Researchers at Sandia National Laboratories have been expanding MELCOR—the severe accident modeling computer code used by the Nuclear Regulatory Commission to evaluate the safety of light water reactors—to study the small modular reactors and non-light-water advanced reactors that are under development. An article published in Sandia Lab News on August 27 describes in detail how MELCOR is being expanded to work with different reactor geometries, fuel types, and coolant systems.