Evaluation for the Effects of a Ring Plate Device to Eliminate FreeSurface Gradients in Liquid Metall Fast Breeder Reactor Vessel UsingMulti-Dimensional Thermohydraulics

Gao Ming Quing*

There is a free surface at the upper plenum in a reactor vessel of LMFBR.The free surface has spatial gradient caused by the internal coolant flow.This is a disadvantageous factor to engineering from the view point of gas entrainment into coolant. To eliminate the free surface gradients,ring plates about 20cm wide are fitted at about 1 meter under the free surface. They interfere fluid flow,and decrease the component velocity in vertical direction.To investigate the efficiency ofthe ringplates, analyses with the AQUA-VOF code were carried out.For contrast, three conditions were given:Case-1:Without ring plates.Case-2:Ring plates,fitted at 1.125m under the free surface.Case-3:Ring plates,fitted at 1.5m under the free surface. The results shown that the ring plateshave a sufficiently high potential to elminate the free surface gradients due to disperse the momentum along reactor vessel axis to radial direction.In the calculations with ring plate (Case-2 and -3),the maximum free surface heig