In the fast reactor BOR-60 there have been conducted experimental and calculational investigations of neutron energy spectrum in a cell of the blanket external row assemblies. Two experiments have been carried out. In the first experiment the cell was surrounded by regular blanket assemblies, and in the second one it was surrounded by assemblies containing zirconium hydride (ZrH₂). In the chosen cell extended sets of activation detectors were irradiated. Measured reaction rates for various thermal and fast neutron reactions were used to adjust the neutron spectra. For this purpose the STAYNL computer code was used. In each case, calculated neutron spectra were used as a priori. Calculations of neutron spectra were carried out in the two-dimensional hexagonal geometry with the NF-6 code and in the three-dimensional hexagonal geometry with the JARFR code with the ABBN cross section library. The results of the presented comparisons for two configurations are discussed and the results of the investigation of the accumulation of ¹⁵³Gd from natural europium in the softened neutron spectrum are adduced.