Orateur
Description
The "Nuclear Data for Reactors" (DNR) group at the Institut Pluridisciplinaire Hubert Curien (IPHC, CNRS/University of Strasbourg) leads experimental research to characterize inelastic neutron scattering and (n, xn) reaction cross sections. These data are essential for the design and safety of advanced nuclear reactors, as they influence neutron energy distribution, material activation, and reactor performance. However, current evaluated nuclear data libraries still contain significant uncertainties, especially for actinides relevant to innovative fuel cycles.
At the Neutrons For Science (NFS) facility, the DNR group recently completed measurements of the 238U(n, 2n γ) and 238U(n, 3n γ) reaction cross sections. Conducted in late 2024, this campaign utilized the MAELS (Multidetector Array for inELastic Scattering) setup, combining up to 12 High-Purity Germanium (HPGe) detectors from international partners (IPHC, JRC-Geel, IFIN-HH). The experiment integrated both prompt γ-ray spectroscopy and activation techniques, leveraging the half-life of 237U. Preliminary results show a good ability to measure the incoming neutron flux, encouraging quality of (n, xn γ) first analysis outcomes, and demonstrates the potential to measure new, precise data that will be used to effectively constrain theoretical models and subsequently the evaluated data used to simulate reactors.
Building on this success, the DNR group envisions a comprehensive measurement program covering many actinides, that started with 238U, and for which the next step will be the study of 232Th(n, 2n γ) and 232Th(n, 3n γ) reactions, to be submitted to the next PAC. Thorium-232 is a key isotope in the 232Th/233U fuel cycle, and precise cross-section data are vital for optimizing neutron economics and addressing radioprotection challenges in thorium-based reactors. The proposed experiment will feature an upgraded MAELS setup, with enhanced shielding and dual fission chambers (235U and 238U) for improved neutron flux monitoring, and activation measurements, using the 25-hour half-life of 231Th to provide independent integral cross-section data.
The DNR group’s activities at NFS highlight its commitment to improving nuclear data precision, supporting next-generation reactor development, and fostering international collaboration. Future plans include extending these methodologies to other actinides, such as 233U, 235U, and 239Pu, while addressing radioprotection constraints and optimizing experimental setups for high-activity samples.