Hello, A yearly allocation for the LCRC cluster has been requested with the following updated information: Submitter/PI: Linyun Liang Project Name: Meso_Nuclear Division: MCS Project title: Gas bubble kinetics in an irradiated U-Mo using a mesoscale simulation approach Associated funding: Nuclear energy system Other Systems: Science: High-performance research reactors require fuel that operates at high specific power to high fission density, but at relatively low temperatures. Research reactor fuels are designed for efficient heat rejection, and are composed of assemblies of thin-plates clad in aluminum alloy. The development of low-enriched fuels to replace high-enriched fuels for these reactors requires a substantially increased uranium density in the fuel to offset the decrease in enrichment. Very few fuel phases have been identified that have the required combination of very-high uranium density and stable fuel behavior at high burnup. Uranium-molybdenum (U-Mo) alloy fuel dispersed in an aluminum matrix was identified as a potential fuel type. However, irradiation tests have shown that fuel operating at higher temperatures and powers cause the U-Mo fuel powder in the meat to react with and almost completely deplete the aluminum in the matrix. It is anticipated that replacing dispersion fuel with a monolithic fuel type can solve both the U-Al interaction and fuel density loading problems. In monolithic fuel the entirety of the fuel meat is comprised of a single foil of the fuel alloy. This fuel type represents the optimum in fuel meat density. The greatly reduced fuel surface area per unit mass and the fact that fuel-aluminum interfaces are in the cooler region of the plates should minimize the fuel-aluminum reaction. We will study the effect of U235 uniformity in U-Mo fuel on the fuel swelling behaviors. The simulations will be performed using MOOSE software developed by Idaho National Laboratory. Project description: We will develop a new phase-field model to incorporate the effect of U235 uniformity in the nucleation and formation of gas bubbles, as well as the coupling with the recrystallization. We will use our developed model to study the effect of U235 distribution on the fission rate. The events employed in the simulation are the absorption and emission of a vacancy, a SIA, and an interstitial U by a single Xe bubble, while an event associated with SIA loops or substitutional U is neglected here for simplicity. We will systematically investigate the effect of Xe, vacancy, and SIA concentration, fission defect generation and their recombination, sink strength, grain boundaries, and elastic interaction on the growth kinetics of gas bubble with the uniformity of U235. The swelling of U-Mo due to fission gas bubble will be simulated and compared to experimental observations. Our study aims to provide insight into understanding of the effect of fabrication condition on gas swelling in irradiated U-Mo materials. In our phase field model, we have four highly non-linear, coupled partial differential equations for phase-field parameter, vacancy composition, SIA composition, and gas atom composition, which must be solved numerically. In the meaning time, the elastic equilibrium equation is also included in each time step, which requires to obtain the elastic solution at the equilibrium state for each time step and can significantly increase the cost of the simulation time. And also in order to avoid the partial loss of interfacial energy, we will extend our model to three dimensional system. Therefore, to effectively solve this problem, we will need about 100,000 core hours including the 4,000 core-hour to debug and test the algorithm and code and 96,000 core-hours (4 cores * 16 nodes * 10 hours of run time * 150 different runs) for the nucleation and growth of gas bubbles calculations. In conclusion, the total core-hours requested for this project throughout the FY2018 will be 100,000 core-hours. Industry partnership: Project URL: Current FY Hours Used: undetermined amount New FY Requested allocation: 100000 Q1: 25000 Q2: 25000 Q3: 25000 Q4: 25000 Justification: Storage requirements: 1TB Thank You, The LCRC Accounts System