The D-T experimental campaign on JET (1997) represented a major step forward for neutron emission spectroscopy (NES) diagnostics thanks to the high count rate measurements obtained with the magnetic proton recoil (MPR) neutron spectrometer in high fusion yield plasmas [1]. NES measurements were made on JET DT plasmas for different heating conditions including those generating energetic deuterons either directly through NB injection, or through ICRH acceleration using the (D)T minority scheme [2]. A multiple-component model has been developed for analysis of dt neutron spectra that is based on a simplified description of fuel ion velocity distributions for different heating conditions [3,4]. The same model is used here for projections of NES spectra from JET deuterium plasmas using the dt results as input. This is done on the basis of a system of two complementary NES instruments, the TOFOR (Time of Flight - Optimized Rate) [5] and MPRu (Magnetic Proton Recoil Upgrade) spectrometers that are presently proposed for installation on JET [6]. Both spectrometers would record neutron spectra in D plasmas but for different viewing lines. TOFOR would have a "vertical" view, i.e. at an angle of 90° relative to the toroidal magnetic field. This is the same viewing line used for some of the previous dd NES measurements on JET [7]. MPRu would have a "tangential" view, i.e. horizontal (on the equatorial plane) at an angle of 47° relative to the toroidal magnetic field and opposite to the beam injection direction. This is the same viewing line used for the 1997 dt measurements using the magnetic proton recoil (MPR) spectrometer. Projections of dd neutron spectra under the assumptions above are used here for an assessment of the performance and requirements of NES as a diagnostic of energetic deuterons in JET.