Morteza Akbari - Department of Nuclear Engineering‎, ‎Science and Research Branch‎, ‎Islamic Azad University‎, ‎Tehran‎, ‎Iran
Farrokh Khoshahval - Reactor and Nuclear Safety Research School‎, ‎Nuclear Science and Technology Research Institute (NSTRI)‎, ‎Tehran‎, ‎Iran

In this research, the governing dynamic equations of the Bushehr NPP core are studied and modeled using Matlab (Simulink) software. The point kinetic equation with the temperature feedbacks and the fuel-coolant energy balance equations in the time domain were used for this purpose. The model is validated against the rod drop accident data available in BNPP-۱ FSAR, and they agreed. Then, this time-domain model is used to find the maximum movement speed of the control rods. For this goal, linear and non-linear rod movement equations have been modeled. In this regard, the maximum withdrawal speed of the working bank (H۱۰) with a worth of ۱.۱ dollars has been investigated. Using the linear CR model, a speed limit of ۹ cm.s-۱ has been obtained to prevent the initiation of a reactor trip. The maximum speed using the non-linear model of the CR was found out to be dependent on its initial position. Thus, in three positions of the H۱۰ bank: ۱۰۰%, ۸۰%, and ۵۰% of the length inside the reactor, the maximum withdrawal speed values were valuated ۱۱.۵, ۷.۷, and ۴.۴ cm.s-۱ respectively. According to the results, among the reactor parameters including power, period, and fuel temperature, which are monitored by the reactor protection system to initiate the reactor trip, the reactor power is the limiting factor for specifying the maximum withdrawal speed. This study is performed using time domain analysis, and the obtained results are consistent with the results reported in the previous research using Laplace transform approach.

Reactor Dynamic Model, Bushehr NPP, Maximum speed of control rod, Simulink Modelling, Time domain analysis