The resulting spectrum at the neutron radiography beam channel of the NUR research reactor derived by the unfolding codes i.e. GRAVEL and MAXED was found to be, unexpectedly, harder. The mean energy was around 1.4 MeV. Those results were duly confirmed following a sensitivity analysis performed using different default spectra and response functions to test the consistency of the unfolding final solution. Despite to some slight variations (around 7%) registered for the neutron fluence rate, in particular, when considering a different response functions, the main components of the final spectrum remained unchanged (19.4% of thermal, 21.6% of epithermal and 59.0% of fast neutrons) comparatively to the reference case (obtained using a MC default spectrum of NUR research reactor).