Thermal-flow analysis of the pebble fuel lattice in the RGTT200K core using fluent

In accordance to the Presidential Regulation No. 5/2010, PTRKN-BATAN develops two variants of conceptual design of the cogeneration advanced power reactor, i.e. RGTT200K and RGTT200KT. Thermal energy of both reactor systems are supplied by the pebble fueled reactor core with 200 MWt thermal powers. The geometry and structure of the core is designed to produce the output of helium gas coolant temperature as high as 950°C to be used for hydrogen production and/or other process industry in co-generative way. Output of very high temperature helium gas will cause thermal stress on the pebble fuel that threats the integrity of fission products confinement on it. Therefore it is necessary to perform thermal-flow analysis to determine the temperature distribution and the helium coolant flow in the pebble fueled lattice. One of the best practices to performing thermal~flow analysis is carried out by three dimensional modeling with proven computational fluid dynamics (CFD) software. The FLUENT 6.3 CFD software was used in this study. Pebble lattice thermal-flow analysis was performed by modeling the fluid dynamics of the coolant with a combination of the three modes of heat transfer, conduction, convection and radiation, as well as considering the turbulence of the helium gas coolant stream. Discrete ordinate and Reynolds-Averaged Navier-Stokes (RANS) models are used in the calculation of the radiation heat transfer and turbulence respectively. From temperature distribution in the pebble fuel that resulting form CFD modeling with turbulent flow in the coolant it was known that the maximum pebble fuel temperature reaches 1036,1°C. This temperature is far from the temperature which can lead to failure of the fission product confinement, i.e. 1600°C. (author)