Patent Number: 
Section: claims

1. A method of hermetically sealing at least one end cap to a nuclear reactor fuel rod cladding tube, the tube being formed from a ceramic composite comprising:(1) providing a tube formed from a ceramic composite, the tube having tube walls, at least one open end, and a circumferential axis, and providing at least one end cap, the end cap having an exterior side and an interior side;(2) applying the at least one end cap to the at least one open end of the tube to define an interface between a portion of the end cap and the tube, wherein the at least one end cap is made from a material selected from the group consisting of multiple layers of a SiC—SiC ceramic composite, a ternary carbide, and a ternary nitride;(3) applying at least one primary electrode to the exterior side of the at least one end cap;(4) applying current to the at least one electrode using a spark plasma sintering means to supply a rapid temperature rise in the interface applied for 0.01 to 6.0 minutes at a rate of 200° C./min up to 1,500° C./min. where the temperatures at the interface are from ambient to 2,500° C. 2. The method of claim 1, wherein the at least one end cap is based on SiC. 3. The method of claim 1, wherein after step (1), the portion of the end cap and tube defining the interface are polished. 4. The method of claim 1, further comprising applying in step (3) a secondary electrode to the exterior side of the tube. 5. A method of hermetically sealing at least one end cap to a nuclear reactor fuel rod cladding tube, the tube being formed from a ceramic composite, comprising:(1) providing a tube formed from a ceramic composite, the tube having tube walls, at least one end, and a circumferential axis;(2) applying at least one end cap to the at least one end of the tube to define an interface between a portion of the end cap and the tube, the end cap being formed from a composition selected from the group consisting of a ceramic composition or a precursor to a ceramic composition, and having an exterior and interior side and;(3) applying at least one primary electrode to the exterior side of the at least one end cap;(4) applying current to the at least one electrode using a spark plasma sintering means (SPS) for 0.01 to 6.0 minutes to supply a rapid temperature rise in the interface at a rate of 200° C./min. up to 1,500° C./min. where temperatures at the interface are from ambient to 2,500° C., and holding a peak temperature for 5 to 60 minutes at pressures from 0.001 MPa to 50 MPa to hermetically seal the tube to the at least one end cap. 6. The method of claim 5, wherein the at least one ceramic end cap is formed from the same composition as the composition forming the tube. 7. The method of claim 5, wherein the operating parameters of the SPS process are applying the rapid temperature rise at a rate of 1000° C./min. up to 1,500° C./min. to raise the interface temperature up to 2,500° C. in 1.0 to 5.0 minutes and the pressures are 0.001 to 10 MPa. 8. The method of claim 5, wherein the tube and the at least one end cap are made of SiC. 9. The method of claim 5, wherein after step (1), the interface of the at least one end cap and tube are polished. 10. The method of claim 5, wherein the tube and end cap are made from a SiC composite comprising monolithic SiC-based layer or multi-layers on the inside and at least one outer layer of SiC-based fibers in a SiC-based matrix. 11. The method of claim 5, wherein the tube is from 2 feet to 18 feet long. 12. The method of claim 5, wherein after step (1), the interface of the end caps and tube are polished. 13. The method of claim 5, wherein a bonding pressure of 4 to 20 MPa is applied after step (3), with a hold time of 5 minutes to 60 minutes applied after step (4). 14. The method of claim 5, wherein an inert gas is inserted into the tube after step (1) or step (2), at a back pressure of 50 psi to 500 psi. 15. The method of claim 14, wherein the inert gas is helium. 16. The method of claim 5, wherein at least step 4 of the method is carried out in a furnace having a temperature of from about 50° C. to 1,500° C. 17. A tubular ceramic composite made by the method of claim 5. 18. The method of claim 5, wherein the method further comprises applying a secondary electrode to the exterior side of the tube and in step (4) applying current to the secondary electrode for 0.01 to 6.0 minutes using the spark plasma sintering means (SPS). 19. The method of claim 1, wherein current is applied to the at least one electrode at a rate of about 1000° C./min to 1500° C./min. for 1.0 to 5.0 minutes at a pressure of 0.001 to 10 MPa.