RECONSTRUCTION OF THE MISSED URANIUM-235 RESONANCES IN ENERGY RANGE 500 TO 2250 eV

Authors & Affiliations

Nikolaev M.N., Pavlova O.N.
Russian Federation State Scientific Centre — A.I. Leipunsky Institute of Physics and Power Engineering, Obninsk, Russia

Abstract

Substantial lack of resonances with small neutron widths in the energy range 500 to 2250 eV has been revealed at the statistical analysis of resolved resonances parameters taken from everywhere used evaluation of L. Leal et al.

The set of resolved s-resonances has been supplied by fictitious resonances which simulate the missed resonances in this energy range. These resonances were added so that full set of the resonances for each of two possible spin satisfied the following statistical properties: (a) distribution of the resulted neutron widths should correspond to Porter-Thomas distribution; (b) distribution of distances between resonances should correspond to Wigner distribution. Also average capture widths and zero fission widths were attributed to all fictitious resonances.

Multigroup constant set was obtained by using the produced data file with really resolved and fictitious resonances and then influence of the introduced changes in the evaluated data on some critical assembly integral characteristics was estimated.

Keywords
resolved resonances parameters, resonances with small neutron widths, spin, resulted neutron widths, zero fission widths, multigroup constant

Article Text (in Russian, PDF)

References

UDC 539.17

Problems of Atomic Science and Technology. Series: Nuclear Constants", issue 1-2, 2006