A workstation-based real-time simulator for two-loop pressurized water reactor plants is developed for classroom training in support of a full-scale simulator, on-site transient analysis, and engineering studies. The present simulator consists of three functional modules: plant module, graphic module, and man-machine interaction module. The plant module includes models for the core kinetics, reactor coolant system, steam generator, main steam line, balance of plant, and control and protection system. Each of the models is optimized to obtain the capability of real-time simulation. For simulating the thermal-hydraulic behavior of the reactor coolant system in the plant module, a fully-implicit safety analysis-2/workstation (FISA-2 /WS) is developed, which adopts implicit algorithms for their inherent stability and efficiency in solving the stiff set of equations that resulted from component models. It allows the use of a larger time step than the Courant limit without any numerical instability, and it also guarantees reasonable accuracy. And the level tracking logic and the peak cladding temperature calculation model on the basis of the simple analytical model are used to track the two-phase water level in the core and to predict the cladding temperature in the uncovered region of the core under accidents, respectively. The graphic module is designed to provide the user with more information at a glance by dynamically displaying schematic diagrams of the systems, symbols indicating the operating status of each component, trend curves, and the main control room. Especially, the CONTROL ROOM menu is designed to enable the user to perform his specific actions through the schematic diagrams of the main control panels in a way similar to which operators do them in the main control room for the KO-RI Nuclear Power Plant Unit 2. In each schematic diagram of five sections, the indicators and alarms display the various operating parameters, alarm signals, and trip signals, and the user can control the various components by operating the corresponding switches in each section through the mouse. Also, the user can initiate his actions through various system diagrams. As tools for the man-machine interface, the man-machine interaction model uses a color cathode ray tube monitor, a standard keyboard, and the mouse. The interactive communication module receives parameters from the user via the keyboard and mouse, and transfers them to the plant module so as to enable the user to perform his specific actions. This module provides the user with various initiating events (malfunctions and manual controls) through SYSTEM, CONTROL ROOM, and ACCIDENTS menus, and thus a wide range of nuclear steam supply system transients can be easily simulated. This module also enables the user to select one of the menu-driven graphic displays. The FISA-2/WS is verified through comparisons with analytical solutions, separated tests and integral tests, and predictions by RETRAN-2 and RELAP5/MOD3. Through the various tests of FISA-2/WS, it is convincing that FISA-2/WS can simulate most transients of the KO-RI Unit 2 with reasonable accuracy in real time.