Optimization of Circulation Power in First Wall of Breeding Blanket Using He-CO2 Gas Mixture as a Replacement of Helium

For heat extraction in the breeding blankets of fusion reactors, Helium gas is widely used as a coolant due to its high thermal conductivity and low dynamic viscosity. It is also chemically inert and has low neutron cross section. A major disadvantage of helium is its low density which leads to high circulation power. Ongoing works have shown that blending Helium with a moderately heavy gas like Xenon (Xe), Argon (Ar), Carbon dioxide (CO<inf>2</inf>), Nitrogen (N<inf>2</inf>) and Krypton (Kr) may compensate for the low density of helium gas. Also, it is found that mixture of He and CO<inf>2</inf> provides the optimum solution to lower the circulation power and maintain the required cooling. The paper presents a numerical assessment of the thermal-hydraulics performance of the First Wall (FW) Channel of the breeding blanket using Helium gas as a benchmark and then compares its performance for the He-CO<inf>2</inf> gas mixture at an optimum mole fraction with minimum circulation power required.