A method of modifying a steam turbine to change from a first maximum thermal power of the steam generator to a second maximum thermal power of the steam generator. The method can include replacing, in the high-pressure module, at least one set of fixed blades sized for the first maximum thermal power by at least one set of fixed blades sized for the second maximum thermal power. The at least one set of moving blades are sized to operate at the first and second maximum thermal powers. The rotor and the at least one set of moving blades of the high-pressure module remain unchanged on changing from the first maximum thermal power to the second maximum thermal power.