b'An accelerated assessmentNew nanoindentation technique reduces time-to-results and of the creep mechanismssample size needed for creep behavior measurements.in uranium-zirconiumU nderstanding the creep on fuel and structural materials in a nuclear reactor is essential for safe reactor operation. The challenges with model alloys conventional creep measurements are the long timescales and high radiation levels from the large samples. These challenges make it difficult to gather data quickly and efficiently for new structural and fuel materials that could improve nuclear reactor operation or for the development of next generation reactors. New innovative testing techniques are needed to decrease the costs and timeline for measuring these creep properties on materials. Nanoindentation PROJECT NUMBER:creep measurements hold promise as they have been shown to produce values 22P1068-002FP similar to macro-scale creep testing at significantly reduced times (minutes versus hours or days). TOTAL APPROVED AMOUNT: $156,490 over 1 year This project delivered nanoindentation creep data in a uranium 50 wt% zirconium alloy (U-50Zr) up to 200C, demonstrating the application of nanoindentation PRINCIPAL INVESTIGATOR:technique on metallic fuel at elevated temperature. A new nanoindentation stress David Frazer relaxation technique was developed and demonstrated on aluminum for measuring CO-INVESTIGATORS: the stress exponent. This method was also applied to U-50Zr. Additionally, a Dewen Yushu, INL nanoindentation model was simulated using the MOOSE and Marmot software Tianyi Chen, Oregon State University codes for aluminum and U-50Zr, respectively. The simulation results showed good agreement with experimental measurements. Both the nanoindentation measurement technique and the simulation work were presented by two Oregon State University graduate students at the ANS student conference.Nanoindentation stress relaxation in aluminum (a) and U-50Zr (b) following different pre-loading displacement rates. This relaxation process was simulated using MOOSE with crystal plasticity model (c) and the relationship between stress relaxation and pre-loading displacement rate is demonstrated as a new approach for stress exponent estimation (d). 56'