Sodium Tests of Head-Flow Characteristics for Prototype Annular Electromagnetic Flow Coupler

A prototype annular electromagnetic flow coupler was tested with high temperature sodium and it worked successfully, verifying the operational principle. The pump head-flow characteristics of the coupler were first clarified from an analysis of its equivalent electric circuit. The pump head and the generator pressure drop decrease linearly with the pump flow rate under the conditions of constant generator flow rate and external magnetic flux density. The gradients of the linear changes are given by ratios of equivalent resistances in the electrical analog, and are independent of the generator flow rate, if the magnetic flux density is kept constant. Sodium tests of the prototype confirmed the above results when the Hartmann number of the test conditions is larger than 170. Both ratios of the differential pressures and the volumetric flow rate between pump and generator ducts exceed 50% while the wall loss of around 40% appears at peak efficiency due to the lack of electrical insulation and the relatively large wall thickness. The peak efficiency of the prototype coupler decreases with the sodium temperature at the rate of (2.33±0.21)x10^?2 %/°C from 200 to 400°C and increases with the external magnetic flux density at 5.8±0.1 %/T from 0.36 to 0.60T.     

Development of Analytical Method for DC Electromagnetic Flow Coupler Including End Effects

To develop an analytical method for a DC electromagnetic flow coupler, an electric circuit analog has been considered. The adopted analog consists of an infinite series of the lumped parameter circuit of the flow coupler cross section and allows an analysis of end effects which appear outside the inlet and outlet of the flow ducts. The ordinary differential equation of the second order was derived for the current distributions from the circuit equations of the present analog. The present method predicted very well the current distributions of the analytical solutions obtained by Birtzvalk et al. for the coupler with infinite width and length.

Further, the overall efficiency of the typical flow coupler evaluated by the present method gave a similar dependence on the flow ratio to that of Hughes & Alexion, although differences appeared in the results of the pressure rise and drop in the coupler's two ducts. From the current distributions obtained, these differences were attributed to the electrical coupling of the pump and the generator ducts in the fringing magnetic field which was considered by the present method, but not by Hughes & Alexion. Finally, the current flow patterns are given with an improved distribution of the external magnetic field including the wall effect.     

Development of Reflux Vapor Trap for Sodium Cooled Fast Breeder Reactor, (I)

With the view of obtaining basic data required for designing durable reflux vapor traps of high performance for use in sodium-cooled FBR's, experiments were conducted to (a) select a suitable packing, and (b) to examine the effect brought on trapping performance by changing the gas flow rate, packing material, packing density and trap outlet temperature. The results indicated that:

(1) As trap packing, plane weave stainless steel mesh proved to ensure lower pressure drop through trap.

(2) Using the plane weave mesh packing, and with the trap outlet temperature kept at 130°C, the reflux vapor trap efficiency was found to exceed 99.6% in the range of vapor trap gas velocity below 1.3 m/s, and packing density below 0.07 g/cc. The efficiency decreased at outlet temperatures above 130°C.     

A Numerical Study on Faraday-Type Electromagnetic Flowmeter in Liquid Metal System, (I)

To predict the three-dimensional steady-state structure of electromagnetic phenomena in the Faraday-type Electromagnetic Flowmeter (EMF), a numerical simulation method using the Galerkin finite element method has been adopted and formatted as a computer code, FALCON.

As the induction equation for the induced magnetic field that is important in a liquid metal system, we have presented B-φ formulation for the induced magnetic field and the electric potential field and A-φ formulation for the vector potential field and the electric potential field, and compared the computational efficiency of both formulations. We have selected the B-φ formulation. The computer simulation of the EMF of the MONJU secondary cooling system has been performed and the calculations have shown a good agreement with the calibration test data. We have investigated qualitatively how far the influence of the end effect extends and the characteristics of the voltage response.

Overall, this study has indicated that the present method can be applied to the estimation of the characteristics of an EMF and the design of a new EMF.