A generalized control system modeling capability has been developed for the SASSYS-1 liquid-metal reactor (LMR) system code, significantly extending the simulation capabilities for LMR systems. An important element is the identification of a general equation form that encompasses all control equations encountered in practical applications. The modeling capability is based on steady-state and transient solution techniques suited to the characteristics of this form. As for the user, his control equations are entered in block diagram form as a collection of individual dynamic, function, logic, and table blocks. Constructing plant control equations in this manner is analogous to setting up an analog computer for simulation. The capability is thus sufficiently general for use in modeling a wide variety of control systems and protection systems.