Xinyu Wei

Multi-Objective Optimization of Double-Tube Once-Through Steam Generator

This paper presents a double-tube once-through steam generator (DOTSG) consisting of the outer straight tube and the inner helical tube. The tube length and pressure drop of are important parameters in optimal design of DOTSG. For optimal design of such a system, it was modeled to estimate its tube length and pressure drop. Pitch of inner helical tube, flow distribution ratio of the primary fluid, and tube assemblage are considered as design parameters. Then fast and elitist nondominated sorting genetic algorithm-II (NSGA-II) method was applied to find the optimum values of design parameters. In the presented optimal design approach, the tube length and the total pressure drop are two objective functions. The results of optimal designs were a set of multiple optimum solutions, called “Pareto optimal solutions.” The sensitivity analysis of change in optimum tube length and pressure drop with change in design parameters of the DOTSG is also performed and the results are reported.

Prediction Study on PCI Failure of Reactor Fuel Based on a Radial Basis Function Neural Network

Pellet-clad interaction (PCI) is one of the major issues in fuel rod design and reactor core operation in water cooled reactors. The prediction of fuel rod failure by PCI is studied in this paper by the method of radial basis function neural network (RBFNN). The neural network is built through the analysis of the existing experimental data. It is concluded that it is a suitable way to reduce the calculation complexity. A self-organized RBFNN is used in our study, which can vary its structure dynamically in order to maintain the prediction accuracy. For the purpose of the appropriate network complexity and overall computational efficiency, the hidden neurons in the RBFNN can be changed online based on the neuron activity and mutual information. The presented method is tested by the experimental data from the reference, and the results demonstrate its effectiveness.

Characteristic Optimization of the Double-Tube OTSG

The OTSG (Once-Through Steam Generator) is usually used in the integral nuclear power equipment which requires smaller size and better effect of heat transfer. The OTSG with double-side heat transfer component is presented in this paper. The heat transfer component is composed of straight tube outside and helix tube inside. In the both sides of the helix tube, the flow is spirally, therefore, the heat transfer is enhanced. The smaller the pitch, the stronger the spirally flow, the effect of heat transfer is better, but the flow resistance is raised. Especially the increased flow resistance in the secondary side brings a great influence to the pump. The heat transfer region of the secondary fluid are divided into three regions: sub-cooled region, boiling region, and superheated region, the effects of heat transfer induced by the spirally flow vary in different regions. Thus, there is an optimization problem which is to find an optimization pitch of the inner helix tube with the best effect of heat transfer and the minimum flow resistance. Based on analyzing the effects of the pitch on heat transfer enhancement and flow resistance, the pitch is optimized by the constrained nonlinear optimization method.Copyright

Transient Simulations of CPR1000 Nuclear Power Plant Implementing Advanced Mechanical Shim Control System

Abstract A novel concept of implementing the advanced mechanical shim (MSHIM) control system on the improved Chinese Pressurized Water Reactor (CPR1000) is proposed. The reactor power control system of CPR1000 is redesigned to adopt the MSHIM control system while the other parameters and control systems remain unchanged. To investigate the control performance and safety margins of this reconfiguration, the CPR1000 Full-Scope Simulation Platform (CFSSP) is first developed in MATLAB/Simulink with relevant control systems and protection system considered. The CFSSP consists of the one-dimensional nodal core model, the nonequilibrium three-region pressurizer model, the lumped-parameters dynamic model of U-tube steam generator with movable boiling boundary, and the balance of plant model. Based on the CFSSP, operational transients of step and linear turbine load changes were simulated and analyzed. The simulation results agree well with physical laws and the control performance is satisfactory. All key parameters are kept within acceptable ranges with enough safety margins and thus the protection system is not triggered. Therefore, the CPR1000 nuclear power plant implementing the MSHIM control system can safely sustain the ±10% full-power (FP) step changes and ±5% FP/min linear changes of load transients. This study can serve as a reference for the MSHIM control system application to pressurized water reactors.

Helical Pitch Optimization of Double-Tube Once-Through Steam Generator

Once-Through Steam Generator (OTSG) is widely used in nuclear reactor system due to its advantages of compactness. The heat transfer performance of DOTSG is studied in this paper. In order to minimize the DOTSG volume and reduce the pressure drop of coolant, the pitch of inner helical tube is optimized with Pontryagin Maximum Principle (PMP). The double-tube is divided to three regions according to the coolant phase in secondary side. With given heat transfer load, choosing a combination function of minimum tube length and minimum pressure drop constructed with linear weighted method as objective function, the pitch optimization proceeds from superheated region to boiling region, and then to sub-cooled region in sequence, using Maximum Principle and gradient method. Then the pitch and temperature distribution along the axis is obtained respectively. The results show that the optimal pitch keeps constant along the axial direction in sub-cooled region and superheated region, but varies in boiling region. In boiling region, compared with minimum tube length optimization, the optimal tube length is 6.4% longer while the pressure drop is 36.3% smaller; and compared with minimum pressure drop optimization, the optimal pressure drop is 29.1% larger while the optimal tube length is 4.6% smaller. With the optimal pitch, the temperature distribution is in agreement with the general physic rules, which proves the correctness and the feasibility of the Maximum Principle method used for the structural optimization of DOTSG in this paper.Copyright