[en] The fluctuations of sodium flow rate due to water injected into the sodium were measured on an experimental sodium loop using two electromagnetic flowmeters. A leak of water into sodium of 0.01 g/s was reliably detected above the level of the noise signal of the flowmeter. The ratio of the signal of the flowmeter that was placed at a greater distance from the point of leak to the signal of the flowmeter nearer to the point of leak changed with the flow rate of sodium and was 2 to 6. The dominant frequency varied in dependence on the sodium flow rate from 1.5 to 8.8 Hz. The application of the results to the ZEUS measuring system shows that the system may well be used for measuring leaks of water into sodium in the order of 10^-1 g/s in a steam generator of the modular type. The results obtained allow the assumption that the electromagnetic flowmeter will be able to operate as a sensor for detecting water leaks into sodium with a sensitivity as high as 10^-2 g/s. (J.B.)