This presentation summarizes the scope and status of the metallic fuel casting modeling. New mode... more This presentation summarizes the scope and status of the metallic fuel casting modeling. New modeling capabilities needed to simulate the casting of metallic fuels are being added to Truchas code. A heat transfer model is developed to analyze the failed casting test. Simulation indicates 18% more heat loss to the top of the mold in EFL design. The EFL skirt design should be modified. The bubble model is implemented into Truchas and tested with old casting model. More testing will be done with the new casting design including vents.
ABSTRACTGrain boundary and crystallographic orientation information of an Al-foil with a columnar... more ABSTRACTGrain boundary and crystallographic orientation information of an Al-foil with a columnar grain structure is characterized by Electron Backscattered Diffraction (EBSD) technique. The starting microstructure and grain boundary properties are implemented as an input for the three- dimensional grain growth simulation. In the computational model, minimization of the interface energy is the driving force for the grain boundary motion. The computed evolved microstructure is compared with the final experimental microstructure, after annealing at 550 °C. Good agreement is observed between the experimentally obtained microstructure and the simulated microstructure. The constitutive description of the grain boundary properties was based on a 1- parameter characterization of the variation in mobility with misorientation angle.
An improved robust formulation for constituent distribution in metallic nuclear fuels is develope... more An improved robust formulation for constituent distribution in metallic nuclear fuels is developed and implemented into the advanced fuel performance framework BISON. The coupled thermal diffusion equations are solved simultaneously to reanalyze the constituent redistribution in post irradiation data from fuel tests performed in Experimental Breeder Reactor II (EBR-II). Deficiencies observed in previously published formulation and numerical implementations are also improved. The present model corrects an inconsistency between the enthalpies of solution and the solubility limit curves of the phase diagram while also adding an artificial diffusion term when in the 2-phase regime that stabilizes the standard Galerkin Finite Element (FE) method used by BISON. An additional improvement is in the formulation of zirconium flux as it relates to the Soret term. With these new modifications, phase dependent diffusion coefficients are revaluated and compared with the previously recommended values. The model validation included testing against experimental data from fuel pins T179, DP16 and T459, irradiated in EBR-II. A series of viable material properties for U-Pu-Zr based materials was determined through a sensitivity study, which resulted in three cases with differing parameters that showed strong agreement with one set of experimental data, rod T179. Subsequently a full-scale simulation of T179 was performed to reduce uncertainties, particularly relating to the temperature boundary condition for the fuel. In addition a new thermal conductivity model combining all available data covering 0 to 100% zirconium concentration and a zirconium concentration dependent linear heat rate solution derived from Monte Carlo N-Particle (MCNP) simulations were developed. An iterative calibration process was applied to obtain optimized diffusion coefficients for U-Pu-Zr metallic fuels. Optimized diffusion coefficients suggest relative improvements in comparison to previous reported values. The most influential or uncertain phase is found to be the gamma phase, followed by alpha phase, and thirdly the beta phase; indicating separate effect testing should concentrate on these phases.
A variant of Anderson Mixing, namely the Nonlinear Krylov Acceleration (NKA), is presented and im... more A variant of Anderson Mixing, namely the Nonlinear Krylov Acceleration (NKA), is presented and implemented in a reconstructed Discontinuous Galerkin (rDG) method to solve the compressible Euler and Navier-Stokes equations on hybrid grids. A nonlinear system of equations as a result of a fully implicit temporal discretization at each time step is solved using the NKA method with a lowerupper symmetric Gauss-Seidel (LU-SGS) preconditioner. The developed NKA method is used to compute a variety of flow problems and compared with a well-known Newton-GMRES method to demonstrate the performance of the NKA method. Our numerical experiments indicate that the NKA method outperforms its Newton-GMRES counterpart for transient flow problems, and is comparable to Newton-GMRES for steady cases, and thus provides an attractive alternative to solve the system of nonlinear equations arising from the rDG approximation.
This paper presents the progress of the fuel performance analysis using BISON [1] fuel performanc... more This paper presents the progress of the fuel performance analysis using BISON [1] fuel performance tool. Within the BISON [1] framework a new Zirconium diffusion kernel was implemented that substantially improved the reliability and stability for solving Zirconium migration problems in metallic nuclear fuels. Several benchmark problems were created, including a simple 1-D rod and several 2-D segments of a fuel rod that covered several temperature regimes. The simulations were then compared to results from the code Pedernal [2], which is a "high-performance solver for coupled, nonlinear heat conduction and multi-component species diffusion". Comparison between the BISON [1] based solver and Pedernal showed exceptional agreement for all benchmark cases. Very small differences appeared at longer time frames (2,000 days) for the hotter fuel simulations; however this is believed to be due, primarily, to the different timestepping algorithms used in the two codes. Overall the domain of the benchmark covered all components of the U-Pu-Zr phase diagram (alpha, delta, beta and gamma phases) and showed excellent agreement when compared to Pedernal based results.
