Encore Accident Tolerant Fuel Receives Approval in the United States
In a first for the USA, the country’s nuclear regulator has approved an increase in the burnup limit for Westinghouse’s Encore accident tolerant fuel design, paving the way for longer and more economic fuel cycle. That is, the fuel in the United States will be able to exceed the burnup limit of 62 GW/day per ton of uranium in one campaign.
The initial phase of the fuel program focuses on chrome cladding of fuel rods to reduce surface oxidation, which will extend service life, provide increased wear resistance and enhance uranium burnup. Such a coating will withstand prolonged exposure to high-temperature steam (1200-300 C) and inhibit the zirconium vapor reaction, which threatens to release hydrogen and large amounts of heat that can cause emergencies.
The second phase includes the development of a silicon carbide (SiC) cladding. Such a cladding will ensure stability in beyond-design-basis accident scenarios due to the extremely high melting point of SiC and high thermal conductivity of modern fuels.
In addition to the cladding, Westinghouse EnCore is also working on higher fuel enrichment and deeper burnup. The LEU+ ADOPT fuel elements with uranium-235 concentrations of up to 8%, which is 3-4% higher than conventional enrichment, contain additives that will improve safety during operation at higher power and extend the campaign. The fuel rods will be manufactured in the form of lead pins that will be included in four test fuel assemblies that will be shipped to the United States next year for testing at Vogtle Unit 2.