Experimental And Numerical Investigations On ADS Liquid Windowless Spallation Targets

As the coupling component of accelerator and subcritical core in theaccelerator driven subcritical transmutation system (ADS), the spallationtarget provides exterior high energy neutron source for the subcritical coreby spallation reaction of bombardment of high energy proton and heavymetal. Hence, the spallation target is one of the essential parts in the ADS.In order to develop the free surface manipulation technology and toinvestigate flow field behavior in the windowless spallation target scaledexperiments and corresponding numerical analysis are carried out. Designof windowless spallation target is optimized. The scaled experiments areconducted to investigate the flow in the target. The free surface motionand the flow structure are visualized with the normal camera and thehigh-speed camera combined with the planar laser induced fluorescencemethod. Experimental results show that the free surface motion issignificantly affected by the inlet flow rate and outlet pressure. The lengthof free surface decreases in the second order with the inlet flow rate, whileit decreases linearly with the outlet pressure. Different turbulence modelsare applied together with the VOF method to predict free surface motionand flow field. The numerical results show that the large eddy simulation(LES) can predict the transient free surface motion better than otherutilized models. Numerical calculation of liquid lead-bismuth eutectic(LBE) windowless target is conducted. Free surface motion and heattransport capability of the LBE target are investigated. The simulationresults indicate that the stagnation vortex zone under the free surface in the windowless target is very unfavorable for heat transport. A new designof up-rotating windowless target is proposed in order to eliminate thevortex stagnation zone. A turbine installed at the lower part of the targetcan generate swirling flow around the axial of the target pipe. Preliminaryresults of numerical analysis show that fluid will leave the target with aconcave surface due to the centrifugal force produced by the tangentialvelocity. There is no vortex region under free surface and the free surfaceis more stable in the new design. The experiments and numericalinvestigations of model windowless spallation target in this thesis arefocused on the forming mechanism and variation discipline of free surfaceand flow field in spallation area. A new design of the windowless target isproposed which is a meaningful trial for the following studies ofwindowless target.