An ADS system, like MYRRHA, requires exceptional reliability and stability performances for the high intensity beam delivered to the subcritical reactor. The last updated Linac design proposes SC cavities for near all the accelerating structures. The number of cavities, their operating frequency and the continuous beam time structure, lead to a very high dynamic thermal load imposing a refrigerator with size comparable to one LHC unit (equivalent power > 15 KW at 4.5K). In this paper, we present a complete evaluation of the Linac thermal losses, the choice of the operating temperature, first refrigerator schemes and preliminary proposals for the cryogenic fluids distribution. The reliability aspects are also discussed stressing the lessons that could be drawn from recent operation results of some high power Helium refrigerators.