Improvement of core control strategy for CPR1000: Load follow without boron adjustment

This paper presents the study of load follow operations without boron adjustment for CPR1000. To enable the CPR1000 to perform load follow maneuvers without changing soluble boron concentration, the worth of Rod Cluster Control Assemblies (RCCAs) are reconfigured with their amount and location unchanged according to the reactivity variations during the load follow transient. To ensure the real-time ability of the reactor core, the target axial offset (AO) during load follow operations is set to the same value with that in based load, and the Delta-I is maintained within the special trapezoidal shaped target band around its target value.For the simulation of the reactor core, the time-dependent one-dimensional two group diffusion equations with the reactivity feedback of moderator temperature, Doppler and xenon–iodine are used. The transverse buckling is adjusted at each time interval so that the one-dimensional model can match the average characteristics of the three-dimensional reactor core accurately. To show the superiority of the improved core control strategy for CPR1000 reactor, the load follow results employing the purposed boron-adjustment free control strategy are compared to those obtained with the typical MODE-G control strategy. It has been demonstrated by the simulation results that the load follow capability of CPR1000 reactor is greatly improved due to the elimination of boron concentration adjustments during load change transients. Full load follow capability of the reactor has been extended from the initial 80% of cycle life to more than 90% of cycle life. Thus, the boron adjustment free improvement on the MODE-G core control strategy is feasible for CPR1000, which can improve the economical performance of the plant and simplify the operational process during power maneuvers.