Homogenization methodology for thermal analysis of HTGR block-type core

Abstract

HTGR has been one of the fore-runners of the next generation nuclear power plants. Rigorous researches have been conducted and even actual operation had been in service during 70s to 90s. However, since one block-type HTGR fuel compact can contain more than six thousands of microscopic fuel particles, its heterogeneity has brought difficulty in thermal analysis of the fuel elements. In this area, homogenization methodology is eminent. For the thermal analysis of the compact in the core of 600 MWth GT-MHR, we used GAMBIT as the grid generator and FLUENT as the solver. For the compact thermal analysis we proposed a combination of volumetric-average and harmonic-average to get the mixed-average value introducing a harmonic weighting fraction, ω. The physical basis of the averaging concept is also given. We tested the sensitivity of ω value to the changes of 50% from the reference volumetric power generation rate. It turned out that the deviations of the centerline temperature of the fuel compact from the reference one are less than 3%. For the thermal analysis of the single coolant channel and the fuel element in the core of 600 MWth GT-MHR, we developed the CFD analysis methodology. Finally, we extended the proposed CFD analysis methodology into a single-column thermal analysis using radially-averaged power peaking factors (PPFs) to demonstrate the core thermal performance.