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