[en] The ²³⁷Np neutron cross-sections have been evaluated in the energy range from thermal to 5 MeV. A set of resonance parameters including a negative level, is recommanded after examination of the available experimental data. This set is used 1) to calculate the cross-sections from the thermal region to 150 ev, and 2) to provide the statistical parameters suitable to the calculations in the unresolved region. At higher energies, the transmission coefficients Te are calculated by the coupled channel optical model code ECIS. They are then used as input in the statistical model code FISINGA. The optical model parameters, including the deformation parameters, are those used by Lagrange for the Pu isotopes, slightly modified to reproduce at 40 KeV the total cross-sections obtained from the pure statistical parameters. The recommendations of Lynn concerning the level density parameters have been used. In this paper we describe the various steps of the evaluation

[en] The question of covariance data requirements is dependent on the energy schemes used for application. It is concentrated here on the needs related to energy schemes in current use at present. It is argued that for many cross sections it is not necessary to have uncertainty information for the resonance parameters but only for the infinite dilution cross sections. This argument is illustrated by calculations for ²³⁸U for both fast and thermal reactors. Nevertheless a limited number of resonances have been identified for which covariance data are required for further investigation of the general problem of resonance parameter adjustment, especially in the case where the self shielding factor is dependent on the resonance parameter. It is proposed that the requirement is for the uncertainties in cross sections averaged over intervals of the order of E to 3E plus uncertainty correlation between these intervals. The requirements for fast reactors are illustrated by the results of a cross section adjustment study. It is shown how the adequacy of the choice of covariance data can be verified in the course of an adjustment study and the information which is gained by varying the covariance parameters

[en] The average spacing of resonances is an important parameter for statistical model calculations, especially concerning non fissile nuclei. The different methods to derive this average value from resonance parameters sets have been reviewed and analyzed in order to tentatively detect their respective weaknesses and propose recommendations. Possible improvements are suggested

[en] Neutron reactions on ²³⁷Np (fission and n, 2n) reaction) are important for dosimetry and for the production of ²³⁶Np → ²³⁶Pu. This nuclide is the beginning of the decay chain leading to ²⁰⁸Te (α ray emitter, Esub(α) = 2.614 MeV). A precise calculation of the ²³⁶Pu production during irradiations is required for optimizing shieldings needed for reprocessing and fuel transport

[en] The cross-section for the ⁶Li(n, α) T reaction is determined from the efficiency of a ⁶Li glass scintillator measured by a coincidence-version associated particle method, for which a description is also given. The number of ⁶Li atoms contained in the scintillator was determined by two methods of nuclear analysis: (a) By comparison with a glass whose ⁶Li-content was calculated on the basis of a measurement of total absorption of thermal neutrons made in the ZOE reactor by the phase oscillation method; (b) a transmission method. In both cases it is assumed that the cross-section for the reaction at 2200 m/s is known. The multiple diffusion of the neutrons in the special case of the experiment was determined by a Monte-Carlo calculation. (author)

[en] The presented methodology is based on a formalism simplified by spin and parity omission and on constraints to account in a consistent manner for all the data of the nuclei involved in the cascades during the (n,xn) process. It appears to work correctly for nuclei like 235-U, 238-U and 237-Np, but fails for 239-Pu

[en] Sensitivity studies are presented of integral parameters of interest for fast reactors to uncertainties of resonance parameters of U-238, Pu-239, Pu-240 and Pu-241. Consequences due to some uncertainty correlation hypothesis are also considered

[en] The evaluation of a set of resonance parameters of ²⁴¹Am was done after examination of all the available data. Only some of the main results are given here, with emphasis on the average parameters obtained, and the consistency between the cross sections calculated with the recommended parameters and some measured total, absorption, and fission cross sections in the low energy range. In the unresolved region a statistical calculation of the cross sections using the Hauser-Feshbach formalism was done, and preliminary results are given. 2 figures, 1 table

No abstract available

[en] The neutrons are produced by the T(p,n)³He reaction, as obtained in the Van de Graaff accelerator at the Centre d'etudes nucleaires, Cadarache. The ³He particles associated with neutrons are detected in a direction making an angle of 10^o with the incident proton beam. This detection is made possible by using a tritium-titanium target on a thin backing of copper, and a spectrometer selecting particles according to their charge. Under beam bombardment, the target emits protons of various energies by elastic and inelastic scattering on copper and titanium, together with recoil tritons and ³He particles. These latter are selected by the spectrometer, which is mainly composed of an electrostatic analyser and a silicium solid-state detector. In a second run of measurements, a magnetic separator was added to the device to eliminate completely parasitic protons. Neutrons associated with detected ³₂He particles pass through a ⁶Li-loaded glass scintillator. The ⁶Li content was determined by a measurement of thermal neutron absorption, using the pile oscillator method. The detector efficiency is equal to the ratio of the number of coincidences between neutrons and ³He particles to the total number of detected ³He particles. The coulomb scattering of ³He particles in the target induce a dispersion in energy and direction of associated neutrons. A Monte Carlo calculation has been made to correct for coincidences lost by this effect and for multiple scattering of neutrons in the scintillator. The resulting cross-section is 3.00 ± 0.1 b at 255-keV neutron energy. Measurements have been carried out in the range between 150 and 280 keV. Further improvements to the method are proposed. (author)