Nodal dynamics modeling of AP1000 reactor for control system design and simulation

This paper presents a one-dimensional nodal core model for AP1000. The reactor core is divided into a number of nodes both along the reactor axis and in the radial direction of fuel rod. To obtain a model of small order with satisfactory accuracy, an optimum nodalization scheme is arrived at by comparing the transient response accuracies and computation speeds of node models with different nodalization schemes, which keeps a good balance between maximizing the computational accuracy and minimizing the computing time. Results of numerical simulations including the Mechanical Shim (MSHIM) load follow simulation show that the trends of transient responses and xenon-induced spatial oscillations agree well with the general physical rules. These results also demonstrate that the developed nodal model can reflect not only the average information but also the distribution information of the reactor such as the axial power distribution and the spatial distribution of fuel temperature. In view of its accuracy, simplicity and fast computation speed, the developed nodal core model can serve as the basis for control system design and simulation of the AP1000 reactor.