A molten salt once-through steam generator system functional on hot molten salt supplied via a supply line, the advanced molten salt once-through steam generator system comprising: a steam generator arrangement having a shell to accommodate non-segmented sections of at least one economizer, an evaporator, and a superheater fluidically configured to each other, the steam generator arrangement utilizes the heat of the molten salt flowing from the superheater to economizer to generate steam; a feedwater supply line configured to supply the feedwater from a feedwater source to the steam generator arrangement, flowing from the economizer to the superheater to utilized the heat of the molten salt to be converted in to the steam; a separator fluidically configured between the steam generator arrangement and the feedwater supply line; characterised in that the molten salt once-through steam generator system further comprises at least one high pressure heater (150, 152) configured in the feedwater supply line between the feedwater source and the steam generator arrangement; a bypass line to bypass at least one high pressure heater (150, 152) to control the feed water inlet temperature flowing to the steam generator system so as to control the molten salt outlet temperature of steam generator at same time; at least one controlled turbine extraction line (180, 182) to control the heat load of at least one high pressure heater (150, 152), respectively, to control the feed water inlet temperature flowing to the steam generator system, so as to control the molten salt outlet temperature of steam generator at same time; and an additional economizer to cool the molten salt, in fluid communication with the economizer and the feedwater supply line. a steam generator arrangement having a shell to accommodate non-segmented sections of at least one economizer, an evaporator, and a superheater fluidically configured to each other, the steam generator arrangement utilizes the heat of the molten salt flowing from the superheater to economizer to generate steam; a feedwater supply line configured to supply the feedwater from a feedwater source to the steam generator arrangement, flowing from the economizer to the superheater to utilized the heat of the molten salt to be converted in to the steam; a separator fluidically configured between the steam generator arrangement and the feedwater supply line; characterised in that the molten salt once-through steam generator system further comprises at least one high pressure heater (150, 152) configured in the feedwater supply line between the feedwater source and the steam generator arrangement; a bypass line to bypass at least one high pressure heater (150, 152) to control the feed water inlet temperature flowing to the steam generator system so as to control the molten salt outlet temperature of steam generator at same time; at least one controlled turbine extraction line (180, 182) to control the heat load of at least one high pressure heater (150, 152), respectively, to control the feed water inlet temperature flowing to the steam generator system, so as to control the molten salt outlet temperature of steam generator at same time; and an additional economizer to cool the molten salt, in fluid communication with the economizer and the feedwater supply line.