[en] The authors have determined the multi-level parameters for description of the total and fission cross-sections for ²³⁹Pu in the resolved-resonance region up to 500 eV. A method has been developed for the construction of the elastic scattering and radiative capture resonance cross-sections using these parameters. The group-averaged cross-sections for experimental and evaluated data have been calculated in the energy region considered. (author). Refs, 4 tabs

[en] The multilevel parameters for the description of total and fission cross sections for ²³⁹Pu in the resolved resonance region up to 500 eV have been determined. The method for the constructions of the elastic scattering and radiative capture resonance cross sections using these parameters have been developed. Group averaged cross sections for experimental and evaluated data have been calculated in the considered energy interval

[en] The aim of this work is development of S-matrix multilevel resonance parameters determination technique with neutron transmission data used in resolved resonance region. Experimental transmission data values were obtained for the Pu-239 thickness range 0.00217-0.1234 nucl/barns on the time-of-flight spectrometer with 70 ns/m resolution. S-matrix Adler's formalism with least square method fit were used for experimental data description. The method developed enables to justify the resonance-resonance interference parameters H. Its possibilities are demonstrated by determination of these parameters for four resonances of the Pu-239 total cross section

[en] In the multilevel model of neutron resonances the common expressions of the mean cross sections are obtained. The factors of resonance parameter statistical fluctuations ape calculated. It is shown that resonance parameter fluctuations are too essential for overlapping resonances as for the case of isolated ones

[en] The authors analyse experimental data on the transmission and fission self-indication functions for ²³⁹Pu in the unresolved resonance region. Use is made of the method of generating a cross-section structure based on the multi-level R-matrix formalism (stochastic K-matrix method). Evaluations of the average resonance parameters and group constants for ²³⁹Pu are made. (author)

[en] A statistical method using a priori information (Bayesian approach) is discussed. The stability of solution to variances of initial data is obtained. The solution itself is characterized by necessary qualities of statistical Gaussian appreciation. It is shown tha the statistical method could be used for the treatment and interpretation of results in measuring the function of neutron mission for determining parameters of resonance structure for heavy nuclei in the region of unsolved resonances. As an axample, the results of treatment of measuring the function of neutron transmission for 8 samples of ²³⁵U with the thickness from 0.5022 to 66.96 g/cm² of neutron energy between 4.65 and 10 keV are presented. The results of determining moments and self-shielding coefficients for ²³⁵U are given

[en] Multilevel resonance parameters of total cross section of Pu-239 are derived in the Adler scheme from thick sample neutron transmission data analysis in 4-50 eV energy region. Samples with the thickness from 0.0165 to 0.1084 nuclei/barns were used in the analysis that gets reliable determination of resonance - resonance interference parameter and allows to describe the neutron cross sections structure. Average total cross sections and their self-shielding factors in dependence on temperature (300, N00, 1200K) and dilute cross sections are calculated using the parameters

[en] An analysis of experimental average transmission and cross-sections data for ²³⁵U was carried out using the multilevel theory. A new evaluation for mean resonance parameters and group constants of ²³⁵U was made in the energy region 0.1-21.5 keV. (author)

[en] Using the latest evaluations of mean resonance parameters for ²³²Th, ²⁴⁰Pu, ²⁴²Pu, group constants are obtained in the region of unresolved resonances (mean cross-sections and resonance self-shielding factors). The results obtained are consistent with the Breit-Wigner formula and the systematics of mean resonance parameters from the optical model. There is lack of experimental data on transmission, which are necessary in order to make a more clearly defined choice of mean resonance parameters and a more accurate definition of resonance self-shielding factors

[en] Results of measurements of neutron mean total cross sections and factors of resonance self-shielding of total cross section and fission cross section in the 2eV-20keV energy range by the neutron transmission and self-indication method for ²³⁵U and ²³⁹Pu are presented. Transmission function T(x) and fission self-indication function Tsub(f)(x) were measured from time of flight by the neutron spectrometer on the base of IBR-30 pulse fast reactor. Counters with ³He were used as neutron detectors in measurements of transmissions T(x). Resolution constituted approximately 100 ns/m. Fast response multilayer fission chambers with uranium and plutonium layers serve as self-indication detectors layer thickness and total amount of ²³⁵U constitute 2mg/cm² and 2g, for ²³⁹Pu - 0.5 mg/cm² and 0.5g, correspondingly. Fragment registration efficiency in the fission chambers were measured in separate resonances and amounted to 50-70%. Resolution in self-indication measurements Tsub(f)(x) is 53 ns/m. Specimens represent disks of metal uranium (with 10% ²³⁸U content) and plutonium 50-80 mm dia in sealed stainless steel cans. The correction for ²³⁸U was calculated from parameters obtained as a result of transmission processing. In the course of measurements inherent detector background was controlled. The data obtained are compared with calculational results published earlier. It is noted that the spread in various evaluations of resonance self-shielding factors is rather big. Data on factors of cross section resonance self-shielding for ²³⁵U and ²³⁹Pu at the energy above 1 keV are systematically lower as compared to calculated values. Considerable exceeding of values obtained in experiments as compared to estimations obtained by using the BNAB group constants system, takes place also for the factors of resonance self-shielding of ²³⁹Pu fission cross section