We compare variants of Anderson Mixing with the Jacobian-Free Newton-Krylov and Broyden methods a... more We compare variants of Anderson Mixing with the Jacobian-Free Newton-Krylov and Broyden methods applied to the k-eigenvalue formulation of the linear Boltzmann transport equation. We present evidence that one variant of Anderson Mixing finds solutions in the fewest number of iterations. We examine and strengthen theoretical results of Anderson Mixing applied to linear problems. 1.
This presentation summarizes the scope and status of the metallic fuel casting modeling. New mode... more This presentation summarizes the scope and status of the metallic fuel casting modeling. New modeling capabilities needed to simulate the casting of metallic fuels are being added to Truchas code. A heat transfer model is developed to analyze the failed casting test. Simulation indicates 18% more heat loss to the top of the mold in EFL design. The EFL skirt design should be modified. The bubble model is implemented into Truchas and tested with old casting model. More testing will be done with the new casting design including vents.
Computers & Mathematics with Applications, 2019
We present a novel method for calculating interface curvature on 3D unstructured meshes from piec... more We present a novel method for calculating interface curvature on 3D unstructured meshes from piecewiselinear interface reconstructions typically generated in the volume of fluid method. Interface curvature is a necessary quantity to calculate in order to model surface tension driven flow. Curvature needs only to be computed in cells containing an interface. The approach requires a stencil containing only neighbors sharing a node with a target cell, and calculates curvature from a least-squares paraboloid fit to the interface reconstructions. This involves solving a 6 × 6 symmetric linear system in each mixed cell. We present verification tests where we calculate the curvature of a sphere, an ellipsoid, and a sinusoid in a 3D domain on regular Cartesian meshes, distorted hex meshes, and tetrahedral meshes. For both regular and unstructured meshes, we find in all cases the paraboloid fitting method for curvature to converge between first and second order with grid refinement.
Additive Manufacturing (AM), the fabrication of 3-D parts from CAD models, is a disruptive techno... more Additive Manufacturing (AM), the fabrication of 3-D parts from CAD models, is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending these principles to additive manufacturing to understand the transient phenomena of repeated melting and solidification during electron beam powder melting process to achieve site-specific microstructure control within a fabricated component. In this paper, we have developed a novel melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) and also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos
A variant of Anderson Mixing, namely the Nonlinear Krylov Acceleration (NKA), is presented and im... more A variant of Anderson Mixing, namely the Nonlinear Krylov Acceleration (NKA), is presented and implemented in a reconstructed Discontinuous Galerkin (rDG) method to solve the compressible Euler and Navier-Stokes equations on hybrid grids. A nonlinear system of equations as a result of a fully implicit temporal discretization at each time step is solved using the NKA method with a lowerupper symmetric Gauss-Seidel (LU-SGS) preconditioner. The developed NKA method is used to compute a variety of flow problems and compared with a well-known Newton-GMRES method to demonstrate the performance of the NKA method. Our numerical experiments indicate that the NKA method outperforms its Newton-GMRES counterpart for transient flow problems, and is comparable to Newton-GMRES for steady cases, and thus provides an attractive alternative to solve the system of nonlinear equations arising from the rDG approximation.
Metal nuclear fuel is a candidate transmutation fuel form for advanced fuel cycles. One constitue... more Metal nuclear fuel is a candidate transmutation fuel form for advanced fuel cycles. One constituent of the fuel, americium, has a high vapor pressure, and there is a concern that excessive volatility losses of americium will occur during casting of the metal. A number of experiments have been performed using americium and surrogate metals, including experiments tentatively slated for FY13, to address the concern. The present task is to model and numerically simulate these experiments. This report describes a system-level model of the relevant experiments that has been developed together with some results. It also describes some supporting 3D, fullphysics simulations of portions of the experiments that have been performed.
