An expert system for operating-procedure monitoring during plant startup, from cold shutdown to power operation, has been chosen as the object of this study. The knowledge base for the system is principally derived from the written form of the standard procedures. The programmed procedures of the system are displayed on a CRT screen to assist the operators understanding. The main features of the system include the following: (1) computerization of the procedures for checking the initial conditions, the precautions, and the operational procedures; (2) plant status monitoring to detect any plant malfunctions or to help with the operators decision-making; (3) the provision of access to technical specifications of the CRT screen at any time during plant operation; and (4) easy prediction of the estimated critical point prior to reactor criticality, without complicated hand calculation. The results of system verification indicate that the system performs the intended functions, and can be used as an effective tool to minimize the operators burden during plant startup.