The default spectrum used herein to initiate the iterative calculation in both unfolding codes GRAVEL and MAXED, is a Monte Carlo neutron spectrum obtained in simulating the NUR core reactor
by MCNP5 (2003), with a 10 bins energy structure to cover the whole interval of energy of interest (103 eV to nearly 20 MeV). This spectrum was obtained at the entrance of the collimator, which is located at the peripheral position of the NUR core reactor