Heat transport and chimney design in a typical MTR reactor during natural convection cooling regime

Abstract

In the present work, three dimensional CFD analysis is presented for a typical MTR reactor coolant loop during natural convection cooling regime. Design optimization studies are carried out. A model consisting of the core, the chimney, and the cold legs is simulated. The research reactor core is simulated as a porous zone with a cosine shape heat distribution. The chimney dimensions are varied to optimize its design for best thermal-hydraulic performance under natural convection conditions. The study is carried out for chimney extension ratio in the range of 1.5 ≤ Lch/Lcore ≤ 7.2 and chimney opening (expansion) ratio in the range of 1 ≤ B/b ≤ 2.5. Contours plot of temperature at different values of chimney extension and opening ratios were illustrated. The Nusslet number, coolant mass flow rate, maximum reactor core temperature, coolant velocity and core pressure drop are correlated as a function of the extension and opening ratios. Comparison with the results of CONVEC and RELAP5 codes shows a good agreement. The recommended optimum design conditions are for Lch/Lcore greater than 3.5, and B/b = 1 for best thermal-hydraulic performance.