Statistical properties of the 235U resonance parameters up to 300 eV

An accurate resonance analysis of the 235U neutron cross sections up to 300 eV is in progress for the ENDF/B-VI files. A detailed discussion of the data base and a description of the method of resonance analysis have been given elsewhere. The purpose of this paper is to report on the statistical properties of the 235U resonance parameters and compare our results with those of previous analyses. The statistical properties of nuclear levels are of both technical and theoretical interest. From the technical viewpoint, these properties are the basis for an extrapolation into the unresolved resonance region, which is of relevance to the calculation of effective group cross sections for reactor design. From the theoretical viewpoint, the resonance parameters obtained from a multilevel R-matrix analysis of a consistent set of neutron cross sections should satisfy a set of statistical properties arising from general properties of the nuclear Hamiltonian