Orientation of x i ,x^,x3 axes Optical Classification Crystal System Convention for Assignment of... more Orientation of x i ,x^,x3 axes Optical Classification Crystal System Convention for Assignment of a, b, c axes *1 *2 *3 Optical Classification Triclinfc c Q < a Q < b o ; a, e > au* J-(010) c biaxial Monoclinic* c o " a o ; p > 9D * : « = y = 90*-L (1U0) b c biaxial Orthorhombic
This presentation summarizes the scope and status of the metallic fuel casting modeling. New mode... more This presentation summarizes the scope and status of the metallic fuel casting modeling. New modeling capabilities needed to simulate the casting of metallic fuels are being added to Truchas code. A heat transfer model is developed to analyze the failed casting test. Simulation indicates 18% more heat loss to the top of the mold in EFL design. The EFL skirt design should be modified. The bubble model is implemented into Truchas and tested with old casting model. More testing will be done with the new casting design including vents.
ABSTRACTGrain boundary and crystallographic orientation information of an Al-foil with a columnar... more ABSTRACTGrain boundary and crystallographic orientation information of an Al-foil with a columnar grain structure is characterized by Electron Backscattered Diffraction (EBSD) technique. The starting microstructure and grain boundary properties are implemented as an input for the three- dimensional grain growth simulation. In the computational model, minimization of the interface energy is the driving force for the grain boundary motion. The computed evolved microstructure is compared with the final experimental microstructure, after annealing at 550 °C. Good agreement is observed between the experimentally obtained microstructure and the simulated microstructure. The constitutive description of the grain boundary properties was based on a 1- parameter characterization of the variation in mobility with misorientation angle.
An improved robust formulation for constituent distribution in metallic nuclear fuels is develope... more An improved robust formulation for constituent distribution in metallic nuclear fuels is developed and implemented into the advanced fuel performance framework BISON. The coupled thermal diffusion equations are solved simultaneously to reanalyze the constituent redistribution in post irradiation data from fuel tests performed in Experimental Breeder Reactor II (EBR-II). Deficiencies observed in previously published formulation and numerical implementations are also improved. The present model corrects an inconsistency between the enthalpies of solution and the solubility limit curves of the phase diagram while also adding an artificial diffusion term when in the 2-phase regime that stabilizes the standard Galerkin Finite Element (FE) method used by BISON. An additional improvement is in the formulation of zirconium flux as it relates to the Soret term. With these new modifications, phase dependent diffusion coefficients are revaluated and compared with the previously recommended values. The model validation included testing against experimental data from fuel pins T179, DP16 and T459, irradiated in EBR-II. A series of viable material properties for U-Pu-Zr based materials was determined through a sensitivity study, which resulted in three cases with differing parameters that showed strong agreement with one set of experimental data, rod T179. Subsequently a full-scale simulation of T179 was performed to reduce uncertainties, particularly relating to the temperature boundary condition for the fuel. In addition a new thermal conductivity model combining all available data covering 0 to 100% zirconium concentration and a zirconium concentration dependent linear heat rate solution derived from Monte Carlo N-Particle (MCNP) simulations were developed. An iterative calibration process was applied to obtain optimized diffusion coefficients for U-Pu-Zr metallic fuels. Optimized diffusion coefficients suggest relative improvements in comparison to previous reported values. The most influential or uncertain phase is found to be the gamma phase, followed by alpha phase, and thirdly the beta phase; indicating separate effect testing should concentrate on these phases.
A variant of Anderson Mixing, namely the Nonlinear Krylov Acceleration (NKA), is presented and im... more A variant of Anderson Mixing, namely the Nonlinear Krylov Acceleration (NKA), is presented and implemented in a reconstructed Discontinuous Galerkin (rDG) method to solve the compressible Euler and Navier-Stokes equations on hybrid grids. A nonlinear system of equations as a result of a fully implicit temporal discretization at each time step is solved using the NKA method with a lowerupper symmetric Gauss-Seidel (LU-SGS) preconditioner. The developed NKA method is used to compute a variety of flow problems and compared with a well-known Newton-GMRES method to demonstrate the performance of the NKA method. Our numerical experiments indicate that the NKA method outperforms its Newton-GMRES counterpart for transient flow problems, and is comparable to Newton-GMRES for steady cases, and thus provides an attractive alternative to solve the system of nonlinear equations arising from the rDG approximation.
This paper presents the progress of the fuel performance analysis using BISON [1] fuel performanc... more This paper presents the progress of the fuel performance analysis using BISON [1] fuel performance tool. Within the BISON [1] framework a new Zirconium diffusion kernel was implemented that substantially improved the reliability and stability for solving Zirconium migration problems in metallic nuclear fuels. Several benchmark problems were created, including a simple 1-D rod and several 2-D segments of a fuel rod that covered several temperature regimes. The simulations were then compared to results from the code Pedernal [2], which is a "high-performance solver for coupled, nonlinear heat conduction and multi-component species diffusion". Comparison between the BISON [1] based solver and Pedernal showed exceptional agreement for all benchmark cases. Very small differences appeared at longer time frames (2,000 days) for the hotter fuel simulations; however this is believed to be due, primarily, to the different timestepping algorithms used in the two codes. Overall the domain of the benchmark covered all components of the U-Pu-Zr phase diagram (alpha, delta, beta and gamma phases) and showed excellent agreement when compared to Pedernal based results.
