Study On Several Key Problems In Dense Fluidized Granular Target

Neutron Source has great influence on material science and nuclear energy engineering.Different requirements have been expressed for different application of Neutron Source.Accelerator Driven Sub-critical System(ADS)as one of most effective tool for handling nuclear spent fuel has to depend on the Spallation Neutron Source for the outer driven neutron,and which poses new requirements to the Spallation Neutron Source.Nuclear Fusion Energy as the cleanest and most effective energy has been seen as the final energy for the human being.Materials used in the Fusion facility need the neutron environment to test and verify,and the Accelerator Neutron Source is most promising option for the material irradiation.The Spallation target is the key component of the Spallation Neutron Source.For the requirements of ADS spallation Neutron Source and Fusion material irradiation Neutron source,Our Team had proposed a new spallation target,the Dense Fluidized Granular Target,which has great advantages in heat removal performance,hydrodynamic stability,Corrosion of structure materials and target material leakage.As a new neutron source design,the dense fluidized granular target has its own problems: granular Jamming,Beam-Target Coupling and Wall Erosion Wear.This paper proceed the physics analysis for the Jamming,coupling and wear engineering problems suffered in the dense fluidized granular target.Granular Jamming is one of most important problem in granular target design,the jamming in the coupling zone will cause the continuously deposition of beam energy in the target,which could melt the target and make serious accident.So study on granular jamming behavior in coupling area is of great importance for the safety.The big difference between granular materials and fluid like liquid and gas is what the granular materials could bear the shear force which could make granular materials act like solid,liquid and even gas.The granular target is driven by gravity and it is possible occurring jamming because of the target structure geometry and other running reason.In the paper,we presents the jamming behavior in the target using DEM.We analyze the jamming process for the different target geometry and find there is a critical value for the outlet size and angle of cone of the target geometry to avoid the jamming.The collapse scale featured a power increase style at left side of peak value and a exponential decrease at right of the peak value,which is coincide with former study.Beam-Graular Target Coupling is also a key problem in dense fluidized granular target.The granular target was proposed as one of candidate for the ADS spallation target because of its own advantages.But it's just conceptual design,validity variation is highly necessary,especially for the Beam-Target coupling design.In this paper,we present a first beam coupling experimental system and detailed the key components in the coupling experimental apparatus;the results of electron beam coupling experiment are also presented.The results indicate that the current design of target coupling part for the beam is feasible;the fluidity of granular in coupling zone is stable and almost in dense packing state which is the expecting results.The irradiation of electron beam shows that the granular temperature increase very fast in the static state with a highest temperature of 500?;And the temperature could keep at the lower value in the fluidized experiments,which indicate that the fluidized granules as the heat removal media is feasible;Besides we calculate the heat transfer in the same target geometry and heat deposit condition using DEM method,the numerical value of mass flow rate and granular volume fraction give a good agreement with the experiment;A contact heat transfer model is developed and used in the DEM,with which we modeled the beam coupling scenario,and temperature distribution in granular is obtained.Another problem could be encountered in dense fluidized granular target is the Wall Wear.The Wear condition is the decisive factor of the running life and safety of the target system and it is very important to understand the wall wear process in the granular target.In this paper,we develope a granular PIC code with a simple wear model,in which we assumed that the wear is only because of the impact of granular on the wall.We calculated the wear with different granular and wall properties(mainly characterized by impact angle weight function)for the different target geometry;The results show,for the 30° and 45° target,under the same other conditions,larger angle causes larger wear;for the same geometry,wear at cone bottom is higher than the cylinder wall;for the both type geometry,the outlet of target get higher wear.In the Accelerator Driven Advanced System,researchers proposed a new idea that separate the Uranium-rich phase and Rare-Earth phase in the spent fuel by dry process,which is very important for the future ADS nuclear system.For this purpose,we use jet classification technique to separate the powder particles with different diameter in this paper.We experimentally investigate different powder with jet classifier and the results shows that the present jet classifier could realize the separation of the powder paticle with different particle size.We also perform the multi-phase flow simulation for the classification,the results also show that the classifier used in the experiments could realize the classification function.And simulation results also show that poweder paticle density have an effect on the classification.