High-temperature reactor

Gas-cooled high-temperature nuclear reactor having a reactor core comprising a multiplicity of individual particulate fuel elements received in a containment structure, said fuel elements being disposed laterally adjacent and on top of one another, each of said fuel elements being provided with means for forming a barrier against the release of fission products producible therein during reactor operation, said containment structure including a cylindrical barrel formed of an inner graphite layer functioning as a reflector, an outer layer of carbon bricks as insulating material surrounding said inner layer, and a metallic receptacle, said inner and outer layers being formed of respective side, bottom and cover portions, said cover portion being nonmetallic, said containment structure directly supporting said cover portion at the top of the cylindrical barrel exclusively by the side portions thereof, said side and cover portions of said inner layer being formed with first channels into which means for controlling a chain reaction in the reactor are insertible, said means being the sole insertion means for controlling the chain reaction in said reactor, said bottom, side and cover portions of said inner layer being further formed with second channels, means for circulating cooling gas during reactor operation through said second channels under pressure from the bottom to the top of said receptacle, and through the reactor core said bottom portion of said inner layer having first openings for introducing cooling gas into said second channels during reactor operation and second openings for withdrawing during reactor operation cooling gas heated by passage through the reactor core;

• said inner and outer layers and said metallic receptacle having a heat conductivity and a thermal capacity and the reactor core having such a size, shape, power density and moderation ratio that a first temperature at which said core becomes subcritical for all possible accident conditions is below a second temperature at which said barrier means are destroyed, and, when loss of pressure of said cooling gas down to about 10 bar or less is experienced, after-heat generated in said core is removable solely by heat conduction and radiation through said inner and outer layers and said core barrel to a passive heat removal system located outside said receptacle, so that said fuel elements remain at a temperature below said second temperature, said barrier being effective against the release of fission products up to a second temperature on the order of 1400.degree. C., and said cooling gas being helium, the reactor having a maximum power output of up to substantially 200 MW thermal, an average power density of substantially 3 MW/m.sup.3 of core volume and a maximum local power density of substantially 4 MW/m.sup.2 of core volume, a power production of substantially 20 MW/m of core height, a core diameter of substantially 3 m, and a heat transfer, for fuel elements having attained said second temperature and with said cooling gas at atmospheric pressure, of substantially 3 to 6 KW/m of the outer surface of said receptacle, said graphite reflector and said carbon insulation, respectively, being formed of blocks disposed in the form of concentric rings, and said metallic receptacle comprising a cylindrical steel jacket surrounding said rings of blocks and holding them together, the after-heat from said nuclear core being removable solely through said side portion and said metallic receptable, when the pressure in said cylindrical barrel drops to about 10 bar or less, said passive heat removal system including a multiplicity of U-shaped tubes having coolant therein, said tubes being vertically disposed and uniformly distributed around the circumference of said cylindrical steel jacket, said tubes having a first leg in heat-transferring contact with said steel jacket and a second leg spaced from said steel jacket, a natural circulation of the coolant in said U-shaped tubes being produced due to a temperature difference in said first and said second legs thereof, and means for connecting said tubes with a heat exchanger located outside said metallic receptacle.