Summary of thermal analyses to determine the refrigeration power for the JT-60SA helium refrigerator

•Procedures to estimate heat loads to JT-60SA cryogenic users are shown.•Monte Carlo method is applied to find reasonable heat load contingency.•By using exergy calculation, heat loads are converted to 5.64 kW at 4.5 K.•Adding pressure drops to heat loads amounts to 7.84 kW at the ACB.•The total exergy for cooling of the JT-60SA components is 9 kW at 4.5 K.