Pushing nuclear fuel toward extended burnup

Optimal use of uranium has always been a corner stone of nuclear power plant operation. Since the elimination of spent-fuel reprocessing, due to a multitude of political, economic and regulatory forces, programs addressing that concern have stimulated ever increasing interest within the industry. The programs have taken many approaches, including in-core fuel-management variations, fuel-burnup extension, use of burnable neutron absorbers, fuel redesign to reduce operating temperatures, etc. In the constraint of the ''once-through fuel cycle'', extended burnup is considered the most straight forward path toward improved uranium utilization and power-generation economies. Fuel exposures have increased steadily since the early days of nuclear power. In today's commercial plants, the state-of-the-art for burnup-measured in terms of megawatt-days of thermal-energy release per metric ton of uranium in the UO2 fuel-is about 33,000 MWd/ton for pressurized-water reactors (PWRs) and 28,000 MWd/ton for boiling-water reactors (BWRs). The optimum burnup extension, as reported by DOE, is about 17,000 MWd/ton, so that the total burnup targeted by the ongoing utilization improvement programs is 50,000 and 45,000 MWd/ton for the two reactor types, respectively