Cooling system is one of the most important part of the power plants and cooling systems based on S-CO2 (Supercritical Carbon Dioxide) coolant seems nowadays perspective alternative to Helium and Rankine steam power cycles. Due to many advantages of S-CO2, these cooling systems are researched on many institutions and the results confirm that it should be successful for the future cooling systems design. One of the main objectives is comparison of the possible cooling mediums of DEMO2 (Demonstration power plant 2) with focusing on different power cycles with S-CO2. The First part of this article targets on comparison of three main coolants: steam, helium and S-CO2. The second part of this article focuses on the new software called CCOCS (Cooling Cycles Optimization Computational Software) which was developed on CTU in Prague. This software works on deeper optimization of the power cycles with various coolants and initial conditions. The third part describes advanced S-CO2 power cycles and enlarges past research, which was based on optimization of S-CO2 Brayton Simple power cycle and S-CO2 Re-compression power cycle both with recuperation and their usage in fusion and Fission energy engineering. It is possible to heighten thermodynamic efficiency of power cycle by changing the layout of the power cycle and the main objective of this paper is to compare four advanced layouts, describe the results of the optimization of these cycles and outline advantages and disadvantages of chosen optimized layouts.