Abstract: The present invention is directed to a method for operating a hermetic, small-size power plant in which a primary circulation is conducted in a main line connecting a high-speed machine including at least a turbine and a generator installed on a joint rotor, a vaporizer and a condenser. Fluid lubrication of bearings of the rotor during the continuing operation is effected by fluid medium passing through the condenser and along the main line of the primary circulation. The vaporizer is connected to the high-speed machine through medium flow paths defining a circulating medium circuit bypassing the condenser and at least partly bypassing the main line of the primary circulation to secure passage of circulating medium accumulated in the vaporizer for lubrication of the bearings of the rotor during stopping of the primary circulation.