The paper presents an approach for the integrated use of expert systems and dynamic models in an intellectualized operator information support system (IOISS) for power units (PU) of nuclear power plants (NPP). The main functions of IOISS for operators of NPP PUs are identified, and the full-scale implementation of these functions based on predictive dynamic modeling of PU parameters and the use of expert systems is shown. The structure of the expert system, which is part of the IOISS operators, is considered. This approach to the IOISS of operators is used in developing upper level systems for instrumentation and control (I&C) systems for NPPs.