What can we learn from (n,xnγ) cross sections about reaction mechanism and nuclear structure?

¹ Université de Strasbourg, CNRS, IPHC UMR 7178, Strasbourg, France
² CEA, DAM, DIF, Arpajon, France
³ Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania
⁴ University of Bucharest, Faculty of Physics, Bucharest-Ma˘gurele, Romania
⁵ IAEA, Nuclear Data Section, Vienna, Austria
⁶ Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA
⁷ European Commission, Joint Research Centre, Geel, Belgium

^* e-mail: maelle.kerveno@iphc.cnrs.fr

Published online: 30 September 2020

Abstract

Inelastic (n,n') cross section is a key quantity to accurately simulate reactor cores, and its precision was shown to need significant improvements. To bypass the experimental difficulties to detect neutrons from (n,xn) reaction and to discriminate inelastically scattered neutrons from those following the fission process in case of fissile targets, an indirect but yet powerful method is used: the prompt γ-ray spectroscopy. Along this line, our collaboration has developed the GRAPhEME setup, optimized for actinides, at the GELINA facility to measure partial (n,xn γ) cross sections, from which the total (n,xn) cross section can be inferred. (n,xn γ) experiments with actinides are still particularly challenging, as their structure presents a high level density at low energy, and the competing neutron-induced fission reaction contaminates the γ-energy distribution. New precise measurements of the partial (n,xn γ) cross sections provide a stringent test to theoretical model and offer a way to improve them. This is a path to a better determination of the total inelastic scattering cross sections. In this contribution we discuss modeling aspects of the ²³⁸U and ¹⁸²W (n,n' γ) reactions, also measured with GRAPhEME, using the three codes TALYS, EMPIRE and CoH. We will highlight the needed/expected improvements on reaction modeling and nuclear structure input.