[en] We analyzed and simulated the throttling orifice RCV001/002/003DI of M310 NPP's RCV System. The defect in the original design of M310 has been found and optimized by using the step-orifice to reduce vibration and noise. This design change has been applied and verified by several NPPs which are either under construction or operation. (authors)

[en] From the perspective of system, the Flowmaster model of the reactor coolant system is combined with the CFD model of the surge line. The transient simulation of the reactor coolant system is to obtain the fluctuation of temperature and pressure at the boundary of the surge line with time, and then the results serve as the input conditions to the surge line CFD model, the flow, temperature and pressure in the surge line are calculated with the distribution of space and time. This kind of combined simulation is used to find the reason of temperature fluctuation of surge line, to explore its law and to provide the basis for the design of nuclear pipeline. (author)

[en] By analysis of the actual operating characteristics of pressurizer in pressurized water reactor (PWR) nuclear power plant and based on some reasonable simplification and basic assumptions, the quality and energy conservation equations about pressurizer' s steam zone and the liquid zone are set up. The purpose of this paper is to build a pressurizer model of two imbalance districts. Water level and pressure control system of pressurizer is formed though model encapsulation. Dynamic simulation curves of main parameters are also shown. At last, comparisons between the theoretical analysis and simulation results show that the pressurizer model of two imbalance districts is reasonable. (authors)

[en] Based on the different type throttling orifices in nuclear power plant, the calculating method for pressure loss was studied. Furthermore, a calculating code for pressure loss was developed. Using this calculating code, the pressure loss of the throttling orifices can be calculated quickly and accurately, and that is significant for selecting orifice and carrying out system test. (authors)

[en] Based on the different type of the throttling orifices in nuclear power plant, a suit of method has been suggested to calculate the pressure loss of the orifices. Furthermore, a computer program for calculating these orifices is completed. Using this program, the pressure loss of the orifices can be calculated fast and exactly, and that is significant for selecting orifice model and system test. (authors)

[en] It is challenging and interesting to establish a precise steam pressure in separator dynamic model of a once-through power plant unit in order to meet large scale load demands from the power grid and the needs of the engineering research. Steam pressure reveals the energy balance of boiler and turbine. This study proposes to establish such a steam pressure in separator mathematical model of a once-through boiler-turbine unit under dry operating conditions. Then the BP neural network model and the RBF neural network model were used to predict the steam pressure in separator, combined with running data. Moreover, in order to improve the performance of the network, the exhaustive method is used to optimize the parameters of the RBF network. After this, to further enhance model performance, the dynamic mathematical model was extended to be the one with different sets of parameters under different load ranges. More importantly, the dynamic model captures the essential dynamic characteristics of the unit. Therefore, the model can be feasible and applicable for simulation analysis and testing control algorithms. (paper)

[en] Fangjiashan nuclear power plant is modeled, by using MAAP4 code. Base on this model, the small LOCA accident is calculated, which will cause the worst consequence. The response of the plant and relevant severe accident phenomena are obtained. The phenomena of DCH (direct containment heat) happened during the accident, containment failure and release of the fission production are analyzed. Then, according to the related severe accident management and characteristic of this accident, the strategy of mitigating the accident consequence is studied and calculated. The result indicated that the mitigation action is very efficient. Therefore, a feasible strategy of mitigating the severe accident consequence is provided for the three-loop plant like Fangjiashan in China. (authors)

[en] As a kind of clean and renewable energy, wind energy is attracting more and more attention from all over the world. But the development of wind power is always hindered by the failure of downtime. The gearbox of wind power unit is one of the components with the highest failure rate in the whole wind turbine. Therefore, it is of great significance to study the fault diagnosis of gearbox in wind turbine. This paper first introduces the mathematical principle of wavelet analysis, and takes Matlab as an experimental platform to analyze and deal with the pitting fault data of a fan gearbox, and identifies the fault frequency by wavelet packet energy method, and diagnoses the type of failure. Finally, the experimental results are compared with other methods to deal with the data. Through the research in this paper, we can see that the data processing method based on wavelet analysis is simple and practical, especially in the engineering field represented by gearbox fault diagnosis. (paper)

[en] The passive containment cooling system may serve to remove the heat from the containment after some accidents by means of natural circulation. However, it may also suffer from the two-phase flow instability during the operation. The mathematical model and constitutive relationships were set up for an open natural circulation system. The conservation equations were linearized by using the perturbation method. The transfer function of the mass flow rate of the system was derived in terms of the enthalpy change of the heating section through Laplace transformation. Based on the Nyquist stability criterion, the influence of thermal-hydraulic parameters on the stability of the natural circulation system was analyzed. The results show that the flow stability of the system is mainly dominated by the relationship between the void fraction and the quality of the two-phase flow. In the studied range, with the increase of the quality, the sensitivity of the void fraction to the quality is weakened, and the system tends to be stable. (authors)

[en] Containment is the last barrier to prevent radioactive material releasing to the environment after accident, the effective containment cooling can avoid containment overpressure failure accident due to the large mass and energy that released into the containment. With the improvement of regulatory requirements and the development of technology, some passive containment cooling system designs are proposed. The aim of this paper is to summary the design and research results of domestic and foreign passive containment cooling systems. Analysis and comparison of advantages and disadvantages of each scheme are performed. Two suitable passive cooling solutions for steel and double-layer concrete containment are proposed respectively, and it can provide some references for passive containment cooling system of the third generation nuclear power plant in China's independent design. (authors)