Initial optimization of DEMO fusion reactor thermal shields by thermal analysis of its integrated systems

Thermal analysis of integrated DEMO cold systems is performed with two main objectives: first to evaluate the static heat loads on the superconducting magnets and thermal shields and second to estimate the optimal working temperature of the thermal shields in order to minimize the total refrigeration power. Thermal radiation and heat conduction loads due to physical connections between the components are considered. Parametric studies are performed to optimize the thermal shields operating temperature based on the theoretical efficiency of the cryogenic cooling system. The effects of vacuum vessel operating temperature and inclusion of passive Multi-Layer Insulation (MLI) on the warm side of the actively cooled thermal shields are analysed. The results suggest that the decrease of vacuum vessel temperature and inclusion of MLI between the vacuum vessel and the thermal shield greatly reduce the theoretical refrigeration power and raise the optimal working temperature of the thermal shields to the values around 100 K.