Work performed on ENDF format proposal for unresolved resonance region

Some additional work has been performed on ENDF format proposal for unresolved resonance region. The scientific background for this is the statistical model of the characteristic function of R-matrix elements distribution and its realization by the code HARFOR. This approach is unique that offer the possibility of calculation the self-shielding factors in the unresolved region directly from average resonance parameters. The Characteristic function method and code HARFOR have been used for calculations of average cross sections and self-shielding factors and tested against the same values calculated by the NJOY Nuclear Data Processing System used for converting evaluated nuclear data in the ENDF format into libraries useful for applications. The experimental and calculated self shielding factors for neutron capture using HARFOR for a dilution cross section σ0 = 1 barn were compared. We included the calculations using the resonance parameters from ENDF 6.8 and from the evaluation of the most recent data of Geel for the 232Th Cross-Sections between 4 and 140 keV. Calculated self-shielding factors for 232Th for diluted cross-section σ0 =1,100 barn with the average resonance parameters from ENDF 6.8 in energy range (4-50) keV using NJOY and HARFOR were compared too. The new experimental data for 232Th cross sections in the resolved and unresolved resonance region and the practical interest to the precision of these, require detailed analysis of the data on the base of the existing schemes and methods of evaluation. The methodology of R-matrix formalism accepted in code SAMMY has been used with some development for unresolved resonance region for effective accounting of the resonance parameters fluctuations. The result of cross sections averaging, of 232Th in particular, over the large energy interval containing many resonances is presented by Hauser-Feshbah formulae. For radiative capture cross section the function, accounting for the resonance fluctuation effects, was chosen roughly the same as in the resolved region. In this approach the values of radius and strength functions can be obtained by fitting to the experimental data. The combined analysis of the total and radiation cross sections in the energy region 4-100 keV confirms the following parameters set, that is same as the set obtained in the resonance analysis of the recent GELINA 232Th capture experimental data. ENDF 6.8 data file is used for 232Th total cross section. The energy dependence of radius and strength functions was not taken into account, but it is necessary at E≥100 keV. There exist unresolved problems of the evaluation of neutron resonance data mainly in the intermediate energy region between resolved and unresolved resonances and these are connected with the detailed description of intermediate structure. The requirement for high precision in the resonance analysis imposes the accounting of neutron width energy dependence that lead to some deformation of resonances though in the single level approximation. This deformation is most apparent near the inelastic scattering threshold and certainly for the lowest resonances