Experimental and calculational study of small sample reactivity in critical assemblies with different heterogeneous structure

The quality of introducing heterogeneous and bilinear resonance corrections to calculations of central reactivity coefficients of standard materials possessing well-known cross sections is investigated using the critical assemblies -BN-600 type reactor models - with different degree of the fuel heterogeneity. For this purpose necessary measurements are performed. Heterogeneous and bilinear resonance corrections are obtained by two methods: on the base of integral-transport approximation and a more correct approximation, developed by Heinzelmann B., accounting in particular, the dependence of neutron flux and validity on the direction of their scattering. It is shown that the reactivity method is a reliable instrument of testing the accuracy of calculating the balance of fissions and captures in fissionable elements. 10 refs.; 1 fig.; 6 tabs