A new method of exponential experiment was developed for a cylindrical subcritical assembly of hexagonal lattices. In this method, higher harmonics are excited by an eccentric point neutron source and are divided into 4 groups. Then, from the attenuation coefficients of the dominant modes in each group, the material buckling and the effective core radius (or the reflector saving) of the assembly are determined experimentally.
Experimental results show that this method is useful for cylindrical assemblies, and the bare homogeneous approximation is rather good even for a subcritical assembly with reflector.
