Hello, A new project on the LCRC cluster has been requested. Please forward the information on to the LCRC Allocation sub-committee. Applicant's name: Zhigang Mei Applicant's institution: ANL Applicant's division: Ne Project Name: PF-gas-bubble Project title: Mesoscale modeling of fission gas bubble formation and evolution in nuclear materials Associated funding: DOE NNSA Other Systems: Carbon Science: Fission-induced gas bubble formation can cause severe swelling in nuclear materials at high fission density, which can affect material performance and raise concern of long-term safety. Therefore, it is important to understand the mechanism of gas bubble formation in nuclear material. In this project we will use mesoscale phase field methods to simulate the formation and evolution of fission gas bubbles in irradiated nuclear fuels. The simulation results will be utilized to control bubble swelling in nuclear fuels through materials design and manufacturing process. Project description: There are two kinds of gas bubbles in irradiated nuclear fuels: (1) nano-sized gas bubbles inside fuel grains, i.e., intragranular bubbles; and (2) micro-sized gas bubbles on grain boundaries, i.e., intergranular bubbles. Our goal is to simulate the formation of both gas bubbles using phase field methods by considering all the critical physical processes, such as bubble nucleation, gas-atom diffusion to bubbles, and irradiation-induced re-solution. The simulated bubble size distribution and bubble-induced swelling will be used to understand the cause of the anomalous fuel swelling in UMo dispersion fuel at high fission density. In this project we will primarily uses MOOSE-based phase field module to do the phase field simulations. MOOSE (Multiphysics Object Oriented Simulation Environment) is an object-oriented C++ finite element framework for the development of tightly coupled multiphysics solvers from Idaho National Laboratory. MOOSE makes use of the PETSc non-linear solver package and libmesh to provide the finite element discretization. The MOOSE framework has been tested on Mira on up to O(10k) nodes with excellent scalability. Due to large size difference between intragranular and intergranular gas bubbles (more than two order of magnitude differences), it is very challenging to simultaneously simulate the formation of both gas bubbles using conventional phase field codes based on Fourier-spectral method. With the built-in smart mesh adaptivity, it becomes possible to do such simulations using MOOSE. To model a typical polycrystalline fuel, we will setup a 2D simulation cell with size of 25 μm * 25 μm. The typical intragranular gas bubble size is about 3.5 nm. Therefore a very fine mesh about 0.5 nm is needed. A typical total fission density for high performance research reactor fuels, such as U-Mo dispersion fuels, is about 7*1027 fission/m3. Our tests show that a 2D simulation of a polycrystalline material with size of 25 μm takes about 120 hours using 256 cores to reach the required fission density. We will test the effect of several parameters on the formation of gas bubbles, including initial fuel grain size, fission rate, temperature, and gas resolution rate. Overall, there will be about 30 production runs. The total core-hours will be about 900 000. Industry partnership: Project URL: Requested allocation: 100000 Q1: 0 Q2: 0 Q3: 0 Q4: 100000 Justification: MOOSE-based phase field simulation code is based on object-oriented C++ finite element framework, which uses the PETSc non-linear solver package and libmesh to provide the finite element discretization. The MOOSE framework has been tested on Mira on up to O(10k) nodes with excellent scalability. Storage requirements: 1 TB The requester has used undetermined amount hours of their initial startup project. In addition to approving an initial amount, please specify a Category and Subcategory for this project. For a list of the current selection of approved categories, please see: https://wiki.lcrc.anl.gov/wiki/Processes/Categories Once the Allocation committee has approved the project, please go to the Project Management page to create it: https://accounts.lcrc.anl.gov/projects.php Thank You, The LCRC Accounts System