Patent Number: 
Section: claims

1. A light water reactor, comprising:a reactor pressure vessel that defines a volume;a core positioned in a bottom portion of the reactor pressure vessel and configured to support a plurality of nuclear fuel assemblies;a riser within the volume of the reactor pressure vessel, the riser extending from a position above the core and toward a top portion of the reactor pressure vessel; anda condensing steam generator positioned adjacent the riser and within the reactor pressure vessel volume, where a primary coolant comprises a liquid pooled at the bottom portion of the reactor pressure vessel, the pool having an upper surface positioned between the bottom portion of the reactor pressure vessel and a bottom of the condensing steam generator such that the condensing steam generator is not in contact with the liquid pooled at the bottom portion of the reactor pressure vessel during normal operation of the light water reactor and an upper portion of the volume located above the condensing steam generator includes a saturated steam dome absent a pressurizer,wherein the light water reactor is a self-pressurizing pressurized water reactor (PWR). 2. The light water reactor of claim 1, further comprising a primary coolant circuit entirely within the reactor pressure vessel volume, the primary cooling circuit extending along a path through the core, through an interior of the riser, along an exterior of the riser, and back through the core. 3. The light water reactor of claim 2, wherein a volume of the primary coolant and the primary coolant circuit are configured to guide a flow of the primary coolant through the primary coolant circuit at a saturation pressure of the primary coolant. 4. The light water reactor of claim 1, wherein the primary coolant is boron-free. 5. The light water reactor of claim 1, wherein the upper surface of the pool is positioned below the condensing steam generator and above the core. 6. The light water reactor of claim 5, further comprising:a containment vessel enclosing the reactor pressure vessel;a feed water input circuit extending through the containment vessel and the reactor pressure vessel to the condensing steam generator; anda steam output circuit extending through the containment vessel and the reactor pressure vessel to the condensing steam generator. 7. The light water reactor of claim 5, wherein the reactor pressure vessel is configured to contain pressures within a range between 1150 psia to 1750 psia. 8. The light water reactor of claim 3, further comprising a secondary coolant circuit thermally coupled to the primary coolant circuit through the condensing steam generator, the secondary coolant circuit controllable to maintain the flow of the primary coolant through the primary coolant circuit at the saturation pressure of the primary coolant. 9. The light water reactor of claim 1, wherein the reactor pressure vessel is pressurizer-less. 10. A light water reactor, comprising:a reactor pressure vessel that defines a volume, the reactor pressure vessel having a bottom portion and a top portion, the top portion forming an interior dome;a core positioned in the reactor pressure vessel and configured to support a plurality of nuclear fuel assemblies;a condensing steam generator positioned within the reactor pressure vessel volume between the core and the top portion of the reactor pressure vessel, the condensing steam generator defining an interior pathway through the condensing steam generator and an exterior annulus between the steam generator and a sidewall forming the reactor pressure vessel, where a liquid coolant surface level of a primary coolant is positioned below a bottom of the condensing steam generator and above the core such that the condensing steam generator is not in contact with the liquid coolant surface of the primary coolant during normal operation of the light water reactor and an upper portion of the volume located above the condensing steam generator includes a saturated steam dome absent a pressurizer;a primary coolant circuit that extends through the core, continues in a direction from the bottom portion toward the top portion through the interior pathway of the condensing steam generator, continues in a direction from the top portion toward the bottom portion through the exterior annulus, and returns to the core to recirculate through the primary coolant circuit; andthe primary coolant comprising a boron-free liquid,wherein the light water reactor is a self-pressurizing pressurized water reactor (PWR). 11. The light water reactor of claim 10, further comprising a riser extending above the core and toward the condensing steam generator. 12. The light water reactor of claim 10, further comprising:a containment vessel enclosing the reactor pressure vessel;a feed water input circuit extending through the containment vessel and the reactor pressure vessel to the condensing steam generator; anda steam output circuit extending through the containment vessel and the reactor pressure vessel to the condensing steam generator. 13. The light water reactor of claim 10, wherein the primary coolant comprises water. 14. The light water reactor of claim 10, wherein the primary coolant circuit is configured to enclose a primary coolant flow at a saturation pressure of the primary coolant. 15. The light water reactor of claim 14, further comprising a secondary coolant circuit thermally coupled to the primary coolant circuit through the condensing steam generator, the secondary coolant circuit controllable to maintain the flow of the primary coolant through the primary coolant circuit at the saturation pressure of the primary coolant. 16. A method for operating a light water reactor that is a self-pressurizing pressurized water reactor (PWR), the method comprising:flowing a primary coolant liquid at saturation pressure through a core that comprises a plurality of nuclear fuel assemblies;boiling the primary coolant liquid with heat from the plurality of nuclear fuel assemblies to form a primary coolant vapor;circulating the primary coolant vapor from above the core through a riser;condensing the primary coolant vapor on a steam generator positioned adjacent the riser to form the primary coolant liquid;circulating the primary coolant liquid, through an annulus defined between the riser and a reactor pressure vessel, to the core; andmaintaining a top water level of the primary coolant liquid at a level between a top of the core and a bottom of the steam generator such that the steam generator is not in contact with the top water level of the primary coolant liquid during normal operation of the self-pressurizing PWR and an upper portion of the reactor pressure vessel located above the steam generator operates absent a pressurizer. 17. The method of claim 16, wherein the primary coolant liquid comprises aboron-free liquid. 18. The method of claim 16, wherein the boiling occurs at a position below the steam generator. 19. The method of claim 16, further comprising transferring heat from the primary coolant vapor to a working fluid in the steam generator through a phase change in the primary coolant vapor to the primary coolant liquid. 20. The method of claim 19, further comprising:circulating the working fluid in the steam generator to a secondary coolant circuit that is fluidly coupled to a power generation system; andcontrolling the circulation of the working fluid in the secondary coolant circuit to maintain the flow of the primary coolant liquid at saturation pressure.