EBR-II Metallic Driver Fuel—A Live Option

The exceptional performance of metallic driver fuel has been demonstrated by the irradiation of a large number of Experimental Breeder Reactor II (EBR-II) driver-fuel elements of uranium-5 wt percent fissium clad in austenitic stainless steel. High burnup with high reliability has been achieved by a close coupling of element design and materials selection. The irradiation performance has been improved by decreasing the fuel smear density, increasing the plenum volume, increasing the cladding thickness, and selecting a higher-strength, lower-swelling cladding alloy which exhibits less fuel-cladding chemical interaction. Quantification of reliability has allowed full utilization of the element lifetime. Lifetimes much greater than 10 at. percent could be achieved by a design change of the restrainer, which currently limits life. Use of U-Pu-Zr fuel alloy with current cladding material would provide higher-temperature capability, as demonstrated by test elements. Metallic fuel systems with their inherently superior breeding and irradiation performance are capable and attractive next-generation power systems.