Nuclear power generation system

A nuclear power generation system including:

• a steam generator including a vertically elongated steam generating vessel fluidly coupled to a reactor vessel having an internal cavity;
• a reactor core comprising nuclear fuel disposed within the internal cavity and operable to heat a primary coolant;
• a primary coolant flow loop formed between the reactor vessel and the steam generating vessel, the primary coolant flow loop being configured and operable to circulate primary coolant through the reactor vessel and steam generating vessel via thermally induced gravity flow;
• a secondary coolant flow loop formed between the steam generating vessel and a single steam turbine, the secondary coolant flow loop being configured and operable to circulate secondary coolant through the steam generating vessel in which the primary coolant heats and converts the secondary coolant from liquid to steam, the steam flowing through the secondary coolant flow loop to an inlet on the single steam turbine;
• a condenser disposed in the secondary coolant flow loop between an outlet from the single turbine and the steam generating vessel, the condenser configured to cool and condense steam exiting the single turbine thereby converting the secondary coolant from steam to liquid;
• and
• a single feedwater heater disposed in the secondary coolant flow loop between the condenser and the steam generating vessel, the feedwater heater configured to receive and heat the liquid secondary coolant from the condenser,
• wherein the secondary coolant flows directly from the feedwater heater into the steam generating vessel without any intervening feedwater heaters between the condenser and the steam generating vessel;
• wherein a temperature differential between the primary coolant leaving the steam generating vessel and secondary coolant entering the steam generating vessel is sufficient to induce natural thermally driven gravity circulation of the primary coolant through the primary coolant flow loop;
• and
• wherein the single steam turbine is a low pressure turbine characterized by steam entering the turbine at a pressure less than 400 psia.

A method for inducing thermally driven gravity flow of primary coolant through a nuclear reactor, the method comprising:

• providing a vertically elongated steam generating vessel fluidly coupled to a reactor vessel housing a nuclear fuel core which heats a primary coolant;
• circulating the primary coolant through a primary coolant flow loop formed between the steam generating vessel and reactor vessel, the primary coolant entering the steam generating vessel from the reactor vessel at a first temperature and exiting the steam generating vessel at a second temperature lower than the first temperature;
• heating a secondary coolant in the steam generating vessel using the primary coolant which converts the secondary coolant from a liquid entering the steam generating vessel to steam exiting the steam generating vessel, the secondary coolant entering the steam generating vessel at a third temperature and exiting the steam generating vessel at a fourth temperature higher than the third temperature;
• circulating the secondary coolant through a secondary coolant flow loop having an external portion outside to the steam generating vessel;
• expanding the steam in a single steam turbine for producing electric power;
• condensing the steam in a surface condenser to convert the secondary coolant from steam back into liquid form;
• heating the liquid secondary coolant received from condenser in a single feedwater heater to the third temperature using fluid extracted from the turbine;
• and
• flowing the heated liquid secondary coolant from the feedwater heater directly to the steam generating vessel without any intervening feedwater heaters between the condenser and the steam generating vessel;
• wherein the temperature differential between the second temperature of the primary coolant and the third temperature of the secondary coolant is at least 175 degrees F. selected to induce natural thermally driven gravity circulation of the primary coolant through the primary coolant flow loop;
• and
• wherein the single steam turbine is a low pressure turbine characterized by steam entering the turbine at a pressure less than 400 psia.