Computational Study of Thermal Striping in an Upper Plenum of Kalimer

A computational study of thermal striping in an upper plenum of the Korea Advanced Liquid-Metal Reactor (KALIMER) was performed. The primary objective of the present study was to find the distribution of the amplitude of temperature fluctuation in the hot pool of KALIMER. The computations were performed using the CFX-4 code with the differential stress and flux turbulence model and the Van Leer convection scheme. Two cases with different outlet velocity of the control rod fuel assemblies are considered. The distributions of the velocity vector, temperature, and temperature fluctuation were obtained from the calculation. In order to quantitatively understand the amplitude of temperature fluctuation at the bottom wall of the upper internal structure (UIS), the amplitude of the fluctuation of temperature in the radial and angular directions was investigated. The amplitude of temperature fluctuation at the UIS bottom plate was largely dependent on the magnitude of the outlet velocity of the control rod fuel assemblies. From the calculated results, it was found that the largest temperature fluctuation occurred at the radial edge of the UIS bottom in the KALIMER design. Since thermal striping is dependent on the amplitude of temperature fluctuations and frequency, the region of the UIS bottom edge needs to be analyzed with a detailed unsteady calculation.