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In this research, axially variable strength control rods (AVSCRs) are developed to solve the problems related to the axial power distribution of a reactor during power maneuvering of pressurized water reactors (PWRs). The control rods are classified into two types: multipurpose control rods and regulating control rods. Two multipurpose control rod...
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Context 1
... For the first index, the desirability function is given as Fig. 7(a) so that the first index may be greater than the value of the upper AO boundary and the distance from the upper AO boundary may be longer than the width between the upper and lower AO boundary. The desirability function for the second index is given as Fig. 7(b) in order to force the second index toward a position higher than the lower ...
Context 2
... For the first index, the desirability function is given as Fig. 7(a) so that the first index may be greater than the value of the upper AO boundary and the distance from the upper AO boundary may be longer than the width between the upper and lower AO boundary. The desirability function for the second index is given as Fig. 7(b) in order to force the second index toward a position higher than the lower AO boundary and, simul- taneously, to make the distance between the second index and the lower AO boundary be one-third of the breadth be- tween the two AO ...
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Citations
The Mechanical Shim (MSHIM) core control strategy makes use of two independently controlled rod groups to provide fine control of both core reactivity and axial power distribution. This paper presents a reactor core fast simulation program (RCFSP) for AP1000 using MATLAB/SIMULINK. A nodal core model including xenon iodine dynamics is used to describe the core thermal power transient with the two group neutron diffusion equation for neutron kinetics modeling and an integral method for thermal-hydraulic calculation. Two closed loop rod controllers with implementation of the MSHIM core control strategy are developed to modulate the insertion of control rods. Based on the developed RCFSP, the MSHIM load follow operations with the original and revised MSHIM control strategies and two typical MSHIM load regulation operations with ten-percent step load change and five-percent per minute ramp load change are simulated. Results of these MSHIM operations demonstrate that the core reactivity and axial power distribution can be well-controlled via automatic rod control only. It has also been demonstrated that the MSHIM capabilities provided by the original MSHIM strategy are not diminished by the revised one. Moreover, the M-bank insertion for the original strategy is much deeper than that for the revised one. Thus, the power distribution perturbations associate with the M-bank movement for the revised strategy are not as pronounced as those for the original one during load change transients, which helps to alleviated peaking factor concerns associated with the control rod insertion. In view of its accuracy, simplicity and fast computation speed, the developed RCFSP can be used for dynamic simulations and control studies of the AP1000 reactor with application of MSHIM control strategy. With the adoption of modular programming techniques, the RCFSP code can be easily modified and applied to other pressurized water nuclear reactors that employs separate, independent control rod banks for respectively controlling core reactivity and axial offset within corresponding deadbands.
This paper presents mathematical modeling of dynamic phenomena in large pressurized water reactors to study load-follow capability. One of the main reactor types in China's national nuclear development, CPR1000, uses a mode G control method, with G banks, N banks, R banks, and soluble boron to adjust reactor power changes and the axial power shape. In this paper, a new control mode is adopted that can follow the daily variation of power demand without changing the boron concentration. The control banks are regrouped to realize reactivity/temperature control by M banks and axial offset control by an AO bank. A two-node dynamic core model is constructed, taking into account the coupling coefficient and the mutual influence. The transient parameters are obtained by steady-state calculation of a single channel using the original design and operation parameters of CPR1000. Then, to adopt a control mode without soluble boron adjustment, the optimal control implementation is connected to the core simulation platform. Simulation results show that this optimal control policy can provide the capability for the CPR1000 to follow a daily load curve.
As the nuclear power percentage increases gradually, it brings more attention to advanced reactor designs, performance and flexibility, including enhanced load follow capability. CPR1000, the main reactor type of China national development, employs a new control mode to perform the load follow operation in this paper, which is different from the traditional mode in current generation plants and replaces the frequent manipulation of soluble boron concentration during daily maneuvers with control banks movements, thereby reducing the amount of waste water generated during the cycle and greatly simplifying the design of the chemical volume and control system. A dynamic multiple model of the ten-node core is built, considering the neutron coupling effect and mutual influence from the neighboring nodes. The control banks are regrouped to realize the reactivity/temperature control by mechanical automatic control banks (M banks) and the power distribution control by axial offset control banks (AO bank). Simulation results show that so long as the optimum control parameters are selected, this boron adjustment free control method can provide the capability till the end of life for CPR1000 reactor core to follow a daily load curve. Crown Copyright
