Nuclear reactor sealing system

Claim 1

A liquid metal-cooled nuclear reactor system, including a vessel containing a cover gas, a body of liquid metal coolant located in a lower portion of the vessel, fuel assemblies positioned in the body of liquid metal coolant, at least one primary coolant flow system for circulating the liquid metal coolant in heat transfer relationship with the fuel assemblies, and a closure head disposed on an upper portion of the vessel in fluid-tight relationship therewith, said closure head comprising: a first and second component defining an annulus therebetween; insulation means disposed adjacent a bottom surface of said components and above the liquid metal coolant for maintaining an upper surface of said components at substantially ambient temperatures; at least first and second inflatable seal means disposed in an upper portion of said annulus for sealing said annulus when they are inflated during normal reactor operation and permitting rotation of one of said components when they are partially deflated; a liquid metal dip seal disposed in said annulus and extending into said insulation means, said dip seal including a trough on one of said components and a seal blade pendently supported from said other component and extended downwardly into the trough, a body of liquid metal in the trough which submerges a portion of the seal blade, the seal blade having at least one aperture located above the liquid metal for providing continuous fluid communication from one side of the blade to the other; means for providing fluid communication between the area above the trough on one side of the seal blade and the cover gas; means for introducing a purge gas intermediate the inflatable seals and the other side of the seal blade for passage through said at least one aperture, said means providing for the introduction of a sufficient amount of purge gas to substantially prevent migration of radioactive cover gas or sodium vapor up to the inflatable seals; and means for withdrawing purge gas and cover gas from the vessel for purification and return to the vessel.