An engineering-scale finite element simulation of pore migration in oxide fuel is presented. The porosity field is governed by an advection-diffusion equation which is coupled to the fuel temperature and stress fields through the thermal conductivity and volumetric heat source term. The engineering-scale porosity equation models the microscopic process of vapor transport of fuel across pores, taking into account thermal and vapor pressure gradients within the fuel. In the simulations, the porosity is initialized to a constant value at every point in the domain, and as the temperature gradient is increased by application of a heat source, the pores move up the thermal gradient and accumulate at the center of the fuel in a time frame that is consistent with experimental observations. Results from representative simulations are provided to demonstrate the new capability, and we show that a sufficiently high power ramp rate limits restructuring and leads to a corresponding increase in fuel temperature. We also discuss the finite element mesh density required to compute pore migration and present multidimensional results.

提出了一种工程规模的氧化物燃料中孔迁移的有限元模拟。孔隙率场由对流扩散方程控制，该对流扩散方程通过热导率和体积热源项与燃料温度场和应力场耦合。工程规模的孔隙度方程考虑了燃料内部的热梯度和蒸汽压力梯度，从而模拟了燃料通过孔的蒸汽传输的微观过程。在模拟中，将孔隙率在域中的每个点初始化为恒定值，并且通过使用热源增加温度梯度，孔隙会沿热梯度向上移动并积聚在燃料的中心。与实验观察结果一致的时间范围。提供了具有代表性的仿真结果，以证明该新功能，并且我们证明了足够高的功率斜率限制了结构调整，并导致了燃料温度的相应升高。我们还讨论了计算孔迁移并显示多维结果所需的有限元网格密度。