[en] Techniques used to evaluate the experiments on reactor or critical assembly criticality disturbances when inserting samples there are presented consistently. It is shown that experimental results evaluated using such techniques may be compared with calculational results using the first-order perturbation theory

No abstract available

No abstract available

No abstract available

No abstract available

No abstract available

[en] Heterogeneous resonance effects in fast critical assemblies are calculated within the framework of the perturbation theory in the integral transport formulation. The equivalence theorem is shown to be valid for the neutron importance function. The ²³⁹Pu/²³⁵U, ¹⁰B/²³⁵U and ¹²C/²³⁵U ratios of central reactivity coefficients have been computered with the account of corrections due to a bilinear averaging relative to the routine averaging over neutron flux. As the results show the heterogeneous effects of the critical assemblies structure on the reactivity coefficient ratios are well described by the calculus

[en] The results of measuring the ratio of the mean capture cross section for ²³⁷ Np to the mean fission cross section for ²³⁹ Pu in two fast critical assemblies are discussed. Two activation methods, namely, the relative method of normalisation to ²³⁷ Np and ²³⁹ Pu thermal cross sections and absolute method of determining the absolute rates of capture in ²³⁷ Np and fission in ²³⁹ Pu are applied in the experiments. The results of measurements are compared with calculations and the data obtained by the reactivity method. The conclusion is made that the reactivity method being hard in interpretation gives nowadays the results which are in good agreement with the discussed results of direct integral verification of errors in ²³⁷ Np capture cross sections within the specified accuracy of ± 4%

[en] For calculations of criticality perturbations it is necessary to use group constants which take into account not only the peculiarities of the intra-group flux but also those of the behaviour of the adjoint flux. A new method is proposed for obtaining bilinear-averaged constants of this type on the basis of the resonance characteristics of the importance function and the difference between the value of neutron importance at the group boundary and the group-averaged value (the bsup(+j) factor). A number of calculations are made for the ratios of reactivity coefficients in the BFS assemblies. Values have been obtained for the difference between the results of calculation with bilinear-averaged constants and those averaged conventionally (over flux). In many cases, this difference exceeds the experimental error. (author)

No abstract available