Henrik Sjöstrand, E. Andersson Sundén, S. Conroy, G. Ericsson, M. Gatu Johnson, L. Giacomelli, C. Hellesen, A. Hjalmarsson, J. Källne, E. Ronchi, M. Weiszflog and JET EFDA contributors A central task for fusion plasma diagnostics is to measure the 2.5 and 14MeV neutron emission rate in order to determine the fusion power. A new method for determining the neutron yield has been developed at JET. It makes use of the magnetic proton recoil neutron spectrometer and a neutron camera and provides the neutron yield with small systematic errors. At ITER a similar system could operate if a high-resolution, high-performance neutron spectrometer similar to the MPR was installed. In this paper, we present how such system could be implemented and how well it would perform under different assumption of plasma scenarios and diagnostic capabilities. It is found that the systematic uncertainty for using such a system as an absolute calibration reference is as low as 3% and hence it would be an excellent candidate for the calibration of neutron monitors such as fission chambers. It is also shown that the system could provide a 1 ms time resolved estimation of the neutron rate with a total uncertainty of 5%.