2017 | AFC ACCOMPLISHMENTS 57 Project Description: The Office of Nuclear Energy (NE) currently funds the investigation of novel ceramic nuclear fuel concepts. One of the primary performance objectives targeted for improved performance of nuclear fuels is mini- mizing fracture in fuel pellets. New materials or composite fuel architec- tures that offer greater resistance to cracking under the extreme environ- ments encountered during nuclear reactor service would provide signifi- cant improvements to steady state (e.g. heat transfer, fuel redistribution) and transient (e.g. radionucleide release at elevated temperatures) conditions. Options currently under investigation include ‘nontraditional’ nuclear fuels designated around high uranium density.These include uranium silicides, uranium borides, and composite fuel materials constructed of these and uranium nitride or uranium dioxide. Preliminary screening of the thermophysical and thermodynamic properties of these concepts has provided confidence in their soundness, but evaluation of their mechanical properties at relevant temperatures must be executed in order to support further study. Devel- opment of novel and improved means of measuring the mechanical proper- ties of uranium-bearing materials is a critical step in advancing toward fuels that are less susceptible to cracking under both normal operating condi- tions and possible transients. Mechanical property measurements of ATF fuel materials provide previously unmeasured data to facilitate more sophisticated fuel performance modeling and provide fundamental inputs to modeling and simulation efforts.