Natalia B. Janeva

Institute for Nuclear Research and Nuclear Energy
Sofia, Bulgaria

Aleksandre A. Lukyanov

Institute for Atomic Energetics, Obninsk, USSR

The basic assumptions of the statistical model are well determined, but there exist some difficulties in the practical calculations of the resonance cross sections. An analytical method of resonance cross sections averaging with account of interference and level width fluctuations at an arbitrary ratio level width to mean spacing has been developed. The expression for radiative capture cross section was obtained under certain approximations as a twofold integral which has to be calculated numerically. The appropriate computer COD was prepared. The case when radiative capture is the unique concurrent of the elastic scattering has been investigated and the values obtained for radiative cross section are in a good agreement with the Monte Carlo results. Further improvements of this method consider the two- and more channels case and the practical scheme for calculation of the transmission exp(-nσ) and other cross section functionals as group constants for reactor calculations. The careful analysis demonstrates the advantages of this method in precision and conversion.

KEYWORDS: cross section, neutron resonance, level interference, analytical method