We compare variants of Anderson Mixing with the Jacobian-Free Newton-Krylov and Broyden methods a... more We compare variants of Anderson Mixing with the Jacobian-Free Newton-Krylov and Broyden methods applied to the k-eigenvalue formulation of the linear Boltzmann transport equation. We present evidence that one variant of Anderson Mixing finds solutions in the fewest number of iterations. We examine and strengthen theoretical results of Anderson Mixing applied to linear problems. 1.
This presentation summarizes the scope and status of the metallic fuel casting modeling. New mode... more This presentation summarizes the scope and status of the metallic fuel casting modeling. New modeling capabilities needed to simulate the casting of metallic fuels are being added to Truchas code. A heat transfer model is developed to analyze the failed casting test. Simulation indicates 18% more heat loss to the top of the mold in EFL design. The EFL skirt design should be modified. The bubble model is implemented into Truchas and tested with old casting model. More testing will be done with the new casting design including vents.
Computers & Mathematics with Applications, 2019
We present a novel method for calculating interface curvature on 3D unstructured meshes from piec... more We present a novel method for calculating interface curvature on 3D unstructured meshes from piecewiselinear interface reconstructions typically generated in the volume of fluid method. Interface curvature is a necessary quantity to calculate in order to model surface tension driven flow. Curvature needs only to be computed in cells containing an interface. The approach requires a stencil containing only neighbors sharing a node with a target cell, and calculates curvature from a least-squares paraboloid fit to the interface reconstructions. This involves solving a 6 × 6 symmetric linear system in each mixed cell. We present verification tests where we calculate the curvature of a sphere, an ellipsoid, and a sinusoid in a 3D domain on regular Cartesian meshes, distorted hex meshes, and tetrahedral meshes. For both regular and unstructured meshes, we find in all cases the paraboloid fitting method for curvature to converge between first and second order with grid refinement.
Additive Manufacturing (AM), the fabrication of 3-D parts from CAD models, is a disruptive techno... more Additive Manufacturing (AM), the fabrication of 3-D parts from CAD models, is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending these principles to additive manufacturing to understand the transient phenomena of repeated melting and solidification during electron beam powder melting process to achieve site-specific microstructure control within a fabricated component. In this paper, we have developed a novel melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) and also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos
A variant of Anderson Mixing, namely the Nonlinear Krylov Acceleration (NKA), is presented and im... more A variant of Anderson Mixing, namely the Nonlinear Krylov Acceleration (NKA), is presented and implemented in a reconstructed Discontinuous Galerkin (rDG) method to solve the compressible Euler and Navier-Stokes equations on hybrid grids. A nonlinear system of equations as a result of a fully implicit temporal discretization at each time step is solved using the NKA method with a lowerupper symmetric Gauss-Seidel (LU-SGS) preconditioner. The developed NKA method is used to compute a variety of flow problems and compared with a well-known Newton-GMRES method to demonstrate the performance of the NKA method. Our numerical experiments indicate that the NKA method outperforms its Newton-GMRES counterpart for transient flow problems, and is comparable to Newton-GMRES for steady cases, and thus provides an attractive alternative to solve the system of nonlinear equations arising from the rDG approximation.
Metal nuclear fuel is a candidate transmutation fuel form for advanced fuel cycles. One constitue... more Metal nuclear fuel is a candidate transmutation fuel form for advanced fuel cycles. One constituent of the fuel, americium, has a high vapor pressure, and there is a concern that excessive volatility losses of americium will occur during casting of the metal. A number of experiments have been performed using americium and surrogate metals, including experiments tentatively slated for FY13, to address the concern. The present task is to model and numerically simulate these experiments. This report describes a system-level model of the relevant experiments that has been developed together with some results. It also describes some supporting 3D, fullphysics simulations of portions of the experiments that have been performed.
Orientation of x i ,x^,x3 axes Optical Classification Crystal System Convention for Assignment of... more Orientation of x i ,x^,x3 axes Optical Classification Crystal System Convention for Assignment of a, b, c axes *1 *2 *3 Optical Classification Triclinfc c Q < a Q < b o ; a, e > au* J-(010) c biaxial Monoclinic* c o " a o ; p > 9D * : « = y = 90*-L (1U0) b c biaxial Orthorhombic
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