Electromagnetic flowmeters for fast reactors

This paper is in four parts. Section 1 explains the theory of the induced-voltage electromagnetic flowmeter and then considers various types which have been used. For the primary circuit of fast reactors both flow-through type and probe type have been proposed, although obtaining magnets which operate satisfactorily at high temperatures has been a problem. In the secondary circuit the high magnetic Reynolds numbers cause the field to be swept out of the magnet gap and this has led to the use of the long saddle-coil flowmeter.In Section 2 flux-distortion flowmeters are described. These have been proposed mainly for monitoring the primary circuit flow and again both flow-through and probe types have been tested. Sections 3 and 4 continue the discussion of the flux-distortion flowmeter by introducing two methods of analysing its performance. The first is a finite difference method which solves the non-linear problem by using a time marching method. It is shown that a linear approximation is adequate for the likely levels of flow encountered in the fast reactor and consequently two linearised solutions are used. The first method is a finite difference one and allows the instantaneous response of a step change in velocity to be observed as well as the effect of bubbles.In Part 4 the second linearized method uses current rings to divide up the conducting material. By considering the interaction of all the rings, it is possible to obtain the current distribution and hence the magnetic field. In conclusion it is suggested that further development would be useful of the devices which are most suited to the liquid metal fast breeder reactor.