Chapter 3 - Worldwide development of accident tolerant fuels, areas of study, claddings, and fuels

Abstract

Until a few years ago, very few considered the possibility of using fuel systems in light water reactor that were not based on a zirconium alloy and uranium dioxide (UO2). All standards and guidelines developed over the last 60 years in the commercial nuclear power business are based on Zr/UO2. Any improvement over the decades was to understand and solve issues related to the performance of Zr/UO2. Now, there is a possibility for newer materials in power reactors, and regulatory bodies and trade organizations may be accepting this change as an unavoidable reality. The newer accident tolerant fuels ATF can be classified broadly into (1) newer claddings and (2) newer fuels. Each one of the cladding and fuels main groups has subgroups. In the cladding, subgroups are (1) coated zirconium alloys, (2) monolithic FeCrAl alloys, and (3) ceramic composites or SiC/SiC made of SiC fibers embedded in an SiC matrix. The subgroups in the fuels are (1) modified or doped UO2 and (2) high-density fuels including uranium nitride and uranium silicide. The most near-term concepts for implementation may include coated zircaloy cladding and modified urania fuel. The second closest implementation could be FeCrAl cladding for urania fuel. The ceramic composite SiC/SiC for cladding and the higher density fuels UN and U3Si2 are concepts that may need longer term developments.