It has been decided that ITER will be operated from day one withWdivertor and Be first wall. In such a wall configuration, one of the most significant issues is impact of W accumulation on plasma fusion performance. In order to investigate the impact, in JET, experiments with ITER-like wall configuration have been performed with an upgraded high-resolution X-Ray crystal spectrometer. This X-ray spectrometer originally monitored Ni concentration, and has now also started monitoringWconcentration since a second crystal and detector were installed. Coincidentally, Mo spectral lines are found in the same wavelength range as the W spectral lines. Hence, from the measured absolute intensities of W and Mo spectral lines, it is possible to evaluate the W and Mo concentrations simultaneously. The present report provides the first output of W and Mo concentrations from the upgraded spectrometer.