| With the development of society, demand in energy is growing for people. As a clean, safe and economic energy, nuclear power receives wide attention around the world. However, the vigorous development of nuclear industry, not only brings huge benefits to human society, but also lets people face the problem of how to properly handle nuclear waste. Whether high radioactive waste produced by nuclear power plants can be properly treated or not, nuclear resources can be fully used and nuclear reactor can operate safely and effectively or not will restrict the progress of nuclear power. Therefore, the research and realization of sustainable development path of nuclear powe is very necessary. In order to solve these problems, the concept of accelerator driven sub-critical system(ADS) has been put forward in the late 20 th century. It is an organic whole that collects energy production and nuclear waste transmutation, and it can improve the utilization ratio of nuclear fuel. It is an innovative route which can realize the sustainable development of nuclear fission.Neutron spallation target is an important component which couples the accelerator and the critical system in ADS system, whose neutronics properties and the thermal hydraulic characteristics is the key technical problems of ADS system. For the spallation target of ADS system, international society put forward a variety of design scheme. This article mainly focuses on the most potential liquid window spallation target and liquid windowless spallation target. In the paper, the Monte Carlo MCNPX program and computational fluid dynamics CFX procedure can be used to carry out the neutronics and thermal hydraulics numerical simulation analysis for the two kinds of targets.The front part of this paper carries out the numerical simulation based on the European PDS-XADS liquid window target model. By adopting MCNPX program, the spallation reaction of protons and target nucleus, neutron transport process in window target have been calculated for the study of neutron flux spatial distribution on target region. Results show that it has the characteristics of firstly increasing then decreasing. Neutrons generated in the spallation reaction are mainly fast neutron, whose main energy range is 0.4-2Me V. Heat deposition density in the target region gradually decreases with the increasing of radial radius and axial depth from the center of the target window. In the target window it appears oval attenuation with the increasing of angle θ. In this part, CFX program is adopted to research the flow pattern of liquid lead bismuth alloy and heat transport process within the window spallation target. In order to obtain reliable numerical simulation results, characteristics of liquid lead bismuth alloy have been studied and different turbulence models provided by CFX are evaluated. SST model is considered to be an appropriate turbulence model for the liquid window target. Heat dissipation characteristics of the target window at different working conditions are discussed. Target window can be cooled better with the increasing of the coolant inlet velocity, temperature and coolant inlet turbulence intensity. Results of heat transfer characteristics of window target at different flow patterns shows that the coolant upward flow pattern is the proper flow pattern for liquid window target. Heat dissipation of the target window is a key point in the study. In order to improve the cooling capabilities of the target window, optimization design of the window target structure is carried out. The inner surface temperature within the target window gradually reduces along with the decresing of the target window thickness. Target window shape has certain influence on heat dissipation, the ellipsoidal target window has better dissipation effect whose macroaxis is in the horizontal direction. Different target geometry has large effect on heat dissipation. After introducing of guide plate and spherical protrusions into the window target, flow field becomes more complicated in the target zone and heat capacity of coolant is improved to a certain extent.Then CFX program is adopted to conduct numerical analysis based on Europe’s newest MYRRHA fluid windowless spallation target model. By using standard k-ε turbulence model, Cavitation model and VOF interface capture method, liquid lead bismuth alloy and two phase flow containing the flow characteristics of Cavitation and morphological characteristics of target coolant free interface are studied. For liquid windowless target, the stability formation of the free interface is a key problem. So the freedom of the dynamic behaviors of the interface under different working conditions and control method are analyst. It is concluded that the target region form two stable free interface when fluid outlet pressure is in the range of 10000-40000 Pa and fluid entrance velocity is in the range of 0.5-1.2 m/s. The flow field near the free interface structure is complex. The vortex region appears, and the disorders in the vortex flow pattern causes the free interface fluctuations. Due to complexity of flow field and phase distribution, only neutronics features of the windowless target feature after forming stable free interface are studied. By using MCNPX program, the spatial distribution of neutron flux is caculated, neutron energy spectrum distribution and energy deposition within the windowless target are researched. Thermal deposition in the target as a heat source is input to CFX program to study the heat transfer characteristics of windowless target. Results show that heat gradually spreads in target area when heat source continuously adding, at the same time, the coolant flow takes away the heat in the target zone. |
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