Progress towards the ENDF/B-VIII.1 release

The efficient, safe, and high-performance design and operation of nuclear reactors, and other nuclear systems, rely on complete and accurate nuclear data files. The ENDF/B library is the main nuclear reaction data library in the United States and one of the main ones in the world. It encompasses sub-libraries for neutron, proton, alpha, deuteron, 3He, and gamma projectiles, in addition to thermal neutron scattering law, fission product yields and three atomic sub-libraries. The last release of ENDF/B was ENDF/B-VIII.0 in 2018. Since then, many important and impactful developments have been made for actinides, structural materials and light elements. Some of these contributions are part of the IAEA-coordinated International Nuclear Data Evaluation Network (INDEN). The scale and impact of these changes warrant a new library release, namely ENDF/B-VIII.1, which is scheduled for early 2024. This release is planned to happen in both ENDF-6 and GNDS-2.0 formats. The present work describes the updates expected to be present in ENDF/B-VIII.1, as well as the review process and quality control procedures developed and implemented at the National Nuclear Data Center (NNDC). Preliminary results from the Beta versions already released are also shown.