Fuel cycle impacts of accident tolerant fuels

As a result of the Fukushima-Daichi nuclear incident in March 2011, the U.S. and other countries that operate commercial light water reactors (LWRs) have been proposing and developing fuels with enhanced accident tolerance, aka "Accident Tolerant Fuel (ATF)". The primary goal is to develop fuel concepts that at a minimum provide additional time for managing beyond design basis accidents ("coping time"), and optimally eliminate the characteristics of current uranium-oxide, Zircaloy clad fuels that contributed to the catastrophic consequences of the accident. Desirable characteristics of proposed ATF concepts include higher thermal conductivity, enhanced fission product retention, and reduced reaction kinetics and hydrogen generation in loss of coolant conditions. The approaches being considered include enhancing or developing new cladding and/or fuel materials. Near-term approaches include Zirconium-based alloy cladding coated with various candidate ceramic or metallic materials to provide corrosion resistance for alleviating oxidation and hydriding degradation, and/or using fuels with high thermal conductivity. In the mid-term, advanced cladding materials are being considered for increasing the maximum tolerable cladding temperature and corrosion resistance before total cladding failure or accelerated oxidation, or advanced fuels with increased thermal conductivity. In order to make the fuel attractive for utility use, its economics must also be improved. In this respect, fuel with increased density (>10%) and cladding with a longer in-reactor lifetime will be attractive. The Advanced Fuels Campaign in the U.S. Department of Energy Office of Nuclear Energy Fuel Cycle Technologies Program Office is assessing and developing ATF options focused primarily on materials characteristics of ATF fuel and cladding options (e.g., fabrication, properties, irradiation behavior) and potential impacts on reactor performance and safety. This paper describes work on a complementary effort that has been initiated under the Fuel Cycle Options Campaign in Fiscal Year 2015 to assess the impact of ATF concepts on fuel cycle performance. This activity expands on the work performed under the Advanced Fuel Campaign to address the broader fuel cycle issues considered in the recently completed study: "Evaluation and Screening (E&S) of Fuel Cycle Options". This paper discusses the impact of several ATF options on the fuel cycle performance of once-through LWRs compared to current uranium oxide-Zircaloy fueled commercial LWRs ("basis of comparison" for the E&S study) by considering the "benefit" metrics employed in the E&S.