[en] A knowledge of diffusion mechanisms and the values of associated coefficients is essential for controlling changes in heated materials and alloys with time. In contrast to solids, where a large literature is available, little research has been done on diffusion coefficients in liquid metals. This is due to experimental difficulties: compatibility of the liquid with the measurement cell, high vapor pressures, convective processes. A significant improvement was achieved by the use of the shear cell, which puts the elements into contact with each other at the selected working temperature and isolates the different sections at the end of the diffusion time. This method employs radioactive sources, generally as tracers, which need counting after cooling. Each alloy composition requires a test, increasing the number of experiments needed. To eliminate the use of tracers, we propose a method based on the shear cell procedure for putting the liquids into contact, which allows determination of the interdiffusion coefficient in a liquid alloy in a single experiment from the measurement of a mass spectrometer signal. The experimental principle is shown schematically. Iron is in the upper ceramic cell and uranium in the lower. After stabilizing the temperature and adjusting the detected signal of the spectrometer to the mass of iron, the iron and uranium are brought into contact by rotating the upper cell from outside the vacuum chamber. The diffusion experiment consists in recording the decrease over time of the signal received by the spectrometer. During the diffusion period, the upper surface of the iron is enriched in uranium, thereby decreasing the thermodynamic activity of the iron and the detected signal. (authors)