Liquid-metal dip seal with pneumatic spring

Claim 1

In a liquid-metal cooled nuclear reactor containing cover gas and which includes a reactor vessel head containing small and large rotating plugs, the small rotating plug being nested within the large rotating plug and defining an isolated plug annulus between the plugs wherein the annulus is sealed at the top by an inflatable seal and at the bottom by the liquid-metal dip seal, the dip seal comprising: a trough on an inner periphery of said large rotating plug and having a bottom formed by a flange extending from the inner periphery of the large rotating plug, a side wall formed by the periphery of the large rotating plug above the trough bottom, and another side wall attached at a right angle to the edge of the flange away from the large rotating plug and extending a distance upwardly therefrom; a seal blade pendently supported from the periphery of a larger diameter section of the small rotating plug, and extending downwardly into the trough and separating the trough into a wide leg and a narrow leg substantially different in width, each in communication with the other underneath the seal blade, the wide leg also being in communication with the cover gas, and the narrow leg also being in communication with the isolated plug annulus; a liquid metal in the trough which submerges a portion of the seal blade; and a constant mass of inert gas in the isolated plug annulus, the gas being in communication with the surface of the liquid metal in the narrow leg, whereby when the cover gas pressure increases and displaces liquid metal from the wide leg to the narrow leg, thereby causing an increase in the level of the narrow leg greater than the decrease in level of the wide leg, the constant mass of inert gas in the isolated plug annulus will be compressed and its pressure increased, thus exerting a greater restoring force on the surface of the liquid metal in the narrow leg and resisting any further decrease in the level of liquid metal in the wide leg.