An essential diagnostic task in a fusion experiment is the measurement of the total neutron yield rate from which the fusion power and energy can be determined. These parameters are the main performance indicators of the success of fusion experiments, and traditionally they have been determined with neutron yield monitors such as fission chambers calibrated with activation systems. Yield monitors have been installed and successfully used in most fusion experiments including JET. Since a large fraction of the signal in these monitors is due to scattered neutrons, their yield calibration relies on neutron transport calculations, which makes it difficult to quantify the uncertainties involved. These difficulties will increase with the size of the fusion device and hence constitute a great problem in burning plasma machines such as ITER. For these reasons, a new independent method for the absolute determination of the neutron rate has been developed, based on the measurement of the direct neutron flux with a high-resolution spectrometer. The measurement of the direct neutron fluxes makes it possible to quantify the uncertainty. The new method is based on an absolute neutron flux measurement and does not need any cross-calibration with other neutron systems.