Abstract: In a nuclear-reactor power-generating installation having a main and an auxiliary steam-generating boiler, both arranged to receive heat from the reactor core (for example by circulation of reactor coolant gas), and having a turbogenerator which includes a multistage steam turbine through whose stages the steam from the main boiler passes in sequence, there being a steam reheater unit connected between two of the stages to provide reheating of the steam from the main boiler, the invention provides that the auxiliary boiler is connected to supply to the reheater unit steam which reheats the said steam from the main boiler.