Patent Number: 
Section: claims

1. A high-temperature containment-isolation system for an HTR, comprising:a reactor vessel disposed inside a reactor cavity having an outer containment wall;a hot-well vessel with a hot-leg pipe coupled to the reactor vessel at a hot-leg penetration of the outer containment wall, said hot-well vessel having an interior surface;wherein the hot-leg pipe provides a coolant liquid flow path from the hot-leg penetration through the hot-well vessel;wherein a section of the interior surface of the hot-well vessel is a liquid-free surface; andwherein the liquid-free surface has a cover gas maintained at a constant pressure and thus prevents coolant overpressures from being transmitted into the reactor vessel. 2. A system as recited in claim 1, further comprising:an isolation valve within the hot-well vessel controlling the hot-leg coolant flow path into the hot-well vessel;wherein hot coolant exiting the reactor vessel flows through the isolation valve into the hot-well vessel. 3. A system as recited in claim 1, wherein the hot-well vessel further comprises a submerged centrifugal pump that circulates the hot coolant through a crossover-leg. 4. A system as recited in claim 3, wherein the hot-well vessel has sufficient volume to accommodate level changes due to thermal expansion of the coolant and level changes within the system due to flow caused by operation of the pump. 5. A system as recited in claim 2, wherein the isolation valve comprises a gate valve to seal and isolate the hot-leg pipe and reactor vessel from the hot-well vessel.