Publisher Summary This chapter discusses nuclide distribution between steelmaking phases upon melting of sealed radioactive sources hidden in scrap. Sealed radiation sources are widely used in industry, medicine, and research. Although there are regulations in many states on the management of disused radioactive sources, the steel industry is aware of the possibility that disused sources are lost to regulatory control. Since most sealed sources have an outer containment made of steel, a certain fraction of the orphan sources might be discarded as plain steel scrap and be sold to the steel industry. The chapter reports the thermochemical calculations related to nuclide partitioning between the steelmaking phases according to equilibrium calculations.