Breach experience with U-Zr and U-Pu-Zr metallic fuels

The metallic fuels U-Zr and U-Pu-Zr were tested in Experimental Breeder Reactor II (EBR-II) from 1985 to 1991 as part of the technical feasibility and technology development phases of the integral fast reactor (IFR) program. In the course of these irradiations, which covered a range of operating condition and involved several thousand elements of different designs, 20 failures were encountered. Fourteen failures involved defective upper closure welds, which could be termed early production failures. This failure type, which can be readily identified and whose only effect on reactor operations (after initial plenum gas release) was a low level of long-lived cover-gas activity, has been eliminated by changes in end-plug desing and welding technique. Three other failures also occurred in the plenum region and could only be attributed to the damage caused by reloading the elements into new subassembly hardware. Finally, three failures were encountered in the fuel column region: one with ternary fuel after [approximately]17 at. % burnup and two with binary fuel after 10 at. % burnup at 2[sigma] cladding temperatures of 660[degrees]C at beginning of life.