Experimental Study on Gas Entrainment Due to Nonstationary Vortex in a Sodium Cooled Fast Reactor—Comparison of Onset Conditions Between Sodium and Water

Abstract

An innovative sodium cooled fast reactor has been investigated as part of the fast reactor cycle technology development project. In the reactor, a compact reactor vessel (R/V) with increased sodium flow velocity was designed to reduce the construction cost. One of the thermal hydraulic problems in this design is gas entrainment at the free surface in the R/V. In most of past studies, water experiments were performed to investigate the gas entrainment in the reactor. It is necessary to evaluate an influence of fluid physical property on the gas entrainment phenomena. In this study, sodium experiments were carried out to clarify the onset criteria of the gas entrainment due to a free surface vortex. Water experiments using a test section in which geometry is the same as that in the sodium tests were also performed. The gas entrainment in water slightly tended to take place in comparison with that in sodium under low velocity conditions. Overall, the onset condition map on the lateral and downward flow velocities in the sodium and water experiments were in good agreement.

Experimental study of gas entrainment from surface swirl

“…The Figure 8 compares the present results with the ones obtained by Kimura et al, 2009 in the case of experiments with a flat plate. The results are close.…”

“…The present experimental set up is relatively close to that of Ezure et al, 2008 andKimura et al, 2009. One of originality of this work is the possibility to introduce obstacles.…”

“…Then, to study intermittent gas entrainment, new analytical experimental facilities have been designed so as to isolate the key mechanism of turbulent shear flows combined with flow suction, e.g. Ezure et al, 2011, Kimura et al, 2009and Cristofano et al, 2014. These new design experiments are based on open channel flows.…”

“…inlet velocity, outlet velocity and suction velocity. Moreover, Kimura et al, 2009 have investigated both sodium and water fluids using the same test section to demonstrate that water experiments simulated well the onset conditions of gas entrainment in sodium. Gas entrainment experiments have also been performed in liquid metal, e.g.…”

“…The present study is an experimental investigation of the gas entrainment occurrence in water. The geometry of the experimental channel is close to that of Ezure et al, 2008 andKimura et al, 2009. The main difference lies in the inlet conditions. To trigger different flow regimes, obstacles of various shapes are added (or not) at the end of the flat plate defining the inlet conditions.…”