Hello, A change in allocation has been requested: Requester: linyun (Linyun Liang) Project: Meso_Nuclear Title: Gas bubble kinetics in an irradiated U-Mo using a mesoscale simulation approach Description: A mesoscale simulation approach is developed to study the gas bubble evolution kinetics in irradiated U-Mo alloy fuels. Density functional theory is first utilized to predict the defect formation energies, the Xe-U-Mo interfacial energy, and the elastic constants of U-Mo alloys, among other quantities. These obtained material properties are then incorporated into a mesoscale model to study the kinetics of gas bubbles in U-Mo under irradiation. By developing a new free energy model of Xe gas bubble based on the van der Walls equation of state, the gas bubble pressure can be estimated. The effects of vacancy and self-interstitial atom (SIA) diffusion on the gas bubble pressure will be further investigated and validated. 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 systemat ically 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. 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 structural damage in irradiated U-Mo materials. In our phase field model, we have four highly non-linear, coupled partial differential equations 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 150,000 core hours including the 6,000 core-hour to debug and test the algorithm and code and 144,000 core-hours (4 cores/node * 4 nodes * 10 hours of run time * 800 different runs) for the nucleation and growth of gas bubbles calculations. We will use our developed FFTW code to solve the problem. By using the Fusion and Blues computing resources will greatly accelerated the code development and calculations. In conclusion, the total core-hours requested for this project throughout the FY2016 will be 150,000 core-hours. Fig. 1 Simulated results of gas bubbles nucleation and growth under the irradiated U-7Mo. Current: undetermined amount Justification: Requested: 250000 A specific reason has been given: I have zero allocation core-hours now. I am requesting additional core-hours below. Q2: 50,000 Q3: 100,000 Q4: 100,000 This needs to be approved and the final allocation amount decided upon. Thank You, The LCRC Accounts System