Model Experiments And Numerical Investigations On ADS Windowless Spallation Targets

Accelerator driven subcritical transmutation system (ADS) has been considered one of the most promising systems in the worldwide to fundamentally transmute long life nuclear wastes. ADS is composed by intense-beam proton accelerator, spallation target and subcritical core. The spallation target provides exterior high energy neutron source for the subcritical core by spallation reaction of bombardment of high energy proton and heavy metal. As the coupling component between accelerator and subcritical core, the spallation target is of crucial importance to the operation safety of the whole system. Hence, the spallation target is one of the most important part in ADS corresponding researches.In the present thesis, the studies are based on the windowless spallation target which is a promising design of spallation target. Model experiments and numerical investigations are conducted under two main questions which are the maintenance of the integrality and stability of the free surface, and the flow field of spallation area.The thesis consists of following parts:In the first part, the control equation of free surface flow in windowless spallation target is analyzed. Five dimensionless numbers are obtained based on the dimensionless control equation. Scaling analysis of model experiment is conducted, which confirms the feasibility of model experiment.In the second part, the preliminary design of model windowless spallation target, the construction of theoretical investigation loop and the model experiments are conducted. In the experiments, the normal camera, the high speed camera and the planar laser induced fluorescence method are applied, in order to perform flow field visualization. The visualized experiments obtain achievements in free surface control method, free surface behavior and flow field inside spallation area.In the third part, two and three dimensional numerical simulations are conducted based on the preliminary design of model windowless target. Different turbulence models are applied together with VOF method in prediction of free surface flow in model windowless spallation target. The applicability of different turbulence models are compared. A preliminarily suitable numerical method is proposed.In the fourth part, numerical optimization is performed based on the preliminary design of model windowless spallation target. By two and three dimensional simulation of twelve design candidates, the optimal design is found out.In the fifth part, the improved design of model windowless spallation target, the construction of multipurpose hydraulic research loop and the model experiments are conducted. The experiments obtain achievements in free surface behavior, free surface width, vortex stagnation length, pressure distribution along conical channel and pressure variation of rectangular chamber at the exit of conical channel.In the sixth part, 360 degree full scale three dimensional simulations are conducted based on improved model windowless spallation target. By the comparison of numerical and experimental results in free surface behavior, free surface width, vortex stagnation length, pressure distribution along conical channel and pressure variation of rectangular chamber at the exit of conical channel, the applicability of the numerical method proposed before for free surface flow in model windowless target is further verified.The model experiments and numerical investigations in this thesis are focused on the forming mechanism and variation law of free surface and flow field in spallation area, in order to preliminarily establish an experimental and numerical data base which will support the following studies of windowless target.