Effect of Permanent Side Reflector on the Temperature Variation in the VHTR Core

The temperature and pressure conditions range from 490°C to 950°C, 7MPa. GAMMA+ was developed to predict the overall phenomena of the VHTR system. The GAMMA+ algorithms focused on the transient condition for the systems. Therefore, the computational control volumes are coarse for reducing the computational time. However, there are difficulties calculating the temperature gradient in the fuel blocks in detail. There is a demand to predict a hot spot and temperature distribution in the reactor core to apply a thermal stress and find the fuel temperature margin. Computational Fluid Dynamic (CFD) tools can be an option to model the VHTR. However, the fluid has to be solved in three dimensions. The long computational time and heavy burden of the memory size have called for an alternative option. The PSR blocks are considered in the prismatic VHTR calculation with the CORONA code. The temperatures of a single assembly with an arc shape reflector by the CORONA code were verified with the results by the CFX calculation. The temperature distributions of the PSR regions did not show significant differences depending on the fixed inlet temperature boundary condition and bypass flow condition