[en] An experimental program has been undertaken to confirm fast neutron spectrum calculations. The verification of calculational methods consists of comparing the measurements in a highly heterogenous media to two dimensional calculations effectuated on approach geometries. The measurements have been carried out in two testing rigs located in the center of the core and near the reflector of the Melusine Pool-type reactor. Counting techniques used for the determination of the reaction rate by beta-gamma activity measurements and activation foils are described. The following reactions have been selected: ¹⁹⁷Au(n,γ)¹⁹⁸Au, ¹¹⁵In(n,n')/sup 115m/In, ⁴⁷Ti(n,p)⁴⁷Sc, ⁵⁸Ni(n,p)⁵⁸Co, ⁵⁴Fe(n,p)⁵⁴Mn, ⁴⁶Ti(n,x)⁴⁶Sc, ⁵⁶Fe(n,p)⁵⁶Mn, ⁶³Cu(n,α)⁶⁰Co, ²⁷Al(n,α)²⁴Na, ⁹²Nb(n,2n)/sup 92m/Nb, ⁵⁸Ni(n,2n)⁵⁷Ni. A spectrum form has been elaborated from such activities by using the unfolding code SAND-II. On the other part, spectrum determinations are performed with Transport codes ANISN and DOT-III. The spectrum obtained from Unfolding and Transport Codes has been compared. Good agreement between the measured (foil activation) and calculated (SAND-II) activities was found with all detectors. Reasonable (SAND-II) solutions are observed in the two test cases