Progress in the Evaluation and Validation of n+^56,57Fe Cross Sections

¹ Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
² NAPC–Nuclear Data Section, International Atomic Energy Agency, PO Box 100, A-1400 Vienna, Austria
³ Commisariat a l’Energie Atomique, Cadarache, DEN/DER 13108 Saint-Paul-Lez-Durance, France
⁴ Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany
⁵ Gaertner LINAC Center, Rensselaer Polytechnic Institute, Troy, NY 12180, United States
⁶ Research Center Rez Ltd, 250 68, Husinec-Rez 130, Czech Republic
⁷ Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen, Germany

^* Corresponding author: andrej.trkov@ijs.si

Published online: 26 May 2023

Abstract

There has been a continued effort since 2019 within the IAEA INDEN collaboration to improve the evaluation of neutron induced reactions on iron isotopes. The reason for the 30% underestimation of the neutron leakage spectrum from a thick iron sphere was found primarily to be due to the overestimation of the inelastic cross sections in the ⁵⁶Fe evaluated data file produced within the CIELO project of the OECD/NEA Data Bank. The over-estimation of the neutron flux between the resonances near 300 keV was traced to neglecting the fluctuating nature of the total cross section of ⁵⁷Fe in the fast neutron energy range, since the evaluated resolved resonance range of ⁵⁷Fe extended only up to 190 keV. The added 1/v background in the "iron window" below 28 keV is in excellent agreement with the independently evaluated one in the JENDL-5.0 library that included the direct capture component in the evaluation. Performance of the updated 56,57Fe evaluations was tested on a set of criticality benchmarks from the ICSBEP Handbook, including the dependence on reflector thickness and on new deep penetration shielding benchmark using a ²⁵²Cf(sf) neutron source undertaken at Rez, Czech Republic. Neutron leakage for 43 MeV incident neutrons was also validated.