Tube reactor for endothermic gas reactions

In a tube-type reactor receiving a pressurized noble gas at a temperature within the range of approximately 600.degree. C. and 1000.degree. C. after heating in a nuclear reactor for carrying out an endothermic chemical reaction with a gas, said tube-type reactor including a pressure jacket with internal insulation, reactor tube assemblies, containing a catalyst when required, extending vertically within said pressure jacket, mounting plate means permanently secured to top end portions of said reactor for support by the upper part of said pressure jacket, noble gas feed means to introduce said pressurized noble gas into the bottom portion of said pressure jacket, and noble gas discharge means in the upper part of said pressure jacket below said mounting means for discharging the noble gas from the pressure jacket, the combination therewith of the improvement comprising cover tubes each surrounding a portion of one of said reactor tube assemblies, each cover tube extending within the space between the bottom surface of said mounting plate means and a point in elevation which is slightly above said noble gas discharge means, a reinforced closure member extending only from the lower end portion of each cover tube to limit the flow of noble gas beyond the closure members into the space above the closure members between the cover tubes and the inner wall of said pressure jacket while allowing the flow of noble gas between said feed means and discharge means, and sealing container means including end members supported by said mounting plate means to form a gas-tight seal between the top side of said mounting plate means and said reactor tube assemblies.