A Numerical Simulation of Thermal Striping in an Upper Plenum of a Liquid Metal Reactor

A computational study of thermal striping in an upper plenum of KALIMER (Korea Advanced Liquid Metal Reactor) is performed. The primary objective of the present study is to obtain the distributions of the amplitude and frequency of a temperature fluctuation in the upper plenum of KALIMER. Two different treatments of the turbulent flow are considered, one is the RANS (Reynolds Averaged Navier-Stokes equation) approach and the other is the LES (Large Eddy Simulation) approach. In the RANS approach, the computation is performed using the CFX-4.2 code with the differential stress and flux turbulence model. In this computation the overall distributions of the velocity vector, temperature and temperature variance are obtained. In the LES the amplitude and frequency of the temperature fluctuation are obtained using the CFX-5.6 code. From the results of the RANS approach, the locations where thermal striping is mattered are obtained. It is found that in the KALIMER design this region is the edge of the UIS (Upper Internal Structure) bottom and the radial and circumferential distributions of the temperature fluctuation in this region are investigated. From the LES results the amplitude and frequency of the temperature fluctuation are obtained for various locations in the upper plenum of KALIMER. These results will be used for the calculation of the thermal stress caused by thermal striping.