END PLUG FOR SEALING COMPOSITE TUBULAR CERAMIC SHELL OF FUEL ELEMENT OF NUCLEAR REACTOR (VARIANTS) AND METHOD FOR MANUFACTURE THEREOF (VARIANTS) Russian patent published in 2021 - IPC G21C3/10 G21C3/07 

FIELD: nuclear technology.

SUBSTANCE: invention relates to nuclear power engineering, namely, to end plugs and methods for manufacture thereof, and can be used to manufacture end plugs based on silicon carbide for sealing the composite tubular ceramic shells of fuel elements (FEs). The end plugs according to three variants are based on β-modification silicon carbide. The end plug according to the first and second variants consists of two parts in the form of coaxial cylinders of various diameters, wherein the diameter of the part configured to be placed inside the shell is smaller than the inner diameter of the shell by 0.06÷0.08 and 2÷3 mm, respectively, for laying various types of solder. The end plug according to the third variant consists of three parts in the form of three consecutive coaxial cylinders of various diameters, wherein the diameter of the two parts configured to be placed inside the shell is smaller than the inner diameter of the shell by 0.06÷0.08 and 2÷3 mm for laying two types of solder simultaneously. The methods for manufacturing the end plug include preparation of a silicon carbide-based powder mixture, hot pressing of the powder mixture and sintering resulting in an end plug of a predetermined shape, and pressing of the finished end plug. In the method according to the first variant, a powder mixture is used, containing, % wt.: β-SiC with the particle size of 0.95 mcm - 10.59, β-SiC with the particle size of 5.19 mcm - 77.91, Al₂O₃ with the particle size of 1.52 mcm - 10.0, Y₂O₃ with the particle size of 1.01 mcm the rest, hot pressing is executed at a temperature of 1,850°C, a pressure of 0.1 MPa and sustaining for 120 min. In the method according to the second variant, a powder mixture is used, containing, % wt.: β-SiC with the particle size of 0.95 mcm - 10.78, β-SiC with the particle size of 5.19 mcm - 79.22, Al₂O₃ with the particle size of 1.52 mcm - 6.0 mm, Y₂O₃ with the particle size of 1.01 mcm the rest, hot pressing is executed at a temperature of 1,850°C, a pressure of 0.1 MPa, and sustaining for 90 minutes. The proposed invention provides environmental safety and a possibility of using the developed end plugs as an alternative replacement for the plugs used in various reactors. The method for manufacturing the end plug is also simplified.

EFFECT: increased mechanical and thermophysical properties of the end plugs.

11 cl, 12 dwg, 5 tbl, 12 ex