Effect of NJOY and Grucon Processing Codes in Nuclear Data Preparation for Steel Nuclides
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EFFECT OF NJOY AND GRUCON PROCESSING CODES IN NUCLEAR DATA PREPARATION FOR STEEL NUCLIDES
A. I. Blokhin, E. F. Mitenkova, and N. V. Novikov
UDC 621.039
The observed differences of the neutron fluxes between experiments and calculations on passage of neutrons through thick layers of iron and steel are conditioning the use of better models for representing the scattering cross-sections and energy-angle distributions of neutrons in elastic and inelastic scattering. The effect of the NJOY99 and GRUCON prepared nuclear data for Fe, Cr, and Ni on Keff and functionals related with the neutron fluxes in systems with a thermal and a fast spectrum is studied. The calculations were performed using MCNP5, and all nuclear data files are based on ENDF/B VII.1.
The neutron transport in a medium is determined by the cross sections of the interactions with the nuclei of nuclides present in the medium. The difference of the measured and computed fluxes on the passage of neutrons through iron and steel plates with thickness to 70 cm conditions special attention to the refinement of the nuclear data on nuclides in the composition of the steel [1, 2]. Strong fluctuations of the scattering cross sections in the interval 0.5–5 MeV cannot be taken into account in the R-matrix model or the conventional optical model, and the problem of nuclear data for iron isotopes remains real [3]. Processing codes. The cross-sections developed for nuclear reactions on the basis of experimental microdata and/or theoretical models using evaluation and reconstruction procedures are presented in evaluated nuclear data files ENDF [4]. The development of a transport library for neutronic calculations presupposes processing of these files with the aid of specialized processing codes in accordance with prescribed options and formats dependent on the specifics of problems and computational codes. The processing codes make it possible to reproduce the cross-sections on a unified energy grid taking into account the chosen model, resonance parameters, and temperature, methods of describing cross-sections near unresolved resonances, for example, taking into account or neglecting probability tables, and so on [5]. Programs of the NJOY family, first and foremost, NJOY99, have for more than 30 years been the most in demand for working with ENDF data files. New methods for representing evaluated neutron data, the use of more complex models with expanded characteristics of nuclear interactions promote improvement of the processing codes. So, significant changes in the NJOY-2012 code pertain to the field of resonance parameters based on the Reich–Moore model (RECONR module), calculations of the uncertainties for cross-sections near resolved resonances (ERRORR module), new options for forming thermalization data (THERMR module), and so on. Among the alternative processing codes PREPRO, AMPX, and FUDGE, we call attention to GRUCON, whose latest version implements the most complete set of models for processing current ENDF data [6–10]. The resonance parameters for elasti
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