available. (3) At present, the thermodynamic properties of sodium according to Golden and Tokar are used in the program. To improve the accuracy of the code for high temperature and pressure, a consistent set of thermodynamic properties of sodium must be incorporated in the program. (Iwakiri, K.)