Patent Number: 
Section: claims

1. A method of hermetically sealing at least one end cap to a nuclear reactor fuel rod cladding tube comprising:providing a nuclear reactor fuel rod cladding tube formed from multiple layers of a SiC—SiC 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;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;applying at least one primary electrode to the exterior side of the at least one end cap;applying current to the at least one primary electrode and 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 accelerating within a range of greater than 1,000° C./min. up to 1,500° C./min. where the temperatures at the interface rise from ambient up to 2,500° C. 2. The method recited in claim 1 wherein the current is applied for 1.0 to 5.0 minutes. 3. The method recited in claim 1 wherein the current is applied at a pressure of 0.001 to 10 MPa. 4. The method recited in claim 1 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. 5. The method of claim 1 further comprising applying a secondary electrode to the exterior side of the tube. 6. 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:providing a nuclear reactor fuel rod cladding tube formed from multiple layers of a SiC—SiC ceramic, the tube having tube walls, at least one end, and a circumferential axis;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 SiC ceramic composition or a precursor to said ceramic composition, and having an exterior and interior side and;applying at least one primary electrode to the exterior side of the at least one end cap;applying current to the at least one primary electrode and 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 accelerating within a range of greater than 1,000° C./min. up to 1,500° C./min. to raise the interface temperature up to 2,500° C., and holding a peak temperature for 0.01 to 60 minutes at pressures from 0.001 MPa to 50 MPa to hermetically seal the tube to the at least one end cap. 7. The method recited in claim 6 wherein the interface temperature is raised in 1.0 to 5.0 minutes. 8. The method recited in claim 6 wherein the peak temperature is held at a pressure of 0.001 to 10 MPa. 9. The method recited in claim 6 wherein the at least one ceramic end cap is formed from the same composition as the composition forming the tube. 10. The method recited in claim 6 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 6 further comprising applying a secondary electrode to the exterior side of the tube.