JEFF-4.0 Evaluated Data: neutron data

Evaluated data associated to JEFF-4.0 nuclear data library: neutron cross section data for 593 nuclides. The neutron-induced reaction data of the JEFF-4.0 library differ on many counts from the JEFF-3.3 library. Major changes were made to the Major Actinides U-235, U-238 and Pu-239 in the resonance region and in the fast region, where new physics models were introduced. Updates were also implemented for Th-232 and U-233 of importance to the Th-U fuel cycle and the Minor Actinides U-236, Np-237, Np-238, Pu-238, Pu-240, Pu-241, Pu-242, Am-241, and Am-243 of interest to spent fuel management, reprocessing and waste transmutation scenarios. Fission product data in the thermal and resolved resonance region were reviewed, updated, and integrated in the latest TENDL library and then adopted in JEFF-4.0, ensuring complete files performing well for fission energy and for fusion activation and decay heat applications. The same approach was applied for many structural materials, coolants and absorbers. Through a close collaboration, neutron-induced reaction data were optimised and adopted from the IAEA International Nuclear Data Evaluation Network (INDEN) project. Furthermore, several files were adopted from JENDL-4.0, from JENDL-5.0 and from ENDF/B-VIII.1 when these were deemed better than what was available. Finally, whenever not already included in the library, the JEFF-4.0 library adopted the available files from the TENDL-2023 library, updated in August 2024 and partially adapted further with files from the TENDL-2025 beta release made available in February 2025.