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Joint Evaluated Fission and Fusion (JEFF) Library

The NEA GitLab is used to rigorously version control all fundamental evaluated nuclear data files and, in some cases, more elementary information such as input data for nuclear reaction modelling codes, resonance or other nuclear model parameters, and other output data that is serialised by evaluated file preparation tools.

Accessing the JEFF evaluated and processed data

These pages provide links to evaluated and processed data files that are developed on the NEA GitLab. Public links are provided for certain data types and are available from the following pages. Wherever content is restricted, it is hosted on GitLab repositories and/or data pipelines executed on the NEA local datacentre.

JEFF-4.0 test libraries

The JEFF-4.0 library is currently in development and test sub-libraries are being prepared. To assist in the effort of testing these datasets, they several evaluated and processed data libraries are provided to the public and are accessible from these pages.


These libraries are in development and have not been officially released. The latest official release remains JEFF-3.3.


JEFF-3.3 is a thorough update of the neutron, decay data, fission yields, dpa and neutron activation libraries in the EAF format, with neutron thermal scattering files for 20 compounds. Special sub-libraries for incident alphas, deuterons, gammas, helium-3, protons and tritons have been contributed by the TENDL-2017 library and adopted as part of the JEFF-3.3 release. JEFF-3.3 was officially released on November 20, 2017.

Latest official release

The JEFF-3.3 library is the latest official release from the JEFF project.

Older JEFF data libraries

These libraries have been released between 1986 and 2014 and while commonly used around the world, the JEFF project has superseded these data with the version 3.3 official release. Access to the data is provided from these pages to secure archives at the NEA Data Bank.

Other evaluated nuclear data libraries

The JEFF project collaborates with other worldwide evaluation initiatives, including national projects and international networks co-ordinated by the IAEA. Several data sets are included in the official JEFF releases and these reflect the best performing data, from the perspective of the JEFF Co-ordination Group, from around the world.

Several libraries are stored at the Data Bank besides the JEFF data and are processed through the NEA GitLab data pipelines.

JEFF development lab (JEFF Lab)

The development of JEFF requires routine and reproducible processing to create application-ready data sets out of the raw evaluated files created in the project. These include several data formats and derived quantities that are required for several kinds of nuclear simulations.

The JEFF development lab (JEFF Lab) contains rigorously version-controlled data for all evaluations, containerised processing codes and pipelines with all stages performed and immediately reproducible using Docker images. Most of this information is included in the public domain, but if you have any questions, please contact


Access to the JEFF Lab is restricted to JEFF delegates. Please contact for more information.