HeavyMetal

HeavyMetal is a compact, object-oriented multiphysics finite element code developed for nuclear fuel and reactor core components. It was designed from the outset to combine structural mechanics, heat transfer, contact, cohesive behavior, surface energy, diffusion, and related physics within a common framework. The code is small enough that its overall architecture remains understandable, while its object-oriented structure makes it relatively straightforward to add, remove, or recombine physics as a model develops. Because the complete source and numerical formulation are under our control, specialized features of fuel-system behavior can be incorporated directly rather than being constrained by the structure of a general-purpose code. HeavyMetal combines the flexibility needed for research with the verification and software engineering practices required for engineering analysis.

The figure at right illustrates the type of problem for which that flexibility becomes especially valuable. It shows a HeavyMetal simulation of thermomigration-induced surface instability in metallic fuel, where temperature-driven material transport changes the fuel surface, alters the local thermal field, and eventually brings portions of the fuel into contact with the cladding. After contact, the resulting stresses provide an additional driving force for material transport. For challenging multiphysics analyses of this kind, HeavyMetal is our preferred tool. For more conventional analyses, commercial finite element packages may be preferable because of the breadth and depth of capabilities they provide. This particular calculation, and the physical questions it is intended to explore, are described more fully in the Simulations section.