A simple dynamic model in physical coordinates (an improved version of our model reported in ) and the corresponding parameter estimation procedure for the primary circuit dynamics of VVER-type pressurized water reactors is presented in this paper. The primary uses of the model are control oriented dynamic model analysis and high level controller design. The most important requirements of the simple physical model are that it should contain the possible minimal number of differential equations and it should be capable of describing important dynamic phenomena such as load change transients between day and night periods. Furthermore, the estimated parameter values should fall into physically meaningful ranges. The parameter estimation method is based on the decomposition of the overall system model into separably identifiable subsystems. The identification of the subsystems is followed by the fine-tuning of the model parameters with the parameter estimation of the entire system model. The constructed model satisfies the predefined requirements and its response shows good fit to the measurement data that were obtained from three units of the Paks Nuclear Power Plant in Hungary.