Patent Number: 
Section: claims

1. A containment tube comprising:a sealed tube comprising silicon carbide, having:a generally constant diameter along its axial length and containing a radioactive material;first and second ends; andan inner bore extending along at least a portion of an axial length of the sealed tube between the first and second ends, the first end having a plug residing in the inner bore to close the first end, the second end having a distal wall that closes the inner bore at the second end, wherein the plug comprises silicon carbide,wherein the silicon carbide comprises silicon carbide in an amount from at least about 91 wt % to no greater than about 99.85 wt %, wherein at least about 95 wt % of the silicon carbide is of the alpha phase. 2. The containment tube of claim 1, wherein the silicon carbide further comprises a carbonized organic material in an amount no greater than about 5.0 wt % and additional carbon in an amount no greater than about 1.0 wt %. 3. The containment tube of claim 2, wherein the silicon carbide further comprises boron in an amount from at least about 0.15 wt % to no greater than about 3.0 wt %. 4. The containment tube of claim 3, wherein the silicon carbide has a predominantly equiaxed microstructure. 5. The containment tube of claim 2, wherein the plug is sinter-bonded to the tube. 6. The containment tube of claim 1, wherein the radioactive material is in the form of pellets. 7. The containment tube of claim 1, wherein the radioactive material is a fuel used in nuclear power generation. 8. The containment tube of claim 1, wherein the radioactive material comprises uranium. 9. A method of forming a containment tube comprising:providing a green ceramic tube having a first end that is unsealed and a second end that is sealed;partially sintering the green ceramic tube, leaving the first end unsintered or incompletely sintered;placing a radioactive material into the partially sintered tube via the first end;inserting a sintered plug into the first end, wherein the sintered plug comprises silicon carbide;sealing the first end by sintering the first end together with the sintered plug, whereinthe sealed containment tube comprises silicon carbide, has a generally constant diameter along its axial length and an inner bore extending along at least a portion of the axial length between the first and second ends, and contains a radioactive material; andthe silicon carbide comprises silicon carbide in an amount from at least about 91 wt % to no greater than about 99.85 wt %, wherein at least about 95 wt % of the silicon carbide is of the alpha phase. 10. The method of claim 9, further comprising forming the green ceramic tube by extrusion. 11. The method of claim 9, wherein partially sintering comprises leaving the unsealed end incompletely sintered so that the first end of the tube is not shrunk to the final dimensions. 12. The method of claim 9, wherein partial sintering is carried out at a temperature not exceeding 2000 degrees C. 13. The method of claim 9, further comprising removing surface contaminants from (i) an inner circumferential surface of the first end of the tube, (ii) an outer circumferential surface of the plug, or (iii) both. 14. The method of claim 13, wherein surface contaminants are removed by mechanical abrading. 15. The method of claim 14, wherein mechanical abrading is selected from the group consisting of: grinding; lapping; and polishing using a free abrasive, a coated abrasive, or a bonded abrasive. 16. The method of claim 15, wherein mechanical abrading is carried out using a silicon carbide abrasive or a superabrasive. 17. The method of claim 16, wherein mechanical abrading is carried out using a superabrasive selected from the group consisting of cubic boron nitride or diamond. 18. The method of claim 9, wherein sintering imparts a performance characteristic from the group consisting of:i) a Shear Strength not less than about 25 MPa;ii) a Nitrogen Seal Performance of not greater than 10%;iii) a Helium Seal Performance of not greater than 10%;iv) a Vacuum Seal Performance of not greater than 10%. 19. The method of claim 18, wherein sintering forms a chemical and mechanical bond having a shear strength of not less than about 40 MPa, such as not less than about 50 MPa, not less than about 75 MPa. 20. The method of claim 9, wherein sealing the first end comprises applying localized heat to the first end. 21. The method of claim 20, wherein the radioactive material is remote from the localized heat. 22. The method of claim 9, wherein sealing by sintering is carried at a temperature greater than 2000 degrees C. and less than 2300 degrees C., such as between 2050 degrees C. and 2250 degrees C. 23. The method of claim 9, wherein the sealed tube comprises an interface bond between the first end and the plug. 24. The method of claim 9, wherein the silicon carbide further comprises a carbonized organic material in an amount no greater than about 5.0 wt %;boron in an amount from at least about 0.15 wt % to no greater than about 3.0 wt %; andadditional carbon in an amount no greater than about 1.0 wt %; anda predominantly equiaxed microstructure.